Biogas Production from Agricultural Waste in the Aral Sea Basin Development of Pilot Plants

Final Report:

Biogas production from agricultural waste in the Aral Sea Basin Development of pilot plants

Authors: Hans-Christian Angele, EBP Schweiz AG/AngeleConsult Werner Edelmann, arbi GmbH Bahtyior Eshanov, Economics Department, Westminster International University in Tashkent Olimjon Saidmamatov, Economics Department, Urgench State University

C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx Date of the Report: 20 of September 2019 Contract Number: 2016.11 Institution: EBP Schweiz AG/arbi GmbH Country: Uzbekistan

Prepared by:

EBP Schweiz AG Zollikerstrasse 65 CH-8702 Zollikon T +41 44 395 11 11, F +41 44 395 12 34, [email protected], www.ebp.ch arbi GmbH Heimelistrasse 35, CH-6314 Unterägeri T +41 763 2121, [email protected], www.arbi.ch

With the Support of: REPIC Platform c/o NET Nowak Energy & Technology AG Waldweg 8, CH-1717 St. Ursen Tel: +41(0)26 494 00 30, Fax: +41(0)26 494 00 34, [email protected] / www.repic.ch

The REPIC Platform is a mandate issued by the: Swiss State Secretariat for Economic Affairs SECO Swiss Agency for Development and Cooperation SDC Federal Office for the Environment FOEN Swiss Federal Office of Energy SFOE

The author(s) are solely responsible for the content and conclusions of this report.

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx Contents 1. Summary ...... 4

2. Abstract in local language ...... 4 3. Starting Point ...... 5 4. Objectives ...... 5

5. Project Review ...... 6 5.1 Project Implementation ...... 6

5.2 Achievements of Objectives and Results ...... 7

5.3 Multiplication / Replication Preparation ...... 17

5.4 Impact / Sustainability ...... 17

6. Outlook / Further Actions...... 17 6.1 Multiplication / Replication ...... 17

6.2 Impact / Sustainability ...... 18

7. Lessons Learned / Conclusions ...... 18

8. References ...... 20 9. Annex ...... 21 Annex 1: Definition of best adapted technology ...... 22

Annex 2: Program of and schedule of Workshop “Sustainable agriculture for human security” ...... 31 Annex 3: Biogas - learning center at NGO KRASS in Urgench ...... 33 Annex 4: Schedule of intensive formation ...... 35

Annex 5: List of participants ...... 36 Annex 6: Pictures of intensive formation ...... 37 Annex 7: Presentations of intensive formation ...... 40

C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx 1. Summary The Urgench region of Uzbekistan has a well-developed agricultural production with high livestock numbers and intensive crop production based on irrigation and high nutrient input. The manure of the farms is not used efficiently and the energy supply of the farms depends primarily on centrally produced gas and electricity. Some areas are not yet connected to the gas grid. The agriculture causes huge environmental damages in its current form. The benefit of biogas production would therefore be fivefold: (1) local energy source, (2) mitigation of environmental impacts, (3) reducing CH4-emissions, (4) producing organic fertilizer as a side product and (5) additional earnings for farmers. The project in discussion had the objective of training the local people and the realization of one to two pilot plants with the ultimate goal of sensitizing the farmers and consultants and showing them the benefits of the biogas technology. However, first meetings in Usbekistan with the relevant stakeholders made clear that the prerequisites for the realization of pilot plants did not exist. For the following reasons: a) Unsuccessful first installation of biogas plants in the region (built from 2013 to 2015). None of these plants is still working due to missing technical understanding and insufficient adaption of the plant design to local conditions. These facilities cannot be used for further development and on top first regional experiences with this new technology were negative. b) At all process stages, the people involved (scientist, consultants, farmers) lack the necessary knowledge for the construction and operation of biogas plants. c) The prices for energy and fertilizer are so low that it is a big challenge to operate biogas plants economically. The process concept was therefore adapted and geared more towards capacity building. In a four-day seminar, interested scientists, consultants and farmers received intensive training. A visit of existing facilities at the end of the seminar allowed to test the gained knowledge and to discuss how the problems could have been avoided. The seminar was supplemented by specific courses for farmers. Moreover, a specific biogas competence center has been set up in the rooms of the NGO KRASS in Urgench. At the same time, the project team analyzed existing concepts for the production of biogas and defined the best-suited technologies for on-site implementation. Unfortunately, no farmer has yet been convinced to make the corresponding investment. To sum up, the project has improved the basic conditions for future biogas projects in the region. The best-suited technologies have been defined, more than 20 people have dealt intensively with biogas production and many of them showed interest to deepen this knowledge in the coming years and make it available to others. The infrastructure on site is available. For the realization of a modern biogas plant that fulfils the needs of the regional environment and actors, additional funding is crucial. To guarantee the requisite financing will be one of the biggest challenges for the local actors, who have already started to develop a new biogas project.. 2. Abstract in local language Orol bo`yi hududidagi ekologik holat mintaqaga biogaz texnologiyalarini tadbiq qilish uchun chu-qur ilmiy tadqiqot ishlarini talab qiladi. Chunki, suvning tuzlilik darajasi, mahalliy chorvachilik tajribalari, ob- havonong keskinligi biogaz uskunalarining ish faoliyatiga to`g`ridan-to`g`ri salbiy ta`sir ko`rsatadi. Qoraqalpog`iston Respublikasi va Xorazm viloyatida bir necha biogaz qurilmalari chorvador fermerlar tomonidan o`rnatilingan bo`lib, ularning ko`pchiligi iqlim sharoiti tufayli texnik nosoz holatga kelgan. Mazkur loyihaning asosiy maqsadi Orol bo`yi mintaqasida qishloq xo`jaligi chiqindilarini qayta ishlash, biogaz ishlab chiqarish va uning ijtimoiy-iqtisodiy samarasini ilmiy va amaliy jihatdan o`rganishdan ibo- rat. Loyiha davomida mahalliy chorva fermerlar bilan yaqindan hamkorlikda mavjud biogaz texnologiya- larining yaroqsiz holatga kelib qolish sabablari o`rganildi. Ushbu kamchiliklarni inobatga olib, Shveydsariya tajribasiga asoslangan holda mahalliy sharoitlarga mos keladigan biogaz modellarini ishlab chiqish ustida izlanish olib borilmoqda. Ushbu modellar yaqin kelajakda mintaqaning organik chiqindilarini qayta ishlab, qishloq hududla-riga juda dolzarb bo`lgan bio-energiya va bio-o`g`it yetkazib berishi kutilyapti. Loyiha natijalarini om- malashtirish uchun, 2016 va 2018-yilning sentabr oylarida mahalliy fermerlar va universitet professor- o`qituvchilari, talabalar uchun bir necha seminarlar tashkil qilinib, biogaz sohasini rivojlantirish uchun zarur bo`lgan bilim va tavsiyalar berildi.

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx 3. Starting Point Agriculture (i.e., farming, horticulture and livestock breeding) is the major economic activity in the Aral Sea basin. The associated use of water is considerable. The land productivity is decreasing due to excessive surface irrigation using salinated water from the Tuyamuyin reservoir causing desertifica-tion. Standard agricultural practices have negative impacts on the quality of soil and are associated with high groundwater and energy consumption. The livestock sector is dominated by small house-hold farms and provides often the best livelihood option for rural families. Since 2001 rising market prices of provender have significantly affected small-scaled Uzbek producers, because of their lim-ited ability to pass on these price effects to the end consumer. Total profits in the Uzbek beef, lamb and pork industries are falling. As a result, large companies with a livestock of minimum 200-300 cat-tle are increasing their market share. Local producers are permanently looking for new possibilities to improve their yield and the earnings and to reduce costs in order to survive in this competitive market field. In this context, the production of biogas could help reducing energy costs (mainly electricity and gas) and increasing crop yields due to the production of a high quality organic fertilizer. Biogas production can also help reducing environmental risks, such as water evaporation caused by agriculture and improving well-being of the families. As an environmental co-benefit, carbon emissions are being reduced. The Uzbek government is aware of the critical environmental situation in the Aral Sea basin, which also puts high burden on agriculture, which represents the most common livelihood option in the rural population. In 1996 President Islam Karimov raised the human-driven environmental catastrophe in Aral Sea basin as a global concern in several United Nations meetings. Recently, Cabinet of Ministers approved a new Decree to support green energy generation by dedicated bank loans with low interest rates and the possibility to sell surplus electricity generated from renewable energies to “Uzbeken-ergo”, the operator of the centralized electricity grid. Based on this analysis a first project proposal has been worked out and finally accepted by the REPIC steering group. The main goal was to realize first biogas plants as pilot projects together with interested farmers. But the in-depth analysis of the local situation showed, that it didn’t make any sense to focus on first pilot plants before improving the local knowledge about biogas production. Therefore a second and actualized proposal was elaborated and accepted by REPIC. 4. Objectives The above mentioned actualized project proposal1 defines the following objectives: 1. Objective 1: Development of economically viable biogas production systems which are well adapted for the local situation and the farmers in the Aral Sea Basin including ecological and social aspects. 2. Objective 2: Development of local capacities (consulting, construction, training) for planning, realization and operation of biogas plants. 3. Objective 3: Understanding of the main challenges in the development of biogas plants and how to overcome them.

These objectives should be achieved by the following working steps: 1. Project Kick-off including fact-finding mission 2. In-depth-analysis of the local situation 3. Definition of best adapted solutions

These three working steps were executed in the frame of the first project proposal. The results can be found in the intermediate report from March 20172. They can be summarized as follows:

1 Actualized Project Proposal: Biogas production from agricultural wastes in the Aral Sea Basin: development of pilot plants; July, 20th 2017 2 Biogas production from agricultural waste in the Aral Sea Basin. Development of pilot plants. Intermediate Re- port from March 2017. 5/40

C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx 1. Biogas production is practically non-existent in Uzbekistan. A few small plants have been built for the digestion of cattle manure. However, they do not work properly or they are out of order. The knowledge of biogas technology and plant operation seems to be very poor. 2. Digesting cattle manure is a challenge in Uzbekistan, because the cattle are usually outside on an unpaved ground. Therefore the excrements of the cows are spoiled with inert material such as sand and stones, which would cause the formation of sediments inside a digester for liquid digestion. For using the droppings of the cattle, it is recommended to improve the management of the manure. 3. Different technologies could be applied in Uzbekistan: For a low gas production, biogas could be produced with an improved technology in locally available steel tanks. For large cattle farms it is recommended to develop simple, low cost batch digestion systems with several containers out of metal or concrete or with several bunker silos covered by a gasholder out of tissue reinforced PVC. The containers or silos, respectively, will be filled and emptied alternately in order to generate a more or less stable biogas production. If there are in addition of solid manure some semi-liquid co-substrates (such as slaughter waste etc.), a simple plug-flow reactor – which has to be adapted to the cold climate in wintertime – could be a good solution. 4. Though, all these technologies need further development, in order to save construction costs and to adapt the plants to the cold climate. Unfortunately, no engineers with knowledge of the fundamentals of biogas production seem to be locally available. However, this is an important prerequisite for developing technologies appropriate to the local situation together with the local counterpart. 5. Therefore, it is proposed to put weight on the formation of engineers and to build up a local group of biogas specialists. At the same time, it is important to show the advantages of the digestate regarding the improve- ment of the soil qualities. Here, there is also lack of information how to bring out the nutrients and the precious organic compounds back to the fields. 6. First, rough estimations showed that it should be possible to find solutions, which are reasonable also from an economic point of view. For an optimal biogas production it is important to find additional, so-called co-substrates, which have not passed through an intestine of an animal yet. Organic wastes seem to be used to a large extent for other purposes in Uzbekistan. Nevertheless it seems to be possible to find some organic wastes increasing the biogas yield of the plants to be constructed.

The following working steps were executed during phase 2 of the project: 4. Investigation of the energy demand of livestock farmers 5. Intensive formation for a biogas competence centre in Khorezm 6. Engaging the external experts from the other regions 7. Arrangements to run a pilot project in cooperation with farmers

The results of these working steps are summarized in the following chapters. 5. Project Review 5.1 Project Implementation

The project began with identifying existing biogas plants that are not in working conditions followed by the field trip to each plant by the project partners. Main technological reasons were identified that is considered as an obstacle for biogas generation. Collected local knowledge with fundamentals of biogas technologies was delivered to the attention of farmers, students, researchers via workshops and seminars in Khorezm region and Karakalpakistan. As explained in Chapter 3 the project objectives changed during the project upon completion of the phase 1. The team was planning to develop a pilot plant and then decided not to do it due to the following reasons: a) Demonstration of the pilot plant demanded many engineering effort that the local partners could not provide. Moreover the budget and funding sources were limited. a) The foreseen pilot plant needs long-term ecological-economic-technological observations that need specific bio-technology specialists, chemists, biology and soil science researchers. The existing knowledge and experience among these specialists was not sufficient. b) Capacity building for local specialists was very important due to the lack of knowledge and experience on biogas technologies. In consequence the project focused mainly on training local biology, chemistry, technology specialists who can support the future biogas development in the region and contribute to a biogas pilot plant demonstration in Aral Sea basin.

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx In phase 2 there were no modifications concerning the objectives.

5.2 Achievements of Objectives and Results

5.2.1 Investigation of the energy demand of livestock farmers From September, 16th to September, 23rd 2016 the project team visited different farms (Fig. 1).

Figure 1; Map of Khorezm region with farm locations

This chapter describes the farms and sums up the first conclusions regarding the energy demand of the farmers. 1. “Biougit” LLC with a biogas digester out of order sold-out the land and the cattle little before the project team paid a visit. It specializes in biofertilizer production through open-air composting of the manure, It receives it from its recently sold-out cattle farm. 2. “Agrofirma” farm of the JSC “Khorezm Territorial Electricity Networks” located in the Gurlen district (with biogas plant). This cattle farm has 130 ha irrigated farmland and owns 280 cattle of different sizes. It produces between others milk and yoghurt. The manure on the cement ground of the stable is collected for anaerobic digestion. The cows are in summer for four hours in the stable during the hottest period of the day and in winter longer when it is very cold. i.e., just a very low percentage of the manure is digested. 3. Cattle farm of the Khorezm branch of the National Holding Company “UzbekNefteGaz”. The farm established in 2014 is allocated 40 ha land in Yangibazar district for breeding 150 cattle mature for beef production. The purpose of the cattle farm is providing meat products for the company employees and local residents at affordable prices. It is planned to increase the number of animals and to add a poultry production. 4. Cattle farm of the JSC “Uzbekistan Railways” in Shavat district has 1000 ha land to keep 1000 adult cattle and 500 calf, as well as 30’000 hens (in cages). Like on the large majority of the farms, the cattle are outside on unpaved ground. That is to say that the manure is mixed with soil and stones, what would cause sediments in the biogas reactor. 5. “Usta Mustafo” cattle farm in Shavat district is allocated 40 ha land for 150 cattle. The “manure” is manually thrown through windows on the backside of the shelter and kept on heaps for long times, where the material should undergo a composting process. However, black regions in the material indicate that there is Hydrogen Sulfide, typical for anaerobic processes. 6. “Ibrohim Bobomurit Baymak”-cattle farm in Bogot district has 100 cattle (50 milking cows and some young beefs) with arable land of 43 ha, whereof 10 ha are cotton and 12 alfalfa. One

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx ton of manure is collected daily and thrown sporadically into the water channels for fertilization and irrigation. Collected manure is distributed among farmer employees for heating domestic ovens (i.e., to make bread and food and for heating in wintertime). The farm intends also to increase its chicken production. 7. “Gulomboy Ikromboy” cattle farm in Khazarasp district: This farm with 400 cattle has also wastes from rice production. On the contrary to “Usta Mustafo” farm in Shavat, here there is a new rice mill, which includes little amounts of starch to the husks. Therefore the husks can be fed to the cows. Nevertheless, the nutritional value of the husks is probably minimal, i.e. it is mainly roughage. The manure remains for several months on the ground. This has the advantage that the input for the biogas plant includes much less earth and stones. On the other hand, there is the disadvantage, that the manure loses quite a lot of its biogas potential while being stored for a long time before digestion 8. “Muslima Sotimova” cattle farm in Yangibozor district owns 80 cattle and 20 ha agricultural land nearby (between others, includes corn production). Annually, the farm produces 300 tons of manure. Here, the animals would stay on a paved ground at least in winter time. 9. “Yuldosh Majid” cattle farm in Khiva with 140 cattle is located next to the border to Turkmen- istan and to the desert. There is a biogas plant digesting a part of the manure. The plant consists of a 10 m3 digester (horizontal steel cylinder mounted on two supports) with a device for mixing the content of the digester manually (horizontal axis in the centre). The gas is stored under pressure in a vertical cylinder. The material (diluted with water) is fed through a funnel on the inlet side and leaves on the opposite side via an overflow tube, which feeds a small lagoon. There, the liquid – containing dissolved inorganic nutrients – seeps into the ground and into the groundwater, respectively. Remaining solids are collected and brought out to the field. Between others, the digester is not insulated and is heated by an open fire under the tank (!!). 10. “Honka parrandachilik” LLC poultry farm in Khanka district. This new and modern poultry farm keeps 150’000 laying hens producing daily 15 tons of chicken manure, which is sold to farmers for 10-15 UZS per kilo. This would be a good place for a biogas plant.

The Project team has interviewed four farmers with an objective of investigating the energy demand of livestock farmers in Khorezm region, Uzbekistan. Farmers had two different types of ownership: (i) company owned (Regional Electric Utility Company’s livestock farm in Gurlen, Regional Oil Stor- age Base Company’s farm in Yangibazar) and (ii) privately owned (Yuldash Majit private chicken farm and Qudrat Turkmen farm”). The following paragraphs aggregate the findings of the responses by the farmers.

Types of crops Farmers in the Khorezm region cultivate large variety of crops. Cotton and wheat still cover the largest part of the farmlands in Khorezm, while cultivation of rice, maize, alfalfa, sorghum and soy- bean are also widespread. According to the state statistics, 80% of the vegetables are produced in household farms (also referred as private plots of 0.1-0.2 hectare/family). Share of large horticulture gardens are increasing significantly.

Average size of farms Farm sizes vary from 10 hectare to 50 hectare in average. Number of farms exceeding 50 hectares are few and they specialize on cotton and wheat production under state order. Horticulture farms usually allocate less than 10 hectares of land. A concept called “cattle equivalent” is used for allocating land to livestock farmers. A bull or a cow elder than two years old and weighting over 200kg is considered one cattle equivalent. Three calves over one-year-old and weighting under 200kg each are also considered as one cattle equivalent. 12 calves under one year old are also considered as one cattle equivalent. Camels and horses are also considered under the above conditions. Livestock farmers get one hectare of farmland for each three units of cattle equivalent. In average 10 hectare of land is offered for a livestock farmer with 40-45 cattle of various sizes. Zootechnicians are responsible for evaluating the cattle equivalent of each farm.

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx Irrigation demand for water and energy For one of the respondents, electricity expenses were 12 million Uzbek Soums for irrigating 40- hectare land during the 2016 agricultural season. Wheat is irrigated six to seven times during the one season. Water demand of cotton is relatively lower and it is irrigated two times during cultivation and the land is leached twice during the winter, leading to four times irrigation during one harvest cycle. Farmers use surface irrigation method to water their large crop fields such as cotton and wheat. In average water is lifted three times with the help of electric pumps on its journey from the main river to the field. Due to the soil type (sandy soil) and structure (high groundwater table), rate of infiltration is also high in the Khorezm province. Therefore, a larger part of the water is lost during the trans- portation. According to some estimates merely 20%-25% of the total water lifted from the main river reaches the crop, while rest is being lost due to evaporation and infiltration. According to the observations, besides the energy demand for irrigation, energy demand of the livestock farms is similar to the energy demand of average households. If available, natural gas is used for heating the household during the five months and in daily average 70-80 cubic meter gas is necessary for the boiler (heating) during this five months (Oct 15th – March 15th). Respondents’ average bill for natural gas during this period was 2000 cubic meters per months. For cooking and water heating additional 500-600 cubic meter natural gas is spent, making the demand for natural gas 2500-2600 cubic meters during the heating season (it equals to ca. 3500 cubic meter of biogas). However, there exist many farms far from the grid of natural gas. There the gas has to be transported to the spot in bottles. Electricity consumption is constant over the seasons for farmer’s households if there is a natural gas supply. It consists of 100-150 kWh per month, which is used for preparing nutrition for the cattle. Additional electricity consumption of up to 150 kWh may arise due to irrigation of the household plot during the irrigation seasons, where they grow vegetables in line with fruit trees. In livestock breeding, electricity is necessary for lighting and straw-cutting (mashing). This annual electricity expenses fare less than 100.000 UZS per month (annual one million UZS according to the records). Cowhide is not heated even in -20° Centigrade cold weather. 40-45 cattle produce enough energy to heat the air of the cowhide. If the temperature inside the cowhide increases to a positive degree, lice (singular: louse – a parasite insect) populate on the cattle. Farmers keep the doors half-open to avoid heating and to decrease the humidity. Some farmers install ventilation chimneys to create ventilation at four corners to keep the cowhide dry. Ventilation chimney in one surveyed farm is made of four metallic pipes with 200 mm diameter and four meters height. None of the surveyed farms has a greenhouse. Farmers were willing to build one if there would be extra heat. Extra heat would also allow them to keep poultry, which requires 20-22° Centigrade constant indoor temperature for hen to produce eggs. Every year livestock farmers sign contracts to keep silkworm, which requires a facility with constant temperature. Silkworm is very sensitive to temperature and cannot survive under 18° Centigrade and above 30° Centigrade. It also does not tolerate smoke, meaning that the facility cannot be heated with firewood, coal or direct combustion of manure. It should have a decent heating system with a boiler and radiators. Hence extra heat would be an asset for one-month period in May. Sometimes farmers suffer from prolonged period of silkworm keeping due to colder environment, which may take up to 45 days instead of usual 30 days, when process is prolonged due to cool weather conditions. Biogas could step-in when drip irrigation is introduced. Farmers can use part of the biogas to generate electricity and pump the water into a large reservoir tank, which then is used for drip irrigation of farms. Drip irrigation cannot be applied to all varieties of crops. Horticulture farms and vegetable producing farms are more suitable for introducing drip irrigation. Therefore, it is suggested to arrange a greenhouse, larger poultry farm and drip irrigation based farming in a farm where a pilot biogas plant is expected to be built. Consequently, a pilot biogas project includes offering a “package solution” which includes the above-mentioned activities as an ad-hoc to biogas station.

5.2.2 Intensive Formation for a biogas competence centre in Khorezm General information The intensive Formation has been held from August, 27th to August, 30th 2018 in Urgench at the NGO KRASS.

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx For the program of the intensive formation see annex 4 und for pictures see annex 6. 37 participants were registered. 18 of them were present during the whole seminar (four days), seven during three days, ten on two days and two people only on one day. The days with excursion (24) and practical exercise (23) were the ones with fewest participants. The list of participants is shown in Annex 5. The presentation in English can be found in annex 7. All the presentations were also translated into the Uzbek Language. All the participants got an Uzbek copy of the presentation with enough space for personal remarks. The Swiss members of the project team gave their presentations in English using also the English version of the slides. Most of the participants had a quite good knowledge in English. Nevertheless, after finishing one slide a short summary in Uzbek was made by the local team members.

Results 20 of the 37 participants filled out the evaluation sheet. They could rate the different parts of the formation with stars from 5 (very good) to 1 (very bad). The results show that the people were very happy with this formation:

Evaluation intensive formation on biogas porduction; Urgench, August 2018

Part Rating Total Average 5 4 3 2 1 1 Biology 19 1 20 4.95 2 Substrates/parameters 17 1 2 20 4.75 3 Technologies, process engineering 16 4 20 4.80 4 Products, safety and operation 18 2 20 4.90 5 Site visit 16 2 1 19 4.79 6 Calculations/case study 13 4 17 4.76

In addition they answered with intensive comments and suggestions for a next edition of this formation. Every student who was present during the three-day-seminar got the following certificate:

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx More than ten people showed interest to work in the competence centre. The infrastructure (rooms, learning and demonstration material, etc.) is available and prepared at NGO KRASS in Urgench (see pictures in annex 3).

Learnings The biogas training course “Digestion – State of the Art and optimal Plant Operation” has been especially elaborated for the Uzbek situation. However, it bases on more than 20 years of experience with training courses for Swiss engineers as well as for farmers and operators of agricultural and commercial biogas plants. The first block gave information on the natural cycles, on the differences of aerobic and anaerobic degradation and on the fundamentals of the biochemistry of anaerobic degradation, allowing conclusions for an optimal running of a biogas plant from a biological point of view. A second block informed about possible substrates and their digestibility, what allowed making estimates about the possible biogas yields of different substrate mixtures. Information was given about constructing easy devices for testing unknown substrates to determine their biogas yields and to calculate the optimal running parameters of the process, Based on this knowledge acquired so far, in block 3 different technologies for constructing batch or continuously fed digesters to digest liquid or (semi-)solid substrates were presented. Special em- phasis was given to show designs with low technical input causing (relatively) low running and construction costs. Block 4 finally referred to the handling of both of the products, biogas and digestate, including information on safety aspects and final thoughts on an optimal digester operation. There was really a lot of information, which required much concentration of the participants. There was the concern that it might be too much – but surprisingly the participants were very attentive all days long and they took always an active part in the seminar. They asked questions showing that they got the points of the presentations and on the excursions one could see that they looked with an enlarged sight to the sites visited.

5.2.3 Engaging the experts from other regions The project team got in contact with two Uzbek experts, who have broad experiences in the realization of biogas plants in region of Tashkent. Unfortunately they were not interested to collaborate. But the project could find another solution. Two external experts with experience and knowledge in biogas production (Dr. Nizomaddin Rahmonov – energy scientist and Mr. Pulat Salikhov – energy engineer) are willing to cooperate upon availability of external funding.

5.2.4 Arrangements to run a pilot project in cooperation with farmers Seminar for farmers On August, 13th to August, 25th 2018 Olimjon Saidmamatov was part of KRASS / UNESCO specialists to deliver training within the Workshop “Sustainable agriculture for human security” for farmers living in rural communities of Karakalpakistan where he presented opportunities about biogas and biofertilization in the Aral Sea basin resulting from the REPIC project. They conducted training at 5 remote districts of the Republic of Karakalpakistan (Shumanay, Ellikqala, Beruniy, Tur- tkul, Amudarya, see figure 2). Training materials covered agriculture/energy/soil/water issues that are needed for farmers (attached agenda provides all details) to improve their livelihoods. In each district, two day training was arranged to teach around 30-40 farmers with theoretical and practical materials, meaning that in total around 200 farmers of Karakalpakistan participated in one of these trainings. The program is shown in annex 2.

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx Figure 2: Regions where the workshop “Sustainable agriculture for human security” was held

Negotiations with interested farmers All the discussions with interested farmers came to the same conclusion: If there are no financial incentives, no farmer will take the risk to invest. As there are no public incentives for biogas generation, no farmer is really interested in pilot plant demonstration. However, If there is external co-funding, 2 - 4 farmers are still willing to install biogas plants.

Built-Operate-Test-Transfer-Model Regarding the biogas technology in Uzbekistan, the following facts may be captured (for more detailed information see Appendix 1 Definition of best adapted technology):

• For the large Uzbek farms and the poultry industry, the method to choose is a solid waste batch digestion. There are two designs, which both are feasible from a technical point of view (container and anaerobic bunker type silo). • The Uzbek raw material is usually spoiled with inert matter (stones and sand), which only can be handled easily in solid waste batch digestion. • Batch “dry” digestion produces a solid digestate, which easily can be stored and brought out to the fields for fertilizing in a good manner at low costs with minimal training of the farmers. • Dry digestion needs significantly less water than liquid digestion due to recirculation and needs less process energy for heating because of the smaller volume of the digestate. • The digesters of dry digestion therefore are smaller than those of liquid digestion and need less technical features, such as stirring devices, what allows realizing relatively cheap solutions.

Unfortunately, it was not possible to build a first plant. The costs of a well-functioning plant imported from Central Europe are too high for a local famer. In Uzbekistan the price of natural gas is very low. Even if a farm is far from the grid of natural gas and therefore the farmer is ready to pay a bit more than Uzbek prices for the energy, it seems to be too risky from his point of view to invest a high sum for a technology, which is new for the country.

Furthermore the development of a functioning low cost plant is also very costly; it was just not possible to find all the information necessary for the development and planning of a BOTT-model im the reginal market within the relatively short time of the two visits in the country, because the level of knowledge was a lot lower than expected; the few existing plants showed all severe construction faults. Therefore it was necessary to organize first a biogas training seminar in order to transfer the fundamentals of biogas production – which seems to have been successful. Now there are some local partners understanding, why which technical detail is favorable in a given situation.

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx One might come to the conclusion that it would be reasonable to find funding (development banks, foundations, etc.) for one or two plants (container and/or silo bunker) planned and realized with companies having already a lot of experience. This would have several advantages:

• The local partners would get not only theoretical, also practical experience while constructing and operating the plants. • There would be well functioning plants in the country reducing the mistrust in biogas technology. • For local business there is an opportunity to deliver parts (such as co-generators, gas balloons, pumps and piping etc.) and to specialize in constructing similar plants. • Start-up’s could get licences for technologies and start to produce plants within the country. They would be able to adapt the designs to the local conditions with the experience of running the first plants.

This proceeding saves time and it would even probably cost less than developing a “new” Uzbek plant together with the local partners.

5.2.5 Conclusions In the following table we will give an overview concerning the achievement of the objectives formu- lated in the actualized project proposal.

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx 5.3 Multiplication / Replication Preparation

As a preparatory work for the multiplication and replication within the project`s framework, new learning materials have been worked out. Information materials, case studies, presentation and video materials were multiplied and shared with participants during the training sessions. 5.4 Impact / Sustainability During the project, the following impacts are noticeable:

a) Until 2016, no problem evaluation research on the existing biogas technologies located in Aral Sea basin had been done. REPIC project team arranged field trips to all four existing “biogas plants” in Khorezm region to study the technological-ecological reasons behind the failure of the technology in the region. So, the intermediate report of the project summarized all technical details of the study. It would serve as a guiding material to demonstrate biogas pilot plants in a near future; b) Since biogas development is in early stage in the region, local specialists have low professional awareness and knowledge on how to rationally manage and run the biogas plants. Conducted three workshops in 2016-2018, raised capacity, provided professional knowledge to over 200 farmers and 30 researchers in Khorezm region and Karakalpaki- stan. Recorded video materials are broadcasted on local TV channels to reach to the attention of the broad community. c) Concept of the appropriate biogas plants (that match with local climate conditions) have been developed during the project. However, the financing options are still limited.

6. Outlook / Further Actions 6.1 Multiplication / Replication

Next planned steps Since the project is coming to the final point, next planned steps are strengthening cooperation between Swiss-University institutions, think-tanks to optimise the practice of biogas, bio-fertilizers in remote communities of Aral Sea basin. In partnership with the University of Bern, the University of Geneva, FiBL (Organic Agriculture Re- search Institute), several research project proposals were developed and submitted to SNIS, R4D, SPIRIT funding programs of Switzerland. Due to high global competition, some proposals have been rejected and others are still in the re-view process.

Promotion of multiplication / replication? Currently, our project partner – Olimjon Saidmamatov is doing a research stay at the Institute of Environmental studies of the University of Geneva focusing on developing water-energy-food nexus solutions in Aral Sea basin. The topic partially covers the REPIC project objectives looking at it with an interdisciplinary approach. To convince the farmers on the economic benefits of the biogas technology, the first step is a demonstration by building and running a successful pilot plant that. For that, the team must insure funding for a real-life demonstration. Potential donors or supporters are SNIS, R4D or SNF programs.

Hurdles to be overcome When we tell about biogas plants, farmers always calculate only their economic, investment aspects. In real situation, biogas generation and its grid connection is not highly subsidized to at- tract farmers, because all the positive side effects of the “package” are neglected; Biogas is not only renewable energy, but also bio-fertilizer production which is as important as the energy generation. The digestate brings back to the soil not only inorganic nutrient, but also organic compounds , which are important for humus formation and keeping back the water within the soil. Considering that most of the livestock farmers have its agriculture, arable lands, bio-fertilizer is always in demand to increase yield as well as providing organic products to the local market. Due to unavailable biogas plants in the basin, chemical fertilizers are highly demanded and are mostly

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx imported from neighbouring countries. In addition, biogas plants will also allow to improve and di- versify the products of the farms and to reduce the water consumption (see above).

6.2 Impact / Sustainability

Dissemination of the biogas and biofertilizer solutions in remote communities of Aral Sea supports the following Sustainable Development Goals (SDGs): 1) By introducing sustainable production systems including organic residue management and renewable energy production (SDG 7), rural livelihoods are improved, dehkan female and male farmers empowered and poverty-driven migration to urban centres reduced (SDG 11). 2) restore degraded soils and counteract ongoing land degradation and desertification (SDG 15), thus ensuring sustainable, resilient and adaptive food production systems (SDG 2, 13). 3) With the replacement of expensive mineral fertilizers by organic amendments and reduced input rates of water and agrochemicals, natural resources will be protected and conserved (SDG 6, 14, 15) while implying substantial economic benefit for farmers (SDG 1). 4) Also in consideration of potential peak oil and peak phosphorus, the findings of the project will help to reduce the dependency on external inputs. By transferring the knowledge and technical knowhow gained in this project across national and international scales, the biogas generation and organic fertilization concept will contribute to ensure inclusive educa- tion (SDG 4) and sustainable consumption and production patterns (SDG 12) and to build resilient infrastructure and foster innovation (SDG 9) by the implementation of sustainable and innovative agricultural practices and technologies.

7. Lessons Learned / Conclusions

Main findings and conclusions Knowledge of biogas technologies and plant operation is very poor in the Aral Sea Zone. Uzbekistan lags behind Kazakhstan, Kyrgyzstan and Tajikistan in terms of introduction of biogas technologies. Most of the biogas plant projects in the country were realized through donor funding and almost all of them halted due to various errors in planning, construction and/or operation and maintenance shortcomings shortly after their launch. Only continuous stirred-tank reactor (CSTR) biogas reactor technology is im- plemented by these projects, which seems not to be the solution for the aral sea basin. Apart from dozen of donor-funded small-scale (30-150 cubic meter) projects, only two commercial biogas projects are known in the country: (i) Bukhara Oil Refinery Factory biogas plant and (ii) “Davron Agrosanoat” livestock farm plant in Bulakbashi district of Andijan region. Both of them were designed for industrial natural gas needs and do not supply gas to residential consumers.

During the project in 2016-2018, the following unique findings were generated: a) Local economic-environmental conditions should be considered before installation of biogas plants, mainly in Aral Sea basin where the water salinity is high with extreme weather conditions; b) Unavailability of high-skilled biogas engineers, bio-technology specialists in rural communities is an important reason hindering wide dissemination of bio-technologies in the basin. Delivered capacity building activities formation within the Repic project helped to create competence of local specialists, students and farmers. However, rural communities need a very simple engineering that can be operated without detailed knowledge. c) Big livestock farms that can financially afford to install biogas plants installed the plant in 2013- 2015 without a prior evaluation of the local climate conditions. In addition, the performance of the plant was affected by inadequate basic engineering and environmental pre-conditions. Technical failure of the early installed biogas plants spreads as negative PR to other farmers who are willing to install it in a near future.

The following lessons were learnt throughout the project realization period:

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C:\Users\hc.angele\OneDrive\Ablage HC\Uzbekistan\90_ENDPRODUKTE\20190920_REPIC_Biogas Aral Sea FinalReport.docx 1) Due to lack of information, there is no abundant source of additional substrates for biogas production other than cattle manure and chicken dung. Although agricultural production is the main livelihood activity for the population of the Aral Sea basin, most of the organic residues are “utilized” for various purposes, which often seem tio be less reasonable the anaerobic digestion.

2) Livestock farm management is arranged in the most primitive way, which leads to high level of contamination of the manure with soil and other inorganic non-decaying hard particles. This was also an important reason of halting of the existing biogas facilities.

3) Sharp continental climate, relatively primitive livestock farm management and many other factors require high-level knowledge of biogas technologies for developing appropriate biogas facilities.

4) Natural gas was abundant in the country for decades and 95% of the country was covered by the central natural gas supply infrastructure. Although some regions are experiencing acute shortage of natural gas in the central grid, low price of the natural gas for domestic consumers remains a main obstacle for commercialization of the biogas plant projects.

5) There is a need for establishing a biogas knowledge competence centre in the Aral Sea Zone with an overarching aim of dissemination of the biogas technologies through technology selec- tion and adaptation. This in turn requires human-capacity building, biology, engineering and economics.

Recommendations for similar projects within this context The following recommendations can be made: • Projects with similar aim and objectives have to start by establishing strong partnership with the local responsible authorities, who are direct beneficiaries of the outcome of the project. • Long-term commitment from the local stakeholders should be taken in advance, not limiting with the transitive interest of the dilettante local partners as a starting point. • Project team have to offer correct, plausible and achievable expectations to the local partners. For this, project team have to synchronize their expectation and targets in advance. • Distribution of roles and tasks has to be based on competence of the local partners and should include countable and verifiable Key Performance Indicators. In order to develop the renewable energy sector (including biogas), first it should be compared with the public incentives, stimulus programs for fossil-fuel promotion which is a main competitor of the renewable energy sector. If there are already established regulations (i.e, feed-in tariff, certificate) for promotion of the renewable energy sector, it would help the project to achieve high results. In the case of this REPIC project, the generation of biogas lacks public subsidies and competes with the cheap prices of fossil fuels (in comparison with EU countries). The few available biogas incentives can hardly help to cover the engineering costs spent during the plant installation. For this reason farmers currently do not consider investing in biogas.

Personal impressions Most of the project aims and targets were achieved. Successful organisation of the Biogas knowledge summer school has increased the potential of the local university in biogas technologies adaptation and dissemination. However, this theoretical and in-class knowledge has to be combined with practical experience and skills-development. Therefore, the project team considers the final aim of the project partly unachieved and will do their best to fill this gap by developing a new project in cooperation with the local authorities, with strong commitment from the local farmers and additional (international) funding.. As an interesting observation, the generation of bio-fertilizers raised more interest among the farmers than the biogas itself. A multiplication effort should consider this aspect

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8. References

• Actualized Project Proposal: Biogas production from agricultural wastes in the Aral Sea Basin: development of pilot plants; July, 20th 2017

• Biogas production from agricultural waste in the Aral Sea Basin. Development of pilot plants. Intermediate Report from March 2017.

• Biogas production from agricultural waste in the Aral Sea Basin. Beurteilung der Erreichung der Meilensteine M1 und M2. 27. April 2017.

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9. Annex

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Annex 1: Definition of best adapted technology

Comparison of liquid and solid digestion

As already mentioned above, in Uzbekistan the main focus of the counterpart is to digest the cattle manure on large farms far from the natural gas grid. For the digestion of cattle manure there are two possibilities: Digestion of liquid manure, i.e. the mixture of urine and solid manure, like primarily practised in Central Europe, or the digestion of just the solid part of the manure in a so-called solid waste digester.

Like described in the mission report, in Uzbekistan the cows live most of the year outside in a fenced yard on an unpaved ground. Their droppings are scattered all over the ground. A large part of the droppings is concentrated behind the cratches, where the cattle spend much time while eating. There is the problem that the droppings are mixed with stones and sand on the ground.

Inert material, such as stones and sand, are undesired in liquid digestion, because they will ac- cumulate within the digester reducing very quickly the operating volume and necessitating costly and laborious revisions of the plant in short intervals, i.e. the digestion process has to be interrupted regularly in order to excavate the sediments. However, in Uzbekistan there is no habit to produce liquid manure and to store it in pits. Therefore, liquid digestion may just be exceptional a solution for small plants, where some cows are kept – at least in winter time - on a paved ground, enabling to collect the manure without spoiling it with much inert compounds and diluting it after collection with water. However, it is not reasonable to dilute the input, because the water added increases the size of the digester, reducing the active biomass per volume of the digester. Also, water has to be heated to digestion temperature, what causes – besides of extra water for the dilution - an extra energy demand.

Therefore, it is recommended to focus on solid waste digestion, which is better adapted to the situation in the Aral see region. There are two different types of solid waste digesting processes: Continuously fed plug flow digesters and batch digesters, where at least 3-4 digesters are filled and emptied by turns.

Plug flow digesters such as Kompogas plants, which show a high degree of automation, are too expensive for digesting manure. In Europe, they are used for the digestion of the organic fraction of municipal solid waste (OFMSW). Because all alternative solutions to treat the OFMSW are costly, it is possible to build sophisticated digestion plants.

Simple plug flow digesters, such as the arbi-digester realized in Tanzania may be a solution in the rare cases, where there is a paved ground and where there are additional substrates, like slaughter waste etc. At the farm Uzbekneftegaz, NHC, in the Yangibozor district, it is possible that a plug flow digester could be the best solution. However, in Uzbekistan this would need additional engineering, because – other than in tropical countries – the digester needs a simple heating device, which is not developed yet. (A report on the arbi plug-flow digester, may be seen on www.repic.ch/in- dex.php/download_file/view/689/794/)

Therefore, in most of the cases a batch digestion seems to be the most appropriate solution for Uzbekistan: Because the digesters are emptied (preferably by a wheel loader) after each digestion period, the inert material is not hindering the digestion; it is exported regularly together with the digestate. The batch solution shows different advantages: There is no need for unnecessary dilution; water just requires volume, does not produce any gas and has to be heated to digestion temperature! Besides of saving water and energy, there is a higher biogas output per digester volume. It does not matter, if the manure is spoiled by earth and stones, because the input is loaded into and discharged from the container by a wheel loader (or by hand), i.e. the inert material remains in the digestate and can be brought out to the fields. It is a modular design, i.e. if in the future there is more input material it’s no problem to add an additional container.

Some information on the different technologies is given in the subsequent chapters.

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Different technologies of Batch digestion

Already in 1985, arbi realized a very simple batch digestion system at the agricultural school of Nyamishaba at the Kiwu-lake in Rwanda. It consisted of three rectangular pits covered by plastic membranes, which were alternately filled manually with manure and wastes from harvesting. They worked very well for about a decade until the civil war and allowed to cook for all the students and the staff of the school.

Fig. A1-1: The batch digesters in Nyamishaba, Rwanda: left: construction; upper right: Gas production, lower right; water seal of the membrane and liquid filled in at the angle (darker brown).

However, for Uzbekistan this seems not to be a viable solution: On the one hand, with the large Uzbek farms and with the higher labour costs it should be possible to fill and to void the digesters by a wheel loader. On the other one, in Uzbekistan the digesters have to be heated – what was not necessary in the tropics. For Uzbekistan two (similar) types of digesters are the most promising:

One is the container batch digestion technology. Here, there are several providers of technical solutions for a cold climate. The containers may be brick built or metallic containers. Inside the containers, circulating water is sprinkled over the solid waste, percolating it and is then pumped back from the bottom into the tank for the percolate water. In some designs, The second possibility is an anaerobic bunker type silo: There, the digester is an underground construction and the solid waste is submerged by the circulating water, which is pumped away totally only at the end of the cycle. These two designs are described in detail subsequently.

Container digestion

Figure xy shows a flow sheet of a container digester. The solid waste is filled into the container by a wheel loader and the door is closed tightly. The water from the percolate tank is sprinkled over the biogenic waste and pumped back from the bottom to the tank. Biogas evolves mainly in the container, but also to some extent in the tank. There are at least three containers plus one tank for the liquid. Because the liquid is used for all digesters, the fresh material is inoculated by the percolate with anaerobic bacteria from digesters, where digestion is ongoing. After 3 to 4 weeks the

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container is opened (carefully, avoiding explosive mixtures!) and the digeted matter is replaced by fresh material. The percolate may be heated in the tank by the waste heat of the co-generator.

biogas

storage

container with drain for the co-gene-ra- percolate tank percolating water tor

heat

Fig. A1-2: Flow sheet of container digestion (here only one container shown)

In Switzerland, the containers usually are built with concrete. Figure A1-3 shows a container digestion planned by arbi and Engeli engineering digesting solid cow manure and garden wastes, which went into operation in spring 2019. Here, 5 containers were realized (metallic doors under the wooden roof at the left). The adjacent cottage between the containers and the percolate tank houses the co-generator, pumps and a working place for the operator with control panel, table and tools etc. The gas storage is located on top of the percolate tank.

Depending on the provider, different solutions will be realized: The percolate tank may be located above or under ground level, the doors will open sideward or upward (in some cases even wilth hydraulic help) and there are different solutions for sprinkling the percolate and for preventing the possibility of an explosive mixture, when opening the door. Figure A1-4, right, shows a solution to keep the solid waste inside the digester while filling: a wooden barrier is mounted on the inside of the door.

Fig. A1-3: The new Renergon container digestion plant at Murimoos, Switzerland.

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Fig. A1-4: Construction and filling of container digestion plants (different providers)

The Austrian company Pöttinger offers a solution with containers out of metal (Fig. A1-5). There the material is first aerated within the box for heating with the heat produced by the aerobic breakdown. Only afterwards the conditions are changed to anaerobic conditions starting the biogas production. This needs quite sophisticated controlling and timing. For Uzbekistan a conventional heating seems to be less complicated. But metal containers, such as used for transporting goods, could be a good solution for container digestion.

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Fig. A1-5: The Austrian Pöttinger plant consists of (insulated) containers out of metal. Inside the container at the left there is the co-generator and the technical devices.

A simple container solution was tested in Ghana by EAWAG and zhaw in a REPIC project (http://www.repic.ch/files/3013/7544/1755/SB_EAWAG_Ghana.pdf). However, for an application in Uzbekistan this solution seems not to be recommendable, because the winters are very cold. I.e. this solution would have to be adapted to the local climatic conditions, what needs further engineering.

In all cases – if not buying a solution already developed in Central Europe - it is not possible to construct a plant without further engineering work. And this needs local engineers, who understand the process in order to find well working solutions and who know the providers and the prices of suited construction materials. That was the reason to organize the training seminar for the local people.

On the occasion of the first fact-finding mission the company “Energiyamontaj” Ltd (www.enm.uz) has been visited. This is a large construction and assembly company with a department constructing all kind of cargo-containers. It would be able to build containers on costumer’s demand as soon as more technical details for a plant adapted to the local conditions can be presented.

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Anaerobic bunker-type silo

This batch solution seems also to be very promising, because it is very simple: It’s a drive-in silo covered by a balloon. It is propagated by Sud-Oest-Biogaz, France. Unfortunately, the Swiss counterpart has no practical experience yet with this kind of construction. However, it should be feasible to find a simple, viable and not too expensive solution. For this it is – between others - important to find an Uzbek manufacturer with experience to provide gastight issue-reinforced PVC foils for covering the bunker. Figure bb shows a possible cut of the plant.

Fig. A1-6: Possible cut of an anaerobic bunker-type plant

In contrast to the container digestion, here the manure is – at least partially - flooded during digestion, i.e. the water is just slowly recirculated. Towards the end of digestion it is pumped from the bottom of the silo to the liquid tank, in order to allow extracting the digestate by a wheel loader. Figure A1-7 shows some examples of bunker type silo plants.

Fig. A1-7: Some examples of silo-type bunker plants

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The pictures in figure A1-7 show different variations of anaerobic bunker-type silos: The bunkers may be placed underground or (partially) on ground with a removable front side. Figure A1-8 shows a layout of an installation with 4 silos. The digestate undergoes a composting post treatment before it is brought out on the fields.

Fig. A1-8: Example of a layout of a silo-type bunker plant

Fig. A1-9: Installation in Dampierre (F) treating cow manure. Picture on the right: in the background fresh material and in the foreground material after digestion.

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Also this type of digester technology needs further engineering and search for industrial partners. Depending on local wind and temperature conditions it might perhaps be necessary to construct a simple shelter above the gas balloons. The most viable way for insulating against the very low temperatures in winter has to be found (especially also for the gas balloon). Is it possible to construction fully underground or is the ground water table locally too high? Are there local providers for suitable plastic membranes and do they have the knowhow to weld the desired forms? Etc.

Treating of the manure

If digesting cattle manure, or the manure has preferably to be collected on a paved ground (at least behind the cratches). Or the ground behind the cratches has to be excavated ~30 - 40 cm and filled with harvesting wastes (cotton, rice etc.; see picture below). Then the upper layer will be a mixture of manure and some harvesting waste – which has to be replaced afterwards – that can be fed into the biogas plant without adding too much inert material. This solution would have also a sanitary advantage: the cows will stay no more in the mud, but on a drier, and therefore more hygienic surface. This mixture will result in a significantly higher biogas yield, because the harvesting wastes don’t have already passed the intestine of an animal, where the easy digestible matter has been broken down.

Theoretically, this mixture could also be fed into a liquid digestion plant. Neverthe- less, it is recommended to digest this input mixture rather in a solid waste digestion plant, because in simple liquid digesters there could be the danger of scum formation by fibres from harvesting wastes floating up to the surface. This would cause extra costs for devices to mix the digester content. Harvesting waste In batch digesters, mixing is not necessary.

Solid batch digestion shows another advantage as compared to liquid digestion: The output is (humid) solid matter. In Uzbekistan, there is no tradition to spread liquid manure on the fields. There exist also no large pits in order to store the manure in wintertime for an application during the warmer growth season – what would be most important for preventing the loss of the precious nutrients seeping away into the ground water (which at the same time would be polluted!). The construction of large pits would cause additional costs!

With digestion of solid wastes, the digestate may be stored in windrows, where an additional composting can take place improving the quality of the fertilizer further. This compost is easier to handle: it may be loaded on an open truck or a trailer for the transport to the fields, where it can easily spread out where the quality of the ground has to be improved. It its no only a precious fertilizer with inorganic nutrients, but the non-degraded organic matter increases at the same time the humus content of the ground, increasing – between others – the capacity of the ground to withhold the precipitations.

Conclusions

Regarding the biogas technology in Uzbekistan, the following facts may be captured:

• The Uzbek raw material is usually spoiled with inert matter (stones and sand), which only can be handled easily in solid waste batch digestion.

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• Batch “dry” digestion produces a solid digestate, which easily can be stored and brought out to the fields in a good manner at low costs with minimal training of the farmers.

• Dry digestion needs due to recirculation significantly less water than liquid digestion and needs less process energy for heating because of the smaller volume of the digestate.

• The digesters of dry digestion therefore are smaller than those of liquid digestion and need less technical features, such as stirring devices, what allows to realize relatively cheap solutions.

Unfortunately, it was not possible to build a first plant. The costs of a well-functioning plant imported from Central Europe are too high for a local famer. In Uzbekistan the price of natural gas is very low. Even if a farm is far from the grid of natural gas and therefore the farmer is ready to pay a bit more than Uzbek prices for the energy, it seems too risky from his point of you to invest a high sum for a technology, which is new for the country.

And the development of a functioning low cost plant is also very costly; it was just not possible to find all the information necessary for the development and planning of a BOTT-model within the relatively short time of the two visits in the country, because the level of knowledge was a lot lower than expected; the few existing plants showed severe construction faults. Therefore it was necessary to organize first a biogas training seminar in order to transfer the fundamentals of biogas production – which seems to have been successful. Actually, there are some local partners understanding, why which technical detail is favorable in a given situation.

One might come to the conclusion that it would be reasonable to find funding (world bank or …?) for one or two plants (container and/or silo bunker) planned and realized with companies having already a lot of experience. This would have several advantages:

• The local partners would get not only theoretical, also practical experience while constructing and operating the plants.

• There would be well functioning plants in the country reducing the mistrust in biogas technology.

• For local business there is an opportunity to deliver parts (such as co-generators, gas balloons, pumps and piping etc.) and to specialize in constructing similar plants.

This proceeding saves time and it would even probably cost less than developing a “new” Uzbek plant together with the local partners.

Without any farmers willing to invest it was not possible to develop a BOTT-Model. Such a model has to be integrated in the specific local conditions.

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Annex 2: Program of and schedule of Workshop “Sustainable agriculture for human security”

TRAINING WORKSHOP PROGRAM on the topic: “Sustainable agriculture for human security” In partnership with UN joint program "Ensuring the livelihoods of people affected by the Aral Sea crisis" for the representatives of the Council of Young Farmers Date: 13 -2 5 August 2018, Location: Karakalpakistan

Day 1

10:00 - 10:30 Registration of participants NGO «KRASS» Specialists

10:30 - 10:45 Opening the workshop, welcome speech Director of NGO KRASS Sin Liliana

Session 1. Raising awareness on issues of human security

10:45 - 11:15 The concept of human security. Relevance to the Aral Sea re- Rudenko I. gion

11:15 - 11:45 Sustainable agriculture in Uzbekistan Egamberdiev O.

11:45- 12:00 Coffee break

Session 2: Environmental safety

12:00 - 13:00 Environmental safety at the global, regional and local levels. En- E. Kahn vironmental crime. Examples of foreign countries of environmental safety.

13:00- 14:00 Closed for lunch

Session 3. Energy security

14:00 - 15:30 Capacity and utilization of biogas, biomass and bio-fertilizers in Saidmamatov O. Uzbekistan (findings of REPIC project)

15:30 - 16:30 Energy security in practice: Thermal insulation of buildings so- Saidmamatov O. lar energy for cooking / solar greenhouses

day 2

Session 4. Food security

09:00 - 09:30 food security: Physical and economic access to food. Autonomy Rudenko I. and economic independence of national food systems (food sov- ereignty).

Session 5: Alternative crops for nutrition

09:30 - 10:00 Alternative crops and cultivation technology in the Aral Sea re- Ruzimov F gion Kuryazov I.

10:00 - 11:25 Mash, cultivation technology, the advantages of Babadjanova Sh

10:25 - 10:45 wheat salt-tolerant varieties Dzhumaniyazova Yu

10:45 - 11:00 Coffee break

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Session 6. The practice of effective and sustainable land use

11:00 - 11:30 Rehabilitation of degraded land through agroforestry Ruzimov J. Windbreaks, etc. (Materials Boatman)

11:30 - 12:00 Conservation agriculture in Uzbekistan. Egamberdiev O.

12:00 - 12:30 Repeated and mixed crops Egamberdiev O.

12:30 - 13:00 composting Egamberdiev O.

13:00 - 14:00 Closed for lunch

14:00 - 14:30 Hlorofillmetr to improve the efficiency of nitrogen fertilizer use Kuryazov I. The optical touch device GreenSeeker:

Session 7. The practice of effective and sustainable water use

14:30 - 15:00 Laser land leveling Egamberdiev O.

15:00 - 15:30 Methods for the field of water conservation (siphon irrigation dis- Ruzimov J. crete irrigation)

15:30 - 16:00 Coffee break

16:00 - 16:30 Evaluation of the training seminar participants All participants and Presentation of certificates of participation organizers Closing of the seminar wishes of participants

Training schedule Dates District Venue Participants 13-14 August 2018 Shumanay district Nukus city farmers , representatives of the 15-16 August 2018 Amudarya district District administration Council of Young Farmers, 17-18 August 2018 Beruniy district Professional college Youth Council, agricultural ad- 23-24 August 2018 Turtkul district Academic lyceum ministration, teachers of agricul- 25-26 August 2018 Ellikkala district Academic lyceum tural colleges,

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Annex 3: Biogas - learning center at NGO KRASS in Urgench

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Annex 4: Schedule of intensive formation

Urgench; August, 27th to August 30th

Time Issue Responsible Remarks Day 1: Monday – August, 27th 0900 – 1030 Introduction, Bahtiyor Eshchanov 0930 – 1030 Biological Fundamentals I Werner Edelmann Translation into Uz- bek Language by 1030 – 1100 Break Olimjon Saimam- 1100 – 1200 Biological Fundamentals II Werner Edelmann atov During the whole 1200 – 1330 Lunch seminar 1330 – 1430 Substrate and Process Parameters I Werner Edelmann 1430 – 1450 Break 1450 – 1550 Substrate and Process Parameters II Werner Edelmann 1550 – 1610 Break 1610 – 1700 Questions, Discussion, Outlook to Day 2 Day 2: Tuesday – August, 28th 0900 – 0930 Short Review Biological Fundamentals Werner Edelmann 0930 – 1030 Biogas Technologies I Werner Edelmann 1030 – 1100 Break 1100 – 1200 Biogas Technologies II Werner Edelmann 1200 – 1330 Lunch 1330 – 1430 Use of the products, operation and safety Werner Edelmann aspects I 1430 – 1450 Break 1450 – 1550 Use of the products, operation and safety Werner Edelmann aspects II 1550 – 1610 Break 1610 – 1700 Economic aspects Bahtiyor Eshchanov 1700 – 1730 Information to case study, definition of HC Angele working groups Short presentation of the farm Bahtiyor Eshchanov Day 3: Wednesday, August 29th Morning Site visit Bahtiyor Eshchanov Afternoon Time to work on case study Working groups Support by W. Edel- mann and HC An- gele Day 4: Thursday, August 30th 0900 – 1000 Presentation of case study 1 1000 – 1030 Break 1030 – 1130 Presentation of case study 2 1130 – 1200 Discussion Werner Edelmann HC Angele 1200 – 1330 Lunch 1330 – 1500 Conclusions, next steps All End of formation

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Annex 5: List of participants

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Annex 6: Pictures of intensive formation

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Annex 7: Presentations of intensive formation

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12.07.2019

Digestion – State of the Art and optimal Plant Operation

Part 1: Biology

Werner Edelmann arbi Bioenergie GmbH CH-6314 Unterägeri ede(at)arbi.ch

Uzbekistan 2018

2 Contents part 1: Biology

• Possibilities to make bioenergy available • Comparison of aerobic and anaerobic degradation • the different steps of anaerobic degradation • Consequences for the technical digestion process • the product biogas

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Life is an eternal build-up and destruction 3 Consumers conversion

Energy

organic compounds

Producers Destruents build-up inorganic, i.e. mineral destruction compounds Uzbekistan 2018

Bioenergy 4

• While building up, solar energy is fixed within the biochemical compounds of the plants (chemical linkages of carbon structures)

• The energy fixed within the plants and subsequently within the animals is called Bioenergy

• Bioenergy is set free during breakdown of the molecular structures • Man uses this energy for example while eating or while burning biomass

• There are different possibilities to set free the bioenergy for our needs!

• Use of bioenergy does not increase the greenhouse potential because the carbon does not originate from fossil sources!

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Possibilities to use bioenergy 5

Photosynthesis O2 Buildup of Biomass

phys./chemical biological

anaerobic CO 2, H 2O anaerobic O O 2 2 Compost products Biogas , of pyrolysis alcohol etc.

aerobic aerobic

combustion biologic combustion combustion of products combustion of products

CO 2, H 2O CO 2, H 2O CO 2, H 2O CO 2, H 2O

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The microbiologic degradation 6

• Microorganisms degrade biomasse for recovery of energy and for extraction of chemical compounds in order to cover their needs for living and for growing • Components, which can not be broken down easily, are not degraded compost remains • Biochemical reactions take always place within the water . • Water is not only within the cells of the microorganisms, but must also be abound in the space between the microrganisms and the material to be broken down. • There is a fundamental difference between aerobic and anaerobic degradation!

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The aerobic degradation 7

C6H12 O6 + 6 O 2 6 CO 2 + 6 H 2O Sugar + Oxygen Carbon dioxide + Water

Energy for the organisms:

2875 kJ/180 g sugar 100 % of the energy • The whole energy content available for the bacteria of the material, which is broken down, is available for the organisms! • Super growth conditions!

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The anaerobic degradation 8

C6H12 O6 3 CO 2 + 3 CH 4 Sugar Carbon dioxide + Methane

Energy for the organisms: < 10% for the bacteria ! only 132 kJ/180 g sugar

> 90% of the • Over 90 % of the energy energy of the remains in the Methane! degraded material • Therefore very few energy for remains in the the growth of microorganisms Methane! • Slow growth, no waste heat!

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The aerobic degradation 9

Aerobic degradation needs all three states of matter !

Oxygen, i.e. air (gaseous)

Biomass (solid)

Water layer (liquid) (living environment for microorganisms)

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The anaerobic degradation 10

Anaerobic degradation needs only two states of matter !

Biogas (gaseous) is a product („waste“)

Biomass (solid)

Water layer (liquid) (living environment for microorganisms)

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Composting 11

• Compared to anaerobic bacteria, the aerobic microorganisms have a very advantageous energetic situation; they should break down biomass more than 10 times faster!

• But: composting may need even more time than digestion! • Because composting needs all three states of the matter, it is a process very difficult to optimize : The organic waste cannot be crushed into small pieces, because then air would not penetrate into the heap. When aerating artificially, the heap gets too hot and/or dries out.

• In nature, there prevail always anaerobic processes, when biomass accumulates to heaps.

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comparison aerobic/anaerobic 12 • 3-s.o.m.-process is difficult to operate properly • 2-s.o.m.-process is less problematic (generally self- regulating) • Anaerobic: possible to generate large surface for microbiological attack (crushing!)

no crushing only small surface

crushing

Increase of the surface for microbiological attack (with exo- enzymes) increase of speed of degradation

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Comparison aerobic / anaerobic 13 aerobic anaerobic no energy within product energy-rich product much energy for growth very little energy for growth quick growth slow growth waste heat is freed no “bio“-heat is freed much biomass build-up few biomass build-up high need of nutrients low need of nutrients suited for low concentrations suited for high concentrations

high energy need (O 2) much surplus energy

high running costs low running costs . very difficult to optimize generally self-regulating

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Anaerobic degradation in nature 14 Anywhere, where oxygen has no access to accumulation of biomass, e.g. :

• Ground of waters, marsh and swampland

• Intestine of organisms

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Different optimal temperatures 15

• psychrophilic = loving the cold; e.g. at 4° C at the ground of deep waters (much too slow for technical use) • mesophilic = ~ 36° C, i.e. at body temperature of mammals and endotherms • thermophilic = 55 - 60° C, i.e. where it is too hot for most aerobic microorganisms (compost..!) • Generally: the warmer, the quicker the duplication of the bacteria! (but smaller diversity at high temperatures) • Temperatures in-between are eventually also possible after long adaptation times! • Important! Keep temperature always stable! Enzyme-sets are usually adapted to a narrow temperature range!

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Biochemistry of anaerobic digestion 16 • Degradation only by bacteria

• Very old (shortly after formation of earth; „Archaea“) (probably «imported from the universe..!)

• Cascade of steps for degradation

• Several groups of bacteria are necessary for anaerobic digestion! (aerobic degradation is feasible by single organisms!)

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Anaerobic biocenoses 17

Optical microscope (fluorescence)

Scanning electron microscope

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Steps of organic solids 18 proteins carbohydrates grease anaerobic ~21% ~40% ~5% degradation ~34%

amino acids, sugars fatty acids Hydrolysis ~20% >1%

Intermediates, such as Fermentation, Propionate, Butyrate ~11% ~8% Acidogenesis ~35% ~11%

? Acetate Hydrogen

Methanogenesis

Methane Zehnder, Guyer Uzbekistan 2018

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Hydrolysis and Fermentation/Acidification 19

• For Anaerobic digestion a pH-range of ~7 to 7.6 is optimal ! • Hydrolysis = chemical separation with the help of water • Makromolecules (forming big structures or long chains) are separated into their single components (e.g. starch or cellulose into single sugar molecules, proteins into amino acids or DNS into nucleic acids) • Hydrolysis would be accelerated by a slightly sour pH – but it is in general not the rate limiting step (except if there is much cellulose). (in general separating hydrolysis and methanisation makes no sense!) • The small components („monomers“) are taken up by the second group of bacteria for fermentation and acidification. • Products are about 2/3 Acetate and 1/3 hydrogen. • Hydrogen is freed while degrading long chain fatty acids and shorter intermediates such as Propionate and Butyrate.

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Methanogenesis 20 • In General, the methanogenesis is the rate limiting step, because the methanogenic bacteria duplicate very slowly (at mesophilic temperature: doubling time up to more than one week!) • About 70% of the methane originates from the degradation of Acetate. For producing methane from CO 2, some Hydrogen is necessary. • But: the concentration of hydrogen has to be very low, because the degradation of Propionate is inhibited, as soon as the hydrogen concentration raises! • If propionate accumulates, the pH will sink below 7 and the anaerobic digestion process will stop! The reactor will run sour and probably have to be emptied! • Therefore, there have to be always enough methanogenic bacteria in the reactor! As long as there are enough Methanogens, they get rid of the Hydroge n!

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Consequences for digester operation Because the Methanogens duplicate very slowly, some instructions have to be followed: • Start up digesters slowly , in order to give enough time for growth! • No shock-loads ! Do not feed much at once, but feed several times small portions! • Do not change the feed composition suddenly in order to give time for adaptation! • Generally: no sudden changes of temperature, feed amount etc. • Increase loading rates , especially of grease and/or of protein, slowly ! (grease sets free much hydrogen time is needed for duplication of the Methanogens; proteins set free much ammonia and also sulphur time is needed for adaptation!)

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Anaerobicly degradable compounds 22

Besides of lignin, all chemical compounds of the cells are degradable: • Proteins (construction material and responsible for chemical reactions [enzymes]; containing N and S!) • carbohydrates: starch (short- and medium term energy reserve) • carbohydrates: cellulose (construction material) • DNA, RNA (carrier of genetic information; containing N and P) • Fats (long-term energy reserve) • Small molecules such as alcohols, fatty acids etc.) Anaerobicly not degradable : construction material of wood: Lignin ! (Lignin is a late development of naturevery resistant to degradation; trees must resist bacterial attack and cold winters for years!)

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Increasing biogas production Bacteria need nutrients for growth and they don't like some compounds • Anaerobic bacteria are for nearly 4 billion years on earth. It‘s a miracle that they can survive with so few energy at their disposal! The degradation process has been optimised over this very long period. There is absolutely no chance to improve the process further by genetic engineering etc.! • Besides of C, H and O – which form the structures of the molecules – bacteria need enough N, P, S, some ions as well as small amounts of trace elements. (per 200 C at least 5 N and 1 P) • Because anaerobic bacteria get very few energy while degrading, they have to degrade much material for one duplication far enough nutrients are freed while degrading in general: no additional nutrient supply is necessary with a common geed mixture! (exception some organic industrial waste waters) • Additives like enzymes or breaking lignin structures with steam explosion etc. would perhaps accelerate the digestion, but all these treatments cost in general too much, i.e. are not profitable.

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Inhibition of biogas production

• Inhibition may occur with some special raw materials containing larger amounts of substances like K +, Na +, Ca 2+ , Mg 2+ , heavy metals, terpenes (citrus fruits), disinfectants or some antibiotica.

• Sulphur is freed in the form of H 2S while digesting proteins and may inhibit in higher concentrations (smell of rotten eggs). + • Ammonium (NH 4 ) is also freed while digesting proteins. It is in a chemical equilibrium with ammonia (NH 3), which is toxic at higher concentrations. • Inhibition caused by a surplus of ions or heavy metals etc. occurs very seldom and in general only with a feed consisting of only one component (e.g. digesting 100% rotten oranges, terpenes will be a problem) The bacteria are similar to us: If we feed 100% chocolate, we will have stomach and digestion problems! We – and also the bacteria – prefer a mixture of inputs !

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Inhibition by Ammonia 25

• Ammonium is freed mainly by digesting amino acids (proteins)

• Depending on pH and temperature, Share of ammonia depending on temperature the equilibrium between ammonium and (toxic) ammonia varies: Higher temperatures and higher pH increase the amount of free ammonia at a specific ammonium level. Ammonia inhibits the formation of methane from Acetate.

• Ammonia may be a problem with manure of pigs fed with protein-rich food or in thermophilic digestion with protein-rich substrates.

• But in general the bacteria adapt to higher ammonia concentrations , if the share of protein-rich feed is increased slowly !

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The product Biogas 26

• CH 4 : CO 2 about 2 : 1 • saturated with water vapour (depending on temperature!) • < 1% traces of gases (H 2S, H 2, etc.) The quality of the gas depends on: • Process parameters (temperature, pressure, loading rate etc.) • Content of nitrate, sulphate etc. in the input (nitrate, sulphate import much O, causing additional CO 2) • Protein content (H 2S, NH 3) • Primarily: degree of oxidation of the carbon in the substrate. • Therefore the chemical composition of the input (see also part 2) is mainly responsible. The water content of the substrate has no influence on biogas quality, however!

one m 3 Biogas = nearly 6 kWh (about 0.6 l diesel fuel)

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++ Degree of carbon 27 oxidation ++ • The higher the oxygen content of a molecule, (degree of oxidation), the higher the share of

CO 2 in the biogas • Fats contain very little -- oxygen. Therefore fats produce biogas with a

very high CH 4 content (up to 80%!) --

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The gas composition could be calculated 28 (formula of Buswell)

Starting material: CcHhOoNnSs (elementary analysis) Calculate! + ¼ (4c – h – 2o + 3n + 2s) H 2O

1/8 (4c – h + 2o + 3n + 2s) C O2

+ 1/8 (4c + h – 2o – 3n – 2s) CH 4

+ n NH 3 + s H 2S • nothing is lost in nature … !

• the oxygen of the CO 2 originates from the raw material and from the water needed for the reactions. • with complex waste mixtures, calculations make not much sense, because it is not clear, which molecules are degraded and which are not…!

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Conclusions: 29

• Biogas is produced by different groups of bacteria working closely together • In general, the process does not need external nutrients and is self- regulating. It is not problematic, if observing some rules: • Because the bacteria (especially the Methanogens) grow slowly:  Slow start up of a continuously fed digester in order not to export more bacteria than are replaced within the digester  Slow changes of process parameters (T, RT, loading rate etc.)  Slow changes of feed composition  Feed your bacteria regularly (if not batch digestion) Then your continuously fed biogas plant will bring you a lot of pleasure!

Thank you for your attention !

Dr. Werner Edelmann arbi GmbH,Uzbekistan Unterägeri 2018

15 12.07.2019

Digestion – State of the Art and optimal Plant Operation

Part 2: Substrates and Process Parameters

Werner Edelmann arbi Bioenergie GmbH CH-6314 Unterägeri ede(at)arbi.ch

Uzbekistan 2018

2 Contents part 2: Substrates and process parameters

• Application areas of anaerobic digestion • Substrates and substrate properties • Composition and digestibility • Substrate parameters • Biogas yields • Process parameters

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3 Historical development 3

For a long time, biogas was just a by-product of waste water treatment plants. Only after the oil crisis one started to use the energy and to look for new substrates

• ~1925 first digesters for waste water treatment (D) • ~1975 biogas from specially designed landfills • ~1980 agricultural biogas plants • ~1985 digestion of industrial waste waters • ~1990 digestion of organic municipal solid wastes • ~1995 co-digestion and optimisations

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Application areas today 4

• agriculture • breweries, distilleries • processing of vegetables and of potatoes • whey from cheese dairies • production of tinned food • wastes from slaughterhouses • sugar refineries • palm oil plants • different industrial organic waste waters (e.g. fruit juices etc.) • organic fraction of municipal solid wastes (OFMS) • food wastes from shopping centres • paper and chemical industries, etc.

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Substrates from agriculture 5

• liquid manure • manure • harvesting residues • silage • cuttings of grass • waste from vegetables

Attention! manure = „bad“ substrat, because it has already passed the intestine of an animal ! (easily digestible components have already been digested within the animal relatively low gas yield!)

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Food surplus and 6 damaged fruits

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spoiled Food 7

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Municipal wastes 8

• Separately collected biowaste • Wastes from gardens and landscape care • Wastes from canteen kitchens and catering • Sludge from waste water treatment

Caution! - aspects of hygiene (rotten food: eventually hygenisation necessary!) - Sludge of waste water treatment may contain heavy metals then not suited for use as an agricultural fertilizer after digestion!

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Main digestible ingredients 9

Carbohydrates • sugars, starch, cellulose

Proteins • peptides (amino acids)

Fats • fatty acids (short or long, saturated or unsaturated)

Lignin is not digestible

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Composition of different wastes 10

The composition will also have an influence on the gas quality (see part biology): The gas from grease of a fat separator will have a higher methane content than that of cereals.

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Digestibility 11

The higher the lignin content, the worse the digestibility: (lignin encapsulates the cellulose)

Lignin degree of hydrolysis vegetables 0% - 5% 95 -100% cereals 0% -10% 90 –95% grass 10% -20% 50 -90 % straw 10% -50% 40 -60 % wood 30% -60% 0 -40 %

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Substrate parameters: FM, DM, OM, COD 12

• Fresh Matter: FM (contains generally much water) (weight of the fresh material)

• Dry Matter: DM FM (weight of FM dried at 105°C) % of FM

• Organic Matter: OM or VS Water (weight of DM ashed at 550°C) % of DM (VS = Volatile Solids; assuming that the material escaping at 550°C is organic and the remaining ash is mineral) • Chemical Oxygen Demand: COD (chemical method to determine how much oxygen could be absorbed by the organic compounds; used OM / VS for industrial waste waters, where the DM determi- DM nation might be false) ash

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Biogas yields 13

Look always well, to what the biogas yield of a publication refers !

• specific gas yield Y: (may refer to biogas or to methane!) 3 3 3 Y [m /kg OM added ] or Y [m /kg OM digested ] or Y [m /kg FM added ] • reactor specific gas yield: (refers to reactor volume and time) 3 3 Y [m / m reactor *d]

3 most reliable: m Biogas/kg OM added (resp. CSB added ) 3 • For determination of Y [m /kg OM digested ] the OM content of the FM as well as that of the digested matter has to be measured. • Be aware that yields of different substrates referring to FM may cause a totally different ascending order than those referring to OM, because the water content may vary significantly – e.g. between dry autumn leaves and wet leftovers from the table…!) • Measuring the gas yield, temperature and pressure have to be observed. Standard conditions are 0 °C, 1013 mbar . (High T: much water vapour! etc.)

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Theoretic biogas yield 14

Biogas yield Methane yield [l/kg OM] [Vol. %]

carbohydrates ~790 ~50% proteins ~700 ~68% fats ~1270 ~71%

• Fats contain about double as much energy compared to carbohydrates and proteins fats serve as long term energy store in our body and oils within seed serve as energetic «starting capital» in some plants (olive, sunflower, rape etc. etc.) • Be aware that the methane gas content measured may be higher, because some CO 2 remains dissolved in the liquid (amount depending on temperature and pressure!)

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Biogas yields of some substrates 15

Biogas yield degradation methane

[l/kg OM added ]%% solid manure 250-280 40-42 55-65 rumen content 260-480 40-65 55-70 liquid manure cattle 250-300 60-65 liquid manure pigs 300-350 60-65 biowaste incl. garden 400-600 70-75 55-62 food leftovers 600-800 > 80% 65-70 fat separator 800-1000 75-85 65-75

The yield per ton of FM may vary much more, because it depends on the water content – and water does not produce any gas ! (e.g. the DM of liquid cattle manure may vary between 4 and 12% depending on method of housing the animals!)

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Biogas yields of FM 16

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Estimation of the biogas yield 17

Before building a biogas plant, it is important to estimate the expected biogas yield for economic reasons. In the internet, there are a lot of tables giving indications about the expected yields – but be aware that with a specific substrate different yields may result depending on water content, temperature, retention time etc. It is recommended to determine at least the DM-contents of the different substrates by taking representative samples and drying them in a oven. • Determination of DM (because water may vary significantly!) • Assume an OM-content looking at published data (in general, the OM- content does not vary very much for a given substrate) • Determine the amount of FM of each substrate you expect in a year. • Calculate the amounts of OM and estimate the gas yields for each substrate and add them up. The following tables give an idea about OM and possible biogas yields: Uzbekistan 2018

Some biogas yields 18

Biogasertrag [m3/t]

LFL Bayer. Landesanstalt für Landwirtschaft Uzbekistan 2018

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Example of an estimation for a big plant 19

FM DM OM Biogas CH 4 Gas Gas kt/a % % m3/kg OM % m3/t FM m3/a Pig manure 6,7 4 80 0.37 65 12 79‘000 Cattle manure 3,1 5 80 0.30 65 12 37‘000 Solid manure 2,5 25 80 0.52 60 103 257‘000 Chicken manure 1,8 50 82 0.45 60 185 332‘000 Horse manure 0,1 30 75 0.37 60 83 8‘000 Hay, silage 0,1 35 90 0.46 56 144 14‘000 Cleaning of fields 3,5 30 90 0.63 59 169 592‘000 Straw from maize 1,5 60 92 0.61 56 335 503‘000 Green waste 4,0 25 75 0.69 59 129 515‘000 Grünschnitt 3,7 25 90 0.69 59 155 572‘000 Dust from milling 1 75 88 0.47 58 312 312‘000 Food leftovers 1 12 92 0.63 65 69 69‘000 Kitchen wastes 1 30 92 0.59 65 164 164‘000 Recommendation: Make an Excel-sheet!

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Assembling a low cost testing device 20

If there are no data published on an available substrate make a test yourself!

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Simple testing device 21

- (good, i.e. active!) inoculum: 40% 4 5 - 2 (better 3) probes of the sample - 2 probes of the inoculum in order to determine its contribution to the gas production 7 3 1 2 litre preserving glass with sample and gastight plug 2 Water bath (simple pan) 3 Thermostat with stirrer and heating device 4 Glass for collecting the evolving gas 5 Meter (for calculating the amount produced) 6 Flat (Δp!) expansion pan with salty water (in order to

2 1 reduce CO 2-solubility) 7 Tap for evacuating the gas (once or twice a day; where appropriate taking a sample for gas analysis)

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Substrates: conclusions 22

• Besides wood, all organic materials are digestible. • Different substrates have different water contents, different elementary composition, different OM-contents thus, a ton of a biomass is not equal to a ton of another one! • If estimating the biogas yield take into consideration the local conditions such as retention time etc. • Water does not produce any gas to much dilution is not interesting from an economic point of view! • It is worthwhile to measure DM-contents and to reflect well, what is available and interesting to be fed into the digester.

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Process parameter: retention time (RT) 23

• HRT («hydraulic retention time») defines how long the digestate remains in a batch reactor or remains on average inside a continuously fed reactor (CFR). • SRT («solids retention time») defines the mean RT of solids in a reactor. • HRT is not imperatively = SRT! • In general: the longer the RT, the better the degradation! • Most of the gas is produced at the beginning; afterwards the curve is flattening.  economic (and ecologic…) Optimisation necessary: - too long : too large and too expensive reactor - too short : biogas potential is not exploited enough - much too short : bacteria are washed out (in a CFR)

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Process parameter: loading rate (LR) 24

• The loading rate specifies how much material is added per fermenter volume in one day. • Dimension: kg OM/m 3*d (or: kg CSB/m 3*d ) • The optimal LR depends on the type of reactor: the LR is not for all technologies the same! (reactors keeping the bacteria back by special devices tolerate higher LR’s) • If LR is too high  overload! (the fermenter runs sour; see biology) • If LR is too low  bacteria are starving; with the reactor volume one could produce more gas.

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Example of a calculation 25

biogas Output = L = 5 m 3/d L – biogas ≈ L – L*(C -C ) 100 m 3 i o L, C V, C r i Co V = 100 m 3 3 Ci= 50 kg OM/m

Calculations: L: load: mass treated [m 3/d] HRT = V/F [d] = 100 m 3/5 m 3/d V: reactor volume [m 3] = 20 d

C : concentration input [kg OM/m 3] 3 3 i LOM Load = L*C i = 5 m /d x 50 kg/m 3 Cr: concentration reactor [kg OM/m ] = 250 kg/d 3 Co: concentration output [kg OM/m ] LR = L*C /V = 250 kg/d / 100 m 3 Ci > C r > C o i = 2.5 kg/m 3.d

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Gas production is influenced by many factors 26

• Substrate: • Process parameters composition retention time digestibility loading rate degree of grinding mixing dilution temperature • Technology: • Start-up amount of inoculum type of reactor activity of inoculum size, geometry adaptation of inoculum But: it is less complicated than it might seem to be at the first sight; the plant operator will gain experience quickly!

Thank you for your attention !

Dr. Werner Edelmann arbi GmbH, UnterägeriUzbekistan 2018

13 12.07.2019

Digestion – State of the Art and optimal Plant Operation

Part 3: Biogas Technologies

Werner Edelmann arbi Bioenergie GmbH CH-6314 Unterägeri ede(at)arbi.ch

Uzbekistan 2018

Contents part 3: biogas technologies 2

This part gives an overview on the most common designs of both, high tech and simple biogas plants. Advantages, disadvantages and applications of the technologies are described in order to better understand, what is important when planning a biogas plant.

• Technological requirements for biogas plant construction • Continuously fed flow-through digesters - stirred reactors - plug flow reactors • Batch digesters for solid wastes • Comparison of the system performances

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Batch or continuously fed biogas plant? 3

There are two modes of biogas plant operation, which are different in principle: • Batch fed : The digester is filled with substrate, inoculated and the door is closed in a gastight way. After a retention time long enough to digest most of the substrate, the digester is opened and emptied for a next digestion. This technology is described further down in detail ! Advantage : simple Technology for usually solid substrates. Disadvantage : Several digesters necessary for a more or less constant gas production. • Continuously fed : Most of the biogas plants are fed continuously, i.e. at least once every day, normally with liquid substrates: The feed is added to the digester and the same amount of (more or less!) digested substrate is displaced from the digester. Advantages : constant gas production; just one digester necessary Disadvantage : Some fresh material may be exported too quickly. The continuously fed technologies are described first .

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The cow is a model for optimal digestion 4

the cow is a mobile biogas plant ! (it farts and burps up to 400 Litre methane per day!)

basic approach cow:

• continuously well heated , • super crushing of substrate, (ruminant!)

• super moistening and mixing of the substrate,

• defined retention time despite of continuous feeding (succession of stomaches).

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Requirements for biogas plants 5

• Feed as continuously as possible with crushed and frayed material (like ruminant animals...!) • Gastight digester, i.e. no access for oxygen • Heat and keep temperature stable! (similar to an intestine….) • Mix gently for intensifying the contact between microorganisms and substrate (peristalsis of the intestines!) • Keep in general the conditions as stable as possible (temperature, retention time, amount and composition of the feed etc.) • Provide eventually devices for attachment and growth of the bacteria to keep them back inside the reactor (like the villi in the intestine!)

Main objective: as many as possible (healthy!) bacteria per volume!

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+/- continuously fed (semi-) liquid digestion 6

• Stirrer tank (+/- Completely ST irred Reactor, CSTR ) • Contact-process (bacteria of the output are recovered and fed back into the reactor) • UASB (Upflow Anaerobic Sludge Blanket; granules of bacteria kept in suspension) • Anaerobic Filter (surface for withholding bacteria inside the reactor) • Anaerobic baffled reactor (solids remain longer inside the reactor) • Plug-flow digester (long reactor, where material enters on one side and leaves on the other one)

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Stirrer tank (CSTR) (high tech) 7

• «mother of all digesters» biogas • No defined retention time ! • Therefore often 2 digesters output in sequence (cascade) • Widespread: - waste water treatment - agriculture etc. • Separation possible: (sediment / liquid phase / scum layer) input • With short retention times: danger of flushing out too many bacteria!

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Stirrer tanks in agriculture 8 Two digesters in succession: digester and covered storage tank («post-digester»)

Animals are kept in a stable with a pit for liquid manure

Normally: besides of manure: digestion of co-substrates (industrial and harvesting wastes, etc.)

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Reasons for (gentle!) mixing 9

• Adjustment of differing concentrations within the digester (intermediates, nutrients as well as inhibiting substances) • Better de-gasification (especially also CO 2 dissolved under pressure at the bottom) • Intensifying the contact between bacteria and substrate • Preventing the formation of sediments and scum layer

a: paddle at the ground, b: (slow) propeller (most common ; normally diagonally mounted) , c: mammoth pump, d: recirculation of liquid, e: injection of biogas • Intermittent mixing saves energy!

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Stirred: fixed dome digester (low tech; orig. China) 10 • max. ~10 m 3 • mixing with changing gas level • mainly for cooking / p lighting • relatively cheap • disadvantages: - gas pressure (p) varies very much! - cracks in the dome gas losses (many installations out of order!) - difficult to maintain (e.g. difficult access to sediments) - size limited (normally 4 - 6 m 3; seldom ~10m 3) • Several million plants constructed – but many of them broken or not operated in an optimal way..!

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examples fixed dome 11

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Stirred: Floating dome (low tech; orig. India) 12

• floating gas dome (metal or plastic) • constant gas pressure p • mixing by turning around the gas dome manually (“stirrer arms”) p • size less limited w • disadvantages: - corrosion with gas holder out of metal - more expensive than fixed dome - gas losses, if dome does not swim in a separate water seal (w), but directly in the slurry (then, gas may escape between gas holder and wall)

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Examples 13 floating dome

Also «Hybrid» between Chinese and Indian design possible (left)

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Contact process (high tech) 14

• CSTR with biogas sedimentation • slurry with solid particles sedimentation and many bacteria is recycled output • higher concentration of bacteria in the reactor! slurry with • quicker and better much bacteria degradation • Higher loading rate and shorter retention time! (Only 8-10 days instaed Recircula- of > 20 days) ted slurry • Application mainly input with “thick” industrial waste waters

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Example contact process 15

sedimentation ! digester

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Anaerobic baffled reactor (clever low tech) 16

biogas

input output

• No mixing; much water with rough particles • Plug-flow-reactor (see below) with vertical separation walls alternately permeable at the top and at the bottom • SRT >> HRT (solid particles are kept back inside the reactor in the sediment and in the scum layer) • Bacteria are immobilised on the solids no wash out short HRT ! • SRT is long enough to degrade most of the solids • Good solution for septic tanks: urine passes quickly, solids remain and are degraded slowly, good sanitation.

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Examples of anaerobic baffled reactors 17

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Upflow Anaerobic Sludge Blanket, UASB 18 biogas • millions of bacteria form millions of pellets (1-3 mm wide) slow upstream motion of the substrate • output pellets float in the substrate; many bacteria with large surface for attack! • Devices to prevent the export of pellets • Very high concentrations of bacteria! • Very high loading rate and quick degradation • Very short retention time (1-3 days) • Application for “thin” industrial waste waters with few particles input • Disadvantage: tricky to run at optimal conditions (upstream speed, etc.)

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Example UASB 19

Dairy factory producing cheese and yoghurt

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Anaerobic filter (upflow, downflow or dynamic) 20

• bacteria grow attached on a large surface (e.g. 200 m 2 / m 3) • very high bacteria concentration • very stable (also against shocks) • very high loading rate and very short retention time! • no clogging and optimal nutrient supply with a dynamic filter (arbi) • For thin waters ! • Plug-flow process

(see surface for growth below) support with large

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Conclusions: liquid digestion 1

• CSTR is often used, but the substrate shows not a defined retention time undigested matter is exported. • If there are particles in the liquid danger of formation of scum layer and of sediments more maintenance! • If there are just few particles (“thin organic waste water”) possibilities to retain bacteria inside the digester high concentration of bacteria (very) quick degradation. • If the organic material is mainly particular: try to add as few water as possible (semi-) solid digestion! (DM = ~12 – 20%; water takes away volume and does not produce any gas!) • A solution for semi-solid and solid substrates is the plug- flow-digester

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Plug-flow digestion 2 • An intestine is an ideal plug-flow reactor: a long tube, where the raw material enters on one side (mouth) and displaces the same amount digested material on the other one (anus) no mixing forwards/ backwards the same retention time for all material! (optimal sanitation!) • DM up to ~30%; often thermophilic digestion because only few water to be heated.

biogas

digester input M

output re-inoculation

• Re-inoculation is reasonable, because slow growing methanogens are mainly in the second part of the reactor (wash out!) back to the input! • Gentle radial mixing, i.e. not in flow direction, is an advantage.

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Behaviour of HRT and sanitation 3

CSTR Cascade of CSTR ideal plug-flow

Export of fresh material fresh of Export HRT HRT not defined! defined HRT

• CSTR: much of the input does not remain long enough in the reactor (depending on reactor size, stirring and feed mode) less gas and weeds and pathogens may survive! • Plug-flow (and also batch-) reactor: defined HRT optimal sanitation!

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Plug-flow (high tech) 4

important: do not forget the digestate! (recycling of nutrients and substitution of humus loss) electricity, heat

pre-treatment

co-generation or

Digesters: (capacities: gas cleaning (grid) 10 - 20‘000 t/a each) dewatering

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Example: plug-flow digester for household wastes 5

Thöni, Roppen (Tirol, Austria)

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Stirring device and driving motor 6 driving motor and Interior of a plug- flow reactor (here: steel and cement) with very slowly, intermittently turning stirring device

These high tech digesters treat material with up to ~28% DM

thermophilic digestion www.thoeni.com (HRT ~18 days)

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Plug-flow reactors (low tech) 7

Above: Simple tubular digester and below large plug-flow plant at a slaughterhouse (Ivory coast)

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Plug-flow digester «arbi» (low tech, improved) 8

stir • size not limited pit • low cost (rectangular pool covered with a plastic membrane) • long plug-flow due to a separation wall (saves outer walls, though saves costs!) • simple manual re-inoculation possible simple wall separation (increase of loading rate and shorter HRT)

• simple access for maintenance stirreraxis • good sanitation • high DM up to ~18% possible (e.g. wood)(e.g. • simple slow mixing in the first section possible (transmission; e.g. by bike) • reduction of sediment import by a sink in the inlet pit may run at low gas pressure (less loss) outlet re-inoculation inlet • pit pit

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Plug-flow digester (arbi, Nivumomingi,Tanzania) 9

(details Theon the internet)

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Discontinuous solid waste digestion („batch“) 10 Continuously fed solid waste digestion is mostly not reasonable : • Water has to be added in order to be able to pump • Intense grinding necessary for pumping energy need! • The water added has to be heated energy loss! • Solid/liquid separation after digestion necessary additional machinery and energy need! • Problems with accumulation of sediments (stones, gravel, sand) possible more maintenance! Batch digestion! • Several digesters are filled and locked up alternately • No addition of water necessary (just some percolate in a closed loop) • Easy filling and emptying (manually or by truck etc.) • No problem with sediments and optimal sanitation • No dewatering after digestion easy post-composting if desired

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Principle of batch digestion 1

biogas

percolate gas storage

solid waste: tank for co-gene- container with drain of percolate percolate ration

percolate

• at least 3 containers (even gas production!) with doors closing gas tightly • Filling with a wheel loader gasification emptying: defined retention time optimal sanitation • no movable parts within the digester • digestate is dappled with percolate, which is recirculated in a closed loop • inoculation with bacteria in the percolate (from the other digesters) • low energy need for operation (some diesel for the wheel loader; relatively few heating demand because of few water to be heated)

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Example Bekon (Allmig, Baar, Switzerland) 2

• encased solution (high tech) • doors closing hydraulically • mesophilic temp.; SRT ~4 w • Sieving and air separation of the product

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Other designs 3

Eggersmann with double membrane balloon on top (right) and Renergon with gas storage on percolate tank (below) (tank might also be underground)

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Process Pöttinger 4 • Metal containers • Substrate is heated by aeration • Before emptying: again aeration in filling aeration for order to export methane and water heating (2-3 d) vapour (danger! Explosive mixture with all batch processes when opening without countermeasures !)

Biogas start production percolation (3-6 w)

aeration emptying (explosive!) Uzbekistan 2018

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Process Sud-Oest Biogaz (relatively simple solution) 5 • (partially) underground bunker silos charged by a wheel loader • Covered by a gas tight membrane • Gas storage on the percolate tank • Retention time 8 w ; 4 digesters • Heating of the input by pre-composting in the bunker; afterwards heating the percolate within the tank

Percolate tank containers: with gas holder gas, pumps etc.

Membrane covering the digester input digester

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Examples Sud-Oest Biogaz 6 • (partially) underground bunker silos charged by truck • Covered by a gas tight membrane • Gas storage on the percolate tank • Retention time 8 w ; 4 digesters • Heating of the input by pre-composting in the bunker; afterwards heating of the percolate in the tank

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Batch digestion (low tech, arbi 1986) 7

École agro-forestière, Nyamishaba, Rwanda Uzbekistan 2018

Solid waste: batch vs. continuous digestion 8

feedingtechnology batch continuous

minimal treating capacity > ~2’000 t/a >10‘000 t/a gas production slightly irregular constant gas quality slightly variable constant filling/voiding wheel loader automated

diesel need ++ + electricity need + ++ noise (mainly wheel loader) + - fresh material - potential for bad odours “waiting” outside… (normally encased)

Output consistency solid (liquid) solid and liquid

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Limit loads of throughput technologies 9

loading rate LR relative volume CSTR 3 kg OM/m 3*d *) 1 contact process 7 kg OM/m 3*d 0,4 UASB 20 kg OM/m 3*d 0,15 anaerobic filter 22 kg OM/m 3*d 0,14

solid waste without re-inoculation 7 kg OM/m 3*d solid waste with re-inoculation 12 kg OM/m 3*d

*) after adaptation; start with < 2 kg OM/m 3d ! (conversion: 1 kg CSB = ~1,5 kg OM)

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Now: be happy that all ecological cycles are closed 10 while producing renewable biogas!

Thank you for your attention !

Dr. Werner Edelmann arbi GmbH, UnterägeriUzbekistan10 2018

5 12.07.2019

Digestion – State of the Art and optimal Plant Operation

Part 4: Use of the products, operation and safety aspects

Werner Edelmann arbi Bioenergie GmbH CH-6314 Unterägeri ede(at)arbi.ch

Uzbekistan 2018

Contents part 4: use of the products 2

• The gas distribution • Utilization of the biogas • Utilization of the digestate • Safety

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Components of the gas line 3

• Condensate trap(s) • Overpressure device • Pressure measuring device • Balloon to store biogas during periods without need • Flame arrester • Flare • Devices to use the biogas (burner, cogenerator)

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Composition of the Biogas 4

• 50 – 60 % methane (CH 4) (max. >70 %; see biology!)

• 30 – 40 % carbon dioxide (CO 2) • 1 – 5 % water vapour (thermophilic up to 10%)

• 20 – 20’000 ppm (parts per million) hydrogen sulphide H 2S

• < 2 % nitrogen (N 2) and oxygen (O 2) • Traces of hydrogen etc.

Heat value (average): 21.5 MJ/m 3 = 6.3 kWh/m 3 1 m 3 of Biogas = about 0.6 litres of diesel fuel.

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Condensation within the gas line 5

• Biogas coming from the reactor is warm and wet there is danger of condensation within the piping ! • Therefore the pipe has to be inclined back towards the reactor and forwards to a cool, deep place, where there is a condensate trap. A condensate trap may be a simple bucket filled with water. Take care that the vertical tube p is always in the water; if not: gas will escape!

p = pressure within the gas line

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Trap combined with pressure relieve 6

A container in a low bucket: If there is no user, pressure p raises reaching the overpressure (op) , the gas may escape to a flare or to the atmosphere (bubbles). Important to protect the gas balloon!

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Simple device to measure the gas pressure 7

Fill an “U” shaped, transparent hose connected with the gas line with a little bit of water and measure the difference of the level = pressure (cm water column = mbar) pressure in the gas line

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Storing the biogas 8

• If biogas is not used continuously, it is reasonable to store the gas for the times when it is needed. • The cheapest possibility is to install a gas balloon out of tissue reinforced PVC (eventually loaded with weight for pressure generation). • If the burner or the cogeneration device is self-aspirating, the pressure in the gas line may be low. (advantage! Less gas losses!) • Protect the plastic from direct sunlight (ageing and gas losses) • Calculate the expected biogas yield and the probable production in times without need for finding the optimal size

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Flame arrester, flare and gas meter 9

• Biogas is explosive in a mixture of about 5 to 12% methane in air take care that the gas installations are gastight! • In order to hinder a flame to wander within the pipe towards the balloon, a flame arrester may be installed: it is just a container filled with gravel within the gas line. (However: the speed of flame wandering of biogas is low: ~25 cm/sec.) • Methane is a powerful greenhouse gas it should not escape to the environment ! • It is recommended to install a simple (flare) device to burn the gas in case of gas production while there is no possibility to use it. (e.g. revision of the burner or of the cogenerator.) • A gas meter should be installed close to the users (be aware of condensate within the meter ! )

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Simple (main) valve 10

• In small and simple biogas plants there is the possibility to use a simple valve, which is 100% gastight and does not corrode: a bucket with water, which may be lifted!

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Simple water heating 11 • Cheap nozzles made of sintered stainless steel can be used for burning the gas at very low pressure (>20 US$; ~3mbar) • They may be used for heating quite large amounts of water.

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Central heating boiler 12

• If there is need for large amounts of hot water (Pasteurization of milk etc.), a professional biogas boiler may be installed. • There is a large variety of central heating boilers available on the market

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Cogeneration plant 13 • A cogenerator consists of a combustion engine driving a generator for electricity production. Most of the waste heat of the motor is recovered for heating purposes. • The engine may be a combustion engine or a micro-gas-turbine Biogas/air exhaust gas • If the engine is a modi- fied diesel engine, it is necessary to add some Heat exchanger pilot oil (diesel) cold water hot water • The heat generated may also be used for vapour electricity production or for cooling with an absorption cooling device.

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Efficiency of a cogenerator 14

35-42 % elect.

100%

50-55 % heat

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Cogeneration: general remarks 15 • Large cogenerators show a better electrical efficiency than small ones (diesel dual fuel engines which need some pilot oil: up to 42% electricity; small Otto-engines 35-38%) • Cogenerators cause relatively high costs for maintenance – especially small ones • Micro-gas-turbines show a higher heat output, but a lower electrical efficiency; though their maintenance is less expensive. • Clarify your needs before buying and choose a size that can run without to many stops (not much too large!) • The engine should be installed in a fully enclosed and insulated container reducing heat losses and emissions of noise. • There is a large variety of relatively inexpensive Chinese and Indian cogenerators (compare before buying..!)

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Examples of cogenerators 16

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Removing hydrogen sulphide (I) 17

• Under anaerobic conditions, the sulphur of the proteins is

reduced to hydrogen sulphide (H 2S) escaping within the gas.

• While being burnt in the engine, H 2S reacts with water and forms sulphurous acid (H 2SO 3) acids corrode metals, i.e. the motor will be damaged! • It is recommended not to use biogas with more than 200 ppm

H2S.

• H2S can be converted to elementary sulphur by pumping few oxygen (i.e. air) into the gas room (not more air than 4-5%!) • The sulphur freed by aerobic bacteria crystallises on ceiling and walls of the headspace; it will fall back into the digestate and will improve the fertilizing quality of the digestate.

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Removing hydrogen sulphide (II) 18 • This biological method is very simple and cheap and reaches concentrations of less than 200 ppm H 2S, if there are not too much proteins in the reactor. • Nevertheless, in Switzerland there is often installed a filter with activated carbon additionally , if there is fed food waste etc. rich in proteins (the filter material has to be replaced regularly additional costs) • The sulphide removal may also take place in external containers. • A very good method is also to add some iron chloride (FeCl 2) directly into the reactor or the percolate. Iron sulphide (FeS) will precipitate and will be exported with the digestate.

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Additional possibilities to use the gas 19 • In large biogas plants treating more than 10’000 tons of biogenic wastes per year it may be reasonable to clean the gas to natural gas quality by removing CO 2 with membranes or pressurized washing or washing with amine solution (about 10% energy loss for the cleaning). • This makes sense, if a gas pipeline is nearby Biogas can be stored in the public gas grid and be used also for driving cars. For Uzbekistan this seems not to be a solution, because biogas will be produced in remote areas and natural gas is rather cheap, where the grid is close. • Another technology called “power to gas” is actually realized in Europe: water is split into Hydrogen and oxygen by electrolysis with surplus photovoltaic electricity. The hydrogen is used for transforming the CO 2 of the biogas into methane. Like this a biogas plant converts all carbon into pure methane!

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Flame arrester, flare and gas meter 20

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Quality of the digestate 21

• Biogas is formed with carbon, hydrogen and oxygen. While braking down the matter, nutrients (necessary for plant growth) are freed and remain dissolved in the water of the digestate . (Only some Ammonia and sulphur may escape with the gas) • The digestate is comparable with compost. In contrary to compost, + nitrogen is freed only in the form of ammonium (NH 4 ); in compost - there may be some nitrate (NO 3 ), because there is abundant oxygen. • Similar to the compost: organic compounds, which are not easily degradable, are still available for improving the soil quality while forming precious humus. • Because in a biogas plant the organic material is degraded, the nutrients are freed and available for optimal plant growth. This saves expensive mineral fertilizer. Crops grow better with digestate than with untreated manure.

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Advantages of the digestate 22 • Nutrients and trace elements are converted in a form, which is easily available for plant growth. • In contrary to mineral fertilizer, digestate provides to the ground organic compounds, which are important for humus formation . • Pathogenic germs (dangerous bacteria, viruses etc.), nematodes, and seeds from weeds are killed under anaerobic conditions! • The organic acids are degraded less damage for the life within the ground and higher diversity of the (important) soil creatures . • Reduction of bad odours , because of degradation of smelling organic compounds. • Degradation of large particles such as straw etc. the digestate is homogenized and liquefied ; therefore the contact with the soil is improved and the liquid enters quicker into the soil, where it is protected from evaporation and nutrient loss. • Some chemicals dangerous to human health, such as some pesticides may be destroyed . • Production of digestate is at least as important as producing renewable energy!

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Hindering nitrogen losses 23 • Nitrogen which is freed while degrading is converted to water soluble + ammonium (NH 4 ). A part of the Ammonium is always converted to Ammonia (NH 3), which is volatile and escapes to the air (typical component of the odours of manures and composts). • The higher the pH and the higher the temperature, the larger the share of ammonia! • Digestate contains more ammonium and shows about 1 unit higher pH compared to untreated material about 10 times higher ammonia volatilization! • Therefore it is important to bring out the digestate quickly – if possible – and to bring it out during cooler hours in the evening (not at noon , when it is hot!) preferably on humid ground. (ammonium enters with the liquid into the ground, where it is fixed for plant growth) • If the digestate has to be stored, try to keep the surface small in order to reduce evaporation. Eventually cover the digestate (liquid or solid) with a simple plastic sheet.

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Bringing out liquid digestate 24

Do not sprinkle! Bring out gently directly on or into the ground

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