16th European Biomass Conference & Exhibition, 2-6 June 2008, Valencia, Spain
BIOGAS POTENTIAL FROM LIVESTOCK AND POULTRY WASTES IN THE REGION OF WESTERN MACEDONIA, GREECE
Goula Ma., Bereketidou Oa,b., Economopoulos Ca., Charisiou Na. aPollution Control Technologies Department, Technological Educational Institute of Western Macedonia, Koila, Kozani, 50100, Greece, b Department of Engineering and Management of Energy Resources, University of Western Macedonia, Bakola & Sialvera, Kozani, 50100, Greece *Corresponding author. Tel: +302461068296, Fax : +302461039682, e mail:[email protected]
ABSTRACT: Animal wastes constitute a high proportion of biomass in the region of Western Macedonia, Greece, and are able to play an important role towards the satisfaction of heat and/or energy and related material supply, with respect to environmental protection targets. Significantly, such wastes could be a significant source of energy if conventional energy prices continue to rise. This paper describes anaerobic digestion as a potential animal waste exploitation method. The aim of the present work is to strengthen the interest in animal waste potential for energy production in the region, through a methodology for the feasibility of utilization of those kinds of wastes as renewable energy resources. A combination of technical, economic and environmental issues is presented here. This study estimates the economically recoverable energy potentially available from livestock and poultry wastes in the region of Western Macedonia, Greece for the base year 2000. Anaerobic digestion of dairy cow, fed beef, goat, sheep and laying hen manures could have produced approximately 129,084 m3/d or 47x106 3 6 m /year of biogas, containing approximately 61.5 x 10 KWh/year that could result at a reduction in CO2 of over 80 x 103 tonnes per year and significant economic savings. Keywords: biogas, anaerobic digestion, animal manure
oxygen and various trace hydrocarbons. Due to its low 1 INTRODUCTION methane content (and therefore lower heating value) compared to NG, biogas is considered a low quality gas The promotion of biogas production and utilization is which is only suitable for use in engine generator sets strongly suited to the Mediterranean region as, to a great and boilers specifically designed to combust biogas as extent, the economies of the countries of the region rely fuel. on agriculture and related activities [1 6]. Currently, the vast majority of agricultural/ animal wastes are not being taken advantage of, despite the potential that they have as 2 BACKGROUND an energy resource. The successful development of such wastes into energy sources can go some way towards 2.1 The anaerobic digestion process mitigating the adverse economic, environmental and The biological conversion of the organic fraction of political effects that the over reliance on imported fossil animal wastes under anaerobic conditions is thought to fuels has upon the Mediterranean countries. This is a occur in three steps. The first step involves the enzyme particularly urgent for two main reasons. Firstly, the mediated transformation (hydrolysis) of higher current climate of uncertainty over security of oil supply molecular mass compounds into compounds suitable for due to the political instability that characterizes the use as a source of energy and cell tissue. The second step majority of oil producing countries, fears over global involves the bacterial conversion of the compounds terrorism and the emergence of the economies of China resulting from the first step into identifiable lower and India as major oil demanding economies, are pushing molecular mass intermediate compounds. The third step the prices of crude oil at record prices, affecting involves the bacterial conversion of these intermediate adversely the economies of the Mediterranean countries compounds into simpler end products, principally and the living standards of their people. Secondly, the methane and carbon dioxide. effects of global climate change are expected to be In the anaerobic decomposition of wastes, a number of particularly negative in the region, due to limited water anaerobic organisms work together to bring about the resources and the sensitivity of local ecosystems. conversion of the organic portion of wastes into a stable Biogas is a renewable energy source similar to natural end product. One group of organism is responsible for gas and is derived from renewable biomass sources, hydrolyzing organic polymers and lipids to basic primarily via a process called anaerobic digestion [7 structural building blocks such as fatty acids, 20]. The most common types of biogas projects involve monosaccharides, amino acids, and related compounds. A biogas collected at landfills (i.e. landfill gas), waste water second group of anaerobic bacteria ferments the treatment plants, and dairy or swine farms where biogas breakdown products from the first group to simple is created from animal manure in anaerobic digesters. organic acids, the most common of which is acetic acid. The processes and equipment for converting biomass This second group of microorganisms, described as sources (such as dairy manure) into biogas via anaerobic nonmethanogenic, consists of facultative and obligate digesters are well known, commercially available and anaerobic bacteria that are often identified in the economically reasonable. In its raw state, the major literature as “acidogens” or “acid formers”. components of biogas are methane (typically 60 – 70%) A third group of microorganisms converts the hydrogen and carbon dioxide (typically 30 – 40%). Additional and acetic acid formed by the acid formers to methane smaller components of biogas include hydrogen sulfide gas and carbon dioxide. The bacteria responsible for this (typically 50 – 2,000 ppm), water vapour (saturated), conversion are strict anaerobes, called methanogenic, and are identified in the literature as “methanogens” or
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“methane formers”. Many methanogenic organisms system, which may be either mechanical or gas identified in landfills and anaerobic digesters are similar based, helps to increase the efficiency of the to those found in the stomachs of ruminant animals and in digestion process as well as accelerate it. Likewise a organic sediments taken from lakes and river. The most built in heating system also increases the efficiency important bacteria of the methanogenic group are the of the digestion process. Typically 10 – 15% of the ones that utilize hydrogen and acetic acid. They have biogas output is used to provide heating for the very slow growth rates, as a result, their metabolism is digester and electricity for other biogas plant usually considered rate limiting in the anaerobic processes. treatment of an organic waste. Waste stabilization in anaerobic digestion is accomplished when methane and • Plug Flow – This type of anaerobic digester is carbon dioxide are produced. Methane gas is highly intended for ruminant animal manure (cows) with 11 insoluble, and its departure from a landfill or solution – 14% solids and is therefore not appropriate for represents actual waste stabilization. manure collected via a flush system. The design is Anaerobic digestion can occur within three different similar to the complete mix digester but without the temperature ranges: psychrophilic, mesophilic, and mixing system. Plug flow digesters are cheaper to thermophilic [8]. construct and operate than complete mix digesters Psychrophilic digestion occurs at temperatures below but are also less efficient. 68°F and is usually associated with systems that operate at ground temperature. Psychrophilic AD has the lowest • Multiple Tank (2 Stage) – This type of anaerobic biogas production rate of the three temperature ranges. digester is similar to the complete mix digester The production rate is susceptible to seasonal and diurnal design except that digestion occurs sequentially in fluctuations in temperature, making it difficult to predict two phases. The first phase is a higher temperature how much biogas will be available. (thermophilic) phase at 55ºC followed by a second, The mesophilic range is between 68°F and 105°F. The lower temperature (mesophilic) phase at 35ºC. optimal temperature for mesophilic AD is approximately While laboratory tests of this design show promise 100°F, which is nearly the same as the body temperature for increased digester efficiency, there is very little of dairy cattle. This allows the same bacteria at work in a data on field scale systems yet. cow’s ruminant system to continue breaking down the excreted organic matter for a period of several days. 2.3 Biogas usage Digesters operating in the mesophilic range require 2.3.1. Heat Production constant heating in order to maintain a temperature of Medium calorific heating value biogas can be used in a 100°F. number of ways. Typically after condensate and The thermophilic range is between 110°F and 160°F. The particulate removal, the biogas is compressed, cooled, elevated temperature allows for the highest rate of biogas dehydrated and then be transported by pipeline to a production and the lowest hydraulic retention time nearby location for use as fuel for boiler or burners. (HRT). The HRT is the amount of time material must Minor modifications are required to natural gas fired remain in the digester before it is sufficiently processed. burners when biogas is used because of its lower calorific Digesters that operate in the thermophilic range require heating value. Another alternative for biogas applications substantial amounts of energy to maintain the proper is to generate steam using a boiler onsite. The biogas, temperature and are prone to biological upset due to after condensate and particulate removal and temperature fluctuations. To avoid upset, they require compression, is burned in a boiler. The customer for this closer monitoring and maintenance. Another drawback is steam would need to be close to the site since high that the effluent is not odor free. pressure steel insulated pipeline is expensive and heat is lost during transport. Heat production is the simplest and 2.2 Anaerobic digesters most common application for biogas. The combustion of The following is a brief description of the major types of biogas gives rise to low emissions of nitrogen oxides of anaerobic digesters [7] currently used: about 35 50mg/MJ, which is around half the level for oil combustion. • Covered Lagoon – This is the simplest and least expensive type of anaerobic digester. It is intended 2.3.2. Electricity production to be used on large volume, liquid manure lagoons Electricity generated on site using a reciprocating engine, with less than 2% solids, typically on a dairy or steam turbine, or gas turbine, is being actively used. swine farm. It consists of a non porous, plastic cover When a reciprocating engine is used, the biogas must over a manure lagoon with a built in biogas have condensate and particulates removed. In order to collection system. The cover traps gas produced move fuel gas into a gas turbine combustion chamber, the during the decomposition of the manure. Covered biogas must have most of the visible moisture and any lagoons are sometimes installed for odor control particulates removed and then compressed. Using a steam purposes (in which case the captured biogas may be turbine requires generating the steam first. Microturbine flared) but with additional equipment, the recovered can be used to generate electricity at a capacity as small biogas can be used to provide heat and electric as 30 kW. However, issues exist in the high cost for power to the farm. biogas clean up and limited engine running time when a Microturbine is applied. The microturbine technology has • Complete Mix – This type of anaerobic digester is not been commercialised. High cost associated with more expensive than a covered lagoon and is biogas clean intended for manure with 2 – 10% solids. It consists up is also an important issue for potential application of of either above or below ground tanks with a built the fuel cell technology. Fuel Cells are power generating in mixing and biogas collection system. The mixing systems that produce DC electricity by combining fuel
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and oxygen (from the air) in the electrochemical reaction. region to establish itself as the major energy center in In a first step the fuel is transformed into hydrogen either southeast Europe. Thus, the region of West Macedonia in by a catalytic steam reforming conversion or by a general, and the prefecture of Kozani in particular, (platinum) catalyst. The H2 is converted to direct demands necessary expertise and knowledge to address electrical current. The by products of the reaction are the modern, energy and environmental problems. water and CO2. Conversion efficiency to electricity is Specifically, cutting edge technology facilities and know expected to exceed 50%. how regarding the use and exploitation of scientific information about renewable energy sources and 2.3.3. Combined Heat and Power Production (CHP) especially biomass utilization for biofuels and The combined production of power and heat is commonly electricity/heat production are urgently needed. encountered alternative to heat production alone. The The treatment of the waste produced in husbandry and split between the amount of electricity and heat produced poultry farms in West Macedonia, demands the is determined by the design of the plant, but the normal installation of specific anaerobic digestion units. These value is about 35% electricity and 65% heat with a total units can be built either by the farmers themselves efficiency of about 90%. In the case of CHP production, (onsite) or by developers/investors that would collect the the biogas must be drained or dried, but in case, the soot waste at central locations. Given the high capital costs emitted must be trapped and certain corrosive involved, the latter option is more feasible, due to the fact components, such as hydro sulphuric acid and that individual farms produce relatively small amounts of chlorinated hydrocarbons must be separated off. waste. It has been calculated that for an economically viable anaerobic digestion unit, the amount of waste 2.3.4. Biogas as a Vehicle fuel demanded is equivalent to that produced by 1,500 cattle. The utilization of biogas as vehicle fuel uses the same An issue that needs to be addressed is the transport of the engine and vehicle con figuration as natural gas. waste to such units. However, an example of how such an However, the gas quality demands are strict. With respect issue may be resolved is provided by urban sewage to these demands the raw biogas from a digester or a biological treatment works. As is well known, sewage is landfill has to be upgraded. In practice this mean that collected from relatively large distances and transported carbon dioxide, hydrogen sulphide, ammonia, particles, to central locations for treatment. The central location trace components and water have to be removed so that makes such units economically feasible as opposed to the the product gas for vehicle fuel use has methane content installation of small units at every town or village. above 95%. A number of biogas upgrading technologies, The transport of animal wastes could be achieved in a such as Selexol, Water Absorption, Chemical Absorption, similar way. It is believed that, for the region of West and Pressure Swing Absorption (PSA) have been Macedonia, it would be possible to install anaerobic developed for the treatment of biogas. Using biogas in digestion units at central locations, such as the seats of towns as a fuel for vehicles such as buses, taxis and the local municipal governments. Such an arrangement communal vehicles can make economic sense and has would mean that the distances involved, between the evident environmental advantages. anaerobic digestion unit and the farms would be short (less than 10 kilometres) and therefore, the wastes could be transported either by lorries or by a specially 3 LANDSCAPE CHARACTERISTICS constructed sewage network. The latter option becomes more advantageous when considering that often, animal West Macedonia is located in the northwest of Greece units, are located at relatively short distances from each on the borders of Albania and the Former Yugoslavic other. Such an example is provided by the municipality of Republic of Macedonia (FYROM) and is mountainous, Servia and the Municipality of Askio, where almost 1500 and geographically isolated. The region is twenty first cattle can be found in each (the critical number demanded (21st) on the list of Europe's poorest regions, with a for an anaerobic digestion unit to be viable), without percapita income (GDP) of 62% of the EU average. West taking into account additional animal units (goat, sheep, Macedonia mainly depends on primary and secondary pig etc). sectors. The primary sector occupies 28% of the When deciding about the anaerobic digestion unit workforce and the secondary sector accounts for 35%. installation location, factors such as geography and Lignite extraction for power production has led to heavy climate need to be taken into account. The climate of industrialization and the region hosts the largest Greek West Macedonia can be described as continental, while electricity power production units, which contribute to the differences observed between the different prefectures 70% of the total electricity production of the country. are relatively minor. However, for the optimal design and This rapid and unplanned industrialization process has operation of anaerobic digestion units, these need to be resulted in significant environmental problems in the over taken into account. reliance of the local economy on the energy sector. On Grevena prefecture is surrounded on three sides the other hand, it has resulted in the concentration of by mountain ranges (east, west and south), considerable energy related expertise, which could prove while its plains are a continuation of the plains advantageous in schemes that look to exploit energy of Kozani and Kastoria prefectures to the north. sources. Notable recent developments in the region 85% of the prefecture can be characterised as include the completion of the Egnatia highway, which mountainous or semi mountainous while the runs through northern Greece and connects West few plains are located besides Aliakmonas Macedonia with every major urban center in the country river. The prevailing winds have a Northern and beyond, along the Turkey, Greece, Italy axis. direction. Grevena prefecture is characterized Certainly, the future completion of the Turkey Greece by large, seasonal temperature variations. The Italy natural gas interconnection, which passes through coldest month of the year is January (with an West Macedonia, presents a further opportunity for the average temperature of 10οC), while the
387 16th European Biomass Conference & Exhibition, 2-6 June 2008, Valencia, Spain
warmest is July (34οC). The average yearly the retention time. Unheated and un insulated plants do rainfall is between 1400 mm at high altitudes not work satisfactory when the mean temperature is and 600 mm at lower altitudes. below 15 °C. Heating systems and insulation can provide optimal digestion temperatures even in cold climates and Kastoria prefecture covers a land area of 1734 during winter, but the investment costs and the gas sq kilometres (while it contains an additional consumption for heating may render the biogas system 1692 sq kilometres of rivers and lakes). The not viable economically. land mass characterization is, mountainous The amount of seasonal and annual rainfall has mainly an (58.9%), semi mountainous (29%) and plains indirect impact on anaerobic fermentation: (12.1%). Temperature variations are similar to Low rainfall or seasonal water scarcity may lead to that of Grevena prefecture. The coldest month insufficient mixture of the substrate with water. The of the year is January ( 7οC) and the warmest is negative flow characteristics of substrate can hamper July (34οC). The average yearly rainfall is digestion. 726mm. Low precipitation generally leads to less intensive systems of animal husbandry. Less dung is available in In the prefecture of Kozani, land central locations. characterization is as follows: 40% High precipitation can lead to high groundwater levels, mountainous, 32% semi mountainous and 28% causing problems in construction and operation of biogas plains. The climate is continental, and plants. temperature variations are large. Here again the The following tables present the daily waste produced by coldest month is January ( 10οC) and the animal type and the different solid content for an average warmest is July (35 οC). Rainfall tends to be animal weight and the biogas produced based on the VS higher at the western side of the prefecture, production. while on average it reaches 745 mm per year. Table I: Daily manure production from different species Florina prefecture covers a land area of 1924 sq and VS content [9] kilometres. The land characterization is as follows: 60,8% mountainous, 13,2% semi Species Fresh manure Average mountainous, 26% plain. The climate is Animal weight continental with very cold winters and hot (kg) summers. The coldest month of the year is TS% VS% ο January ( 12 C), while the warmest is July (33 Cows 16 13 135 800 ο C). Beef 14 12 340 420 In summary, for the four prefectures comprising West Pigs 16 12 30 75 Macedonia, the climate is continental with considerable Sheep/Goat 30 20 30 100 seasonal temperature variations, while yearly rainfall is Poultry 25 17 1.5 2 relatively high (over 700 mm on average). The area is Human 20 15 50 80 mountainous (containing some of the highest peaks in Greece). Anaerobic digestion units should be constructed at central locations, preferably at the local municipality level. Such a design would mean that the units will be Table II: Biogas Production from different animals base located close to the husbandry farms, which would allow on VS production [10] the transport of wastes either by road or by a specially constructed sewage network. The optimal operation of Production Average Production Animal the units would demand constant temperatures, preferably (l/kg VS) (l/kg VS) o in the range of mesophilic organisms, i.e., 30 33 C with Pigs 340 550 450 careful insulation and heating of the anaerobic digester. Beef 150 350 250 Poultry 310 620 460 Horse 200 350 250 4 BIOGAS POTENTIAL Sheep 100 310 200
The data that was used to calculate the potential of Based on the above, the daily biogas production rate per West Macedonia was derived from the National Greek municipality/prefecture can be calculated. To determine Statistical Service (1999 2000). The available data the parameters that would constitute an anaerobic presents animal distribution by prefecture, municipality digestion unit economically feasible, it was deemed and the composite villages of the municipality. All types necessary to develop specialised computer software. of animals have been used for this study, i.e., cattle (both Only appropriate designs will perform satisfactory and beef and dairy), horse, sheep, goat, pig and poultry. will have a favorable cost benefit ratio. Existing basic Naturally, different animals have different waste designs of biogas systems have to be adapted to the production, while the solid content of the wastes also following framework conditions: (i) climatic and soil differs. Thus, the potential amount of biogas to be conditions; (ii) the quality of substrate to be digested; (iii) produced differs between animal types. the quantities of substrate; (iv) the prioritization of Biogas technology is feasible in principle under almost expected benefits; (v) the capital available; (vi) the all climatic conditions. As a rule, however, it can be availability of skills for operation, maintenance and stated that costs increase for biogas production with repair. sinking temperatures. Either a heating system has to be installed, or a larger digester has to be built to increase
388 16th European Biomass Conference & Exhibition, 2-6 June 2008, Valencia, Spain
Τhe design selection is determined largely be the Table IV: Biogas Production in the Prefecture of prevailing design in the region, which, in turn takes the Kastoria climatic, economic and substrate specific conditions into consideration. Large plants are designed on a case to case Municipalities / Production Viable basis. Typical design criteria are: Communities (m3/day) Space (determines mainly the decision if the fermenter Kastoria 532 is above ground or underground, if it is to be constructed 1,106 as an upright cylinder or as a horizontal plant) Agia Triada Existing structures may be used like a liquid manure Agioi Anargiri 1,483 tank, an empty hall or a steel container. To reduce costs, Akrites 1,403 the planner may need to adjust the design to theses Aliakmona 1,242 existing structures. Minimizing costs can be an important design parameter, Vitsi 808 especially when the monetary benefits are expected to be Ionos Dragoumi 3,451 low. In this case a flexible cover of the digester is usually Klisoura 205 the cheapest solution. Minimizing costs is often opposed 1,044 to maximizing gas yield. Koresti Available substrate determines not only the size and Macedonians 1,133 shape of mixing pit but the digester volume (retention Nestori 453 time!), the heating and agitation devices. Agitation Orestiada 1,716 through gas injection is only feasible with homogenous substrate and a dry matter content below 5%. Mechanical Arrenon 587 agitation becomes problematic above 10% dry matter Kastraki 773 Presented in the following tables are the maximum biogas Total 15,936 potentials per municipality in West Macedonia, while the proposed distribution of anaerobic digestion units is Table V: Biogas Production in the Prefecture of Kozani presented. Municipalities / Production Viable Table III: Biogas Production in the Prefecture of Communities (m3/day) Grevena Kozani 5,658
Agia Paraskevi 333 Municipalities / Production Viable Eani 2,423 Communities (m3/day) Askio 3,981 Grevena 4,313 Velvedos 552 Ventzi 2,212 Vermio 1,306 Gorgiani 840 Dimitrios Ipsiladis 960 Deskati 4,834 Elimia 1,514 Irakleoton 1,573 Εllispodos 7,209 Theodoros Ziakas 1,290 Κamvounia 2,145 Kosma Etolos 1,320 Mouriki 2,223 Hasia 1,425 Neapoli 1,624 Samarina 39 Ptolemaidos 2,083 Smixi 25 Servion 8,621 Total 17,872 Siatista 1,908 Tsotili 2,749 Vlasti 71 Livadero 3,074
Pedalofos 359 Total 48,794
389 16th European Biomass Conference & Exhibition, 2-6 June 2008, Valencia, Spain
Table VI: Biogas Production in the Prefecture of Florina Table VII: Description of the calculation program
Municipalities / Production Digester Viable 3 Communities (m /day) Building meterials Florina 4,613 Building Cost Aetos 4,370 Thermal protection Amindeo 4,679 Kato klini 10,249 Heating Meliti 8,273 Mixing Perasma 6,665 Cleaning System Prespes 4,340 Fire Protection Filota 1,272 CHP Variko 933 Biogas Purification Kristalopigi 816 Capital Cost Lehovo 263 Dieselization Nimfeo 9 Compression Total 46,482 Water Removal Case Studies It should be noted that the potential biogas production Geological presented in the tables above are the maximum that can Mechanical be derived on a daily basis. This would demand that the Electrological animals remain indoors and all wastes produced are Construction Cost collected and are anaerobically treated. Naturally, this is an ideal scenario, while conditions on the ground are Elctrological markedly different. Specifically, the practice among Biogas Storage Greek husbandry rears is to let their animals free on Biogas Depends on manure and summer pastures, which makes the collection of the Production calculating base on daily waste produced practically impossible. Thus, true biogas production potential would be considerably lower. Incomes Depends on selling products (electricity, Heat, Manure)
Operation Cost Digester Operation Cost 5 MAIN CHARACTERISTICS OF THE AD UNIT Maintainance cost The recommended type of anaerobic digester for the Cost of biogas purification region of West Macedonia is the complete mix digester. The main characteristics of the complete mix digester are Maintenance of the fire the stable temperature, the multiple types of solids in the protection system feedstock and the mechanical mixing system. Due to the above characteristics, these units may operate in multiple A micro turbine with an efficiency of 30% was studied as feedstocks, even with agricultural residues, leading to an the main system for electricity production and a system increase in the system potential. The calculation program of recovering the produced heat was also studied. The used in this study is referred to the design of the digester, main advantage of the above technology is the long the storage systems and the biogas purifications systems. lifetime and the low maintenance cost, compared to the More specifically, the parameters taken into account for high construction cost of a unit related to reciprocated the design and the capital and operation costs in the engines.An alternative technology that may be used in anaerobic digestion units are presented below: biogas applications for combined heat and electricity The calculation software used in this study was generation is the use of fuel cells. The fuel cell developed in the Laboratory of Fuels, Measurements and technology however, does have a prohibitively high Air Pollution Control in the Department of Pollution construction cost and for this reason it is not yet Control Technologies of the Technological Educational considered as a viable choice for an investment. Institute of West Macedonia (Greece) and was based on Nevertheless, it is believed to be the optimum technology published results that led to the determination of a viable for biogas usage in the medium and long term. volume of a digester for biogas production using animal Biogas is a low quality (i.e. low calorific or heating manure and usage of the produced electricity [1]. The value) gas with limited uses. It is typically used as a fuel critical size of a viable unit was taken into account for the source for local heat and electrical power generation. The case study of the AD unit in the region of West boilers and engine generator sets (“gen sets”) used to Macedonia and it is estimated to be 1,500 m3biogas/day. produce heat and/or electric power from biogas are specifically designed or modified to operate with biogas. For example, biogas typically has a heating value of around 550 – 600 BTUs whereas natural gas (a high quality gas) typically has a heating value of around 1,000 BTUs/cubic foot. This directly affects the amount of air that must be mixed with the fuel in order to combust the fuel efficiently. In practice, some “clean up” of the raw biogas may be performed prior to using raw biogas in biogas gen sets and boilers. This “clean up” typically
390 16th European Biomass Conference & Exhibition, 2-6 June 2008, Valencia, Spain
consists of removing enough of the hydrogen sulfide 6 RESULTS AND DISCUSSION (H2S), water vapor (H2O) and particulates from the biogas to prevent mechanical damage from occurring to 6.1 Economic effects of biogas plants the engine or burner jets provided appropriate When evaluating biogas plants from a macro economic maintenance schedules are followed. However biogas point of view there are several reasons why price may also be combusted directly (i.e. without prior “clean adjustments in favour of the biogas technology are up”) if minor necessary engine modifications are made required. and a more frequent oil change schedule is implemented. The production of biogas creates external economies. It Depending on the biomass feedstock and biogas means that the biogas production influences the utility production process, the H2S content of the raw biogas function of the consumer (i.e. better sanitary and hygienic may vary from 50 to 3000 ppm or higher. Pipeline gas conditions) and the social welfare function of the society and vehicle fuel standards require an H2S content of less (i.e. reduced health costs). Considering national wide than approximately 16 ppm. Some of the technologies effects on energy balance, the biogas supply creates used to reduce the H2S content to acceptable levels are: external economies on the balance of payments to the • In situ reduction of H2S within the digester economy (import substitution of fossil fuels). As well vessel by adding metal ions (e.g. iron chloride) external diseconomies then should be included, to form insoluble metal sulfides or creation of amounting to less income of import duties because of elementary sulfur through oxidation substitution of traded fuel (i.e. petroleum) by biogas. • Removal of H2S with metal oxides (e.g. iron Biogas use, replacing conventional fuels like kerosene or oxide and zinc oxide) and hydroxides (e.g. iron firewood, allows for the conservation of environment. It hydroxide) therefore, increases its own value by the value of i.e. • Oxidation with air forest saved or planted. • Adsorption of H2S on activated carbon The price of supplied energy produced by biogas In the present study, the technologies proposed for biogas competes with distorted prices on the national or regional purification were the technologies related to the use of level of the energy market. Monopolistic practices, which biological filters, with a significant lower cost compared enable energy suppliers to sell their energy at a price with the other old technologies. The anaerobic digestion higher than the competition price, still dominate the process is preferred because the treatment of animal energy market in many countries. A decentralized, manure results in environmental benefits but more economically self sufficient biogas unit therefore, under importantly, the farmers can earn additional income competitive conditions provides its energy without through the production of electricity and heat. market distortions. The main drawback in the above technology, if someone Furthermore, other macro economic benefits arise when would like to use the produced biogas for vehicles is the comparing on the one hand the benefits of decentralized storage systems. It’s low heating value and the low energy generation (improved power system security) and energy content raise the biogas storage difficulties. In the the disadvantages of centralized energy generation: table below the energy content of fossil fuels vs the incremental costs of investment in additional networks biogas fuel is presented. and the costs of losses on the transmission network, due to the distance of energy customers, may be added to the Table VIII: Energy Content of fuels benefits of decentralized energy generation from the macro economic point of view. Fuel Energy Content Labour intensive decentralized biogas units, on the Lignite 1,300,000 kcal/ton regional level, improve income distribution amongst Diesel 551,000 kcal / lt income brackets and reduce regional disparities, Petrol (Reg) 479,000 kcal / lt enhancing the attractiveness of rural life. Butane (L.P.) 415,000 kcal / lt Investors should aim at carrying out the construction of Propane (L.P.) 367,000 kcal / lt biogas plants without any imported materials in the long Ethanol (190ο) 319,500 kcal / lt run. The lower the import content of the total plant costs Electricity 3,602 kcal / kWh (i.e. amount of steel), the less the external diseconomies 3 which may arise in consequence of sliding exchange Natural Gas 30 kcal / Νm rates. Biogas 18 kcal / Νm3
6.2 The benefits for biogas users It can be concluded that the energy content of biogas as a Individual households judge the profitability of biogas fuel in standard conditions is much lower than the one of plants primarily from the monetary surplus gained from fossil fuels. As a result, using biogas in portable utilizing biogas and bio fertilizer in relation to the cost of applications requires fuel compression. The difference in the plants. The following effects, to be documented and the heating value will vary due to the pressure used in the provided with a monetary value, should be listed as application. Biogas storage in liquid form, such as benefits: propane and butane storage is not viable because of a expenditure saved by the substitution of other energy required pressure of 345 bar. Using pressure of a value of sources with biogas. If applicable, income from the sale 200 bar, biogas energy content approaches the value of of biogas; expenditure saved by the substitution of 3 4,643 Kcal/m . mineral fertilizers with bio fertilizer. Increased yield by using bio fertilizer. If applicable, income from the sale of bio fertilizer; savings in the cost of disposal and treatment of substrates (mainly for waste water treatment);
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time saved for collecting and preparing previously used • Lignite amount for 1kWh production: 10.9 kg fuel materials (if applicable),time saved for work in the lignite stable and for spreading manure (if this time can be used • Lignite savings per day: 1,834,895 kg to generate income). • Lignite savings per year: 669,736,711 kg • Fly ash savings in atmosphere :133,947 kg / 6.3 Environmental benefits year For many years the rational behind using biogas • Ground that can not be damaged : 4,018,420 technology (or anaerobic technology) was the search for ton / year renewable sources of energy. In the meantime, other • Upper amount on area : 30 – 300 hectars environmental protection aspects gain additional (depends on depth 10 – 100 meter) importance: A technology which previously just filled a "niche" is now becoming a key environmental technology for integrated, solid and liquid waste treatment concepts Especially for West Macedonia region the economic and climate protection both in industrialized and benefits of biogas utilization to savings due to electricity developing countries. Biogas technology is linked to the generation by biogas, fertilizer savings and rising atmospheric budgets of many greenhouse gases. Another productivity in agriculture are very important. Biogas major environmental target is the mitigation of technology not only supports national economies and the deforestation and soil erosion through the substitution of environmental protection, but as its main outcome for the firewood as an energy source. The macro economic local population it provides for a wide range of benefits from biogas use in this field should be improvements in overall living conditions. Moreover, the approached within the scope of the specific condition in environmental benefits due to substitution of energy the household energy sector and possible alternative sources based on wood (firewood, charcoal) or on fossil protection measures. energy sources are outstanding. To assess correctly the macro economic benefits of biogas production in small 6.4 West Macedonia case study size biogas plants is a difficult undertaking. Generally, The region of West Macedonia is the electricity very optimistic assumptions on positive effects on production centre of Greece, as over 75% of electricity is employment, balance of payments and health sector can being generated, from locally extracted lignite, in the cause overwhelming expectations on planning biogas area. The environmental problems associated with this based energy systems. Nevertheless, these external practice are various, the most important of which are the economies are substantially influenced by the quantity degradation of atmospheric quality (in particular the vast and (regional) density of biogas plants, contributing to the countries’ share of energy sources. Facing more and quantities of CO2 released) and the scarring of the landscape (through the shifting of millions of tonnes of more the challenging phenomena of global warming and soil every year). setting global standards of polluting potentials, On the other hand, the region has a considerable environmental external economies are getting steadily husbandry industry, employing approximately 3% of the very important issues and may stimulate a government to local population. Currently, the animal wastes produced start investing in appropriate energy technologies rather remain untreated and pose significant environmental risks than to follow the conventional way to solve the problem (especially through the contamination of ground and of generating energy in remote areas by rural surface water) and health hazards. In this study, it was electrification based on fossil fuels. though beneficial to estimate the environmental benefits that could be derived if these animal wastes were used to produce biogas derived electricity and to calculate the 7 CONCLUSIONS potential savings/benefits as compared to lignite derived electricity. The main findings are summarized below. Well functioning biogas systems can yield a whole range of benefits for their users, the society and the environment in general: (i) production of energy as heat • Biogas potential in W. Macedonia: 129,084 and electricity (ii) transformation of organic waste into m3/day high quality fertilizer (ii) improvement of hygienic • Biogas energy content: 600 Btu/scf ή 6.21 conditions through reduction of pathogens, worm eggs kWh/m3 and flies (iv) environmental advantages through • Biogas consumption for AD operation : 30% protection of soil, water, air and woody vegetation (v) • Biogas to electricity conversion : 30% micro economical benefits through energy and fertilizer • Lignite to electricity conversion : 30% substitution, additional income sources and increasing • Lignite extraction / land removal : 1 / 5 yields of animal husbandry and agriculture (v) macro • CO2 production / kWh : 1,350 g. CO2/ kWh economical benefits through decentralized energy • Price CO2 / ton: 22.93 (average price 2007) generation, import substitution and environmental • AHV Lignite : 1100 kJ/ kg ή 0.30556kWh/ kg protection • Fly ash content in lignite :20% Besides the willingness and ability to invest considerable • ESP performance: 99.9% funds in biogas technology, there is a complex process of • Biogas available for electricity production : decision making involved when moving from traditional 90,359 m3/day practices to a ‘modern’ way of producing fertilizer and • Electricity production: 168,339 kWh/day acquiring energy. Hopes and fears, expected reactions from the society, previous experiences with modern • CO2 profit /day : 218,841 kg/day technology, all these feature in a decision. For a biogas • CO2 profit /year: 79,876,965 kg/year ή 79,877 tonnes/year program, it is important to realize that economic considerations are only part of the deciding factors in • CO2 economic profit: 1,831,580 €
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favour or against biogas technology. All these factors can [16] An analysis of energy production costs from be subsumed under acceptance. Acceptance is not a anaerobic digestion systems on U.S. livestock production collection of irrational, economically unjustifiable pros facilities, United States, Department of agriculture, and cons that a biogas extension project is called upon to Natural resources conservation services, October 2007 dissolve. Rural households, as a rule, take rational [17] Biogas Digest, Volume I, Biogas Basics– decisions. But rural households and biogas programs Programme Implementation, Information and Advisor often have information deficits that lead to non Service on Appropriate Technology, ISAT acceptance of biogas technology by the target groups. [18] Biogas Digest, Volume II, Biogas Application and Bridging this information gap from the farmer to the Product Development Biogas Digest, Volume I, Biogas project and vice versa is a precondition for demonstrating Basics– Programme Implementation, Information and the economic viability in a way that is understandable, Advisor Service on Appropriate Technology, ISAT, relevant and acceptable to the farmer. Information and Advisor Service on Appropriate Technology, ISAT [19] Feasibility study on implementing anaerobic 8 REFERENCES digestion technology on Humboldt dairy farms, Schatz energy research center, June 2003 [1] A. Albanis, C. Economopoulos, M.A. Goula*, [20] California Energy Commission, www.energy.ca.gov ‘Economic viability of waste treatment units livestock farms for electricity and heat production’, Journal of Environmental Protection Ecology’, accepted for 9 ACKNOWLEGEMENTS publication. [2] C. G. Economopoulos, O.A. Bereketidou, M.A. The work has been financially supported by the Ministry Goula*, ‘Electricity production from biogas’, Protection of Development, General Secretariat for research and and Restoration of the Environment, 3rd – 7th July, 2006, technology, 3rd Community support framework, Chania, Crete, Greece Operational programme “Competitiveness” Creation of [3] I. Kostaki, O. Bereketidou, H. Latsios, M.A. Goula*, regional Innovation Poles, Regional Network of Western ‘Energy potential of the biogas produced by an urban Macedonia. waste landfill in Northern Greece’, 1st Conference on Environmental Management, Engineering, Planning and Economics (CEMEPE), 24 28 June 2007, Skiathos island, Greece [4] O. Bereketidou, N. Charisiou, M.A. Goula*, ‘Prospects for hydrogen and biogas production from biomass residues in Greece’, World Hydrogen Technologies Convention, Montecatini Terme, 4 7 November 2007, Italy [5] O. Bereketidou, M.A. Goula*, “Hydrogen and electricity production potentials from biomass in Greece’, 2nd International Hudrogen Energy Congress & Exhibition, 13 17 July 2007, Instabul Turkey [6] www.cres.gr [7] An Analysis of Energy Production Costs from Anaerobic Digestion Systems on U.S. Livestock Production Facilities, NRCS, 2007 [8] Biogas Digest, Volume III, Biogas – Cost and Benefits and Biogas – Programme Implementation, Information and Advisor Service on Appropriate Technology, ISAT [9] Biogas Plants, Ludwig Sasse, GTZ 1988 [10] Biogas Plants in Animal Husbandry, Nicolai Hees, GTZ 1989 [11] Estimating Water Usage on Michigan Dairy Farms (100 head), Dr. Craig V. Thomas, Michigan State University Extension [12] Methane Fuel Gas from Livestock Wastes, Prof. James C. Barker, Professor, North Carolina State University, Raleigh, NC, March 14, 2001 http://www.bae.ncsu.edu/programs/extension/publicat/wq wm/index3.html [13] Biomethane from dairy waste: A sourcebook for the production and use of renewable natural gas in California, July 2005 [14] California Biogas Industry Assessment, White paper, April 2005 [15] Dairy waste anaerobic digestion handbook, Option for the recovering beneficial products from dairy manure, Dennis A. Buke P.E., June 2001
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