THE METHANIZER

A Small Scale Biogas Reactor for a Restaurant

R. Vasudevan, O. Karlsson, K. Dhejne, P. Derewonko, J.C. Brezet

Delft University of Technology, Faculty of Industrial Design Engineering, Landbergstraat 15, 2628CE, Delft, The Netherlands, [email protected], +31 152782738.

Abstract The purpose of this study is to determine the technical and economic feasibility of a small- scale bioreactor called the Methanizer for a restaurant. The bioreactor converts organic waste produced by the restaurant into methane. This methane can be used to power the restaurant’s cooking stoves. The system proposed is a double-tank, batch-fed bioreactor. This product will help reduce the need for natural gas as well as cut down on landfill use. Results from the technical analysis showed that the product would take 6 m3 of space, but is capable of saving a natural gas equivalent of 735 m3/year and 1470 m3/year for a small and medium sized restaurant, respectively. Economic analysis showed that the product is not economically viable for a small-scale restaurants but increased gas prices, subsidies, payment plans and scaling up to larger restaurants would make the Methanizer marketable. Producing a marketable Methanizer is estimated to take around four years and would therefore be possible in 2013.

Keywords Bioreactor, Sustainability, Restaurant Industry, Food Waste, Biogas

1. Introduction It has become increasingly clear that the way that man interacts with the natural environment needs to change. Climate change caused by greenhouse gas emissions has become a major issue and the amount of waste being produced is causing a multitude of problems. All industries need to take a hard look at how they can change their activity to have a smaller impact on the environment. Restaurants are one such industry.

Knowledge Collaboration & Learning for Sustainable Innovation ERSCP-EMSU conference, Delft, The Netherlands, October 25-29, 2010 1 Restaurants use a significant amount of fuel to power gas stoves. This primary source of this fuel is natural gas, a fossil fuel. Restaurants also produce a large amount of organic waste, which is usually taken by the municipality to sit in landfills. These two factors cost restaurants money and impact the environment in different ways. The product described in this report called the Methanizer decomposes the waste and produces fuel that would be able to power a gas stove. If done correctly, the utilization of the Methanizer would save restaurants money as well as reduce their impact on the environment.

The following paper discusses the feasibility of producing the Methanizer for a restaurant. First, the technical concepts are explained. This is followed by some preliminary design decisions. Afterwards, energy and economic analyses are performed to really test the feasibility of this product. Finally, recommendations for implementation in the future are discussed.

2. Project Definition The research question asks if it feasible to implement a small-scale bioreactor for a restaurant? The concept being explored here is a bioreactor that will take a restaurant’s organic waste and produce methane, which can then be used to power a stove in the kitchen. This must be analyzed on a technical, energy and economic level. This would reduce a restaurant’s need for fossil fuels, reduce their waste processing cost, and burn up the methane that would become another greenhouse gas added to the atmosphere if the waste were to end up in a landfill.

3. Project Approach In order to determine whether or not the Methanizer is feasible, both technical and economic aspects must be investigated. Technical feasibility refers to whether or not the waste produced by a restaurant is sufficient to produce a significant amount of methane. The energy payback for the bio reactor is also taken into account in the technical feasibility. This means the energy used to run the Methanizer must be less than the energy that the Methanizer saves. The economic feasibility depends on the cost payback of the bio reactor system.

The data used in the technical and economic feasibility analyses were determined through literary research and interviewing restaurants and experts in bioreactors. The restaurant interviews produced figures for volume of biomass waste, natural gas usage, and monthly

The 14th European Roundtable on Sustainable Production and Consumption (ERSCP) The 6th Environmental Management for Sustainable Universities (EMSU) 2 gas cost for an average restaurant. The bioreactor research produced figures for capital cost, maintenance costs and schedule, and the food waste to methane production rate.

4. Background Research In this Section the theory behind the biogas production is described. First, biogas is explained. This is followed by an explanation of the reactor. After that, biogas functionality is explained both the generally and specifically for a restaurant.

4.1 What is Biogas? Biogas is considered as a renewable energy source that does not contribute to the greenhouse effect. The gas consists mainly of methane, CH4, and carbon dioxide, CO2, and resembles the commonly used fossil fuel, natural gas. Biogas can be used directly for heating or for electricity production in a generator. When it is burned with oxygen the exhaust gas contains of carbon dioxide and water. This carbon dioxide is the same that is absorbed by the material while it is still alive so biogas is “carbon neutral.” On the other hand, if the methane is not burned it can be released into the air where it acts as a much stronger greenhouse gas than carbon dioxide (R. Kleerebezem, personal communication, January 13, 2010).

4.2 The Biogas Process Biogas production is complicated since it includes many steps with different organisms and reactions. In this report, however, only the basic concept will be presented. It is a chemical process that occurs in anaerobic (oxygen free) surroundings. Inside a cow’s rumen, biogas is produced naturally, for example. Biogas is produced when microorganisms degrade organic material. The organic material can contain carbohydrates, fats and proteins that all breaks down to methane and carbon dioxide plus a remnant product. The remnants contain a lot of nutrients and can be used as fertilizers by farmers. The microorganisms that degrade the material exist naturally in the organic waste, so nothing needs to be added to the process (Carlsson & Uldal, 2009).

The schematic picture in Figure 1 shows the different steps that take place in a biogas reactor. Pretreatment is sometimes needed for the reactor to work properly. This can mean chopping the waste material or mixing it with water if it is too thick. The upgrading is a process where the methane content is increased to get a gas that is more similar to natural gas and therefore more easily can be used in an existing gas grid (Carlsson & Uldal, 2009).

Knowledge Collaboration & Learning for Sustainable Innovation ERSCP-EMSU conference, Delft, The Netherlands, October 25-29, 2010 3 There are a variety of possible substrates. For instance, pulp from sewage plants, manure from animals or food scraps from restaurants and households are all possible substrates. There are usually no problems in mixing different types of substrates. In fact, a mixture of substrates can increase methane production. Different substrates will have different energy content which gives the maximum biogas output (Carlsson & Uldal, 2009).

Figure 1: Basic Flowchart for a Biogas Reactor (Carlsson & Uldal, 2009)

4.3 The Chemical Process The schematic picture in Figure 2 shows the chemical process of biogas production. It can be divided into three main steps: hydrolysis of the raw material, fermentation and methane production. In each step, different microorganisms work together to degrade the organic material into smaller components, which results in biogas production. The microorganisms are diverse and prefer different environments. The temperature used in a biogas reactor is usually either the mesophilic temperature, around 37°C, or the thermophilic temperature, around 55°C. Since the biogas process does not produce heat, this has to be added to reach the desired temperatures (Carlsson & Uldal, 2009). However, heating to this value would require a significant amount of energy. Using a reactor at room temperature is slower, but would be appropriate for a reactor at a small scale (R. Kleerebezem, personal communication, January 13, 2010).

The 14th European Roundtable on Sustainable Production and Consumption (ERSCP) The 6th Environmental Management for Sustainable Universities (EMSU) 4 Figure 2: Schematic Picture of the Chemical Process in a Biogas Reactor (Carlsson & Uldal, 2009)

4.4 Biogas from Restaurant Waste Food waste is a good substrate for biogas production with high methane exchange. However, food waste creates an imbalance in the degrading process that lowers the pH-value in the reactor. This is caused by a fast degrading process in which fat acids are produced rapidly and are not consumed quickly by methanogens. Low ph-values can have a toxic affect on the methanogens, and the methane production can be stopped (GTZ & ISAT, n.d.).

Food waste also needs some preparation to optimize the production. It is important to have good separation of all the non-organic materials that cannot decompose, such as plastics and metals. Otherwise the remnant product cannot be used as a fertilizer. The food also would need to be chopped and maybe some water needs to be added due to its high percentage of dry substance.

With optimal conditions the biogas from restaurant waste has a methane level of 63%, if it is digested in a batch process. The methane exchange is 0.441 Nm3/kg TS, where TS is the

Knowledge Collaboration & Learning for Sustainable Innovation ERSCP-EMSU conference, Delft, The Netherlands, October 25-29, 2010 5 dry substance of the food and is 27% for restaurant waste. This gives a biogas production of 0.119 Nm3/kg waste, which can be used directly to power stoves. The energy content of the waste then becomes 1.17 kWh/kg (Carlsson & Uldal, 2009).

As Figure 3 shows, food waste digests in about 20 days when almost all the methane is extracted, but this is for digestion of batch type and not continuous feeding. Continuous feeding would prolong the process a bit. A good approximation would be 30-35 days in a smaller reactor (J. Johansson, personal communication, January 11, 2010).

Figure 3: Methane exchange for Various Substrates (Carlsson & Uldal, 2009)

4.5 Potential Small restaurants in Delft produce around 20kg of organic waste per day. These restaurants are running on two to three gas stoves (Resturant worker, personal communication, January 6, 2010). Approximately 1500 tons of organic waste is produced in a medium sized restaurant in Stockholm, Sweden (Stockholms stad, 2007). This is around 41 kg per day on average.

4.6 The Reactor Even though the chemical process to produce biogas is complicated, the concept of the reactor is very simple. All that is needed is an oxygen free container with some organic material for the process to start. The microorganisms that degrade the organic material are

The 14th European Roundtable on Sustainable Production and Consumption (ERSCP) The 6th Environmental Management for Sustainable Universities (EMSU) 6 already in the waste and will start working when the anaerobic conditions occur. The biogas that is produced has lower density than the other material within the reactor and will therefore be found at the top, where it can be collected through a valve in the lid.

5. Reactor Design There are several design parameters that need to be considered when designing a bioreactor for a restaurant. The main parameters include process optimization, cost, usage, safety and the feeding method used.

5.1 Process Optimization The optimization of the degrading process and the methane exchange on a microbial scale will not be dealt with in this report but the major system design choices associated with the degradation will be taken into account, such as temperature and the acidity of the substrate. There are two optimal temperatures for biogas production, which are the mesophil (37°C) and the thermophil (55°C) temperatures. In both these cases, the reactor would need additional heating from an outside source. Large scale bioreactors are most often heated to the mesophil temperature, and on the smaller restaurant scale, a non-heating solution can be considered. The degrading process is still active at a temperature range of 20-25°C. However, the biogas production decreases with decreasing temperature. Using good insulation and by starting up the process with hot water, the process can be improved without a heating system.

A digesting process is also sensitive to the acidity of the substrate. The system’s acidity level can be controlled in different ways depending on the system design methodology chosen. This design parameter will be discussed further in Section 5.6.

5.2 Cost In order for wide-scale implementation of the Methanizer to be realized, the cost of the product and pay-back period must be found through a comprehensive economic feasibility study. The cost analysis for the recommended design can be found in Section 6.2.

5.3 Usage This product will be used by restaurant personnel, who are assumed to have no technical knowledge of the processes occurring within the bioreactor. Therefore, the bioreactor should be user friendly and complicated manuals and technical specifications should be avoided. Ideally, the product will be highly automated to reduce the level of interaction between the

Knowledge Collaboration & Learning for Sustainable Innovation ERSCP-EMSU conference, Delft, The Netherlands, October 25-29, 2010 7 non-technical restaurant personnel and the bioreactor. This means the worker’s interaction with the product will be limited to loading and unloading the organic material. Additionally, the restaurant will need to apply an efficient sorting system to separate organic matter from other wastes.

5.4 Safety Methane is an explosive gas when it is mixed with air, which makes the safety requirements extensive for a reactor used in a restaurant filled with people. Bioreactor vessels are often made from either glass or stainless steel. Due to the explosive nature of methane, the more expensive stainless steel option must be used. Also, another safety advantage is that stainless steel tanks have a higher pressure threshold within the vessel, thereby reducing the chance of a tank rupture occurring. There are also health requirements for restaurants and handling food waste must be done in a sanitary manner. There are further requirements that must be considered if the remnant organic material will be used as a fertilizer. The fertilizer needs to go through a sanitation process before it can be used. This means heating the remnant to about 70°C for at least one hour (Carlsson & Uldal, 2009).

5.5 Feeding Methods The feeding method options are: batch reactor, continuously-fed reactor and batch-fed reactor, and their advantages and disadvantages are explained below.

5.5.1 Batch-Reactor The batch-reactor feeding method involves filling the tank with waste and allowing it to degrade for the specified retention time, which is roughly 20 days for restaurant waste. After the retention time the tank is emptied, cleaned and filled again with new waste. This type of reactor has a simplistic design, but there are many disadvantages associated with it. The tank must be frequently emptied and cleaned, increasing the labor workload for the restaurant personnel. With this feeding method, restaurant waste accumulates while the previous batch is degrading within the bioreactor. This means an additional tank is required to store the accumulating waste before it is inserted into the bioreactor. The storage tank has two potential problems, the first is the odor of the organic material and the second is the loss of biogas from the degradation within the storage tank. The biogas production within the storage tank should be minimal because the organic waste will be degrading in an aerobic environment.

The 14th European Roundtable on Sustainable Production and Consumption (ERSCP) The 6th Environmental Management for Sustainable Universities (EMSU) 8 5.5.2 Continuously-Fed Reactor A continuously-fed reactor pumps waste into the tank in specified time intervals and amounts. At the same rate remnant organic material is removed from the tank. Even if the waste is chopped and mixed with water, pumping this sludge would be very energy intensive and pipe problems would arise throughout the lifetime of the product. This is the most sophisticated feeding method, but a restaurant application is too small-scale for this to be economically feasible.

5.5.3 Batch-Fed Reactor A batch-fed reactor significantly reduces labor for the restaurant personnel. The concept is that you put the organic waste into the reactor on a daily basis. The tank must be sized appropriately to be capable of holding a certain amount of material for a specified length of time. For this restaurant application, the time frame should be between 6 months and a year’s worth of waste in order to reduce the number of times per year the tank must be emptied and cleaned.

The size of the tank can still be designed to be relatively small because the organic material’s volume reduction after digestion is up to 70% (R. Kleerebezem, personal communication, January 13, 2010). Therefore, the first time the tank is loaded, the majority of the tank will be empty and the waste will begin to degrade. Subsequent loads are added daily and the tank begins to fill up because there is more organic waste, but simultaneously there is also a reduction of material in the reactor because of the digestion process. The net effect is a slow increase in material within the tank, which results in a full tank at the end of the designed period (between 6 months and a year). The major drawback of this feeding method is that the tank must remain air tight during loading. A smart technical solution to this problem is needed, and the solution must be easily implemented by the restaurant personnel.

The batch-fed reactor design was chosen for this bioreactor restaurant application. The batch reactor feeding method was found to involve too much restaurant personnel labor because the bioreactor must be emptied and cleaned on a daily basis. The continuously-fed reactor feeding method is effective for large-scale biogas production, but is too expensive for a restaurant application. The batch-fed reactor is a good compromise because it must be loaded daily, but only emptied once or twice yearly, thereby drastically reducing the workload for the restaurant personnel. An added benefit is that when a new batch is loaded into the bioreactor, there already exists a large microbe culture within the tank. Therefore, the digestion process begins faster than for a simple batch reactor.

Knowledge Collaboration & Learning for Sustainable Innovation ERSCP-EMSU conference, Delft, The Netherlands, October 25-29, 2010 9 5.6 Design Options 5.6.1 One Tank Design The one tank system, shown in Figure 4, is the simplest bioreactor design that includes one stainless steel air tight pressure tank, an opening for unloading the remnant organic waste and loading new organic waste, and an outlet for biogas extraction. The system is odorless during operation because the tank is air-tight, which is an advantage. Also, it is assumed that an innovative design can be conceived so that the tank remains air-tight during the loading sequence. Therefore, if the air-tight loading is found to be possible, then the restaurant will never experience the digesting organic waste smell. Also, this is the optimal design for space utilization.

Figure 4: Single Tank Reactor Design (Hoetmer, 2008)

A problem with the one tank design is when food waste digests, it causes production of volatile fat acids which makes the pH-value drop. Biogas production can stop if the pH-value falls below 6.2. The solution to this is to add more methanogens that consume fat acids. A healthy ratio of methanogenesis and fat acids production keep the pH-value constant.

5.6.1 One Tank Design The two tank design, shown in Figure 5, consists of one tank for the organic waste, another tank for sludge, a pump and piping connecting the two tanks. The organic waste is located in an aerobic tank where the first half of the chemical process is carried out. In this tank, the organic material is converted into fat acids and alcohols, as shown in Figure 5. Occasionally, water is sprinkled over the organic waste to extract the fat acids and the water mixture is collected beneath a sieve at the bottom of the tank. This water and fat acid mixture is called sludge. Using a pump, the sludge is injected into the second tank, which is under anaerobic

The 14th European Roundtable on Sustainable Production and Consumption (ERSCP) The 6th Environmental Management for Sustainable Universities (EMSU) 10 conditions, where the second half of the chemical process will occur, anaerobic oxidation and methane production.

Figure 5: Two Tank Reactor Design (Hoetmer, 2008)

The one tank design suffers from poor pH control within the system. This major drawback is avoided in the two tank design. The chemical process is split into two phases, the first tank produces fat acids and the second tank produces methane. The pH level is important for the methane production step. Therefore, the pH level in the methane production tank can be controlled by increasing or decreasing how much fresh sludge is pumped into the second tank. If the second tank’s pH value is too high, then no new sludge will be pumped into the tank, thereby naturally decreasing the pH level. Alternatively, if the pH value is too low, then more sludge can be pumped to increase the pH level towards the healthy value of around 7 for methane production (R. Kleerebezem, personal communication, January 13, 2010). This pH control system is simpler, more effective and less expensive than using methanogens to consume fat acids.

Another problem with the one tank design is keeping the tank air-tight during the loading sequence. The two tank design avoids this problem because the first tank is under aerobic conditions, therefore new organic material can be added using a simple hatch opening. The drawback to this design is that the digesting organic matter will create strong odors that will be released into the restaurant. This effect can be minimized by locating the bioreactor in a well-ventilated area, which may not always be available depending on the restaurant. It is also important to create a good seal for the hatch opening, so that the odor is retained within the tank during operation.

Other disadvantages include larger space usage, and increased maintenance and installation costs. The larger space utilization translates into an economical loss because the

Knowledge Collaboration & Learning for Sustainable Innovation ERSCP-EMSU conference, Delft, The Netherlands, October 25-29, 2010 11 restaurant may not be able to sit as many customers due to the loss of floor space. Installation and maintenance costs will also increase because there are more components that must be installed and a larger chance for break-downs to occur.

5.7 Recommended Design The recommended design is a batch-fed double tank bioreactor, without additional heating. These design parameters were chosen to minimize restaurant personnel labor, obtain better pH control, and avoid loading issues. Also, using a two tank approach is expected to have lower capital costs than the one tank approach.

The first tank does not have any specific requirements. It can be made of plastic or another cheap material. Good insulation should be used to keep the temperature of the tank as high as possible. The tank size can be approximated from the remnant material left after the retention time and the emptying frequency. One year’s waste of 15 tons would leave about 4 tons of dry substance (Carlsson & Uldal, 2009) that would further be reduced 70% to about 2.8 tons after the digestion (R. Kleerebezem, personal communication, January 13, 2010). The tank size is accordingly approximated to be about 3-4 m3 if the remnant is cleaned out every year and half the size if it is cleaned out every six month. The second tank has more requirements to meet because it must be air tight and must be capable of withstanding the pressure created from the methane production inside the tank. Therefore, the methane production tank should be made from pressure vessel grade stainless steel. This tank size is about four times smaller than the first tank (Hoetmer, 2008). The stainless steel pressure vessel represents the largest capital cost investment, and since the two tank design’s methane production tank is four times smaller than the one tank designs, the capital cost of the system is drastically reduced.

One additional aspect of the design is the organic waste pre-treatment. Before the waste can be inserted into the first tank, it must be chopped into smaller particles to promote better digestion conditions. There are commercially available garbage disposals that can perform this chopping pre-treatment at a low cost. The only concern is whether this pre-treatment step will use a significant amount of energy which can negatively affect the technical feasibility of the product. The chopper’s energy analysis is performed in Section 6.1.1.

6. Analysis The following chapter of this study shows the analysis behind determining the Methanizer’s feasibility. This is done in two Sections. First, the analysis on how much energy the

The 14th European Roundtable on Sustainable Production and Consumption (ERSCP) The 6th Environmental Management for Sustainable Universities (EMSU) 12 Methanizer saves a restaurant each year is calculated. Secondly, the economic analysis shows how long it will take a restaurant to start saving money with this product.

6.1 Energy Analysis The first stage of analysis focuses on how much energy is produced by the Methanizer as compared to how much energy is consumed by it. All calculations assume that a restaurant is operating for 350 days in one year and that the restaurant is open for around 12 hours each day.

6.1.1 Energy Consumption There are two major contributors to energy consumption in the design of the Methanizer. They are the chopper, which is used to process the organic waste before entering the system, and the pump, which is used to move the water holding the fatty acids to the second tank in the system.

The chopper will use the same amount of power as an industrial strength garbage disposal. This is around 746 watts (KitchenAid, 2010). This chopper will need to run for around one hour per day to process the 20kg of waste that a small restaurant produces. Therefore, for each day, the chopper consumes 0.746 kWh and for 350 days of operation this means 261 kWh per year.

The pump that is necessary for operation takes around 58 watts (Water Pumps Direct, 2010). The pump is necessary to transport water from the primary tank to the secondary tank. This operation does not need to be continuous throughout the day. It, in fact, should not be because time is needed for the fatty acids to be converted into methane in the second tank. For the amount needed to be pumped and the volumetric flow rate in the pump used, only 3 minutes of a 58 watt pump needs to be used per day. This may be increased with a lower power pump, but all in all about 2.90 watt hours per day are needed or around 1.02 kWh per year.

This means that for a small scale restaurant, 262 kWh per year are necessary to run this system. For a medium sized restaurant this can be doubled to 524 kWh per year.

6.1.2 Energy Savings Energy savings as calculated here represent how much natural gas is saved per year. Obviously this device does not increase the efficiency of stoves, but it does reduce the need

Knowledge Collaboration & Learning for Sustainable Innovation ERSCP-EMSU conference, Delft, The Netherlands, October 25-29, 2010 13 to consume fossil fuels. Therefore, “Energy Savings” really means how much Natural Gas does one save by using the Methanizer. From interviews with various restaurants in Delft it was found that small restaurants produce about 20kg of organic waste (Resturant worker, personal communication, January 6, 2010). In medium sized restaurants usually produce twice that (Stockholms stad, 2007). The energy content of restaurant biomass is about 1.17 kWh per kg, so that means that in one day a restaurant would save around 23.4 kWh of energy if all of that was converted to biomass (Carlsson & Uldal, 2009).

It may be more useful to view this in terms of amount of natural gas saved per day. Natural gas has an energy content of 11.1 kWh per m3 so with savings of 23.4kWh per day, there are 2.1 m3 of natural gas saved each day as well. Table 1 shows the summary of the energy savings of the Methanizer for small and medium scaled restaurants. As expected, the larger the restaurant the more energy they save since both the costs and savings scale linearly. The more organic mass is produced, the more energy savings there are.

Table 1: Energy Analysis Small Restaurant Medium Restaurant Energy Content of Organic Biomass 8.2 MWh/year 16.3 MWh/year Energy Required to Run Reactor 0.3 MWh/year 0.5 MWh/year Net Energy Savings 7.9 MWh/year 15.8 MWh/year Net Gas Equivalent 735 m3/year 1470 m3/year 6.2 Economic Analysis In determining viability of the Methanizer it is important to analyze the economic aspects of it. First the costs of the system need to be estimated. These costs then need to be compared to the savings associated with the Methanizer.

6.2.1 System Costs There are two main costs associated with the Methanizer. These are capital costs, or one- time costs, and costs over time. In order to determine the capital costs, all the components have to be analyzed. These are mainly the two tanks, the chopper, the piping and the pump. Estimates on these materials were made using various sources. They can be found in Table 2. These values were taken at cost for one unit each. These costs may be dramatically reduced if these units were bought in bulk or made by a company that produces the Methanizer. It is worth noting that piping and installation costs were estimated without real sources because those numbers are difficult or impossible to find. The estimates are quite

The 14th European Roundtable on Sustainable Production and Consumption (ERSCP) The 6th Environmental Management for Sustainable Universities (EMSU) 14 high and this may reduce the overall capital costs. Finally it should be seen in Table 2 that the only difference between the capital cost of a bigger restaurant is in the airtight secondary tank. All of the other components are acceptable for both sizes of restaurant.

Table 2: Capital Costs of Methanizer (Hanson, n.d.) (Water Pumps Direct, 2010) (KitchenAid, 2010) Component Price for Small Price for Medium Restaurant Restaurant Primary Tank (Plastic Bucket) €500 €500 Secondary Tank (Airtight Vessel) €3134 €4441 Pump €72 €72 Chopper €350 €350 Piping €1000 €1000 Installation €5000 €5000 Total Capital Costs €10056 €11363 6.2.2 Continuous Costs To perform a proper economic analysis, the continuous costs also have to be considered. These are costs that must be paid on a yearly basis in order to keep the Methanizer running. There are two main contributors to continuous costs. These are maintenance and electricity. Maintenance costs of reactors such as these can be approximated to around 5% of all capital costs except for installation (J. Hoogen, personal communication, January 14, 2010). This includes the costs of emptying the tank on a yearly or bi-yearly basis and repairing components that may break with continuous use. The Methanizer requires electricity to power the pump and the chopper. In order to calculate these values energy usage of these devices is given. The current price of electricity is assumed, but it should be noted that the price of electricity will steadily increase over time so these costs may be less than the actual costs. All continuous costs can be found in Table 3.

Table 3: Continuous Costs (J. Hoogen, personal communication, January 14, 2010) (KitchenAid, 2010) (Water Pumps Direct, 2010) (Europe's Energy Portal, 2010)

Small Restaurant Medium Restaurant

Maintanence Costs €252.80/year €318.15/year

Chopper Energy Consumption 261.10 kWh/year 522.2 kWh/year

Pump Energy Consumption 1.015 kWh/year 2.03 kWh/year

Electricity Cost (0.237€/kWh) €62.12/year €124.24/year

Total Continuous Costs €314.92/year €442.39/year

Knowledge Collaboration & Learning for Sustainable Innovation ERSCP-EMSU conference, Delft, The Netherlands, October 25-29, 2010 15 6.2.3 Economic Savings due to Energy Now that costs have been analyzed, they can be compared to the savings that are involved with a restaurant using the Methanizer. Since restaurants are already producing food waste they are now saving money on energy. In Section 7.1.2 the net energy savings for small and large restaurants were calculated to be 735 m3/year and 1470 m3/year respectively. Currently, the Netherlands has one of the highest gas costs of any country in the world, see Figure 6. So for a small sized restaurant the economic savings from gas consumption would be 383.75 €/year and for a medium sized restaurant it would be 767.19 €/year.

Figure 6: Gas Costs in Various Countries (CBS, 2007)

6.2.4 Economic Savings due to Waste Processing Another source of significant economic savings comes from waste processing. Restaurants in the Netherlands have to spend €1.66 to dispose of a garbage bag (Resturant worker, personal communication, January 6, 2010). However, using the Methanizer they would be putting all organic waste to use so they would be able to circumvent this cost. The Methanizer, itself, does produce waste, however, this waste is ideal for fertilizers and could be collected by the municipality to use in farms or public gardens.

A small restaurant produces one full bag of organic trash per day whereas a medium sized restaurant produces two. Again assuming that a restaurant is operating for 350 days in a year, a small restaurant would save 581€/year and a medium sized restaurant would save

The 14th European Roundtable on Sustainable Production and Consumption (ERSCP) The 6th Environmental Management for Sustainable Universities (EMSU) 16 1162€/year. It is important to note that because of current economic environments, the savings due to waste processing are more significant than those due to energy savings.

6.2.5 Economic Conclusions Using all of this data the following plots can be made for the overall economic impact of owning a Methanizer.

Figure 7: Economic Plot for a Small Restaurant

Figure 8: Economic Plot for a Medium Restaurant

Knowledge Collaboration & Learning for Sustainable Innovation ERSCP-EMSU conference, Delft, The Netherlands, October 25-29, 2010 17 The intersection of costs and savings in Figure 7 and Figure 8 show at what point will the Methanizer start paying for itself. These numbers are not very optimistic. For a small restaurant this “payback point” is 15.5 years and for a medium restaurant this would be 7.7 years. It is very unlikely that a restaurant would invest in such a device if these estimates were all that they were given.

This does not mean that the Methanizer is not a viable product. In the limited time given to write this report, only this simple economic analysis was feasible. However, there are many factors that were not considered when putting together these figures. Firstly, subsidies were not included. Many governments, including the Netherlands, subsidize individuals and companies who use sustainable energy, so it would follow that they should also provide subsidies for other products that would cut down fossil fuel use such as the Methanizer. Currently there are no such subsidies so it would be very difficult to model here. Also, this model kept gas and electricity costs constant. With fossil fuels becoming sparser, gas and electricity costs would skyrocket and since the energy savings far outweigh the electricity demand of the Methanizer, this would also raise profitability. Finally, scale was not totally factored. In this report only small and medium restaurants were observed because that is all that was accessible in Delft during this short assignment time. However, larger restaurants and perhaps groups of restaurants that are close together would likely be a much better model for implementation of a Methanizer. More information about this is available in the following chapter.

7. Implementation The implementation of the Methanizer can be split into two critical areas, the technical feasibility and the economic feasibility.

7.1 Technical Implementation The technical feasibility is related to the Methanizer’s integration into an existing restaurant. The most important issues are the size of the Methanizer system, whether it is realistic to install it within a restaurant and the product’s integration with the existing gas line. In Section 5.6, the volume of the fat acid production tank was found to be 3-4 m3. The volume of the methane production tank is four times smaller than the fat acid production tank, meaning it will be around 0.75-1 m3. The additional components such as the pump, chopper and piping system can be given a total conservative volume of 1 m3, which gives the total system a maximum volume of 6 m3. This system cannot be placed outdoors because the bioreactor design temperature should be between 20-25°C (R. Kleerebezem, personal communication,

The 14th European Roundtable on Sustainable Production and Consumption (ERSCP) The 6th Environmental Management for Sustainable Universities (EMSU) 18 January 13, 2010). Therefore, it must be located inside the restaurant and will use space that would otherwise be used for food storage or seating for customers. The placement of the reactor within the restaurant depends specifically on the restaurant’s floor plan set-up, but ideally, the bioreactor would be placed inside a small storage room with good ventilation. The 6 m3 Methanizer volume is a realistic value that can reasonably fit somewhere within most restaurants.

The Methanizer will not be able to supply enough biogas to take a restaurant off the natural gas grid. The stoves will utilize the biogas produced from the Methanizer first, and once the supply runs out then the stoves can be disconnected from the Methanizer and switched over to use natural gas by using a simple valve.

7.2 Economic Implementation To reduce the ownership risk, restaurants are given the option to sell the product back to the company under certain extreme circumstances, such as a change in restaurant location or bankruptcy. This buy-out option will make the Methanizer more appealing to restaurant owners as it reduces the risk of investment.

In Section 6.2.5, it was determined that the economic feasibility of the Methanizer increases with increasing restaurant size. The possibility of improving the economic feasibility for small restaurants is also available if multiple small restaurants agree to buy the Methanizer as a joint venture. This economic strategy works effectively if the restaurants are located beside one another.

Many markets for the Methanizer exist, including small to large restaurants and joint ventures between restaurants. There is also a possibility to expand the market to include apartment buildings, hotels and even single homes. These expanded markets have the drawback that you rely on many individuals to sort the organic matter from the other waste. Also, the Methanizer system would need to be scaled up or down depending on the market. For example, a single home will need a smaller bioreactor than a small restaurant.

The future is promising the Methanizer because it addresses today’s key environmental issues while providing economic benefits for the owners. Also, natural gas prices and the price to dispose of waste will increase over time, which increases the Methanizer’s economic feasibility and will lead to more wide-spread adoption.

Knowledge Collaboration & Learning for Sustainable Innovation ERSCP-EMSU conference, Delft, The Netherlands, October 25-29, 2010 19 7.3 Product Roadmap The Methanizer’s product roadmap is shown in Figure 9. This is a preliminary product roadmap that gives a rough time estimate of how long it will take to bring the Methanizer onto the market. The roadmap begins with engineering and building a pilot plant to test the performance of the Methanizer. This process is estimated to take a year to complete and can be broken down even further into more specific tasks such as design finalization, procurement of materials, and construction. After the pilot plant is built in 2011, the product performance testing process will commence to determine the specifications of the system, such as biogas production rate, ease of loading, severity of the odor and pH controllability. The testing is scheduled to occur for a full year, and is followed by a re-design and optimization phase. These two phases can include significant overlap because the re-design can begin as soon as the preliminary test results are found. The re-design will resolve the problems found during testing and optimize the system to reduce costs and improve performance. If the Methanizer successfully progresses through this product roadmap, it will be ready to be sold on the market by 2013.

Figure 9: The Methanizer's Product Roadmap

8. Evaluation of Results and Approach This report discussed the feasibility of producing a methane bioreactor called the Methanizer for a small to medium scale restaurant. The reactor will take organic waste as an input and use microbes to produce methane which will be used to fuel a stove. The approach used to determine feasibility was to utilize a combination of interviews with experts, literary research and analysis to produce technical and economic specifications for the Methanizer. This approach was extensive and provided the proper information to perform this feasibility study.

The 14th European Roundtable on Sustainable Production and Consumption (ERSCP) The 6th Environmental Management for Sustainable Universities (EMSU) 20 It was found that it would be technically feasible to produce such a reactor. Two important design decisions were made. First, a double tank system was chosen to cut costs because a smaller airtight tank can be used in combination with a large cheap tank. It also allows for easier loading. The second design decision was to make the reactor a batch-fed system. This means that organic waste can be added on a daily basis and then cleaned out on a bi- yearly or yearly basis. This works well with the two-tank system described and would be the simplest for restaurant workers to use.

Energy and economic analyses were also performed on this design. In terms of energy analysis it was shown that a small scale restaurant would save 735 m3/year of natural gas and a medium scale restaurant would save 1470 m3/year using the Methanizer. The economic analysis was not so optimistic. Taking capital and operating costs into account it would take a small scale restaurant 15.5 years to break even and a medium scale restaurant 7.7 years to break even. This coupled with an initial investment cost of around €10000 to €12000 does not make the Methanizer seem like a very viable product. However, there were many factors such as increasing gas prices and subsidies that were not able to be taken into account due to time constraints. Concerning system volume, the Methanizer was found to take around 6 m3 of space and is thus more suited for medium to large scale restaurants, which also agrees with the conclusions made in the economic analysis.

In terms of economic implementation, an investment plan for the restaurants can be used where they are able to sell the product back to the manufacturer if they encounter bankruptcy problems. This makes purchasing the Methanizer a much less riskier investment. There are also other markets that could be tapped once the Methanizer technology is optimized. This would likely occur after the completion of the product roadmap, which predicts that if a company began serious work on producing the Methanizer, it would be marketable by 2013.

Knowledge Collaboration & Learning for Sustainable Innovation ERSCP-EMSU conference, Delft, The Netherlands, October 25-29, 2010 21 References Carlsson, M., & Uldal, M. (2009). Substrathandbok för biogasproduktion. Malmö: Svenskt gastekniskt center.

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