Research and Development Cluster Unit of Waste Utilization and Management Laboratory King Mongkut s University of Technology Thonburi (KMUTT)

Transcription

1 Thai Biogas Plants-High Rate Anaerobic Fixed Film Technology for Agroindustrial Wastewater Submitted to The Award Contest of Best Program on New and Renewable Sources of Energy (Off-Grid) in Year 2003 By Research and Development Cluster Unit of Waste Utilization and Management Laboratory King Mongkut s University of Technology Thonburi (KMUTT) Research Team Asst. Prof. Dr. Pawinee Chaiprasert Dr. Annop Nopharatana Tanong Chayawattana Chinnapong Wangnai Warin Rukruem Pratin Kullavanijaya Assoc. Prof. Dr. Sakarindr Bhumiratana Prof. Dr. Morakot Tanticharoen

2 Thai Biogas Plants-High Rate Anaerobic Fixed Film Technology for Agroindustrial Wastewater 1. Originality Countrywide, agroprocessing industries remain one of the most significant industrial generators of water pollution and consumers of fossil fuel energy. Most of agroindustries generate wastewater containing organic matter and emit carbon dioxide from fuel combustion, which would cause the environmental problem. As the national and global environmental issue has become a crucial concern to communities, especially on water pollution and global warming & climate change, energy and environment have also become an integrated issue to deal with. Air and water pollution, stemming from industrial sources and pollution centers, remains priority issue of energy and environment for Thailand s policy making and enforcing agencies. The Eight and Ninth National Economic and Social Development Plan of Thailand ( and ) placed major emphasis on energy conservation and controlling the environment. The issues are especially on greenhouse gases emission and water pollution because of its impact to the world, communities, climate, agriculture, portable water supplies, the ecology of aquatic life that are crucial sources of food, etc. R & D group at King Mongkut s University of Technology Thonburi (KMUTT) is constantly on the lookout for technologies that will allow for more efficient and cost effective waste treatment. One technology that can successfully treat organic fraction of wastewater is biogas technology (anaerobic digestion). The biogas technology can treat wastewater and produce biogas as renewable energy. 1.1 Design The research activities on biogas technology have been supported initially by the National Center for Genetic Engineering and Biotechnology (BIOTEC) and Australia under the ASEAN-Australia Economic Cooperation Program (AAECP). Active cooperation has enabled KMUTT to develop its capacity in biogas technology from research level to the design and operation of industrial biogas pilot plant using anaerobic fixed film reactor. In addition, the biogas technology for agroindustrial application has been promoted through the pilot plant demonstration and several training workshops in country and region. The lessons learned from these experiences have led KMUTT to establishment of the industrial biogas plant for treatment and biogas production from agroindustrial wastewater. The industrial fixed film biogas plant was designed and constructed by KMUTT, partially subsidized by Energy Policy and Planning Office (EPPO). The project has been start-up and implemented by KMUTT for one year and taken over to the industrial factory. The Biogas Technology Research Group (BTRG) at KMUTT has been conducting research on anaerobic digestion technology for over 10 years. The BTRG applied an anaerobic fixed film technology at industrial scale for several agroindustries. When used in a fully engineered system, the biogas technology not only provides pollution prevention, but also allows for energy, liquid fertilizer and nutrient recovery. Thus, the biogas technology can convert a disposal problem into a profit center. As the technology continues to mature, the biogas technology is becoming a key method for both wastewater reduction and recovery of a renewable fuel and other valuable co-products. Biogas

3 projects have implications not only in the agroprocessing industrial sector, but in the agricultural and energy sectors as well, and among the environmental consequences, mitigation of pollution, greenhouse gas (GHG) emission reduction and reduced eutrophication of water etc. are important external effects. This technology for energy conservation seems to be the most effective method to mitigate air pollution, greenhouse gases and water pollution. Anaerobic treatment has been widely practiced to treat strong organic wastewater. In Thailand, a system of anaerobic open ponds is the most popular treatment, since it can offer the lowest treatment cost as well as simplicity in design and operation (figure 1). However, it has several drawbacks such as extremely low treatment efficiency, and there can be a problem of odors. A long retention time is required for treatment using anaerobic ponds, hence a series of several ponds is commonly needed and required a reasonably large land area. Moreover, the generation of methane from these open ponds will be emitted to atmosphere. Nowadays, the crisis of oil price including low environmentally sound and very high land price makes the anaerobic open pond system unattractive. Modern anaerobic digestion can provide very reasonable means of wastewater treatment and will further make available a strongly needed renewable energy source like biogas. It provides benefits to the environment through energy and nutrient recycling, while also mitigation of odors and atmospheric methane. A new innovative biogas technology, anaerobic fixed film (AFF) reactor, can be applied to replace the conventional biogas by advanced high rate anaerobic reactor (HRAR), produced by systematic engineering design. The new type of reactors can handle large quantities of wastes per unit volume and produce biogas at much faster rate. Consequently, both the capital investment cost and operating cost of the process are lowered resulting in a more economic system. 1.2 Application The types of anaerobic reactors commonly used in industrial applications include conventional reactors and high rate anaerobic reactors (upflow anaerobic sludge blanket, anaerobic fixed bed, etc.). The advantages of these technologies compared to aerobic processes include low sludge production, high loading rates, low nutrient requirements, low maintenance, and, of course, the production of biogas. The AFF reactor has proved in laboratory and pilot scales by KMUTT s research team to be a good system for treatment and to produce energy from agroindustrial wastewater that normally contain high strength of organic substances and suspended solids (SS), such as from starch factories. After six years of testing in laboratory and two years in pilot scale (figure 2), there were no clogging and less sludge washout problems resulting to high efficiency in wastewater treatment and biogas production. These studies were also demonstrated the technical feasibility of the system and provide to gain more experience on engineering design and operation. The high strength wastewater with high amount of SS was not found to be the problem in retaining of biomass like biofilm in this system. Whereas washout biomass was found in the suspended growth reactor when treating high SS wastewater due to the microbial granule was breakdown and loss its activity. The performance in close-type AFF reactor showed the higher performance when compared to anaerobic open pond. ph adjustment and nutrient supplement were less required. This system is also good for diluted wastewater. Therefore, biogas would not be the main product in the case of diluted wastewater. Another advantage of the AFF reactor is its

4 ability to recover from shock loading. When ph dropped to 5, loading was stopped and system recovered within a few days. The AFF reactor can be used for low and high strength of organic wastewater. The advantages of the AFF technology is over other high rate reactors are able to treat wide range of wastewater types, able to treat high suspended solid content, resisted to high toxic and required low energy consumption. The agro-processing industries can be applied this biogas technology for wastewater treatment range from: Food processes such as vegetable canning, milk and cheese manufacture, slaughterhouse wastes, potato processing. Drink industry, breweries, soft drinks, distilleries, coffee, fruit juices, etc. Industrial products, paper and board, rubber, chemicals, palm oil, starch, pharmaceuticals. 1.3 Approach The BTRG (KMUTT) has been approached this biogas technology, an AFF reactor, at industrial scale to several agroindustries such as rice starch factory, vegetable and fruit canning factories. Ups to now, these biogas plants are in operation for wastewater treatment and/or biogas production. Furthermore, KMUTT has been proposed the project to Energy Policy and Planning Office (EPPO) implementing AFF technology for 5 tapioca starch factories in Figure 1 Open anaerobic lagoon Figure 2 Fixed film biogas-pilot scale

5 2. Environmental and Social Consideration The first generation of the biogas AFF plant in KMUTT was built with the only aim of treating wastewater and producing of renewable energy. The enhancement of the energy related to environment awareness, the research development and demonstration (RD&D) programs was promoted and partially financed by the government (EPPO). The comprehensive documentation of production results in provided by the successive followup programs proved that the concept offers integrated solutions to a range of environmental problems related to energy production and industry was comprehensive in both environmental and social consideration when compared to the conventional open anaerobic lagoon (table 1). Table 1 Performance of open anaerobic pond and anaerobic fixed film reactor Criteria Open pond Closed AFF 1. Investment cost High investment cost if the price of land is expensive. The cost for construction (open earth lagoon) is low. 2. Area for wastewater treatment system Large land area is required. In case of tapioca starch factory, the area for wastewater treatment ponds is about 16 hectares. 3. Operation - Simplicity and low maintenance - The mixing of wastewater in the pond is not well mix and the channeling often found resulted in low efficiency. 4. Treatment efficiency - Low efficiency - Organic loading rate ~ 0.25 kg COD/m 3.d and HRT ~ days 5. Biogas Production - can not recover biogas (open pond) 6. Environmental impacts 6.1 CO 2 emission 6.2 CH 4 emission 6.3 Odor nuisance problem to the community 6.4 Groundwater Yes Yes Yes (H 2 S and volatile acids, etc.) Wastewater contaminate to groundwater 7. Chemical usage - High dose of chemical usage (CaO, NaOH etc.) for adjust ph of wastewater and reduce the smell - High operating cost The investment cost relies on the volume and BOD strength in wastewater. Due to AFF is the high rate anaerobic technology, it can reduce the land to 1/10 of open anaerobic pond. - require the train operator to understand how the system work and how to control the biological system. - The system is not too complicate to operate. - High Efficiency - Organic loading rate ~ 6-10 kg COD/m 3.d and HRT ~ 3-4 days - The biogas production yield is ~ m 3 /kg COD removed - Biogas can be used as energy substitution in factory. - Biogas is renewable fuel and use as energy in the factory. It reduces methane and carbon dioxide emission. - Less impact from odor nuisance - no contamination of wastewater to groundwater - Less chemical usage for adjust wastewater - Low operating cost

6 2.1 Amount of Emissions Avoided The consideration of environment and social issues on amount of emissions avoided are listed as following: Reduced load of BOD/COD discharge: Anaerobic digestion of agroindustrial wastewater results in reduction of organic carbon (BOD/COD) load to the environment. This biogas technology can convert organic carbon to methane and produce less microbial cell. The control of water pollution results in less impact on communities, agriculture, surface water, groundwater and ecology of aquatic life. Reduced greenhouse gas emissions: Biogas is a renewable energy source. Biogas plants contribute to reducing greenhouse gas emissions as the replacement of fossil fuels results in the reduction of CO 2. In addition, CH 4 emissions from open anaerobic lagoons of agroindustrial wastewater treatment can be reduced. CH 4 are much stronger greenhouse gas than CO 2. Further, methane is a potent greenhouse gas (GHG). According to authorities, the 100- year Global Warming Potential (GWP) of methane is estimated to be 21. This means that a given mass of methane could increase the greenhouse effect by 21 times greater than the same mass of carbon dioxide. The AFF technology generated biogas from agroindustrial wastewater, such as rice starch and tapioca starch factories, is used to substitute fossil fuel for thermal heat from fuel oil and electricity from natural gas fired power plant including reduced water pollution. The results were shown in table 2. Table 2 The amount of emissions reduced from rice and tapioca starch factories when applied AFF technology Items Rice starch factory 2 Tapioca starch factory 3 Production capacity (t/d) Number of factories in Thailand Life span of project (years) Total amount of CH 4 emission reduced (million t) ,320 Total amount of CO 2 emission reduced (million t) Total amount of COD load reduced to water reservoir (million t) Sources: Department of Industrial Works, Ministry of Industry (2003) 2 The estimation of total amount emissions base on production capacity of 350 t-rice starch/d in each factory. 3 The estimation of total amount emissions base on production capacity of 200 t-rice starch/d in each factory. 4 The reduced of CH 4 emission bases on to compare with conventional open anaerobic pond and the reduced CO 2 emission is based on utilization of biogas for electricity. Electricity generated from natural gas is assumed to emit 452 g CO 2 /kwh (Referring from Kyoto Protocol). 2.2 Community/ People Participation The AFF biogas technology for agroindustrial application has been promoted through the pilot plant demonstration and several training workshops in country and region for industrial, organization, and private participants before construction of full scale AFF. In addition, this biogas project for rice starch factory was introduced to neighbor community to understand how this technology can solve the odor problem and reduce pollution to

7 water and atmosphere before construction. By discussing with the community located near the factory, the attitude of community to this factory was quite good. After establishment of AFF plant, there is very less community protest to the factory Benefit to user There are a number of benefits resulting from the use of biogas technology. Energy Benefits Net energy producing process Generate high quality renewable fuel Biogas proven in numerous end-use applications Wastewater Treatment Benefits Natural wastewater treatment process Requires less land than anaerobic lagoon Reduces disposed sludge volume and weight to be disposed Environmental Benefits Significantly reduces carbon dioxide and methane emission Eliminates odor Produces a nutrient liquid for algal cultivation and plant irrigation Maximizes recycling benefits Economic Benefits Is more cost-effective than other treatment options from a life-cycle perspective Benefit to Community A project is contributed gains for the community/society e.g. concerning human development, education-train the operator, skilled labor for biogas plant construction, etc. relative to the reference activity or a business as usual situation, which must be taken into account. Increase manpower and income to the family especially in skilled labor for biogas plant construction and train operator. Less odor nuisances: Anaerobic digestion of agroindustrial wastewater results in less odor nuisance than open impoundment lagoon to the adjacent community. Anaerobic digestion mitigates a number of other environmental concerns. Emissions of volatile solids and volatile fatty acids are directly related to odor strength released from organic fraction wastewater. The process can control odor and displaces fossil fuels. Reduced water pollution to surface water (canal and river) and groundwater, that means to improve their healthy and aquatic life Benefit to Country Reduced the amount of imported fossil fuel and save the money for the country Reduced the GHG (CH 4 and CO 2 ) emission to the atmosphere that will effect to the country and world. Cheap and environmentally sound waste recycling: It is possible to achieve environmentally attractive recycling of a number of suitable agroindustrial wastewater.

8 The environmental aspects include the sanitary effect of the digestion, as well as efficient fertilizer utilization of the effluent. In doing so the biogas plants provide industries with a lasting and relatively cheap solution to their waste disposal problem. Treating commodities to produce another energy yield while recycling nutrients creates a virtuous cycle of sustainability. Promoting the AFF technology transfer in country and region The AFF technology is a local technology and local know-how. Therefore, the cost is lower than foreigner s technology. It will save money for country to import the foreigner s technology. Most materials for AFF plant are available in local. 2.3 Other Features Improved utilization of liquid fertilizer: The liquid fertilizer product is nutritionally defined. Consequently, treated agroindustrial wastewater is more efficiently used as fertilizer, replacing chemical fertilizer production. The farmer can apply to their agricultural lands. More efficient fertilization at the same time results in less loss of nutrients and less water pollution from nutrients. - Irrigation: KMUTT has been studied the utilization of treated tapioca starch wastewater to irrigate of Eucalyptus more than 5 years. During monitoring for a long time it was not found any problem to the growth of tree. - Algal cultivation-cultivation of Spirulina using secondary treated starch wastewater: Spirulina can be cultivated in effluent from an anaerobic reactor. The occurrence of Spirulina corresponded to high alkalinity and ph of water in effluent. Moreover, inorganic nutrients from degrading of starch in anaerobic reactor appeared to support growth of Spirulina. It was found that the growth of Spirulina in effluent from an anaerobic reactor was equivalent to that in complete media. It was therefore suggested to use the effluent from biogas reactor to cultivate Spirulina in order to minimize the cost of nutrients and therefore the production cost. This would make Spirulina more competitive in the animal feed market. This integrated approach will not only produce a more cost-effective biogas and algal product but will also reduce the environmental impact of the wastewater produced by starch factories. 3. Technical, Economic and Market Consideration 3.1 Installed Capacity The installed capacity of AFF reactor related on sources of wastewater such as organic concentration in wastewater and its volume. The organic loading rate of AFF reactor can be varied from 2-10 kgcod/m 3 reactor.day. For example, the 350 t/d of rice starch factory, the installed capacity of AFF reactor was 5,000 m 3 and required 0.08 hectare of land area. The AFF reactor for tapioca starch factory which has production capacity 200 t/d, require the installed capacity 12,000 m 3 and required 0.16 hectare of land area. 3.2 Technical Design The AFF reactor is the biological system and designed as a high rate anaerobic reactor. As, the efficiency of the anaerobic reactor depends on the amount of methanogenic bacteria. The more matahnogenic bacteria was kept inside the system, the higher of

9 organic loading rate was handle. The main concept of the high rate anaerobic reactor is to retain the biomass especially the methanogenic bacteria in the reactor. The AFF reactor is that lets the biomass adhere and grow on the media. Therefore, the reactor can maintain more biomass that will increase the efficiency and the stability of system. The high efficiency in degrading organic materials in wastewater and producing biogas is due to the attached microorganism on the supporting material (biofilm) in the system. The main component of the AFF reactor is the packed media. KMUTT has selected the nylon net as material to be fixed film media in AFF reactor. As the cost of material and the weight of media were low comparing with other commercial packed media and it is available in local market. The installation is vertically and carefully arrangement. These are for avoiding clogging of suspended solid and/or biomass. The wastewater is fed from the bottom of reactor through the biofilm, which reaction will occur, and go to the top of reactor. The treated wastewater (effluent) will go out of reactor and biogas will recover in gas-holder. The diagram of AFF biogas plant layout was shown in figure 3. Anaerobic Fixed Film Wastewater Ex-Open anaerobic lagoon Biogas Effluent from biogas plant Effluent from ex-lagoon Layout of Biogas Plant Model of AFF Plant Biogas piping line Burner Generator H 2 S scrubber Gas blower Water trap tank Figure 3 The diagram of AFF biogas plant

10 3.3 Technical Performance The AFF reactor can handle organic loading rate at 2-10 kg COD/m 3.day and HRT 2-4 days. The biogas yield was m 3 /kg COD removed which contain % of methane. The efficiency of COD removal was %. This high rate biogas plant had high performance stability. ph adjustment and nutrient supplement were less required. Another advantage of the AFF reactor is its ability to recover from shock loading. When ph dropped to 5, loading was stopped and system recovered within a few days. No clogging and channeling was found during operate the AFF system. This system required low energy consumption and less chemical reagent that resulted in low operating cost. 3.4 Investment Cost The investment cost including AFF reactor construction, biogas utilization system and indirect cost for 350 ton-rice starch production per day was 20 million baht whereas that for 200 ton-tapioca starch production per day was 39 million baht. 3.5 Financial Scheme/ Livelihood Projects/ Funder KMUTT submitted the proposal to EPPO for using the biogas convert to electricity. EPPO subsidized ~ 25% of investment cost to rice starch production company. The rest of 75 % of investment cost was paid by factory itself. The other factories can be applied proposal to EPPO for approval and the criteria to subsidize are shown in table 3. Table 3 The maximum subsidize to each factory by EPPO Amount of investment cost (million baht) Maximum subsidize (% of investment cost) > > > > >50 - The biogas technology is a technically feasible option for converting organic fraction in wastewater. It provides benefits to the environment through energy and nutrient recycling, while also mitigating odors and atmospheric methane. The biogas technology for agroindustrial wastewater such as starch wastewater is an economically feasible. However, like most renewable energy options, its economic merit relies on conditions dependent on a variety of factors. The decision to use biogas technology for treating agroindustrial wastewater rather than alternative technologies depends on a number of factors: Wastewater quality; Site specific circumstances; Availability of outlets for the energy produced; Energy prices and taxes; Cost of alternatives/taxes on alternatives; Policy (e.g. renewable energy and recycling policies); Land prices; Level of capital and labor costs technology end-use applications can increase the economic value of biogas.

11 Discussion of the economics of the digestion of wastewater treatment is complex due to the wide range of parameters that effect the costs and the number of external benefits that are accrued. Biogas technology is now widely used throughout Thailand due to the crisis of oil and environmental enforcement. The economic feasibility of an anaerobic fixed film reactor for wastewater treatment and energy production was studied for a factory and shown in table 4. Table 4 Cost benefit analysis of AFF biogas technology for starch factory Items Rice starch factory Tapioca starch factory Production capacity (t/d) Investment cost (million baht) Construction - Gas utilization system - Indirect cost Annual expense (million baht/year) Operating and maintenance Profit (million baht/year) - Biogas 6.1 (replace the utilization of electricity 900,000 kwh/y and this profit is included the saving of chemical reagent usage) 14.4 (replace the utilization of fuel oil 1,800,000 liter/year) Payback period (year) Market Size (Potential within the period of 5 years) An AFF reactor is technologically and economically feasible to treat high strength agroindustrial wastewater. Nowadays, the price of land and fuel oil and the strict enforcement makes the AFF technology more acceptable. Several seminars, pilot plant demonstration and training workshops under the project entitled Treatment and Utilization of Starch Wastewater organized by King Mongkut s University of Technology Thonburi, the biogas technology is widely spread and recognized among the factory owner and tapioca starch association. In addition the project helps to create a market even spending a long time to go this point. Currently, a full-scale AFF reactor is being operated at a new starch factory since This factory produces rice starch 350 tons a day. Additionally five full-scale of anaerobic fixed film reactors will be planned to construct for five tapioca starch factories. To cope with the oil import and price, the government will partially support and be granted by EPPO for full-scale demonstration projects to prove their viability for renewable energy and energy conservation. Moreover, AFF technology has been established in 3 factories of fruit and vegetable canning (Doikum, Thai Royal Project). These factories generate low strength of wastewater which contain COD ~ 500-2,000 mg/l. These technology was also approved that can be used as the purpose to treat wastewater not for biogas production as energy. 3.6 Local Manufacturing/ Content of System) This AFF technology is a local technology and local know-how. All used materials for AFF reactor are available in local market as well as used local labor for reactor

12 construction. Therefore, the cost is lower than foreigner s technology. Furthermore, KMUTT can provide a quick and convenience of technical advice and consultant after the reactor was constructed. 3.7 Amount of Energy Avoided The AFF technology can produce biogas as renewable energy, which can substitute of fossil fuel. This technology can save energy consumption. In case of 350 ton-rice starch/d, it will save the electricity consumption from natural gas fired power plant about 0.9 million kwh/y. The 200 t/d of tapioca starch production factory can save energy for using 1.8 million liter of fuel oil/y or for consuming electricity 4.8 million kwh/y. Summarize: Rice starch factory (high strength wastewater) Objectives: To design and build biogas reactor based on anaerobic fixed film technology that would treat the wastewater from agro-industry and generate the biogas. This would include the utilization of biogas as energy substitution inside of factory. Description of the activity: The company generates around 1,000 m 3 /day contains carbohydrate based with COD concentration 5,000-7,000 mg/l. Previously, the company uses the open pond treated their wastewater. The problem is that odor from these pond interfere their neighbors. The company approached KMUTT to solve the odor issues. KMUTT proposed the AFF technology to treat their wastewater, which reduce odor problem and chemical cost. Moreover, KMUTT submitted the proposal to EPPO for using the biogas convert to electricity. EPPO subsidized ~ 25% of investment cost to company. AFF reactor treating rice flour wastewater produced 2,500-3,000 m 3 -biogas/day. In addition, the biogas has been converted to electricity up to 100 kw. Funding: BIOTEC for research and development technology and EPPO for energy conservation Impacts: The demonstration project at this rice starch factory was illustrated that the company can daily save 3,000 kwh. Lessons Learned: AFF reactor has high potential for agriculture and food industries. The biogas utilization depends on the source of energy use in each factory. The subsidization some of investment cost from government would accelerate the implementation of biogas technology. Potential for Replication: The replication project for tapioca starch factories are underway for further implementation throughout the country. This technology may be applicable to other ASEAN countries. Partnership: KMUTT/Rice starch factory/ EPPO Technology components: Trust in the competence of KMUTT s staff by private sector partner This technology is a local technology and local know-how. Therefore, the cost is lower than foreigner s technology. Furthermore, KMUTT can provide a quick and convenience of technical advice and consultant after the reactor was constructed. The increasing in energy (oil and electricity) price is the promoter factor for this biogas project.

13 4. Operation and Maintenance Scheme Biogas technology produces an order of magnitude less solids, with the difference converted to biogas with energy value. There also are favorable operation and maintenance benefits associated with biogas technology, normally including lower energy requirements for operation. The operating cost in treating wastewater is quite low approximately 2-3 baht/m 3 -wastewater. The operation and maintenance (O&M) scheme of AFF technology is shown in table 5. Table 5 Operation and maintenance scheme for AFF technology O & M Scheme Operational hours Maintenance scheme Detail 24 hours/day Monthly routine check by factory and consulting with KMUTT: - pump - piping - gas blower - others Other maintenance measures - train the operator before start-up and operate the plant - KMUTT will help to start-up and follow up the operation and performance of AFF reactor for 1 year - KMUTT will provide consulting when factory meet the problem Local service content - design and implementing AFF - consulting for start-up and improvement for the existing anaerobic digester 5. Replicability 5.1 Replicability Project The concept was continuously developed, improved and represents today an integrated system of renewable energy production, organic wastewater treatment and nutrient recycling (algal cultivation and irrigation), generating intertwined agroindustrial and environmental benefits. This AFF biogas plant has been implemented in fruit and vegetable canning and starch production factories. Not only these factories, the AFF biogas plant can be approached to various agroindustries such as palm oil mill factory, soft drink factory, fish canning factory, etc. which are the major industries in Thailand that generated high strength and volume of organic wastewater. 5.2 Life of Project The lifetime of the project in AFF reactor is estimated for 15 years.

14 5.3 Cost Effectiveness The AFF technology is a local technology and local know-how. The capital cost of biogas that produces from AFF biogas system in replacement of fuel oil and electricity is approximately 0.80 baht/m 3 and 1 baht/m 3, respectively. This technology is cost effective; even though high in investment cost but low in operating cost and gain in valuable of biogas resulted in short pay back period and high internal rate of return (IRR). 5.3 Sustainability of Project Overall biogas plants compares favorably with its competitors as it provides recycling of nutrients as well as generating renewable energy with a minimum of air and water pollution emissions. The biogas plant will generate biogas as renewable energy, reduce water pollution, utilize of treated wastewater for algal cultivation and plant irrigation, reduce in CH 4 and CO 2 emission, and decrease the odor nuisance problem to the adjacent community. It is possible to achieve energy related to environment scheme via to biogas technology and waste recycling. In doing so the biogas AFF plants provide agroindustries with lasting and relatively cheap and environment sound solution to wastewater problem. Economic benefit is more cost effective than other treatment options from a life-cycle perspective. It will create a virtuous cycle of sustainability. 5.4 Other As mention in item 3.6, the AFF technology can be approached to low/diluted and high strength agroindustrial wastewater. The purpose to apply the AFF technology in low strength wastewater is for treating wastewater and this technology consumes low energy resulting in low operating cost. The AFF technology can be applied to high strength wastewater is the purpose of energy production and wastewater treatment. The examples of the AFF technology for low and high strength of agroindustrial wastewater are shown below. Fruit and vegetable canning factory (low strength wastewater) The research study from BTRG, KMUTT, found that anaerobic fixed film (AFF) technology not only applied to high strength wastewater but can use in low strength wastewater. Since 1995, KMUTT has been established 3 anaerobic waster treatment plants (figure 4) at district of Phang, Mae-Jun and Toa-Ngao. These factories are small scale and wastewater is generated m 3 a day containing 500-2,000 mg/l of COD. These system were designed for wastewater treatment purpose. The amount of biogas production is too small to use as energy substitution. These systems can remove 80-90% of COD, low energy requirement for wastewater treatment and are proved that AFF technology is good to handle wastewater from factory that raw materials are seasoning.

15 Figure 4 Anaerobic fixed film reactor for fruit and vegetable canning factory Tapioca starch factory (high strength wastewater) Furthermore, KMUTT proposed the project to EPPO implementing AFF technology for 5 tapioca starch factories in For one AFF reactor treating tapioca starch wastewater would produce ~25,000 m 3 biogas/day, which can replace all of the consumption of fuel oil in the factory (~9,000 litres of fuel oil), and the rest of biogas could generate electricity 4,680 kwh/day. This project would reduce the import of fuel oil at least 1,800,000 litres annually. Furthermore, these plants would reduce the polluted wastewater to the environment.