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Promotion and Demonstrationof Energy Production from Solid Waste

(Monitoring and Evaluation of Biogas Production System for Organic Waste)

STFE Co., Ltd.

Consultant

Executive Summary Report

June 2008

Acknowledgement

Department of Alternative Energy Development and Efficiency (DEDE) had hired STFE Co., Ltd. as a consultant for promotion and demonstration of energy production from solid waste (monitoring and evaluation of biogas production system for organic waste). Small-scale biogas digesters installed in 100 sites in 2006 fiscal year were modified to enhance their efficiency. Their efficiency has been monitored, and a contest of the best biogas digester use was held. In addition, in 2007 fiscal year 200 additional sites have been selected to install the digesters. In these sites, the digesters have been started-up. Demonstration and training of how to operate the system have been done. Data on the operation of these digesters have been collected. All mentioned work has been successful, reaching the project objectives, due to the good cooperation from all parties.

DEDE would like to express her gratitude to local administration organizations, schools, Alternative Energy Division, Defense Energy Department and organizations under Ministry of Defense for their support the installation of biogas digesters and for their kind cooperation in operating and monitoring the system.

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Promotion and Demonstration of Energy Production from Solid Waste (Monitoring and Evaluation of Biogas Production System for Organic Waste)


Table of Content

Page Chapter 1 Introduction 1-1 1.1 Preface 1-1 1.2 Objectives of the study 1-1 1.3 The project scope 1-1 Chapter 2 Results of monitoring, evaluation and modification 2-1 of the biogas digesters installed in 2006 fiscal Year 2.1 Survey results of problems and obstacles to use biogas digester 2-1 2.2 Modification of biogas digesters 2-2 2.3 Solutions to the administrative problems and 2-6 obstacle to biogas digester use 2.4 Monitoring results of the modified biogas digester use 2-8 2.5 Efficiency of biogas digesters 2-9 2.6 Biogas digester use contest 2-12 Chapter 3 Extension of biogas digester use in 200 sites across the country 3-1 3.1 Designing and preparing of technical specifications and tender documents 3-1 3.2 Selection of appropriate sites for biogas digester installation 3-4 3.3 Survey of biogas digester installation sites 3-5 3.4 Digester start-up, demonstration and training of biogas digester use 3-5 3.5 Monitoring the biogas digester operation 3-6 Chapter 4 Economic feasibility analysis 4-1 4.1 Assumptions 4-1 4.2 Analysis results 4-2 Chapter 5 Summary and suggestions 5-1 5.1 Summary results of monitoring and modification 5-1 of biogas digesters installed in2006 fiscal year

5.2 Results of the extension of biogas digesters use 5-2 of 200 sites in every region of the country

5.3 The results of the project economic feasibility analysis 5-3 5.4 Suggestions 5-3

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List of Table

Page Table 2.5-1 The amount of biogas produced from biogas digesters in 24 hours 2-9 Table 2.5-2 Characteristics of biogas produced from biogas digesters using organic waste 2-10 Table 2.5-3 Characteristics of liquid fertilizer from biogas digesters using organic waste 2-10 Table 2.5-4 Characteristics of compost from biogas digesters using organic waste 2-10 Table 2.5-5 Pollutant removal efficiency of biogas digesters using organic waste 2-11 Table 2.6-1 Results of biogas digester use contest among schools/organizations 2-12 Table 3.2-1 Summary of appropriate sites (organizations) for biogas digester installation 3-5

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List of Figure

Page Figure 2.2-1 Flow diagram of the modified biogas digester 2-4 Figure 2.2-2 The biogas digester before and after the modifications 2-5 Figure 2.2-3 The example of modification worked at the digester installation sites 2-5 which had been done from 11 July to 8 October 2007 Figure 2.3-1 Experience sharing meeting on the use of biogas digesters using organic waste 2-6 Figure 3.1-1 Side view 1 of the small-scale biogas digesters using organic waste designed 3-2 for hiring to fabricated and installed through e-Auction process Figure 3.1-2 Side view 2 of the small-scale biogas digesters using organic waste designed 3-3 for hiring to fabricated and installed through e-Auction process Figure 3.1-3 Biogas digesters fabricated and installed by a contractor hired by DEDE 3-4 Figure 3.2-1 Selection procedure of 200 appropriate sites for biogas digester installation 3-4 Figure 3.4-1 Sample pictures of digester start-up, demonstration and training of 3-6 biogas digester use

Promotion and Demonstration of Energy Production from Solid Waste Chapter 1 (Monitoring and Evaluation of Biogas Production System for Organic Waste) Introduction Executive Summary Report

Department of Alternative Energy Development and Efficiency, Ministry of Energy

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Chapter 1 Introduction

1.1 Preface The strategic aims of alternative energy have been set that by 2011, solid waste shall be promoted to be used to generate heat and electricity 100 MW. In the mean time, municipal solid waste nationwide is estimated to be as high as 40,000 tons a day. There are still problems regarding the collection and disposal of the solid waste. The readily biodegradable organic waste which makes up 50% of the municipal solid waste is the main cause of environmental problems such as odor, leachate contamination, disease transmission as well as methane emission which is the cause of global warming. Still, if every households/communities separate organic waste and treat it in anaerobic digestion system, the organic waste will be disposed efficiently in environmental friendly manner. Moreover, the by-products are compost and biogas. This disposal method helps reserve energy and environment.

Department of Alternative Energy Development and Efficiency (DEDE), hence, launched a project in developing and demonstrating small-scale biogas digesters using organic waste. In 2006 fiscal year, biogas digesters were installed in 100 sites. The installed digesters are needed to be monitored, evaluated and improved to make them easier to be used with higher efficiency. In addition, biogas digesters will be installed in the additional 200 sites nationwide aiming to generate biogas energy from organic waste for sustainable benefits of the country. 1.2 Objectives of the study

1) To make the installed 100 biogas digesters using organic waste in use continuously. 2) To improve the digester design to make the digesters easier to use with higher efficiency. 3) To extend the use of the small-scale biogas digesters using organic waste nationwide.

1.3 The project scope 1) Survey for identifying problems and obstacles to use the installed biogas digesters

2) Improve the biogas digestion system for more convenience use and higher efficiency with capacity not less than 85 kg of receiving organic waste a day (10% total solid content) with the output of over 2.5 cubic meters of biogas a day; and also preparing the system design, equipment specifications, and tender documents

3) Report the result of the operation of the installed 100 digesters by considering operation status, organic waste input, quantity and quality of the biogas produced, system efficiency, residue properties, biogas use, problems and obstacles in running the digester, users’ satisfaction, etc.

4) Select 200 sites nationwide to install small-scale biogas digesters using organic waste 5) Improve the installed 100 digesters for more convenient use

Promotion and Demonstration of Energy Production from Solid Waste Chapter 1 (Monitoring and Evaluation of Biogas Production System for Organic Waste) Introduction Executive Summary Report


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6) Hold a contest and presenting awards to at least 10 schools and organizations which best use the digesters by continuously using and maintenance the digesters, create participation and raise awareness of the students and the public

7) Start-up the biogas digesters in 200 selected sites, collect data and report the operation results 8) Compile the operation manual, conduct the system operation and maintenance training 9) Analyze economic feasibility of the project 10) Prepare posters and brochures, and hold conferences to publicize biogas production by

biogas digesters using organic waste in 5 regions: north, northeast, central, east, and south. The conference shall be held once in each region with not less than 100 participants each time.

Promotion and Demonstration of Energy Production from Solid Waste Chapter 2 (Monitoring and Evaluation of Biogas Production System for Organic Waste) Results of Monitoring, Evaluation

and Modification of the Biogas Digesters Installed in 2006 Fiscal Year



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Chapter 2

Results of Monitoring, Evaluation and Modification of the Biogas Digesters Installed in 2006 Fiscal Year

2.1 Survey results of problems and obstacles to use biogas digester

The following are the survey results of problems and obstacles to use the biogas digesters installed in 2006 fiscal year in 94 schools under Bangkok Metropolitan Administration (BMA), Office of The Basic Education Commission and a private school, and in another 6 organizations during 14 may 2007 to 1 August 2007.

1) Status of the biogas digester use

- Used continuously 42 sites - Not used continuously/ temporarily stopped 32 sites

because of lack of staff/ too much workload/ responsible person changed and not knowing how to use the digesters/ thinking that there is no advantage of using the digesters/ too little waste/ equipment damaged/ digester sites changed and sludge drained out of the digesters

- Stopped operation for 6 months or more/ never used 25 sites because of not knowing how to use the digesters/ thinking that it is too complicate to use or giving the same reasons as in the group of not using continuously.

2) Digester conditions

- In good condition/ having good maintenance 3 sites - In normal condition but needing some maintenance 35 sites - Leaked or needing big maintenance 60 sites - Digesters severely damaged/cannot be repaired 1 site

3) Digestion conditions - In appropriate condition 74 sites

pH between 6.6-7.8, normal smell of digested sludge, flammable gas, active microorganism

- In fair condition 9 sites pH a bit too high or low but can be fixed, normal smell of digested sludge, flammable gas, active microorganism

- Inappropriate condition/ no digested sludge in digesters/ digestion failed 16 sites





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4) Opinion of user, problems and obstacles to the digester use

(1) Opinions on equipment - Equipment needs modifications 56 sites

because of the inconvenience and complication in substrate feeding, mixing and digested sludge removal/too much workload/ needing more biogas storage and durable equipment

- Lack of some accessories 6 sites such as pH meter and weighing scale

- Satisfied, no problems 34 sites - No opinions 3 sites (2) Opinions on administration - Having problems 22 sites

such as lack of staff and budget/ too much workload/ no cooperation from others in the organization and no support from management/ too little waste

- No problems 74 sites - No opinions 3 sites (3) Satisfactions on the project and biogas digesters - Satisfied 25 sites - Satisfied but needs equipment improvement 72 sites as specified in item 4) sub item (1) - No opinions 3 sites Note: The survey of problems and obstacles to the biogas digesters use were conducted in 99 sites, excluding Phranakhon Rajabhat University where the digester had been modified to be used in research.

2.2 Modification of biogas digesters

The modification of the installed 100 biogas digesters for more convenient use and efficiency and to be in line with the needs of users, had been done as follows:

1) A new tank and a pump were stalled for pumping prepared organic waste into the digester and for circulating sludge in the digesters to mix together with the newly-fed organic waste in place of manual agitator use. The pump is also used to pump the digested sludge drained from the digesters to the sand-drying trays or for fertilizing plants directly. This helps reduce workload and time for operating the system.





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2) The gas storage tank was modified to store the produced gas with the pressure of 150 mbar. More gas can be stored and the gas can be used longer (the old set of the gas storage tank could store gas with the pressure approximately 40-42 mbar).

3) The waste feeding pipe, digested sludge draining pipe and manometer have been changed to be in line with the modification in 1) and 2).

Figure 2.2-1 shows the flow diagram of the modified biogas digester. Figure 2.2-2 is the biogas digester before and after the modifications and figure 2.2-3 is an example of modification worked at the digester installation sites which had been done from 11 July to 8 October 2007.


and Modification of the Biogas Digesters Installed in 2006 Fiscal Year Executive Summary Report

Department of Alternative Energy Development and Efficiency, Ministry of Energy 2 - 5

(A) before modification (B) after modification

Figure 2.2-2 The biogas digester before and after the modifications

Figure 2.2-3 The example of modification worked at the digester installation sites which had been done from 11 July to 8 October 2007





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2.3 Solutions to the administrative problems and obstacle to biogas digester use

Apart from problems concerning equipment which have been tackled in 2.2, the survey also found administrative problems and obstacles to the use of biogas digesters. They can be summarized as follows.

- Lack of responsible persons or no cooperation from others in the organization - Too much workload that not able to use the digesters - The management level does not realize its importance and no support from them - Lack of budget to buy auxiliary tools such as pH Meters and weighing scales

To find solutions to the problems together, a meeting to share experience of the use of biogas digesters using organic waste was held at Department of Alternative Energy Development on 21 and 22 August 2007 (figure 2.3-1). One hundred representatives from the schools and organizations where the digesters were installed participated in the meeting.

Figure 2.3-1 Experience sharing meeting on the use of biogas digesters using organic waste





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The meeting came up with many insights and proposed solutions to the administrative problems. The proposed solutions can be summarized as follows:

Problem: Lack of responsible persons or no cooperation from others in the organization Brief solutions: - Confide with the management to assign co-responsible persons

- Set the working team whose members are colleagues, students, janitors, cooks and volunteers in school or set a school club to operate the digester

- Do public relations within the organization about importance and benefits from using the digesters, and work process should be informed to everybody so that more people may join the project.

Problem: Too much workload that not able to operate the digesters Brief solutions: - Have the assistant of the responsible person work with him/her every time when

operating the system so that the assistant can be in charge when the responsible person has other work.

- In case of schools, integrate this project with other lessons so that students and teachers can take part in the project.

Problem: The management level does not realize its importance and no support from them Brief solutions: - Have the management take part in the project by having the person in charge report

work procedure, and work results or obstacles that occurred to the management. - Make the management see a success of using the digesters in a concrete picture or

send the project to participate in a contest so that support and cooperation from the management will be received.

- The organizations which the schools/organizations report help monitor or support biogas digester use.

Problem: Lack of budget to buy accessories such as pH meter and weighing scale Brief solutions: - Set up the project or do public relations about the operation and benefits of the

biogas digester to organization/community in order to get budget from the management, organization reports to, or to raise fund from community, parents, donators and local administration organization, etc.

- Make the biogas digestion project a lesson for schools or learning centers so that a

proposal for a budget can be done. - Sell by-products of the digesters such as compost, or vegetables. - Get money from other sources such as environment school club, or garbage bank

project, etc.





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2.4 Monitoring results of the modified biogas digester use

The schools/organizations were monitored twice from 14 November 2007 to 31 January 2008. The results are as follows.

1) The biogas digester use

- Continuously used at moderate to high level 48 sites - Rarely used 17 sites - Never used (because of administrative problems) 22 sites

2) Amount of organic waste fed to the digester

- 20 kilograms a day or more 15 sites - Less than 20 kilograms a day 24 sites - Less than 10 kilograms a day 26 sites - No feeding 22 sites

3) Biogas utilization

- Usually used for cooking, culinary classes, 30 sites boiling water for cleaning plates and spoons, etc.

- Used sometimes/ on trial 14 sites - Never used/ gas is inflammable because of 43 sites

inappropriate digestion conditions

4) Digested sludge utilization

- Used as liquid fertilizer or dry fertilizer 41 sites - Never used because sludge in the digesters 45 sites

was not reached the set level, no sludge in the digesters or the digesters were not in-use

- Never used because think that it is not effective 1 sites

5) Problems and obstacles to running digesters

- No problems 63 sites - Having problems such as too much workload, 24 sites

management not support, lack of cooperation from colleagues, lack of pH meters, and flooding at the installation site

6) Satisfaction of the users after improvement

- Satisfied/ highly satisfied 59 sites because of easier use, more convenience, saving time and gas used lasting longer





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- No opinions on this topic 27 sites with different reasons such as having just been responsible for the work, no success in digester use yet, or digesters not in use

- Modified equipment not in use 1 sites because of concern about safety of electricity use, electricity system not ready so the old method used

Remark: The number of schools/organizations that monitored the digesters use is 87 sites in total, excluding 7 schools that returned digesters to DEDE, 2 schools which were not ready for digester modification, and another 3 organizations, one of which uses digesters for research, another is a private organization and DEDE (the project owner).

2.5 Efficiency of biogas digesters

Efficiency of modified biogas digesters can be summarized as follows:

1) The amount of biogas

The measurements of the amount of biogas produced in 24 hours with different factors: the method of mixing, storage time of organic waste before feeding, and temperature are illustrated in table 2.5-1

Table 2.5-1 The amount of biogas produced from biogas digesters in 24 hours Factors Amount of biogas

Date Installation sites Amount of waste (kg., TS 10%) Mixing Method Avg. temp.

(ºC)

Difference of temp.

(ºC/hr.)

(liter, pressure 150 mbar, 29 ºC)

Using pump 1 time for 25 minutes

30 no data 2,303

Using pump 1 time for 25 mins. together with stirring with agitator twice 15 mins. each with 4 hrs. interval.

29.86 0-3 2,076 10-17/8/07 DEDE 20 kg.

(retained for 21 hrs. before feeding)

Using pump twice for 25 mins each with 8 hrs. interval

31.37 0-2.5 2,579

5-6/11/07 DEDE

20 kg. (retained for

69 hrs. before feeding)

28.75 0-4 1,819

Wat Pradu 8-9/11/07 thammathipat BKK

20 kg. (retained for

1 hr. before feeding)

Using pump 1 time for 25 minutes

26.67 0-4 1,980

2) Biogas characteristics

The characteristics of biogas produced from the digesters sampled from different sites from 5 February to 4 March 2008 are presented in table 2.5-2.





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Table 2.5-2 Characteristics of biogas produced from biogas digesters using organic waste

Parameters (%v/v) Installation sites

CH4 CO2 Other gases Total

Sri Bunyanon School, Nonta Buri 60.85 37.48 1.67 100.00 Wat Madua School, Nonta Buri 60.19 36.70 3.11 100.00 Wat Praduthammathipat School, Bangkok 59.71 36.33 3.96 100.00

Wat Sai School, Bangkok 58.97 35.87 5.16 100.00

3) Digested sludge characteristics

2 types of digested sludge from biogas digesters were analyzed according to different use: (1) liquid digested sludge used as liquid fertilizer and (2) sun-dried digested sludge used as compost. Their characteristics are illustrated in table 2.5-3 and table 2.5-4.

Table 2.5-3 Characteristics of liquid fertilizer from biogas digesters using organic waste Digester Installation sites

Parameters Unit Wichuthit School BKK Wat Praduthammathipat School BKK N %w/w 0.21 0.2 P2O5 %w/w 0.03 0.03 K2O %w/w 0.02 0.03 pH - 7.6 7.8 EC dS/m 14.95 17.9 TS Content %w/w 1.0 1.1

Table 2.5-4 Characteristics of compost from biogas digesters using organic waste

Digester installation sites Parameters Unit

DEDE Wat Madua School Nonta Buri

Standard*

Organic Matter (OM) (%w/w) 24.39 28.69 Not less than 30

C/N Ratio 5 5 Not over 30

N (%) 2.62 3.44 Not less than 1

P2O5 (%) 1.35 2.26 Not less than 0.5

K2O (%) 0.42 0.61 Not less than 0.5

pH 8.89 6.22 5.5-8.5

EC (dS/m) 5.37 3.39 Not over 6

CaO (%) 2.27 2.27 Not specified

MgO (%) 0.26 0.26 Not specified Moisture Content (%w/w) No data 35

Remark: * Standard of organic fertilizer quality set by Department of Agriculture, BE. 2005.





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4) Pollutant removal efficiency

The pollutant removal efficiency of biogas digesters using organic waste is presented through the removal rates of BOD, COD and Total Kjeldahl Nitrogen (TKN) as shown in table 2.5-5.

Table 2.5-5 Pollutant removal efficiency of biogas digesters using organic waste

Digester installation sites

DEDE Wat Praduthammathipat

School Wichuthit School Parameter Unit

Inf. Eff. % Rem. Inf. Eff. % Rem. Inf. Eff. % Rem.

BOD mg/l 104,700 1,824 98.26% 40,980 180 99.56% 91,500 589 99.36%

COD mg/l 307,948 20,992 93.18% 109,591 7,424 93.23% 122,117 7,936 93.50%

TKN mg/l 3,193 2,455 23.11% 1,648 2,054 - 2,187 2,005 8.32%

Remarks: 1. Abbreviations Inf. = Influent (organic waste fed into digesters) Eff. = Effluent (digested sludge drained out of digesters) %Rem. = Pollutant Removal Efficiency

2. (-) mark means cannot be calculated





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2.6 Biogas digester use contest

To promote continuous use of biogas digesters, a contest of best biogas digesters use was held after the modifications of the digesters to enhance their efficiency were done. The judging criteria were continuous use and maintenance of digesters, and creativity the participation in using digesters and raising awareness among students and public. The results of the contest are presented in table 2.6-1.

Table 2.6-1 Results of biogas digester use contest among schools/organizations Awards

Prize Schools/ organizations Money (baht)

Awards

1st prize Wat Praduthammathipat School, Bangkok 50,000 Plaque 2nd prize Khlong Nongyai School, Bangkok 15,000 Plaque Wat Bangnoi Sch. (Jamprachanukul), Samut Songkham 15,000 Plaque 3rd prize Wat Madua School, Nonta Buri 10,000 Plaque Wat Donwai School, Nakorn Pathom 10,000 Plaque Honorable Wat Phonmanee School, Bangkok 4,000 Certificate mention Wat Muong School, Bangkok 4,000 Certificate Chumchon Wat Buakaewkeasorn School, Pathum Thanee 4,000 Certificate Wat Lanbun School, Bangkok 4,000 Certificate Thai Islamic College, Bangkok 4,000 Certificate Chumchon Wat Phichitpityaram School, Pathum Thani 4,000 Certificate Wat Sai (thavornprommanukul) School, Bangkok 4,000 Certificate Sri Bunyanon School, Nonta Buri 4,000 Certificate Bangbo Witthayakom School, Samut Prakarn 4,000 Certificate Special prize Wat Kamphang School (Reanlommananukul) Sch. BKK 1,000 Certificate Nakdee Anusorn School, Samut Sakorn 1,000 Certificate Phunbamphen Community Museum, Bangkok 1,000 Certificate Princess Chulabhorn's College, Buriram 1,000 Certificate

Promotion and Demonstration of Energy Production from Solid Waste Chapter 3 (Monitoring and Evaluation of Biogas Production System for Organic Waste) Extension of Biogas Digester Use

in 200 Sites across the Country



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Chapter 3 Extension of Biogas Digester Use in 200 Sites across the Country

3.1 Designing and preparing of technical specifications and tender documents

Designing and preparing of technical specifications and tender documents for hiring to fabricate and install 200 sets of biogas digesters through e-Auction process were done on 1 August 2007. DEDE hired a contractor to fabricate and installs digesters separately from the project. The timeframe for it was from 27 September 2007 to 9 January 2008. The designed biogas digesters have the capacity of 2.5 cubic meters with specifications similar to the modified digesters in 2006 fiscal year as shown in figures 3.1-1 and 3.1-2. The biogas digester that has really been fabricated by a contractor hired by DEDE with small changes from the design is shown in figure 3.1-3.





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Figure 3.1-3 Biogas digesters fabricated and installed by a contractor hired by DEDE

3.2 Selection of appropriate sites for biogas digester installation

The target groups of the selection of 200 sites for biogas digester installation are local administration organizations, schools, and other government organizations which show interest in joining the project. The area covers every regions of the country. The selection procedure is presented in figure 3.2-1.

Figure 3.2-1 Selection procedure of 200 appropriate sites for biogas digester installation

Invited target groups to join project (5 regions, 1,445 Organizations)

Organizations showed interest in joining project (5 regions, 282 Organizations)

Meeting to promote understanding of Biogas production using biogas digesters

(5 regions, 610 people)

Evaluated and selected appropriate organizations to join the project

(5 regions, 200 sites)





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The results of the selection of appropriate sites can be summarized in table 3.2-1.

Table 3.2-1 Summary of appropriate sites (organizations) for biogas digester installation

Number of organizations selected Region

municipality local admin org. schools others* total

Central 5 15 13 12 45

North 5 11 19 4 39

Northeast 6 19 14 3 42

East 13 13 21 2 49

South 5 4 16 - 25

Total 34 62 83 21 200 Note: * are 20 organizations under Ministry of Defence and 1 hospital.

3.3 Survey of biogas digester installation sites

The survey of biogas digester installation sites of the 200 selected organizations came with consultant’s suggestion of site preparation before installation. The survey was done from 26 October 2007 to 14 December 2007.

3.4 Digester start-up, demonstration and training of biogas digester use

Start-up the digester, demonstration and training of biogas digester use (figure 3.4-1) began on 30 November 2007 and finished on 10 April 2008. The following are the work process.

- Make an appointment with the organization at least 1 week in advance so that the organization can prepare inoculums for digester start up (dung of cows, buffaloes, and pigs) for about 200-600 kilograms and 0.5 kilogram of food residue for feeding into the digesters. The organization also prepares their staff for demonstration and training of biogas digester use.

- Start-up the digester by mixing the prepared dung with water in the same amount and sort out foreign substances. Then pump it into the digester and add water into the digester to the specified level. After that, feed 1 kg. of shredded waste that has been mixed with water (see details of start-up process from biogas digester system operation manual).

- Demonstrate and train biogas digester use, and give biogas digester system operation manual to the responsible person and receive signature from that person.





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Figure 3.4-1 Sample pictures of digester start-up, demonstration and training of biogas digester use

3.5 Monitoring the biogas digester operation

The operation of biogas digesters were monitored by the following methods:

- Monitored the digester start-up by phone calls to ensured understandings and clarification of the demonstration and training of biogas digester use. In addition, the problems and obstacles to digester use were also probed and suggested solutions were given. This was done from 25 December 2007 to 12 March 2008.

- Did a field trip to the sites to monitor the digester operation. This monitoring started on 18 February 2008 and finished in the total of 200 sites on 2 May 2008.

- Monitored the digester operation records that users send to the consultant. If problems are found in any places, they will be contacted for suggestions and possible solutions. This will be done during the entire contract of the consultant.

The results of the monitoring can be concluded that most organizations where biogas digesters have been installed start to operate the system with satisfied results. That is to say, the produced gas is flammable, and they started using the biogas for cooking, and started using the digested sludge as compost. Still, the use of digesters and their products should be monitored onwards to promote the use of digesters continuously.

Promotion and Demonstration of Energy Production from Solid Waste Chapter 4 (Monitoring and Evaluation of Biogas Production System for Organic Waste) Economic Feasibility Analysis



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Chapter 4 Economic Feasibility Analysis

An analysis of economic feasibility of the project is a financial analysis that studies the

appropriateness of investment on the extension of biogas digester use which DEDE installed 200 biogas digesters in new locations across the country in the 2007 fiscal year. The analysis employs the following indexes.

- Internal Rate of Return: IRR - Net Present Value: NPV - Payback Period - Benefit/Cost Ratio

4.1 Assumptions 1) Discount rate or opportunity cost of capital is 10% 2) Average inflation rate is 5% a year 3) The time required for fabrication and installation of biogas digesters in 200 sites is 3.5 months. 4) The service life of the digesters is 5 years. The digesters are operated 300 days/year to produce biogas. 5) The maximum capacity in receiving organic waste of a digester is 40 kg/day/set (with 20% solid content). The feeding of organic waste into the 200 sets of biogas digesters is at 70% of the maximum capacity or 28 kg/day/set (with 20% solid content). This equals 1,680 tons/year for 200 sets of digesters. 6) The costs of production, transportation, and installation of 200 sets of biogas digesters are 11,000,000 baht or 55,000 baht/set. 7) Operation and maintenance expenses of biogas digesters are divided as follows. - Operation expenses comprise labor wage, electricity charge, and tap water charge which are estimated at 9,210 baht/year/set or 1,842,000 baht/year for 200 sets of biogas digesters. - Maintenance expenses are made up of annual maintenance expense which is estimated at 2% a year of the investment cost. Expense for equipment/part replacement in the 3rd year of the operation is 4,000 baht/set or 800,000 baht for 200 sets. 8) Income from biogas digesters is calculated from expenses that can be saved from utilizing the digesters and their product. They are as follows. - Money saved from using biogas in stead of buying LPG for cooking is 6,840 baht/year/set or 1,368,000 baht/year for 200 sets. - Money saved from using the digested sludge of biogas digesters as liquid fertilizer is 16,200 baht/year/set or 3,240,000 baht/year for 200 sets. - Money saved from local government organizations not having to collect, transport and dispose organic waste is 8,400 baht/year/set or 1,680,000 baht/year for 200 sets.

Promotion and Demonstration of Energy Production from Solid Waste Chapter 4 (Monitoring and Evaluation of Biogas Production System for Organic Waste) Economic Feasibility Analysis



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4.2 Analysis results

The analysis results of the project’s economic feasibility can be summarized as follows.

- Internal Rate of Return: IRR is 28.94% which indicates that the project is worth investing since the return is higher than the 10% discount rate. - Net Present Value: NPV is 6,019,945.56 baht which indicates that the project is feasible for investment since the value is higher than 0. - Payback Period is 2.60 years which is rather short. This implies that the investment has low risk. - Benefit/Cost Ratio is 1.55 which indicates that the project is worth investing since it is higher than 1.

Promotion and Demonstration of Energy Production from Solid Waste Chapter 5 (Monitoring and Evaluation of Biogas Production System for Organic Waste) Summary and Suggestions



Chapter 5 Summary and Suggestions

5.1 Summary results of monitoring and modification of biogas digesters installed in 2006 fiscal year

5.1.1 The survey results of problems and obstacles to use small-scale biogas digesters using organic waste installed in 2006 fiscal year can be summarized as follows.

- 42 schools/organizations (42.42%) where biogas digesters have been installed continuously use the digesters. 32 sites (32.32%) do not use them continuously/temporarily stopped using them. 25 sites (25.26%) have stopped using them for over 6 months/never used them. The total number of the biogas digester surveyed is 99 sites since 1 site has adapted its biogas digester for research.

- Problems that contribute to schools/organizations stopping using biogas digesters are:

• Equipment problems: users thinking that the system too complicated; requiring a lot of work; yields too little compared with workload; inconvenience of waste feeding, mixing, and draining digested sludge; and the gas storage tank too small able to use only little amount of gas.

• Administrative problems: lack of person in charge, responsible person having too much work, no time for running the system, no cooperation from other people in organizations, too little support from management, no budget for buying pH meters and weighting scales, and too little organic waste to feed into the digesters.

5.1.2 Solutions to problems and obstacles to biogas digester use are two folds.

- Improvement of biogas digesters which has been done as follows: • Installed a tank and a pump for pumping organic waste into the digester and

to pump sludge within the digester for mixing in place of using manual agitator. The pump is also used for pumping digested sludge from the digester to the sand-drying tray or for fertilizing plants. This makes the work easier, and reduces time and work in operating the system.

• Improved of the gas storage tank. The tank was modified to store the gas at the pressure of 150 mbar. More gas can be stored and stored gas can be used longer (the old set of the tank could store gas at the pressure of only 40-42 mbar).

• Changed the valve, waste feeding pipe, digested sludge draining pipe, biogas pipe, and manometer to be in line with other modifications mentioned above.

- Holding a meeting among schools/organizations where biogas digesters have been installed to share experience and solutions together. Their shared experience and proposed solutions were useful for tackling the administrative problems of biogas digester use. 5.1.3 The results of conducting a field trip to the sites to monitor biogas digester use after the digester improvement show that 55% of the biogas digesters have been used continuously which increased. However, 19.54% of the digesters show relatively low use,




and 25.25% of the digesters never been used. The main causes of these are administrative problems. For those who use the digesters, almost all of them (90.76%) are satisfied with the digesters after modification. Easier use, more convenience, saving time and work, and longer gas use are reasons supporting their satisfaction. 5.1.4 The efficiency of biogas digesters after modification can be summarized as follows - Biogas produced from a biogas digester in 24 hours with 10 kg of organic waste as input (20% solid content) is 1.81-2.58 cubic meters. Factors contributing to the difference are substrate mixing method, organic waste retention time before feeding, and temperature. - The biogas composed of methane 58.97-60.85%, CO2 35.87-36.33% and other gases 1.67-5.16%. - The digested sludge that is used as liquid fertilizer contains nutrients for plants: N 0.2-0.21%, P2O5 0.03% and K2O 0.02-0.03%. As for the digested sludge used as dry compost contains nutrients for plants: N 2.62-3.44%, P2O5 1.35-2.26% and K2O 0.42-0.61%. - The biogas digesters have pollutant removal efficiency of BOD, COD and TKN at 98.26-99.59%, 93.18-93.50% and 8.32-23.11% respectively. This is close to the standard of the pollutant removal efficiency of the commercial MSW anaerobic digesters.

5.1.5 The results of biogas digesters best use contest for schools/organization which continuously use and maintenance the digesters, create participation in using the digesters and raise awareness among students and public are presented below. 1st prize Wat Praduthammathipat School, Bangkok 2nd prize Khlong Nongyai School, Bangkok and Wat Bangnoi School (Jamprachanukul), Samut Songkham 3rd prize Wat Madua School, Nonta Buri and Wat Donwai School, Nakorn Pathom In addition, there were 9 other schools which received honorable mention prize and 4 schools/organizations which received special prize as morale for the operating staff. Awards were plagues for 1st to 3rd prizes, and certificates for honorable mention prize and special prize; and cash in total of 140,000 baht. 5.2 Results of the extension of biogas digesters use of 200 sites in every part of the country 5.2.1 Designing, preparing technical specifications and tender documents were done by the consultant. They were used for the hired contractor that would fabricate and install biogas digesters in 200 sites. The contractor selection was done through e-Auction process. The designed digesters were similar to the modified digesters installed in 2006 fiscal year. DEDE hired a contractor to fabricate and installs digesters separately from the project. The timeframe for it was from 27 September 2007 to 9 January 2008.




5.2.2 The appropriate locations for the new 200 sites of biogas digester installation comprise 96 local administration organizations, 83 schools, 20 organizations under Ministry of Defense and 1 hospital. They are in different regions of the country: 45 sites in the central part, 39 sites in the north, 42 sites in the northeast, 49 sites in the east, and 25 sites in the south. 5.2.3 The survey of the 200 biogas digesters selected sites with suggestions of site preparation before installation started on 26 October 2007 and ended on 14 December 2007. 5.2.4 Biogas digester start-up, demonstration and training of the 200 sites started on 30 November 2007 and ended on 10 April 2008.

5.2.5 The monitoring of the biogas digester use was done through telephone calls, field trip to the sites, and the return of operation records from the sites. They were done from 25 December 2007 to 31 May 2008. They can be summarized that the users are in the beginning of the digester operation. Most of them had satisfied the operation results. That is, the produced gas is flammable, and they started using the biogas for cooking, and started using the digested sludge as compost. Still, the use of digesters and their products should be monitored onwards to promote the use of digesters continuously. 5.3 The results of the project economic feasibility analysis The analysis of feasibility of investment for the extension of the biogas digester use by installation of the new 200 biogas digester across the country in 2007 fiscal year. The results can be summarized as follows. - Internal Rate of Return: IRR is 28.94% - Net Present Value: NPV is 6,019,945.56 baht - Payback Period is 2.60 years - Benefit/Cost Ratio is 1.55 The analysis found that the project is economic feasible. 5.4 Suggestions

5.4.1 Further improvement of biogas digesters should be done. Equipment and tools

that require less maintenance should be used. Additional equipment should be installed to increase the efficiency of the biogas digesters to produce biogas. Bigger size of the gas storage tank should be considered. The cooking burner should have more efficiency so that less biogas will be used and that more cooking gas is replaced by biogas.

5.4.2 Selection of biogas digester installation sites in the future should be done on the basis that the users are ready and see the importance of organic waste management such as local administration organizations which are responsible for solid waste management in their




area. They should have staff that can be responsible for running the digesters since the results of the project show that what contribute to the success of biogas digester use are staff, good administration, and internal support of the organization.

5.4.3 Continuous monitoring of the biogas digester use should be done so that support, suggestions and solutions to problems that occur will be given to the users. Continuous use of the digesters should also be promoted. If possible, the organization that the user reports to should take part in the monitoring.

5.4.4 Problems that occur whether they are related to digester operation, damage of equipment or installation faults should be solved immediately by the responsible party. Immediate solutions prevent discouragement of users who do not succeed in using the digesters and eventually stop using them.

Energy Research and Development Office Department of Alternative Energy Development and Efficiency Ministry of Energy 17 Rama 1 Rd. Pathumwan Bangkok 10330

Tel 0-2222-4102-9 Fax 0-2225-2548

STFE CO., LTD 17th Floor., S.P. Building, 388 Phaholyothin Rd.,

Bangkok 10400 Tel 0-2273-0037 Fax 0-2273-0735

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