ABSTRACT DESIGN, FABRICATION AND CALIBRATION OF A PORTABLE BIOGAS GENERATOR (PortaGas) R.N. Concepcion, Ph.D., G.P. Nilo, Ph.D., A.H. Anida, C.F. Serrano, L.P. De Leon, and V.V. Babiera, The feasibility and development of the portable biogas generator, as an alternative source of fuel and/or energy, for homes, farms inthe countryside have been undertaken for a period of five years, starting from 2001 to 2005. Basically, the portable biogas generator, unlike its existing fixedstructure counterpart, is ofthe split-batch type. Moreover, the portable biogas generator developed by the Bureau of Soils and Water Management (BSWM) utilizes biosolids, and rice straw - in contrast to the former type, which utilizes primarily hog manure. Furthermore, the concept was based from an earlier study on the use of digested rice straw as compost for soil fertility enhancement ( Weerasinghe, et al., 1999; Concepcion, personal communications, 2000). ABSTRACT (continuation) The study results have indicated that the 100 kg fresh rice straw charged into the generator, produced: - 25 cu.m. of biogas (63 64% CH 4 ) and is equivalent to one cylinder LPG of 11 kg - N content of the compost that was produced from the anoxic process, increased from 0.6% in fresh rice straw, to 1.5%, this is equivalent to two bags of organic fertilizer - liquid fertilizer significant volume of 750 liters were produced Series of trials were made to improve the performance of the biogas generator and quality of the by-products. OBJECTIVES General - To maximize utilization of farm/agricultural waste - Development of a relatively sustainable and economically-viable alternative source of fuel for the typical Filipino family - Determine portagas feasibility as a community-based source of livelihood. Specifics - Design / develop a simple methane recovery implement. - Determine the viable substrate combination and proportion of deriving biogas from rice straw + chicken manure + water. - Determine the potential of digested compost and effluent byproducts from biogas generation as organic fertilizers for crop production, and direct means of mitigating the methane gasgreenhouse effect. 1
METHODOLOGY Design and Fabrication Batch-fed industrial-scale generator Continuous flow industrial -scale generator For the past few decades, the most common biogas plants in the Philippines are made up of steel reinforced concrete structures, popularized by Maya Farms (Felix D. Maramba Sr., et al. 1978). May it be at industrial or domestic scale. Some of them were patterned from other Asian countries and these models were designed primarily for animal manure. Designs from temperate countries are also shown in. Continuous-fed digester for slaughterhouses (MARAMBA- TAGANAS) Vertical, continuous -fed biogas plant (MAYA FARMS - INDIA) Fixed-dome continuous-fed biogas plant (MAYA FARMS - CHINA) Double -walled continuous-fed biogas plant (MAYA FARMS TAIWAN) Taiwan single stage biogas plant Taiwan 2 -stage methane generator China biogas plant Anaerobic digestion of pig waste (Japan) Sri Lankan batch type bio gas generator for rice straw Gas generating plant for veg. Wastes (BURKE-JACOBS; AMES, IOWA) SCHMIDT EGGERS GLUSS SYSTEM (GERMANY) 2
BSWM Concepcion model with three digesters (2000) The PortaGas Model 1 (2001) Increase in the number of digesters and modified gas holder assembly Plan for the first modified version ( PortaGas) Gas Holder fittings with simplified fittings PortaGas Model 2002 Gas lines repositioned on the sides of the digesters Preparation of fittings and other accessories Gas holder assembly 3
METHODOLOGY con td.. Calibration (Gas holder and Digester) 10 kgs substrate 15 kgs substrate 12 kgs substrate Gas Space Gas Space Gas Space Substrate ½ filled Substrate ¾ filled Substrate 2/3 filled 1 st Trial 2 nd Trial 3 rd Trial Calibration of the digesters Gas holder / collector Steps in Installation / Setting-up Fully installed set-up A B C D E F G H I 4
RESULTS AND DISCUSSION RESULTS cont d The bluish, very hot flame (18 th day after installation) Biogas generated (cu.m./week) Active growth phase Biopause period Senescence stage Weeks Weekly Biogas liberation pattern Rice Vegetables Fish RESULTS cont d Difference of NPK and C content of digested and fresh rice straw By-products of the first trial using 100 kg rice straw + 25 kg chicken manure + 0.5 kg Urea + water. 25 m 3 of biogas Rice Straw Digested* % N 1.5 % P 1.4 % K 0.81 % C 0.86 2 bags (100 kg) digested compost 750 liters of liquid fertilizer Fresh** 0.6 0.1 1.5 40.0 Difference 0.9*** 1.3*** -0.7**** -39.14**** Note: * Results from BSWM Laboratory Services Division ** Ponnamporuma (1982) *** Increase in %N and %P **** Decrease in %K and %C (Note: The difference is brought about by the microbial a ctivities within an anoxic condition) 5
Result of prototype revisions Results of Calibration / Refinement of the Implement and Substrate Previous Present A. Implement The most simplified PortaGas Model 2005 1. Installation of fittings and hose on top of the digesters 2. Placement of hose clamps and faucets 3. Attachment of ball valve between the digester and gas holder 4.. Usage of improvised burners 5. Complicated gas holder fittings / attachments 6. Gas holder (2 sets) Repositioned on the sides of the digesters Not necessary Not necessary (to avoid accidental pressure build up within the digesters) Should be done only if a manual cast iron burner is not available Simplified with the use of ½ x 3/8 in. reducer coupling Additional set of gas holders (making it 3 sets) for every 10-drum unit portages is necessary (Medium-scale demo unit) Previous Present Benefit-Cost Analysis B. Substrate / mixture 1. Compressed level of rice straw inside the digesters + enhancers + water (1/2 and ¾ filled) 2.. Urea (46 0 0) Should be maintained at 2/3 level of any size container by putting weights on top (CHB is preferred) Optional, N content can be replaced by increasing the amount of animal manure (5 6 kg per drum) 3. 48 hours soaking of rice straw before Not necessary. The digesters can completing the substrate. be sealed immediately after the level and proportion of the mixture is completed. Materials and Labor (PhP) 14 pieces plastic drums*, plastic hose, sealant, burner and fitting accessories 13,500.00 Labor 1,500.00 Total 15,000.00 6
Estimated Cost Per Set-up 10 Digester with detachable cover (200 lit. cap) @ P800/piece = 8,000.00 2 Water Holder with fixed cover (200 lit. cap) @ P500/piece = 1,000.00 Benefit for a three-month cycle (PhP) 25 cu.m. Biogas = 1 cylinder LPG (11 kg) 500.00 2 bags organic fertilizer (200 / bag) 400.00 750 liters liquid fertilizer (1.00 / L) 750.00 2 Gas Collector open (100 lit. cap) @ P350/piece = 700.00 Total 2,050.00 / cycle Accessories (Burner, Sealant, etc.) @ P3,800 = 3,800.00 Maintenance cost after the initial cycle = 750.00 / cycle Labor @ 2 persons x 3 days x P250/day = 1,500 At First 11 cycles: Total Benefit (PhP) = 2,050.00 + [10 (2,050.00-750.00)] = 2,050.00 + 13,000.00 = 15,050.00 BCR @ 11 cycles = 15,050.00 = 1.003 (breakeven) 15,000 Return of Investments (ROI) starts on the 12 th cycle Estimated minimum usable years of the implement = 10 yrs. CONCLUSIONS 1. The simplified biogas generator is capable of recovering / deriving biogas from the mixture of fresh rice straw + chicken manure + water. 2. The generator has the potential of reducing the unintentional free emission of CH 4 to the atmosphere. Through the direct utilization of biosolids as sources of biofuel, CH 4 free compost and OLF for household and crop production, respectively. 3. The ideal level of substrate is 2/3 for every digester. 4. Putting of weights on top of the mixture is proven effective in avoiding the rising up of substrate that will tend to obstruct gas flow. 7
RECOMMENDATIONS 1. The implement can also be used for pure animal manure (pig, chicken, etc.) plus small amount of crop / plant residues and water. In case of this substrate, a five-drum digester and three sets of gas holders will do. 2. Increase in by-products can be achieved by increasing the number of digester-drums. 3. Gas pressure may be adjusted according to the distance of the burner / gas outlet. This can be achieved by attaching a rubber-compressor on top of the gas holder and unto the sides of the water holder or additional weights can be placed on top of the gas collector. 4. Further studies to improve by-products making use of the different combinations of substrate ratios and on the usage of digested compost and OLF as by products of anoxic decomposition for crop production, is highly recommended Thank you...... Conserve soil and protect Mother Earth, Go Organics!!! 8