Determination of Performance of Biogas Production from Blended Selected Agricultural Waste Materials

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1 Futo Journal Series (FUTOJNLS) e-issn : p-issn : Volume-2, Issue-1, pp Research Paper July 2016 Determination of Performance of Biogas Production from Blended Selected Agricultural Waste Materials Egbufor, U.C. 1, Okereke, C.D. 2 and Asoegwu, S.N Department of Agricultural and Bio-Environmental Engineering, Imo State Polytechnic Umuagwo, Owerri, Imo State, Nigeria. 2,3 Department of Agricultural and Bio-Resources Engineering, Federal university of Technology Owerri, Imo State, Nigeria. uchenna.egbufor2013@yahoo.com, chidiokereke234@yahoo.com and asosab49@yahoo.com Abstract Fermentation of selected animal waste and water hyacinth materials was carried out at various blending for biogas production with a cylindrical digester of 84 litres capacity on a batch basis for 24 days. The animal waste were cow dung, pig dung and poultry droppings. The materials were characterized in terms of moisture content, bulk density and volatile matter constituent. The different materials were blended in combinations of two each of 10 kg making 20 kg mixed with water at the ratio of 1:2 before it was fed into the digester. The performance of the digestion of the blended materials was based on biogas production. The gas produced was determined using gas chromatographic mass spectrometer (Perkin Elmer) which indicates the presence of Methane (CH 4 ) and impurities. The impurities namely carbon di-oxide (CO 2 ), hydrogen sulphide (H 2 S), ammonia (NH 3 ) and water (H 2 O) were removed with filter system made of calcium oxide, iron fillings and activated charcoal. The biogas (CH 4 ) was measured daily and flared using a biogas burner. The biogas yield increased linearly on daily basis with stirring of the digester. The results showed that the blending of cow dung and poultry droppings had the highest biogas yield of litres in 24days followed by blending of cow dung and poultry droppings with biogas production of litres. The least in terms of biogas production was obtained from the blending of poultry droppings and Water hyacinth. It was concluded that Pig dung blended with Poultry droppings performed better than the other materials studied in terms of biogas yield. Key words: Biogas, cow dung, pig waste, poultry droppings, water hyacinth Introduction Biogas, a renewable energy which provides an alternate source of energy in the rural area can be obtained by the fermentation or decomposition of organic matter from plant, animal or human waste under anaerobic condition. It could be a means of solving the energy challenges in the country. Nigeria is endowed with enormous bio-resources including waste from cow, pig, poultry farm and plant materials such as water hyacinth which can be used to generate energy if well harnessed. Studies showed that Nigeria produces about 227,500 tons of fresh animal waste daily (Ozor, 2014). One kilogram of fresh animal waste produces about 0.03 m 3 of biogas; therefore Nigeria can potentially produce about 6.8 million m 3 of biogas every day from animal waste alone (Ozor, 2014). This process of gas production involves a complex biochemical reaction that takes place in the presence of highly sensitive microbiological catalyst mainly bacteria. Biogas production could be a profitable means of reducing or even eliminating the environmental menace and nuisance of urban wastes in many cities in Nigeria (Akinbami et al., 2001) while producing needed energy with the attendant employment opportunities and wealth creation. Many waste materials in 169 Egbujor et al., Determination of performance

2 Nigeria have been assessed for their possible use in biogas production; they include refuse and sewage generated in urban areas, agricultural residues and manures (Odeyemi, 1987). It could be seen that poultry manure generated in Nigerian homes and in commercial poultry farms could be economically feasible substrates for biogas production. Biogas technology can replace or supplement wood as an energy source for cooking and electric power generation in developing countries and the effluent in the digester can be used as fertilizer for plant growth known as bio-fertilizer which when applied to the soil enriches it with no detrimental effect on the environment (Energy Commission, 1998). The composition of the biogas involves a mixture of gases produced by methanogenic bacteria which consist mainly of methane of % in volume. Major impurities in biogas are carbon( iv) oxide which is about %, hydrogen sulphide about 1-2 %, water vapour, nitrogen, hydrogen and oxygen are found in traces (FAO, 1996). The impurities are removed before the biogas can be used for effective combustion by the process of purification. This paper describes the biogas technology and gives results on the performance of biogas production plant made of blended bio-materials. 2.0.Materials and Methods 2.1. Sample Collection and Preparation The waste materials used in this study as substrates were cow dung, pig dung, poultry droppings and water Hyacinth plant. The cow dung and pig dung were collected from FUTO farm. The poultry droppings were procured from a poultry farm at Ihiagwa, near FUTO, while water Hyacinth plant was collected from Otammiri River at Ihiagwa near FUTO, and was cut into pieces with matchet to allow the substrate to flow easily into the digester. 10 kg of each of any of the different materials were blended in the following combinations: cow dung + pig dung, cow dung + poultry droppings, pig dung + poultry droppings, cow dung + water hyacinth, pig dung + water hyacinth and poultry + water hyacinth. The blended waste materials were collected in batches of 20 kg. Each of the blended 20 kg waste materials was mixed with water at the ratio of 1:2 on weight basis and fed into the modified metallic digester of 84 liters (0.084 m 3 ) working volume for 24 days retention time; the digester was cleaned up before another substrate is introduced into the digester. The experiment was replicated three times to determine the average volume of gas produced. Preliminary tests were conducted with 2.0 g of each of the waste material replicated three times for characterization of their moisture content, bulk density and volatile matter of the material before blending the waste material fed to the digester. The volumes of the biogas production from the respective blend of waste materials fermented in the digester were subjected to statistical analysis. The comparison of mean values of the biogas produced was at 95 % confidence interval Study Area and Digester Type The study was carried out at the Federal University of Technology, Owerri, Nigeria using a digester made from an existing empty gas cylinder. During the modification of the digester, extreme care was taken to avoid leakage. The digester used in the study was a cylindrical metallic tank 39 cm diameter, 70.5 cm height which was made of mild steel. The modification done involved the fabrication of the input and the outlet chamber of the digester. The inlet (input) chamber is the side through which the substrate flows into the digester and it was designed and positioned at an angle of 60 0 to the tank so as to allow the substrate flow into the digester under gravity. The outlet (discharge) 4.5 cm in diameter is the side through which the digested effluent inside the digester chamber could be removed from the digester. It is positioned directly under the digester. Figure 1 is the Isometric view of the Biogas digester connected to the filter system and biogas production measurement manometer. 170 Egbujor et al., Determination of performance

3 Figure 1. Isometric view of biogas digester assembly 2.3. The Experimental Waste Characteristics Waste characterization was carried out to determine the moisture content and volatile as described below Moisture Content 2.0 g of each of the waste material to be digested was weighed (W 1 ) with a digital balance and taken to the rotary oven set at C for 24 hrs. After oven drying, the samples were taken to the desiccators, cooled and reweighed (W 2 ) to obtain the loss in weight. The moisture content was calculated using the formula. % moisture = (W 1 -W 2 )/W1 x 100 (2.1) where, W 1 = weight of wet sample + crucible (g) W 2 = weight of oven dried sample + crucible (g) Volatile Matter 2.0 g of each of the waste material was weighed with a digital balance and taken to a rotary oven set at 105 O C for 24 hrs for moisture removal. After oven drying, the samples were taken to dessicator, cooled and reweighed to obtain the loss in weight. The oven dried samples were taken to the muffle furnace at a temperature of C for 3 hrs after which the samples were taken to the dessicator for cooling followed by weighing. The volatile matter of waste was calculated as, 171 Egbujor et al., Determination of performance

4 Volatile matter = weight of sample from oven weight of sample from furnace /weight of sample (2.2) Also % volatile matter = loss in weight/weight of sample x 100 (2.3) The Filter System The filter system of the digester shown in Fig.2 used in this study is a cylindrical Polyvinylchloride (PVC) pipe of 12 cm diameter and 21 cm height partitioned into three compartments. The first compartment (lower part) contains calcium oxide (CaO); the second compartment (middle part) contains iron fillings (Fe) while the third one consists of carbon (activated charcoal). Biogas flowing into the filtering system contains CH 4, CO 2, H 2 S, NH 3 and H 2 O as determined using gas chromatography mass spectrometer (perkin Elmer model). The mechanism of the filtering system works in such a way that biogas from the digester flows into the filtering system through the lower part of the filtering system where the carbon iv oxide reacts with calcium oxide (Equation 1). The middle phase is the reaction of hydrogen sulphide and iron filling (Equation 2), while the last stage is the reaction of ammonia with activated charcoal (Equation 3). The chemistry of the reactions are as follows: CaO (s) + CO 2(g) CaCO 3(s) (1) Fe (s) + H 2 S (g) FeS (s) + H 2(g) (2) 3C (s) + 4NH 3(g) 3CH 4(g) + 2N 2(g).. (3) 12cm C Fe 21cm CaO Biogas Figure 2: The Filter system 172 Egbujor et al., Determination of performance

5 3.0.Results and Discussion The results of the waste characterization and biogas production from blended waste materials are shown in Tables 1 and 2, and Figures 4 9. Table 1. Characteristics of the Waste Materials. Waste Average moisture Bulk density Average volatile Material Content (%) (g/m 3 ) Matter (%) Cow dung Pig dung Poultry dropping Water hyacinth The result of the characteristics of the waste materials showed that water hyacinth has the highest moisture content with 45.4 %, with pig waste having the least of 24.3 %.Result equally showed that volatile matter for cow dung has the highest value of 24 % and therefore has the highest potential to produce biogas followed by poultry droppings. The pig dung had the least volatile matter content that is a function of gas production. Table 2 shows the biogas production from the various combinations of waste materials/bioresources. At a mean daily gas production of 2.13 litres, pig dung blended with poultry droppings gave the best performance in terms of biogas production of litres after 24 days followed by cow dung blended with poultry droppings. The use of water hyacinth for biogas production is better blended with cow dung than any other waste material examined in this study. Table 2. Biogas Production from Combined Waste Materials Waste material Cumulative gas yield Mean rate of gas Lag time after 24 days (l) production (l) (hr) Cow and pig Cow and poultry Cow and water Hyacinth Pig and Poultry Pig and water Hyacinth Poultry and water hyacinth Egbujor et al., Determination of performance

6 Figure 3: Daily gas yield of blended cow with pig dung at various temperatures. Figure 3 indicate that gas from blended cow with pig started within 48 hrs of charging the digester and produced combustible gas on the 8th day at the temperature of 28 0 C and biogas volume of 1.50 litres/day. Between 15th and 18th day, gas generated was at the maximum with highest volume of 3.55 litres/day at a temperature of 31 0 C. Total volume of gas generated was litres at the end of 24 days. Figure 4. Daily gas yield of blended cow dung with poultry at various temperatures. Figure 4 shows that gas from blended cow dung with poultry droppings started after 72 hrs of charging the digester. The combustible biogas production commenced on the 7th day at the temperature of 174 Egbujor et al., Determination of performance

7 C and the biogas volume was 1.70 litres/day. Biogas production was highest on the 18th day at the temperature of 30 0 C with volume of 3.65 litres/day. Total gas generated was litres after 24 days Figure 5: Daily gas yield of blended cow dung with water hyacinth plant at various temperatures. The gas from blended cow dung and water hyacinth plant waste commenced after 72 hrs of charging the digester and the combustible biogas started on the 7th day at the temperature of 28 0 C at rate of 1.25 litres/day. Biogas production was highest on the 19th day with a volume of 3.85 litres/day at temperature of 30 0 C. Total volume of gas generated was 48.4 litres in 24 days. In figure 6, the gas from pig waste blended with poultry dropping started after 48hrs of charging the digester and the combustible biogas commenced after the 8th day at a temperature of C and biogas rate of 1.85 litres/day. Gas production was highest on the 19th day at a volume of 3.45 litres/day and temperature of C. Total gas generated at the end of the experiment was litres Figure 6. Daily gas yield of blended pig with poultry at various temperatures. 175 Egbujor et al., Determination of performance

8 Figure 7: Daily gas yield of blended pig dung with water hyacinth plant at various temperatures. The gas from blended Pig dung and water hyacinth (Fig. 7) started after 48 hrs of charging the digester and combustible biogas started on the 8th day at the temperature of 30 0 C at rate of 1.70 litres/day. Biogas production was highest on the 19th day at the temperature of 32 0 C and volume of 3.35 litres/day. The total gas generated was litres at the end of 24 days. Figure 8. Daily gas yield of blended poultry dropping with water hyacinth plant at various temperatures. Figure 8 indicate that the gas from Poultry droppings blended with Water hyacinth started evolving after 72 hrs of charging the digester and the combustible biogas production began on the 7th day of fermentation at a rate volume of 1.30 litres/day at temperature of 28 0 C. The volume of biogas was highest on the 18th day at 176 Egbujor et al., Determination of performance

9 the temperature of C and biogas volume rate was 3.65 litres/day. Total volume of gas generated at the end of the experiment was 43.6 litres. The observed delay before the production of biogas began as seen from Figures 3 to 8 for all the waste materials during fermentation is the lag time. The lag time is the time during which the initial autochthonous microbial population in the medium acclimatized and grew to establish adequate biomass, population of acid forming bacteria (acid formers) and methane forming bacteria (methane formers) that digested the carbohydrates in the waste materials in a catalytic process that led to production of biogas and other gases such as carbon dioxide and ammonia removed by the filter system as impurities (Figure 2 and Eqs 1-3). The biogas production process reaction was favoured by the temperatures of C and mixing. The mixing by stirring or agitation was to re-distribute bacteria to contact the organic matter for enhanced performance observed. The lag time was in the range of 48 to 72 hrs. The shorter lag time in this study of 48 hrs is preferred to 72 hrs because of time/ cost saving consideration that is important in the biogas production system. 4.0.Conclusion The result of the biogas digester experiment showed that 47.94, 49.68, 48.42, 51.08, and litres of methane gas were generated after 24 days from the respective 10kg material blended with one another to 20 kg mixed with water at the ratio of 1:2. The results also showed that the blending of Pig dung with poultry dropping had the highest biogas yield of litres followed by blending of cow dung with poultry dropping of biogas production of litres. The least in terms of biogas production was obtained from blending poultry droppings with Water hyacinth. It was concluded that blended Pig dung and Poultry droppings performed better than the other materials studied in terms of biogas yield at 95 % confidence interval. Further study is required to reduce the lag time of 48 hrs prior to biogas production from the agro-waste materials. References Akinbami, J. F. K., Ilori, M. O., Oyebisi, T. O., Akinwumi, I. O. & Adeoti, O. (2001). Biogas energy use in Nigeria: Current status, future prospects and policy implications. Renew Sustain Energy. 5, Energy Commission of Nigeria (1998). Rural renewable energy needs and five supply technology: Papers prepared for the joint ENC-NYSC Rural Renewable Energy project Training workshop FAO (1996). Food and Agricultural Organization, China: Azolla propagation and small biogas technology. Agriculture Service Bulletin FAO Rome.41, 9-11 Inyama, S.C. & Iheagwa, V.A. (2006). Statistic and Probability. A focus on Hypotheses Testing ( 3 rd Ed), Perfect Strokes Global Ventures Owerri, Nigeria. Odeyemi O. (1987). Research needs priorities and challenges in biogas production and technology in Nigeria. Paper delivered at the Water and Centre for Genetic Resource and Biotechnology (NACGRAB) Seminar, Ibadan, Nigeria Ozor, O. C. (2014). Biogas production using cow dung from Abakaliki abattoir in South- Eastern Nigeria. International journal of Scientific and Technology Research 3, Stout, B. A. & Best, G. (2001). Effective energy use and climate change: need of rural areas in developing countries. Journal of Scientific Research and Development. 3, Uzodinma, E. O & Ofoefule, A.U (2009). Biogas production from blends of field grass (panicum maximum) with some animal wastes. International journal of physical Science, 4 (2), Egbujor et al., Determination of performance