Universidad Autónoma de Coahuila Escuela de Ciencias Biológicas The University of Georgia Department of Biological and Agricultural Engineering TIES PROGRAM PHASE III Project review Student Jesús Emmanuel Chavarría Palma
Responsibles
K.C. Das
Senthil Chinnasamy
Nagamani Balagurusamy
Friday, June 19th 2009 Summary The anaerobic digestion has been applied for the biogas production as an alternative for the necessities of combustible sources for the energy obtaining. The biogas produced is useful for that purpose only if the biogas contains more than 55% methane. Typically the biogas is compounded by methane (50‐70%), CO2 (20‐40%) and in smaller quantities CO, H2S, NH3, N2, H2 and water vaporized (Energy commission, 1998). The biota responsible of producing the biogas under anaerobic conditions considers, principally hydrolytic bacteria which decomposes the organic matter into simpler organic compounds; acidogenic bacteria converts those monomers to organic acids of low molecular weight (C1‐C8), mainly acetate, which is the precursor of the 70% of the methane produced (Schmidt, 2000); methanogens that reduces the methyl group from the organic acids to methane. One interesting novelty for the enhancement of biogas production is the charcoal addition that works as physical support for the microorganisms involved in the process (Kumar et. al., 1987). In this study is being applied as fed batch modality for digestion of animal wastes (poultry litter and cow manure) and one co‐digestion of cow manure and dried powdered spirulina. Is well known that the fed‐batch processes favors the second metabolites production and according with Chowdhury and Fulford (1992) this kind of processes present higher digestion rates than batch digestions. Materials and methods The experiment was developed considering 3 treatments and 4 sub‐treatments that are described below: •5% charcoal + inoculum
•7% charcoal + inoculum
•10% charcoal + inoculum
•Inoculum
Contol (distilled water)
•5% charcoal + inoculum
•7% charcoal + inoculum
•10% charcoal + inoculum
•Inoculum
100% dairy manure
•5% charcoal + inoculum
•7% charcoal + inoculum
•10% charcoal + inoculum
•Inoculum
75% dairy manure + 25% algae
100%poultry waste
Figure 1. Experimental plan. •5% charcoal + inoculum
•7% charcoal + inoculum
•10% charcoal + inoculum
•Inoculum
The experiment was planned to test the differences of three different substrates (poultry litter, cow manure, cow manure+algae) considering one co‐digestion. Besides that, the experiment was planed to test the effect of the addition of three diferent concentrations of vegetal charcoal. 10% of the bioreactors working volume was used as inoculum using filtrated cow rumen fluid. The carbon‐nitrogen content was analyzed using the LECO 932 equipment which gives the percentages of the dried samples. The chemical oxygen demand (COD) was done using HACH equipment and reagents for HR (0‐1500 mg/L) based on the dichromate method. The biogas produces was measured by water displacement. The gas composition was measured through gas chromatography (GC) using a thermal conductivity detector (TCD). The volatile fatty acids (VFAs) were C10%CH
quantified using GC and flame ionization detector (FID). pH was monitored with help of pH strips 0.5 graduated. Total and volatile solids were done using C7%CH
the proximate analyzer TGA‐701 from LECO Co. C5%CH
Results C
Biogas production The total biogas production is the result of the PW10%CH
anaerobic process of the hydrolytic bacteria that produces the VFAs and the methane, which is product of the methanogenic activity of the correspondent PW7%CH
microorganisms. The charcoal has been added pulverized to increase the available surface for the PW5%CH
microbial development, hence that hypothesis (Fig. 2) in the treatments 100% poultry waste and 100% dairy manure algae showed a reversed tendency while the PW
75% dairy manure/25% treatment did show an expected tendency showing as the 7% of charcoal as DM/AL10%CH
the higher subtreatment tested. DM/AL7%CH
DM/AL5%CH
DM/AL
DM10%CH
DM7%CH
DM5%CH
DM
0
2000
4000
Volume(mL)
6000
Figure 2. Total biogas produced The graph shows the total biogas produced during 56 days of digestion. The higher concentration of charcoal in the bioreactor should have been the higher biogas producer but according with the graph the treatments 100% dairy manure and 100% poultry waste did not tend such way. C10%CH: Control – 10% char C7%CH: Control – 7% char C5%CH: Control – 5% char C: Control PW10%CH: 100% poultry waste – 10% char PW7%CH: 100% poultry waste – 7% char PW5%CH: 100% poultry waste – 5% char PW: 100% poultry waste DM/AL10%CH: 75% dairy manure/25% algae – 10% char DM/AL7%CH: 75% dairy manure/25% algae – 7% char DM/AL5%CH: 75% dairy manure/25% algae – 5% char DM/AL: 75% dairy manure/25% algae VFAs Acetate is well identified as the prime precursor for the methane production in anaerobic digestion by methanogens what have driven the attention to that specific groups of microorganisms. Methanosarcina spp. and Methanosaeta spp.have been identified in the acetate conversion to methane, and those two genera can be distinguished from each other morphologically and according with their affinity to acetate (Schmidt et. al., 2000). The production of acetate and propionate was higher in the treatments with poultry waste, being the PW5%CH the one with the best acidogenic activity. Figure 3. VFA total production. Treatment Acetic acid Propionic acid Isobutyric acid Butyric acid Isovaleric acid Valeric acid Isocaproic acid Caproic acid DM DM5%CH DM7%CH DM10%CH DM/AL DM/AL5%CH DM/AL7%CH DM/AL10%CH PW PW5%CH PW7%CH PW10%CH C C5%CH C7%CH C10%CH 142.7 99.1 126.3 113.8 1663.3 851.4 908.5 789.0 937.7 2085.7 1999.1 1887.5 58.8 32.3 34.2 28.4 93.7 51.5 46.0 46.9 333.0 344.6 304.8 285.4 355.5 326.4 311.5 316.6 12.8 7.6 7.0 4.2 3.4 2.4 7.0 5.3 72.4 66.9 70.3 67.9 10.6 26.4 25.5 17.4 0.6 0.0 0.0 0.0 23.2 11.1 10.9 8.6 331.2 181.8 205.9 192.8 86.9 200.3 143.9 160.1 6.0 3.6 3.3 1.7 5.5 4.1 4.0 7.7 110.8 97.5 103.5 83.9 12.7 19.5 16.0 12.9 1.3 0.6 0.5 0.2 4.1 1.1 0.7 1.8 89.2 47.2 43.4 36.6 6.4 14.3 12.1 10.8 0.0 0.0 0.0 0.3 1.2 0.2 0.0 0.3 18.2 15.7 18.7 18.0 0.5 0.7 1.1 0.0 0.0 0.0 0.0 0.0 2.0 0.2 0.0 0.1 23.0 11.7 13.8 14.4 0.8 6.4 5.7 4.4 0.0 0.0 0.0 0.0 The chart shows the total addition of the VFAs production for each treatment. The highest acetate producer was the PW5%CH thus DM/AL7%CH was the best biogas producer and that treatment got the second best acetate production during 56 days of anaerobic digestion. Gas composition One of the objectives of the anaerobic digestion is methane, same that was produced in higher volumes by the treatments that were a co‐digestion between spirulina‐dairy manure in 25%‐
75% respectively. It is important to mention that the treatments that had more biogas production were not the treatments that produced more VFAs, this suggest that even the charcoal addition increased the biota in the bioreactors, the methanogens were not equally stimulated and supported on the additional surface for microbial activity. Figure 4. Methane production 80
70
Methane (%)
60
50
40
30
20
10
0
2
9
16
23
30
37
44
51
58
DM
DM5%CH
DM7%CH
DM10%CH
DM/AL
DM/AL5%CH
DM/AL7%CH
DM/AL10%CH
PW
PW5%CH
PW7%CH
PW10%CH
C
C5%CH
C7%CH
C10%CH
Days
The highest methane producers were the treatments with 75% Dairy manure/25% spirulina, the highest VFAs producer (PW5%CH) got 39.4% methane as maximum. References Energy commission of Nigeria, 1998. Rural renewable energy needs and five supply technologies. pp. 40‐42. Chowdhury and Fulford, 1992. Batch and semi‐continous anaerobic digestion systems. Renewable energy, Vol. 2, No. 4/5, pp. 391‐400. Schmidt et. al., 2000. Acetate conversion in anaerobic biogas reactors: Traditional and molecular tool for studying this important group of anaerobic microorganisms. Biodegradation, No. 2, pp. 359‐364. Kumar et. al., 1987. A note on stimulation of biogas production from cattle dung by addition of charcoal. Biological wastes, No. 20, pp. 209‐215.