EVALUATION OF HEAT PRE-TREATMENT ON BIOGAS PRODUCTION FROM CORN STOVER AND GOAT MANURE UNDER ANAEROBIC CONDITION

Abstract

Biogas technology, which is meant to produce methane rich gas through anaerobic digestion of biological materials, is an environmentally friendly technology that decreases environmental pollution through decomposing organic wastes and positively impacts the socio-economy of the society. Therefore, the research was conducted to investigate the production of biogas from corn Stover co-digested with goat manure through anaerobic digestion. In this study, five different proportions of Corn Stover and Goat manure (100%Corn Stover, 75%Corn stover+25%Goat manure, 50%Corn Stover+50%Goat manure, 25%Corn Stover+75%Goat manure, 100%Goat manure) were used to obtain the suitable mix ratio by incubating at 38ºC using batch fermentation after the substrates were thermally treated at a temperature of 80°C and untreated separately. Having determined the optimum mix ratio, thermally treated substrates at 80ºC were applied to compare the results with those obtained with untreated substrates. In all treatments, physico-chemical parameters such as total solid (TS), volatile solid (VS), organic carbon, total nitrogen, carbon to nitrogen ratio and pH were measured before and after anaerobic digestion (AD). Gas production was noticed in all of the digesters from the 1st day of AD. The daily biogas production was subsequently measured by water displacement method for 30 days. Results showed that, in untreated substrates, biogas yield was minimum in the first three days of incubation and peaked at around 7th day of incubation with gradual reduction and close to none on 30th day. For thermally pre-treated substrates, however, biogas yield was even higher on the first day of incubation and peaked earlier (on the 3rd day) than untreated substrates. Out of the five treatments, treatment 4 (T4=25%CS+75%GM mix ratio) has produced high cumulative amount of biogas in both 80°C thermal pre-treatments and untreated (1426.72 and 1177.65mL), respectively. Better cumulative biogas yield was observed on the all treatments pre-treated under 80°C than untreated. The highest reduction of TS (22.01%) and VS (11.33%) were recorded in T4 thermally treated at 80°C. The result also revealed that co-digestion enhances the production of biogas and an increment of biogas was observed with the increment of the GM concentration in the co-digestion. Generally, the T4 was the best mix among all other treatments which produced high cumulative biogas in 80°C thermal pre-treatment (1426.72mL). Overall the results indicated that the biogas yield and VS and TS reduction of the 25%CS+75%GM mix ratio can be enhanced with the use of thermal pre-treatments prior to anaerobic digestion