Lipids anaerobic digestion

Anaerobic digestion yields of the slurries are given in Table 2.5. Due to the higher proportion of lipids in manure, the methane production is higher than in wheat straw. The total amounts of lipid and protein, in particular, are lower in straw than in manure and thus the theoretical methane yield is significantly lower in wheat straw than in manure (Table 2.5). The average methane yields of manure and wheat straw were 14.7% and 10.4% of volatile solids, respectively (Demirbas and Ozturk, 2004). 

Most often, the rates for feedstock destruction in anaerobic digestion systems are based upon biogas production or reduction of total solids (TS) or volatile solids (VS) added to the system. Available data for analyses conducted on the specific polymers in the anaerobic digester feed are summarized in Table II. The information indicates a rapid rate of hydrolysis for hemicellulose and lipids. The rates and extent of cellulose degradation vary dramatically and are different with respect to the MSW feedstock based on the source and processing of the paper and cardboard products (42). Rates for protein hydrolysis are particularly difficult to accurately determine due the biotransformation of feed protein into microbial biomass, which is representative of protein in the effluent of the anaerobic digestion system. 

Methane is formed in anaerobic environments, e.g., in fresh water or marine sediments, flooded soils, anaerobic sludges, but also in the animal digestive system, from complex organic compounds such as carbohydrates, proteins, and lipids. In the rumen, methane appears to be almost exclusively produced by reduction of CO2. In nongastrointestinal habitats methane appears to be built chiefly from acetate and secondarily from CO2. In both types of habitats the main hydrogen source is molecular H2. 

---