Optimization of Biogas Generation Through Anaerobic Co-digestion of Diverse Biomasses

Abstract

Poor biogas productivity has been delineated due to presence of macro- and micronutrients in anaerobic digestion at low levels. The present study assessed the capability of the different biomass i.e., water hyacinth (Eichhornia crassipes), corn (Zea mays), giant reed (Arundo donax) and poultry waste etc., for biogas production through co-digestion process. The proposed substrates were characterized biochemically and assessed for biogas generation during monodigestion and co-digestion. The effects of inocula and toxicity of some antibiotics were also assessed on the process performance. On the basis of chemical characterization, water hyacinth was considered as suitable for mono and co-digestion due to high volatile solids (VS) and total soluble contents. However, poultry substrate is appropriate only if it is co-digested with other biomass. The ratio experiments of different plant biomasses and poultry wastes demonstrated that water hyacinth and poultry (50:50) produced 262 mLgVS-1, giant reed and poultry produced (80:20) produced 235 mL gVS-1, maize and poultry (60:40) produced 193 mLgVS-1. However, the pretreatment of plant biomass with Fenton’s and Fenton’s plus ultrasonic had no effect on biogas generation as compared to co-digestion. In batch experiments, all the antibiotics concentrations had severely inhibited biogas production as compared to control. However, erythromycin and tetracycline showed greater inhibitions as compared to bacitracin and monensin. The continuous addition of residual antibiotics in manure may affect the hydrolysis of organic matter during anaerobic digestion. The accumulated residual antibiotics had additive effects on daily and cumulative biogas production when poultry substrates and stillage were fed into the CSTRs against the two different inocula (cattle rumen microflora and municipal sludge). The Reactor with cattle inocula produced optimum biogas generation until it was perturbed with antibiotic monensin on 100 day. We recommend the co-digestion of substrates like water hyacinth and giant reed produced on marginal lands for biogas production to overcome the energy crisis in developing countries. The molecular analysis of the microbial composition showed that the microbial consortia found in a particular digester varied based on the biochemical nature of substrates used in the bioreactor.