Enhanced Biogas and Biofertilizer Production from Anaerobic Codigestion of Harvest Residues and Goat Manure

Abstract

Comparative assays were conducted to assess the biogas and biofertilizer production efficiency from anaerobically codigested goat manure (GM) and harvest residues: corn stover (CS) and rice straw (RS). All digesters were operated simultaneously under mesophilic temperature of 40°C and notable phosphate solubilizing and nitrogen fixing bacterial populations indicated qualitative biofertilizer quality of the digestates. Codigestion of the substrates significantly increased biogas yield (p < 0.05) compared to monodigestion, and the highest cumulative yield of 573 ml/g VS was obtained from codigested rice straw (RS) and goat manure (GM). With a significant decimation in number of pathogens (p < 0.05), a 2 – 3 fold increase in populations of plant growth promoting bacteria (Bacillus and Pseudomonas species) was observed in digestate from codigestion assays when compared to monodigestion (control) and were identified as Clostridium sp., Bacillus subtilis, Bacillus megaterium, Lactobacillus sp., Pseudomonas fluorescens including methanogens: Methanothrix sp., Methanobacterium sp. and Methanosarcina sp. On the average, codigestion assays resulted in enhanced biogas yield and biofertilizer quality that was 2.3 – 4.1 times higher than single substrate digestion and generally improved the efficiency of biogas and biofertilizer production.