Comparative Anaerobic Co-Digestion Effects of Some Agricultural Biomass on Their Digestates Biochemical Properties

Abstract

The huge agro-industrial biomass wastes had engendered the need for appropriate treatment technology, which could be deployed to sustainably manage and convert them to useful by-products. Consequently, the comparative anaerobic co-digestion effects of some agricultural biomass on their digestates biochemical properties were conducted. Twelve (12) replicates slurries from four mixing ratios of maize cob, poultry droppings and cow dung (1:0, 1:0, 1:0 and 1:1:1) as treatments TA, TB, TC and TD respectively, were separately digested in 13.6L locally fabricated batch-digester reactors, for eight weeks. Proximate and amino acids constituents were evaluated by standard procedure prior to and at post anaerobic digestion (AD). The biogas yields followed the sequence of TD (2200.7ml/kg) > TB (2197.9ml/kg) >TC (2079.0ml/kg) > TA (1713.2ml/kg), showing co-substrate effects. Proximate assay depicted a decrease in crude lipid across the treatments, with TC (86.82%) and TD (64.66%) as highest and lowest values. Crude fiber and nitrogen free extract had similar observation, apart from TB and TC with increased values. Percentage moisture and percentage ash contents increased across treatments. Carbon - Nitrogen ratio reduction (C/N Reduction) was in the range of 12.94 -85.79%. The Percentage chemical oxygen demand reduction (CODR), followed the order of TA (46.81%) > TB (34.15) >TC (25.81%) >TD (8.00%). There was increased histidine, glycine, cystine, methionine, total nonessential amino acids (TNEAA) and total aromatic amino acids (TArAA), with decrease in aspartic acids and serine. Percentage arginine, threonine, glutamic acid, proline, alanine, isoleucine, tyrosine, total amino acids (TAA) and total essential amino acid (TEAA) decreased only in TB. While, only TA had Percentage increased lysine (25.00%), valine (40.98%) and TArAA (6.13%), with phenylalanine unaffected (0.00%), Percentage leucine of TB (60.14%) and TD (23.08%) were reduced after AD. The process had revealed the alternative waste management, energy options, and useful industrial by-products for agro-allied industries.