Influence of biochar on physico-chemical and microbial community during swine manure composting process

Excessive nutrients and toxic gas emissions from animal manure management are of great global concern, with negative environmental and economic consequences worldwide. Due to biochar recalcitrance and sorption properties, this study investigated the effect of the biochar(BC) derived from bamboo, amendment on swine manure(SM) composting efficiency through physical, physio-chemical, gaseous emissions, microbiological, and phytotoxic analysis during the 56 day process of in-vessel composting. The treatments were set-up from different ratios of biochar to swine manure mixed with sawdust(SD)(i.e. SM + SD + 3%BC(T1), SM:SD + 5 %BC(T2) and SM:SD + 10 %BC (T3)), while treatment without biochar amendment was used as a control, SM:SD(C). The results showed that, compared to the control, biochar amended compost mixtures had significantly reduced (p ≤ 0.05) bulk density, organic matter(OM), C:N ratio, NH₃ emission, pathogenic microorganisms, and phytotoxicity effect (Cress seed, Lepidium sativum Linn.). On the other hand, biochar amendment mixtures had increased total porosity, water holding capacity, rapid thermophilic temperature, and nitrate nitrogen. However, with the most prominent effects in terms of the nutrient quality and degradation rate of compost mixtures, the amendment of 10% biochar is recommended for swine manure management through the composting process.