Low-Cost Crop Residue Pyrolysis System for Biochar Production.

Judicious management of crop residues may contribute not only for building soil fertility by increasing soil organic matter content but also sequestrating carbon into manageable land by returning to the soil as a carbonized biomass (biochar) through pyrolysis process. Pyrolysis (i.e., thermal conversion of biomass under oxygen controlled conditions) generates biochar and bio-oil. Biochar is stable against decomposition under natural conditions. Biochar can be used to increase carbon pool and cycle nutrients back into agricultural fields. Biochar from crop biomass residues can be used as a potential energy source as well as to sequester carbon (C) and improve soil fertility. We built and evaluated two different types of low-cost pyrolysis systems to produce biochar using rice hull as a feedstock. Low-cost pyrolyzer produces rice hull biochar without precise temperature control in the furnace. Averaged 0.43 kg of biochar was produced using 1 kg of dried rice hull feedstock. Bio-oil study is not included in this report. The C content of the biochar ranged from 44% to 47% in the rice hull biochar. A large proportion of N (i.e., 11 g/kg), P (i.e., 1,000 mg/kg), and K (i.e., 4,500 mg/kg) was conserved in the rice hull biochar. The results indicate that, low-cost pyrolyzer could produce biochar, which have potential to serve as nutrient sources as well as sequester C.