Integrated Thermochemical Conversion Processes for the Production of Soil Amendments and Biofuels from Agricultural Waste

Abstract

The demand for food and energy resources is continuously increasing as the global population grows. Conventional fertilizers are used to promote crop growth to meet these demands, but also lead to adverse environmental issues such as nutrient runoff. Biochar is a promising soil amendment alternative that is produced from hydrothermal carbonization (HTC) or pyrolysis technologies. However, neither process is ideal - HTC is suitable for wet biomasses, but the produced hydrochars suffer from low surface area; Pyrolysis is suitable for dry biomasses, but the produced biochars contain low nutrient content. We proposed an integrated HTC/pyrolysis process to produce biochars by co-pyrolyzing cow manure hydrochar with raw agricultural residues. The physical characteristics (i.e. proximate analysis, pH, surface area, nutrients…etc.) and heating value of char products were investigated for use as solid fuels. The integrated HTC/pyrolysis process demonstrated an enhancement in bioavailable nutrients, but the surface area is sample dependent. Results revealed that the biochars are ideal for soil amendment, while the hydrochars are generally more suitable for solid fuel applications.