Jatropha - Potential of biomass steam processing to convert crop residues to bio-coal and thus triple the marketable energy output per unit plantation area

摘要

Jatropha curcas cultivation is being undertaken mainly for fuel oil production, but it also results in biomass residues such as fruit husks, seed shell, seed cake or kernel meal, together making up > 80% of the dry fruit weight. Additionally, plant biomass from crop management is also generated. The various biomass residue fractions have gross energy contents ranging from 13 MJ/kg to over 18 MJ/kg. The conversion of these residues into marketable products would contribute to broadening the circumstances under which the jatropha crop is profitable. Biomass Steam Processing (BSP) is a steam assisted thermochemical conversion process, which aims to increase the energy density of lignocellulosic feedstock. Basically, during this process biomass is heated to a temperature of 250-400 degrees C in a steam atmosphere at atmospheric pressure. It converts biomass residues efficiently into bio-coal in a relatively short time period of about 1 h. In the current investigation, BSP was deployed to transform different potential jatropha crop and seed processing residues into marketable high quality bio-coal. The energy density of jatropha residues could be raised considerably, resulting in an estimated total marketable energy yield of 90 GJ per year per hectare of a 5-year-old jatropha plantation compared to a total yield of 30 GJ per year when jatropha oil alone is marketed, as currently practiced.