Implementation of a Forest Biomass-based Biofuel Industry: A Canadian Experience

Abstract

The forest biomass is an abundant renewable resource from which biofuels can be derived. In the Kraft process the cellulose is extracted from the wood to form the paper pulp while the other organic components, primarily hemicelluloses and lignin, are burnt to produce steam. It is possible to divert part of the hemicelluloses or lignin to produce fuels on site, a mode of operation referred to as the integrated forest biorefinery. Hemicelluloses can be hydrolysed into sugars which in turn are converted into ethanol or butanol while lignin can be extracted from a residual process stream, the black liquor, by acid precipitation, de-ionized, dried and directly used as a fuel or further processed into value added chemicals. Biorefinery processes have been proposed and analysed by simulation on ASPEN PLUS. Intensive integration of thermal energy, water and material systems is of paramount importance to the sustainability of the global site; the increased energy load on the utility systems could cause rising dependency of the global site on fossil fuels. To avoid this consequence, a new original energy efficiency analysis an enhancement methodology has been developed and validated on actual Canadian Kraft mills before being applied to the integrated biorefinery and has produced remarkable results far superior to the current engineering practice. This has led to the concept of the green integrated forest biorefinery (GIFBR). i.e. an industrial site with zero fossil fuel consumption and reduced GHG emissions vs. the Kraft process and biorefinery plant alone. The GIFBR incorporates a woody biomass gasifier producing syngas as a fuel for the integrated biorefinery and for steam production or sale. It can also include a combined heat and power (CHP) unit driven by steam made available by liberated production capacity from the installed power plant.