Biomass conversion technologies

Biomass can be converted into several useful forms of energy using different processes (conversion technologies) which are described in this chapter. Bioenergy is the term used to describe energy derived from biomass feedstocks. Several processing steps are required to convert raw biomass into useful energy using the three main process technologies available: bio-chemical, thermo-chemical, and physio-chemical. Bio-chemical conversion encompasses two primary process options: anaerobic digestion (to biogas) and fermentation (to ethanol). For the thermo-chemical conversion routes, the four main process options presented here are pyrolysis, gasification, combustion, and hydrothermal processing. Physio-chemical conversion consists principally of extraction (with esterification) where oilseeds are crushed to extract oil. Bioenergy consists of solid, liquid, or gaseous fuels which can be obtained from the available technologies. Liquid fuels are commonly used in transportation vehicles, but can also be used in stationary engines. Solid fuels are directly combusted to obtain heat, power, or CHP. Gaseous fuels can be applied to the full range of end-uses. Several factors affect the choice of conversion process including the type, quantity, and characteristics of biomass feedstock, end-use requirements, environmental regulations, economics, location, and project-specific factors. It is the form in which the energy is required and feedstock availability determines the process route. How biomass conversion technologies are implemented and operated will affect the GHG emissions that may arise from their use. This chapter therefore outlines the main conversion technologies available to provide an overview of where potential GHG emissions may arise and to provide references to more detailed GHG assessments. Since there are a wide variety of feedstocks, pre-processing, processing, and end-use options available, here we provide context to the LCA practitioner of the considerations of emissions sources from the different biomass conversion pathways