Thermal Conversion of Biomass

Bioenergy is presently the largest global contributor of renewable energy. Biomass thermal conversion has significant potential to expand in the production of heat, electricity, and fuels for transport. In addition, energy from biomass can contribute significantly toward the objectives of reducing greenhouse gas emissions and alleviating problems related to climate change. There are three main thermal processes – combustion, gasification, and pyrolysis – to convert the biomass into various energy products. Combustion is well established and widely practiced with many examples of dedicated plant and co-firing applications. At present, biomass co-firing in modern coal power plants is the most cost-effective biomass use for power generation. Due to feedstock availability issues, dedicated biomass plants for combined heat and power (CHP) are typically of smaller size. Gasification provides a competitive way to convert diverse, highly distributed, and low-value lignocellulosic biomass to syngas for combined heat and power generation, synthesis of liquid fuels, and production of hydrogen (H2). A number of gasifier configurations have been developed. Biomass integrated gasification combined cycles (BIGCC) using black liquor are already in use. Gasification can also coproduce liquid fuels, and such advanced technologies are currently being investigated in research and pilot plants. Pyrolysis is thermal destruction of biomass in the absence of air/oxygen to produce liquid bio-oil, syngas, and charcoal. Fast pyrolysis for liquid fuel production is currently of particular interest because liquid fuel can be stored and transported more easily and at lower cost than solid biomass. Pyrolysis technology is currently at the demonstration stage, and technologies for upgrading the bio-oil to transport fuels are applied at the R&D and pilot stage. This chapter provides an overview of the state-of-the-art knowledge on biomass thermal conversion: the recent breakthrough in the technology, the current research and development activities, and the challenges associated with its increased deployment.