PNNL

Abstract

Significant efforts have been devoted to develop processes for the conversion of biomass, an abundant and sustainable source of energy, to liquid fuels and chemicals, in order to replace diminishing fossil fuels and mitigate global warming. Thermochemical and biochemical methods have attracted the most attention. Among the thermochemical processes, pyrolysis and liquefaction are the two major technologies for the direct conversion of biomass to produce a liquid product, often called bio-oil. This chapter focuses on the liquefaction, a medium-temperature and high-pressure thermochemical process for the conversion of biomass to bio-oil. Water has been most commonly used as a solvent and the process is known as hydrothermal liquefaction (HTL). Fundamentals of HTL process, key factors determining HTL behavior, role of catalyst in HTL, properties of produced bio-oil, and the current status of the technology are summarized. The liquefaction of biomass by using organic solvents, a process called solvolysis, is also discussed. A wide range of biomass feedstocks have been tested for liquefaction including wood, crop residues, algae, food processing waste, and animal manure.