**3. Biomass conversion**

The primary goal of biomass conversion is to break down the rigid and complex structure of biomass polymers into smaller and lower molecular weight (MW) compounds. Typically, the reaction time, temperature, and reaction medium influence the rate of destruction of the biomass polymeric structure. Chemical, biochemical, and thermochemical conversion processes convert biomass into end products such as chemicals, biofuels, or heat. Chemical conversion processes use chemicals to convert biomass into biofuels. Biochemical conversion processes utilize microorganisms or enzymes to convert biomass into products. Thermochemical conversion processes employ high temperatures in oxygen free, reduced, or normal oxygen environments. The thermochemical conversion approaches are applicable for a wide range of biomass types using different temperatures to break down the bonds of organic matter in a relatively short period. The advantages of thermochemical conversions over biochemical conversions include better conversion efficiency, handling a wide variety of feedstocks, shorter reaction times, and high energy efficiency. In most situations, the selection of the conversion process is based on the biomass feedstock available and the desired form of end products. Environmental standards, policy, economic conditions, and specific factors related to the project may influence the selection process. The moisture content of biomass is a primary aspect determining the conversion process. Thermochemical conversions, such as pyrolysis, gasification, or combustion, generally require relatively dry biomass with a moisture content of less than 30 wt.%, but moisture contents of 10 wt.% are preferred. The low energy density of wet biomass due to higher moisture content makes it unsuitable for these processes. The biochemical conversion process, a wet conversion process, is suitable for processing high moisture

*Hydrothermal Conversion of Lignocellulosic Biomass to Hydrochar: Production… DOI: http://dx.doi.org/10.5772/intechopen.112591*

content biomass. Hydrothermal (HT) processing is a thermochemical conversion that involves applying heat (and pressure) in subcritical or supercritical water. It can process high moisture content (> 70 wt.%) biomass feedstock without dewatering or drying. Biochemical conversion consumes less energy compared to HT processing but requires more time. Subsequently, cost-effective HT processing has gained growing attention as a method suitable for processing wet biomass [1, 5–8, 19, 20].
