Carbonization temperature and feedstock type interactively affect chemical, fuel, and surface properties of hydrochars.

The hydrothermal carbonization (HTC) process that converts wet/dry biomass to hydrochars (for use as solid fuels or adsorbents) needs to be optimized. We investigated the interactive effects of feedstock type and HTC temperature on chemical, fuel, and surface properties of hydrochars produced from lignocellulosic (canola straw, sawdust and wheat straw) and non-lignocellulosic feedstocks (manure pellet) at 180, 240 and 300 °C. Increased HTC temperature decreased hydrochar yield and surface functional group abundance, but increased hydrochar thermal stability due to increased devolatilization and carbonization. Hydrochar surface area ranged from 1.76 to 30.59 mg, much lower than those of commercially available activated carbon. Lignocellulosic and non-lignocellulosic feedstocks were distinctly affected by HTC temperature due to variable carbonization from ashing. Hydrochars produced from lignocellulosic biomass at 240 and 300 °C resembled high-volatile bituminous coal. Hydrochars should be designed for specific applications such as fuels by selecting specific feedstock types and carbonization conditions.