Researchers at the University of Saskatchewan tested four crop residues, canola straw, hemp straw, oat hulls, and wheat straw, as feedstocks for solid biofuel. Oxidative torrefaction at 300 C raised carbon content from about 45 percent to around 65 to 70 percent and lifted heating value to as high as 29 MJ/kg for hemp straw, which puts it in range of sub-bituminous coal. Steam explosion, by comparison, only changed the physical structure and did little to improve fuel chemistry. The study is useful because it does not ignore the practical problems. Most torrefied fuels show high fouling and slagging risk from alkali metals, and torrefied biomass is harder to pelletize. The authors suggest leaching or acid treatment before torrefaction, and they identify 275 C as the sweet spot for energy yield across most feedstocks. That kind of detail matters for anyone trying to move this out of the lab and into a real supply chain.
