Production of functionalized carbon from synergistic hydrothermal liquefaction of microalgae and swine manure

Conventional approaches of making biochars are typically through single sourcing of the feedstock. Here, we hypothesize that multi sourcing can be used to develop tailored functionalized biochar where select functional groups are inherently grafted onto the biochar surface. To test this hypothesis, we used hydrothermal co-liquefaction to produce biochar from various blends of microalgae Cyanidioschyzon merolae (CM) and swine manure (SM). We further characterized each biochar's physicochemical and surface properties to qualify them for applications in construction and manufacturing. In the blended cases, 20–80 CM-SM had the highest biochar yield of 27.06 wt.%, while 80–20 CM-SM had the highest volatile matter, 32.2%. The crystallinity of the biochars ranged from 40–55%. The specific surface area was measured to be in the range of 1.53–5.86 m²/g and average pore size was in the range of 250–360.56 Å. The study results showed presence of functional groups such as alcohols, amides, free fatty acids/esters, cyclic- and straight-chain hydrocarbons on the surface of biochar, which could in turn promote biochar's application as a free-radical scavenger in construction and manufacturing. It should be noted that the use of biochar as a soil amendment is not enough to address the growing piles of biowaste. The outcomes of this study could enable development of non-conventional applications for functionalized biochar. Considering the urgent need for forest management and biowaste valorization, developing viable applications for biochar is significant not only for resource conservation, but also for forest management and environmental sustainability.