Bioenergy is one of the important renewable energy sources for future. It has been debated what would be the scale of bioenergy in our future energy mix and what would be its total impacts. Some of the challenges associated with bioenergy is its low energy density and high-water content, which limits their transportation distance and centralized conversion technologies. Thus, in our research group, we have been developing an energy conversion technology that can convert biomass with minimum reaction and processing steps and moderate reaction conditions. The overall scheme allows the integrated carbon capture and storage, and thus, the overall energy conversion would be not only carbon neutral but also carbon negative. Most importantly, this reaction scheme allows the direct conversion of wet and salty biomass.
The “alkaline thermal treatment of biomass (ATT of biomass)” is one of the less studied biomass conversion reactions. Here biomass (some ratio of C, O and H) are reacted with base (e.g., group I andgroup II hydroxides like NaOH and Ca(OH)2). By adding hydroxides as one of the main reactants, we were able to pull C into the solid phase while doing the biomass conversion to hydrogen. We were able to convert the biomass (e.g., wheat switch grass, seaweeds) to high purity H2 in a single step reaction at around 300 oC and atmospheric pressure.
This reaction is very interesting because it basically trickles down the carbon into the lowest energy level of solid carbonates while all the energy is pushed up to H2. This truly integrated reaction scheme can be considered as an innovative BECCS concept. As shown in this photo, biomass pyrolysis leads to black char/ash residue (left) but ATT of biomass leads to white solid residue which is mostly solid carbonates (right). This reaction also likes water and thus we should be able to convert wet biomass (e.g., food wastes, algae, seaweeds) to H2 without going through the energy intensive drying step.