Food waste is an awkward resource: abundant, heterogeneous and usually destined for landfill or digestion. A Yonsei team led by Professor Sumin Kim has found a higher-value use, carbonising mixed food waste at 400 degrees Celsius to produce biochar, then combining it with graphene and docosane, a phase change material that absorbs and releases heat as it melts and solidifies. The composite is bonded to commercial paper to form a membrane for building ventilation systems.
The engineering results, published in the Springer journal Biochar in August 2026, are substantial. Biochar activated at 700 degrees Celsius reached a surface area of 323.1 square metres per gram with 82.8 percent mesopores, and adding graphene raised latent heat storage by up to 72 percent over pristine biochar composites. The optimised composite stored 93.1 joules per gram at around 48.4 degrees Celsius and survived 1,000 heating and cooling cycles.
As a membrane, the material conducted heat 96.1 percent better than a reference paper membrane while retaining 80.2 percent of the bulk composite's latent heat, and it still allowed water vapour through, a property essential for energy recovery ventilation. The authors are candid that production energy and techno-economic performance need further study, but the prospect of circular, waste-derived materials doing real thermal work in facades and ventilation units is a compelling one for sustainable construction research.