Food waste hydrothermal carbonization: Study on the effects of reaction severities, pelletization and framework development using approaches of the circular economy

Abstract

Food waste (FW) is difficult to manage during thermal treatment. In this study hydrothermal carbonization (HTC) of FW was carried out at increasing temperatures and retention times using the approach of reaction severities (logR0 = 5.31–7.09). The hydrochar sample with the best-obtained energy yield was further pelletized using molasses as a binder at different ratios (5%, 10%, 20% and 30%). A conceptual framework was proposed using the circular economy concept. As severity increases, hydrochar yield declines while its fuel properties improve. Decarboxylation and dehydration allow functional groups to become impaired, including C-O and –OH. Carbon microspheres were observed on the hydrochar surface due to extensive FW carbonization. The pellets with 30% molasses as binder showed the highest mass density (1683.24 kg/m3), while the energy density for it was 37.54 GJ/m3. Food waste management will generate local employment and new business prospects by integrating HTC and pelletization.