Hydrothermal carbonization of kitchen waste

Abstract

Hydrothermal carbonization is a suitable method for energy and material recovery of wet heterogeneous kitchen waste. The paper examines the ability of the process to produce stable, energy-rich material without harmful by-products from lunch leftovers, raw potatoes, creamy yogurt and raw onions. Results of the batch experiments confirm the hypothesis that waste processing results in homogenous energy-rich (> 24 MJ/kg) and carbon-rich (> 63 % wt.) material. The biochar of creamy yogurt reaches the highest lower-heating value of 31.75 MJ/kg. In terms of energy use and emission concentrations, all samples meet legal requirements for incineration in combustion devices. Phytotoxicity tests prove the harmlessness of the liquid by-product for agricultural purposes.