Beneficial synergetic effect of feedstock characteristics and reaction conditions on bio crude production from hydrothermal liquefaction of mixed residential waste

Hydrothermal liquefaction (HTL) is a promising method for sustainable waste management and renewable energy production, converting mixed feedstocks into bio-crude, a precursor to various biofuels. A study focused on mixed residential waste (MRW) as an HTL feedstock investigated temperature ranges (280–-360 °C) and residence times (30 min–90 min), achieving a maximum bio-crude yield of 39.16% at 340 °C and 75 min. Also, a thorough investigation of the synergistic relationships between all subcomponents of the MRW feedstock was conducted and concluded that the mixed waste (MW) feedstock samples containing a higher proportion of food and plastic wastes and MRW sample presented with a co-liquefaction percentage (CE) of around 60% and 107% respectively for production of bio crude. Also, solvents such as ethanol, glycerol and aqueous phase (AQ) were tested for their potential as hydrothermal mediums and found that bio crude yield of 46.19% was obtained in case of AQ phase recirculation. Further, the quantitative and qualitative effect of usage of four different catalysts were tested individually and in combination with AQ phase recirculation and found that, although individually nanoporous ZnO and diatomaceous earth (DE) yielded bio crude in the range of 46.86% and 42.68% respectively, when used in combination, DE cat–HTL with AQ resulted in maximum bio crude yield of 54.35%. Furthermore, qualitatively, the bio crude from DE cat–HTL with AQ presented with a high carbon and energy recovery percentage of 62.20% and 72.95% respectively and a high hydrocarbon content of 58.98%.