Product yield, quality and energy in the hydrolysis of urban bio-waste compost from laboratory-scale runs

The valorisation of bio-waste is pursued to cope with the increasing amount of waste that results from human food consumption and also to find renewable feedstock for manufacturing fuel and chemicals, as an alternative to fossils. Bio-waste is currently processed using fermentation and thermo-chemical technologies, to produce bio-fuel, compost and small platform molecules. Commercial low temperature chemical processes to valorise the bio-waste lignin fractions as feedstock for value-added chemicals do not as yet exist. The present work addresses this technology gap showing that the low-temperature hydrolysis of municipal bio-waste compost is a safe eco-friendly, cost effective process for converting the lignin-like material from compost into value-added speciality chemicals. It is reported that the process produces a 30%–70% yield of soluble biopolymers (SBO) as temperature increases from 60 to 150 °C. The SBO at 150 °C exhibit the best surfactant properties, making them promising for multipurpose uses in the future. The reaction yield is limited by non-hydrolysable lignin-like matter present in the pristine compost. Energy changes occur due to endothermic and exothermic reaction during hydrolysis at different temperatures. The process allows most of the process water and reagent to be recycled and saves on reagents, water and processing energy. No secondary treatment of the process effluent is necessary. The data lead to the conclusion that it will be feasible to produce SBO at commercial level through low-temperature hydrolysis of compost or biomass from different sources.