Sustainable paths for managing solid and liquid waste from distilleries and breweries

Attempts towards a more sustainable food industry focus on reducing the energy intensity of biomass conversion processes and finding better alternatives for the management of the large amounts of agro-industrial waste produced in such industries. While various sustainable practices for managing waste streams have been set forth in recent studies, their integration into established production schemes is lagging due the lack of an assessment of their technical feasibility and economic practicality. This study investigates the use of anaerobic digestion (AD) and hydrothermal carbonization (HTC) on wastewater and solid waste streams generated by the brewing and distilling industry to be considered for further implementation in a German brewery, which has already implemented AD for treating wastewater generated in brewing and distilling processes. The layout of the HTC reactor is based on previous experimental studies, which, when converting 895 kg h⁻¹ of wet spent grains, produces 257 kW of excess heat available to cover energy demands in the brewing process. Exploitation of solid wastes by AD and HTC enables energy conversion in combined heat and power (CHP) systems which can meet more than 40% of electricity demands and more the 23% of thermal energy demands. Moreover, the mass of remaining solids is reduced to 43% of initial mass in the case of AD and 58% in the case of HTC treatment, which reduces energy demand for dehydrating solids significantly.