Energy recovery and waste valorization in a frozen food processing facility: a case study from Lazio, Italy

Food and Agriculture Organization of the United Nations (FAO) estimates that food, beverage, and tobacco sector is currently responsible for about 30% of total world energy consumption and approximately the same percentage of food is wasted during its industrial transformation. Improving the sustainability of food processing is fundamental to reduce the environmental impact of this sector as well as to lower the disposal cost of industrial waste. The objective of this work is to propose an efficient and technically feasible solution for the management and energy recovery of residual biomasses and industrial processing by-products, such as sewage sludge produced by industrial wastewater treatment. The above solution is developed for a real frozen food factory operating in Lazio region (Italy) introducing a sewage sludge dryer and a gasifier to produce syngas. The software Aspen Plus is adopted to numerically simulate the gasification process, using a literature validated model, while the dryer and the already present combined heat and power (CHP) plant are dynamically modelled in TRNSYS environment. The results demonstrate that the proposed solution is feasible and attractive from both an environmental and an economic perspective. The Simple Pay Back of the investment is less than 3 years, while the Net Present Value stands at about 2.4 M€. Furthermore, the CO2 proposed system allows to save 179 t of equivalent CO2 emissions compared to the current system.