Energy and exergy assessment of different strategies for energy use and residues valorisation in citrus processing facilities

The citrus production chain stands out in the Brazilian agribusiness, being responsible for the production of citrus fruits for fresh consumption and mainly for processing. Particularly, the orange processing's main product is frozen concentrated orange juice (FCOJ); from the total raw material, on average 50% is transformed into juice and approximately 46.6% is production waste, that can have different destinations. Orange bagasse can be sent for composting or further processed to obtain citrus pulp pellets. Large industries can produce pellets for animal feed commercialization. Others use this residue directly as feed, skipping the drying and pelletization stages. Nevertheless, small industries lack the capability to recover part of this residual fraction, leading to biomass disposal in landfills. Thus, the aim of this study is to accomplish an energy and exergy assessment of different routes of waste processing and destinations including the production of by-products. Thus, mass, energy and exergy balances were performed for different scenarios such as: a) A Base Case, where the orange bagasse is discarded, b) Using orange bagasse as fuel in boilers, c) Drying of orange bagasse and pelletizing to produce citrus pulp pellets (CPP). The main results indicated that electricity consumption in Case B increased by 5.3%, while orange bagasse was reduced by 32%. Furthermore, no external fuel was required. Case C presented increases of 60.7% in electricity consumption and 69.9% in fuel consumption; however, valuable by-products such as CPP and d-limonene were obtained. Regarding exergy analysis, preliminary results indicated the higest irreversibilities in orange bagasse dryer (70%) and in steam boiler (27.8%).