Simulation and Economic Assessment of Citrus Waste Valorization Through Supercritical CO2 Extraction of Essential Oils

In this work we present an integrated market, experimental, technical and economic approach to citrus waste valorization based on the extraction of essential oils from orange, lemon, lime and tangerine peels using supercritical CO2, comprising nine varieties of citrus fruits with high production in Brazil and varying harvesting seasons. This approach has been applied to such a variety of citrus waste as a novelty, allowing the observation of specific results for each kind of citrus fruit and a robust evaluation of the proposed process solution, which includes pre-treatment and extraction and may feature energy recovery. The varieties of fruits and volumes of production were selected based on a market assessment for a proposed capacity of approximately 500 kg/d of citrus waste in the extraction facility. Samples of citrus fruit waste were pre-processed by drying at 60 °C for 24 h and submitted to extraction using CO2 at 150 bar and 35 °C for 30 min. The provisional results of the extractions (0.33% to 4.00% wt. oil yield) were used to perform the simulation of the extraction facility and estimate the cost of manufacture of essential oil, which ranged from US$26.70 to US$323.86/kg of extract, depending on the variety of citrus fruit. As an illustrative result of the application of the present screening approach, the cost of the production of essential oils from terra, bahia, seleta and lima oranges, as well as lemons, limes and tangerines, was compatible with the market price, while the costs of manufacturing pera and valencia orange essential oils were higher than the average price for cosmetic-grade and food-grade orange oil. The use of energy recovery in the CO2 cycle would further increase the environmental sustainability of this strategy, with 55% lower energy consumption.