Subcritical or supercritical? A comparative life cycle assessment of bioactive compound extraction from apple pomace

Apple pomace (AP), a by-product of the apple juice and cider industries, represents a significant waste challenge, generating approximately 5 million tons produced worldwide in 2021. Often disposed of in landfills, AP contributes to health and environmental risks. Despite its disposal, AP remains a valuable source of bioactive compounds, recognized for their biological properties. This study assesses the carbon footprint associated with extracting these bioactive compounds using innovative technologies, namely supercritical CO₂ (SC–CO₂) and subcritical water extraction (SWE). Utilizing SimaPro software and the ecoinvent database, the Life Cycle Assessments (LCA; cradle-to-gate) were conducted for extracting 1 g of bioactive compounds from AP. The findings reveal that the SC-CO₂ process emits 71.42 kg_CO2eq, while the SWE results in significantly lower emissions of 6.20 kg_CO2eq. These results highlight the environmental impact of different extraction technologies and emphasize the potential for more sustainable practices in valorizing AP. This study highlights the importance of conducting Life Cycle Assessments (LCAs) for sustainable technologies, offering critical insights that can inform future industrial practices and policy decisions. Furthermore, the findings indicate that a technology labeled as 'green' is not necessarily environmentally superior, prompting a reconsideration of current sustainability definitions.