Impact of Solvent Extraction on Compound Recovery and Biomethane Production Kinetics from Foodwaste Leachates

This study proposes an integrated and more circular management approach, grounded in the principles of sustainable and green chemical processes, for the food waste leachates management, combining the assessment of biomethane production potential via anaerobic digestion with the evaluation of value-added compound recovery through extraction processes. The food waste leachates were characterized, while total carotenoid profile and total phenolic content were quantified using liquid–liquid extraction with mixed organic solvents. An HS-SPME coupled with GC–MS was employed to identify volatile organic compounds present in the leachates. Prior to the extraction procedure, D-limonene exhibited the highest abundance among identified volatiles. Crucially, the subsequent solvent extraction is highly likely to have effectively removed this inhibitory terpene from the liquid matrix. Extracted leachates exhibited a total carotenoid content of 0.64 mg/100 g and a total phenolic content of 127.0 μg/g, acting as preliminary indicators of significant potential for recovery and utilization in pharmaceutical and cosmetic applications. Biomethane potential tests were conducted in laboratory-scale anaerobic bioreactors using both raw food waste leachate and extracted food waste leachate. Comparable biomethane yields were obtained for both substrates, with FWL yielding 442.5 NmL/g VSadded and FWLextr yielding 452.2 NmL/g VSadded. These results demonstrate that the liquid–liquid extraction of value-added compounds does not adversely affect biomethane production from food waste leachates enabling the recovery of valuable by-products.