Anaerobic digestion of defatted castor seeds (Ricinus communis) cakes: Integrating ricin detoxification and biogas production within a circular economy framework

Ricinus communis is a promising second-generation oilseed crop, suitable for biodiesel production from oil and for the recovery of the defatted seed cakes (DSCs) as a biogas substrate. Its large-scale use, however, is limited by the presence of ricin, a highly toxic lectin that complicates DSCs distribution and utilisation. This study evaluated anaerobic digestion (AD) as an integrated strategy for detoxifying R. communis DSCs (RCC) while simultaneously producing renewable energy. Batch biomethane potential (BMP) assays were conducted under mesophilic (and thermophilic conditions, followed by a continuous stirred tank reactor (CSTR) trial to assess both ricin degradation under continuous feeding and the stability of biogas production.These results highlight that AD enables the detoxification of RCC via a circular approach, allowing both energy valorisation and the production of a safe digestate with no residual ricin.