BIOMETHANE POTENTIALS FROM CASTOR CAPSULE SHELLS PRETREATED WITH WHITE-ROT FUNGI

Castor (Ricinus communis L.) is a member of the Euphorbiaceae family that is found across all the tropical and semi-tropical regions of the world. It is an important oilseed crop and its inedible oil is widely used in industrial, pharmaceutical and agricultural sectors. Castor plants show a high potential to be converted and use as a biorefining feedstock. Castor oil can be utilised for biodiesel production, while the main by-products generated in the castor oil production (capsule shells and castor oil cake) and the residual biomass, are potentially applicable as feedstocks for advanced ethanol and biomethane production. The production of biomethane through anaerobic digestion using agricultural waste has been widely adopted as innovative, sustainable and cost-effective technology. Similarly to others lignocellulosic materials, in order to use these biomass residues in bioenergy production process it is necessary a pretreatment to expose their compact structure to enzymatic hydrolysis. The aim of this work was to evaluate the effects, on the theoretical biomethane potential, of biological pretreatment using two white-rot fungi (Pleurotus ostreatus and Irpex lacteus) of capsule shells of castor fruits obtained from a trial with two different nitrogen fertilization treatments (0 and 120 kg ha-1). Compared to untreated treatment the fungal pretreatment using P. ostreatus showed an increase of theoretical BMP from castor shells in the biomass harvested in the nitrogen fertilized treatment, (+5%). By contrary, Irpex lacteus pretreatment reported a theoretical BMP similar to that of untreated biomass.