Influence of particlesize and chemicalcomposition on the performance and kinetics of anaerobicdigestionprocess of sunfloweroilcake in batchmode

Biochemical methane potential (BMP) assays of sunfloweroilcake (SuOC) were carried out to research the effect of different particlesizes and their chemicalcomposition on methane yields and kinetics. Particlesize ranges of (1) 0.355–0.55 mm, (2) 0.710–1.0 mm and (3) 1.4–2.0 mm in diameter were evaluated. The highest methane yield 213 ± 8 mL CH4 g−1 VSadded was obtained for the largest particlesize analyzed (3), against 186 ± 6 mL CH4 g−1 VSadded obtained for particles 1 and 2. This may be attributed to the different lignocellulose compositions of the various particlesize ranges studied and to organic matter removals (47.2% for 3, against ∼41.5% for 1 and 2). The evolution of propionic acid concentration was found to be fundamental for explaining the lowest rate of biogas production for the smallest (1) particlesize studied, with a specific rate constant k of 0.45 ± 0.02 d−1, while values of 0.61 ± 0.02 d−1 and 0.50 ± 0.01 d−1 were obtained for particles 2 and 3, respectively.The authors wish to express their gratitude to the Spanish Ministry of “Ciencia and Innovación” (Project CTM 2008-05772/Tecno) for providing financial support, to the contract JAE-Doc from “Junta para la Ampliación de Estudios del CSIC” co-financed by the European Social Funds, as well as to the Program “FPI” of the above-mentioned ministry for contracting graduates.Peer reviewe