Influence of particle size and chemical composition on the performance and kinetics of anaerobic digestion process of sunflower oil cake in batch mode

Biochemical methane potential (BMP) assays of sunflower oil cake (SuOC) were carried out to research the effect of different particle sizes and their chemical composition on methane yields and kinetics. Particle size 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 particle size 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 particle size 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) particle size 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.

► We sieve Sunflower Oil Cake to analyze three different particles sizes.
► We analyze the effect of particle size and chemical composition on biogas production.
► Higher particle size, with low lignin content, increases biogas production.
► We model the effect of particle size on methane yield.