Effect of Particle Size on the Biomethanation Kinetics of Mechanically Pretreated Sargassum spp. Biomass

The collection and use of Sargassum spp. as feedstock for the production of valuable products such as biomethane by anaerobic digestion (AD) would mitigate the negative impact of the blooms and the costs related to waste management in the Dominican Republic. In this work, the effect of the particle size of pelagic Sargassum spp. biomass, as a result of mechanical pretreatments, on the biomethanation was determined. The granulometric analysis of the mechanically pre-treated biomass was carried out using a Mastersize2000. The Biochemical Methane Potential (BMP) of the samples was determined using an Automatic Potential System Test II (AMPTS® II). The kinetic parameters of the reaction were scientifically evaluated by using First order kinetic Model and modified Gompertz Model. The granulometric analysis showed a monomodal distribution on crushed biomass (505 μm) and a bimodal distribution on the milling sample (107 μm). The bimodal biomass means the biomass is characterized by the presence of fine and large particles. We observed that BMP increased by 78.85% when particles were reduced from 50,000 μm to 505 μm and by 73.61% when particles were reduced from 50,000 μm to 107 μm. A low methane yield from the milling biomass (107 μm) compared to the crushed biomass (505 μm) could be related to the excessive reduction of particle size. The fine particles are subject to the formation of aggregates and consequently, the contact area between the algae cells and the microorganisms that operate the anaerobic digestion process decreases.