Evaluation of biomethane potential and kinetics modelling of green macroalgae from the South Atlantic Sea: Codium sp. (Codiaceae) and Ulva sp. (Ulvaceae)

Abstract

Several uses for macroalgae have been reported in the literature, including in agriculture, pharmaceuticals, and human and animal feed. While many authors have recognised the potential use of algae biomass for bioenergy, specific research on their energy potential is less abundant. The wide east coast of the Argentine Sea is frequently impacted by seasonal macroalgal blooms that nowadays are managed as a residue of land disposal. The feasibility of bioenergy production from two species of macroalgae from the South Atlantic Sea was evaluated through the analysis of the biomethane potential determined according to a standard protocol. Fresh, washed and chopped samples of Codium sp. (Codiaceae) and Ulva sp. (Ulvaceae) were studied in anaerobic batch digestion under the mesophilic regime and with an inoculum: substrate ratio of 3: 1. The results showed 35 higher methane production of Codium sp. (205.2 mL CH 4 /g volatile solids), which revealed that the composition of Ulva sp., rich in sulfated anionic polysaccharide (Ulvan), reduces the activity of methanogenic bacteria. The kinetics of methane production was studied through the first-order kinetic, the modified Gompertz and the Cone models, which all showed an adequate adjustment of the experimental data (R > 96 ) but the Cone model yielded the best performance (R > 98.6 ). The potential methane production L 0 and the hydrolysis rate constant k were respectively 30 and 124 higher for Codium sp. than Ulva sp., which demonstrated a higher biodegradability of this algae. Despite the differences observed, the results obtained revealed an interesting bioenergy potential of the studied species of seaweed from the Argentine Sea.