Use of marine and freshwater macroalgae collected in the Sea of Azov and Lithuania for the biogas production

Abstract

As the climate warms and water pollution increases, macroalgae have become an actual problem as ecosystems are unable to break them down in natural ways. However, macroalgae can be used as an energy source to produce the biogas. Biogas yield and energy values depend on the concentration of glucose, proteins and fats in algae, so it is very important to evaluate these parameters. The green, brown, and red macroalgae found in the Sea of Azov were collected on the seashore, whereas the green macroalgae that grow in Lithuanian freshwaters, were collected from surface waters. Spectrophotometrical methods and lipid extraction (Folch method) were used for the determination of total protein, glucose and lipid concentration, respectively. Glucose and total proteins have been found to be the most prevalent in macroalgae, which affect the yield of biogas and energy value, whereas the lipid content in samples investigated varied between 1.6-3.6 %. Brown algae biomass was found to have the highest resource potential in terms of biogas production due to their high protein content, with concentrations of up to 22.6%. Glucose concentrations were up to 13.3%. Due to the abundant glucose and protein content and suitable C/N ratio in macroalgae, nutrient availability is improved, which is essential for cell growth and metabolism of various groups of microbial populations in anaerobic digestion (AD). The measurement of biogas production parameters using various types of collected macroalgae is under way. This work was funded by the Research Council Lithuania, grant number S-LU-22-2 and Ministry of Education and Science of Ukraine.