ABSTRACT This study evaluated the production of biogas by anaerobic digestion, using three groups of marine macroalgae: Chlorophytes (green), Phaeophytes (brown), Rhodophytes (red), and their mixture (GRB). The objective was to investigate how the composition of each group influences the production of biogas and methane, as well as the use of digestate as a biofertilizer. The macroalgae were collected on the coast of João Pessoa, Paraíba, homogenized with anaerobic sludge (AS) and microcrystalline cellulose (MCC) in batch reactors, operated at 35°C for 60 days. Physicochemical parameters such as COD, total nitrogen, total phosphorus, C/N ratio, as well as biogas production and composition were monitored. Thermal analysis (TGA/DSC) was performed to evaluate both the Higher Heating Value (HHV) and the thermal degradation profile of biomass. The red + AS + MCC system exhibited the highest cumulative biogas production, exceeding 800 mL/gCOD, likely due to the greater availability of fermentable carbohydrates provided by co‐digestion. Meanwhile, the GRB + AS + MCC mixture achieved the highest methane yield (461.14 mL CH 4 /g CODconsumed), revealing superior efficiency in methane generation. This distinction highlights that volumetric biogas production and methane yield represent different performance indicators in anaerobic digestion. The co‐digestion of the GRB system with MCC increased the degradation of organic matter reaching COD removals of up to 96.91%. Statistical analysis revealed a significant difference only for the red macroalgae group, confirming the influence of substrate composition on biogas production. Marine macroalgae have promising results for biogas and biofertilizer production in a circular economy approach.
Pontes et al. (Wed,) studied this question.