The feasibility of South African brown seaweed in biogas production and conversion to electricity

Abstract

South Africa is faced with persistent energy shortages and the need to develop sustainable, renewable resources. This research aimed to produce biomethane (biogas) via anaerobic digestion using a synthetic inoculum and the brown seaweed Ecklonia maxima. The biogas can be utilised in a simple combined heat and power process and converted to electricity and heat. Biogas production is estimated using the biomethane potential utilising the chemical composition of the seaweed. This is then compared to the actual biogas production from the anaerobic reaction of the seaweed and the inoculum at both mesophilic and thermophilic conditions. The research found that seaweed yielded 190.00 ml/g volatile solids (VS) of biogas after 28 days at a pH of 7.0 ±0.2 at mesophilic conditions, which is equivalent to 38% of the calculated biomethane potential of 499.64 ml/g VS. Ecklonia maxima can produce 255.18 kg biogas per ton of dry seaweed, with a possible associated 1417.71 kWh of electricity per ton of dry seaweed. Future work would investigate pre-treatment options for the seaweed to increase the biogas yield and increase the potential electricity output per ton of dry seaweed.