Techno-economic and carbon emissions analysis of biogas utilisation systems in the UK

Biogas is a renewable and carbon neutral fuel, that can help the UK meet its increasing energy demand, while simultaneously reducing the net greenhouse gas emissions. All the biogas utilisation routes modelled, return positive avoided greenhouse gas (GHG) emissions. Biogas to combined heat and power (CHP) returns higher avoided emissions than biogas upgrading to biomethane and injection into the gas grid across the entire heat utilisation range (0% to 100%). The current renewable energy incentives, offered by the UK government, allow utilising biogas via either CHP, or biomethane production to return positive net present values (NPV). A theoretical membrane with improved separation properties (termed "future" membrane) allows reduction in energy consumption and increase in NPV. The future membrane returns positive net present values without the aide of subsidies, however, subsidies are required in order to compete with biogas to CHP. When 2014 subsidies were applied (7.7 pence/kWh of biomethane), the future membrane returned a higher NPV (£28.3million) than biogas to CHP (£27.5million). The proposed development fuel maximum buy-out for biogas derived transport fuels would make the minimum selling point (MSP) of upgraded biogas transport fuel lower than diesel by 2-10 pence/kWh. Enriching biogas with natural gas is a lower cost method of achieving a gas mix that complies with internal combustion engine specifications than upgrading biogas with either current membranes, or future membranes. However, the renewable fraction of the final transport fuel would only contain a maximum renewable energy fraction of 30%, if enriching biogas with natural gas. The largest overall contributor to producing biogas derived transport fuel is the cost of producing biogas