Biogas from renewable electricity – Increasing a climate neutral fuel supply

• Published in: Applied energy Vol. 90; no. 1; pp. 11 - 16
• Main Authors: Mohseni, Farzad, Magnusson, Mimmi, Görling, Martin, Alvfors, Per
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier Ltd 01.02.2012; Elsevier
• Subjects: Applied sciences; Biogas; biomass; Byproducts; Carbon; Carbon dioxide; climate; Digestion; Electricity; electrolysis; emissions; Energy; energy content; Exact sciences and technology; Fuels; Gasification; hydrogen; Intermittent power; Methane; methane production; raw materials; Renewable energy; Sabatier reaction; Synthetic fuels; wastes; Intermittent power; Synthetic fuels; Sabatier reaction; Biogas; Renewable energy
• ISSN: 0306-2619; 1872-9118; 1872-9118
• DOI: 10.1016/j.apenergy.2011.07.024

► The paper suggests a way of exploiting intermittent power in a resource optimised way. ► Biogas production via water electrolysis and Sabatier reaction is presented. ► The processes could be used in retrofitting digestion plants or gasification plants. ► Biogas production potential would increase drastically. ► Feasible way of introducing renewable electricity to the transport sector in short time scale. If considering the increased utilisation of renewable electricity during the last decade, it is realistic to assume that a significant part of future power production will originate from renewable sources. These are normally intermittent and would cause a fluctuating electricity production. A common suggestion for stabilising intermittent power in the grid is to produce hydrogen through water electrolysis thus storing the energy for later. It could work as an excellent load management tool to control the intermittency, due to its flexibility. In turn, hydrogen could be used as a fuel in transport if compressed or liquefied. However, since hydrogen is highly energy demanding to compress, and moreover, has relatively low energy content per volume it would be more beneficial to store the hydrogen chemically attached to carbon forming synthetic methane (i.e. biogas). This paper presents how biogas production from a given amount of biomass could be increased by addition of renewable electricity. Commonly biogas is produced through digestion of organic material. Recently also biomass gasification is gaining more attention and is under development. However, in both cases, a significant amount of carbon dioxide is produced as by-product which is subject for separation and disposal. To increase the biogas yield, the separated carbon dioxide (which is considered as climate neutral) could, instead of being seen as waste, be used as a component to produce additional methane through the well-known Sabatier reaction. In such process the carbon could act as hydrogen carrier of hydrogen originating from water electrolysis driven by renewable sources. In this study a base case scenario, describing biogas plants of typical sizes and efficiencies, is presented for both digestion and gasification. It is assessed that, if implementing the Sabatier process on gasification, the methane production would be increased by about 110%. For the digestion, the increase, including process improvements, would be about 74%. Hence, this method results in greatly increased biogas potential without the addition of new raw material to the process. Additionally, such model would present a great way to meet the transport sector’s increasing demand for renewable fuels, while simultaneously reducing net emissions of carbon dioxide.