Anaerobic digestion (AD) is a process of decomposition of organic matter made by a microbial association in an oxygen-free environment. This natural process can be harnessed and used for human benefit with many successful examples of implementation (Meegoda et al., 2018; Sakar et al., 2009; Seo et al., 2009; Ward et al., 2008). It can be applied to a wide range of feedstocks including industrial and municipal waste waters, agricultural, municipal, and food industry wastes, and plant residues (Ward et al., 2008). It provides a viable alternative to landfill category 3 wastes (these include food industry wastes, domestic wastes, and some slaughterhouse wastes). The residue from AD, after stabilization, can be used as an organic soil amendment or a fertilizer for the land, thus creating a circular economy (Wainaina et al., 2020). The residue can be sold as manure depending upon the composition of the input waste (Chum et al., 2011). This circular flow avoids sending organic waste to landfills and incineration.
Solutions that use organic waste as a feedstock and add value to it do not change land use significantly, unlike solutions that are driven by energy crops (Shilpi et al., 2019). The only additional land used is for the AD plant itself and its supporting infrastructure. It is possible to find the most suitable and favourable locations for these plants on AD systems using specific criteria (Metson et al., 2022; Sliz-Szkliniarz & Vogt, 2012). However, this area can be easily offset by the amount of scarce landfill area which can be saved.
A herd of cattle grazing on a lush green field in Azores, Portugal – Photo by Joana Pires via Unsplash
Power plants based on AD systems can be used as dispatchable distributed power generation systems (DPGS AD), thus contributing to the climate-proofing of local energy systems. Dispachable power means that the power is ready to be produced on-demand. Each DPGS AD plant usually has built-in low pressure biogas storage called a gasometer, thus in practice it operates much like its fossil fuel counterparts. It’s ready to go at moments notice. Other renewable energy sources, like wind and solar, can use energy storage to make the energy supply more reliable, but this is an extra investment which may use more valuable land area.
Biogas plant of GASAG Bio-Erdgas Schwedt GmbH in Schwedt/Oder showing the gasometer in green colour. – Photo by Vasyatka1, [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0), via Wikimedia Commons
DPGS AD power plants can be placed across the landscape as energy-independent generators. For isolated, poorly grid connected or non-connected energy systems, like those in many islands or other remote regions, the DPGS AD power plants can improve the reliability and recovery of the energy service. They can contribute to a more flexible and swifter recovery from power outages caused by knock-out events (e.g., tree falls on energy lines), excess demand (e.g., during heat waves) or other causes. They can also contribute to the establishment of renewable energy communities and citizen energy communities as defined in the Renewable Energy Directive and in the Internal Electricity Market Directive. In hot climates, heat can be converted into cooling thus adding combined benefits. DPGS AD power plants also can make sense to integrate in larger power systems. They can be turned on and off by a centralized dispatch utility service, helping to ensure the quality and reliability of the energy service.
DPGS AD power plants have combustion process that burn biogas in order to extract its energy. Burning biogas causes CO2 emissions but they are considered neutral to the climate due to biogenic origin and the short CO2 cycle of the feedstock. They also avoid methane (CH4) emissions which would otherwise be more harmful to climate change. However, Life Cycle Assessment (LCA) analysis of specific system types can reveal specific risks and unexpected surprises in emissions (Beylot et al., 2013; Hijazi et al., 2016).
Project RethinkAction is building six local Systems Dynamics (SD) models that will assess the implementation of solutions through time and across society, in six case studies. These case studies represent different contexts and realities in the European landscape. Within the project, the solutions to be tested are called Land use-based Adaptation and Mitigation Solutions (LAMS). The AD solution will be part of the LAMS catalogue that the project will produce and make available in its platform. The local SD model will provide a tool to assess this AD solution in a context where different economic sectors and different LAMS interact at the same time. From this, the project will provide policy recommendations and feed an online platform designed to help inform decision-making in the context of climate change.
Further reading and watching
Beylot, A., Villeneuve, J., & Bellenfant, G. (2013). Life Cycle Assessment of landfill biogas management: Sensitivity to diffuse and combustion air emissions. Waste Management, 33(2), 401–411. https://doi.org/10.1016/J.WASMAN.2012.08.017
Chum, H., Faaij, A., Moreira, J., Berndes, G., Dhamija, P., Dong, H., Gabrielle, B., Goss Eng, A., Lucht, W., & Mapako, M. (2011). Bioenergy. In IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation [O. Edenhofer, R. Pichs-Madruga, Y. Sokona, K. Seyboth, P. Matschoss, S. Kadner, T. Zwickel, P. Eickemeier, G. Hansen, S. Schlömer, C. von Stechow (eds)], Cambridg. https://www.ipcc.ch/site/assets/uploads/2018/03/Chapter-2-Bioenergy-1.pdf
Hijazi, O., Munro, S., Zerhusen, B., & Effenberger, M. (2016). Review of life cycle assessment for biogas production in Europe. Renewable and Sustainable Energy Reviews, 54, 1291–1300. https://doi.org/10.1016/J.RSER.2015.10.013
Meegoda, J. N., Li, B., Patel, K., & Wang, L. B. (2018). A Review of the Processes, Parameters, and Optimization of Anaerobic Digestion. International Journal of Environmental Research and Public Health 2018, Vol. 15, Page 2224, 15(10), 2224. https://doi.org/10.3390/IJERPH15102224
Metson, G. S., Feiz, R., Lindegaard, I., Ranggård, T., Quttineh, N. H., & Gunnarsson, E. (2022). Not all sites are created equal – Exploring the impact of constraints to suitable biogas plant locations in Sweden. Journal of Cleaner Production, 349, 131390. https://doi.org/10.1016/J.JCLEPRO.2022.131390
Sakar, S., Yetilmezsoy, K., & Kocak, E. (2009). Anaerobic digestion technology in poultry and livestock waste treatment - A literature review. Waste Management and Research, 27(1), 3–18. https://doi.org/10.1177/0734242X07079060
Seo, S. N., Mendelsohn, R., Dinar, A., Rashid, ·, Pradeep Kurukulasuriya, H. ·, Seo, S. N., Mendelsohn, R., Dinar, A., Hassan, R., & Kurukulasuriya, P. (2009). A Ricardian Analysis of the Distribution of Climate Change Impacts on Agriculture across Agro-Ecological Zones in Africa. Environmental and Resource Economics 2009 43:3, 43(3), 313–332. https://doi.org/10.1007/S10640-009-9270-Z
Shilpi, S., Lamb, D., Bolan, N., Seshadri, B., Choppala, G., & Naidu, R. (2019). Waste to watt: Anaerobic digestion of wastewater irrigated biomass for energy and fertiliser production. Journal of Environmental Management, 239, 73–83. https://doi.org/10.1016/J.JENVMAN.2019.02.122
Sliz-Szkliniarz, B., & Vogt, J. (2012). A GIS-based approach for evaluating the potential of biogas production from livestock manure and crops at a regional scale: A case study for the Kujawsko-Pomorskie Voivodeship. Renewable and Sustainable Energy Reviews, 16(1), 752–763. https://doi.org/10.1016/J.RSER.2011.09.001
Wainaina, S., Awasthi, M. K., Sarsaiya, S., Chen, H., Singh, E., Kumar, A., Ravindran, B., Awasthi, S. K., Liu, T., Duan, Y., Kumar, S., Zhang, Z., & Taherzadeh, M. J. (2020). Resource recovery and circular economy from organic solid waste using aerobic and anaerobic digestion technologies. Bioresource Technology, 301, 122778. https://doi.org/10.1016/J.BIORTECH.2020.122778
Ward, A. J., Hobbs, P. J., Holliman, P. J., & Jones, D. L. (2008). Optimisation of the anaerobic digestion of agricultural resources. Bioresource Technology, 99(17), 7928–7940. https://doi.org/10.1016/J.BIORTECH.2008.02.044