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Reduction of environmental impacts through optimisation of biogas value chains.

Drivers, barriers and policy development

Biogas production from anaerobic digestion of organic resources can potentially contribute to a reduction in greenhouse gas emissions in several sectors and can play a central role in both the bioeconomy and the circular economy. Several European countries have political goals to increase biogas production and to increase the amount of manure to anaerobic digestion. The treatment method is, however, known to be costly and the markets for biogas and for digestate are immature. There is a need for a better understanding of how the biogas value chains should be designed to minimise environmental impacts while at the same time achieving profitability for the actors.

The objective of this thesis was to make a contribution towards knowledge regarding ways of optimising Norwegian biogas value chains to reduce environmental impacts, by developing models that can provide decision support. The aim is to suggest improvements to the regulatory systems and the preconditions for further development of the biogas industry in Norway. Systems theory and system analysis methodology was applied, and three different domains were assessed: environmental impacts, economy of the actors in the value chain and policies.

The results showed that the amount of organic waste and manure used for anaerobic digestion should be increased to reduce environmental impacts. The most preferable option for the use of biogas is as a fuel for transport to substitute diesel, and the best use of the digestate is as a fertiliser in agriculture as a substitute for mineral fertiliser, which requires a high level of sector integration in the value chain. To obtain a maximal reduction of greenhouse gas emissions, efforts should be made to avoiding diffuse emissions and reducing emissions from the storage of digestate.

The economic calculations showed that large-scale biogas plants in general lack economic incentives to include the agricultural sector in the value chain. Inclusion of the transport sector is the most profitable option for use of biogas only for the largest scale biogas plants and for those who are able to sell biomethane for a high price. The most profitable option regarding the management of manure for cattle and pig farms was the supply of manure to a centralised biogas plant and the return of the digestate as biofertiliser.

The current support system has contributed to an increase in biogas production. Based on the assessments performed as part of this thesis, however, some recommendations were made to improve the framework conditions of an optimised biogas production in Norway, to reduce environmental impacts and achieve the political objectives.

Kari-Anne Lyngs PhD thesis