Is renewable also sustainable? – The case of biogas: Understand biogas sustainability beyond its climate contribution
Biogas is promoted to play a role in the renewable energy transition and to serve as a multifunctional environmental solution. Its rapid growth and cross-sectoral benefits highlights the need for a holistic understanding of biogas beyond its climate contribution. Under the lens of the United Nations Sustainable Development Goals and Planetary Boundaries frameworks, biogas appears as a dynamic component within broader natural, agricultural, and recycling systems.
This perspective led us to investigate societal recycling practices surrounding biogas feedstocks and to assess biogas production’s impact on current carbon and nitrogen recycling in agriculture, including associated emissions. The research bridges knowledge across agricultural production, energy generation, and recycling systems. It culminates in three main outcomes: a machine-learning-based inventory of alternative uses for biogas feedstocks, a systematic study revealing conflicting nitrogen-related benefits across system boundaries, and the first substance flow model examining biogas impacts on carbon recycling at the farm level.
Complementing these outcomes, the thesis discusses how biogas production systems are intricately linked to existing recycling practices and natural substance cycles. Although originally conceived as a waste-based solution, biogas implementation can disrupt established recycling systems and lead to unintended environmental and agricultural consequences. Moreover, the pursuit of renewable energy through biogas may involve trade-offs and raise concerns about lower-than-expected biogas deliverables or high investment cost. The trade-offs must be carefully evaluated to ensure biogas production truly contribute to sustainable development.
Though focused on biogas, this thesis offers broader insights to advance bioenergy and biomaterial discourse by emphasizing context-specific assessment, holistic thinking, and alignment with bioeconomy and circular economy initiatives.