Combining biogas LCA reviews with stakeholder interviews to analyse life cycle impacts at a practical level

Abstract

Biogas presents an increasing energy production form in municipalities and rural locations, and it is also a feasible waste management option. In terms of environmental life cycle assessments (LCA), biogas production seems to offer a unique opportunity to combine nutrient recycling with energy production using various underutilised resources such as municipal biowastes or manure. LCAs of biogas production suggest benefits related to CO2 emission savings and the replacement of chemical fertilisers, for example. Existing biogas plants have varying practices related to biogas production and actualisation of the life cycle benefits is influenced by policies, local contexts, and the purposes of the biogas production activity. This paper identifies and explores critical points related to biogas production by reviewing LCA studies and comparing them to actual choices made at Finnish biogas plants based on stakeholder interviews. The most critical points related to biogas production involve the end use of the biogas and the end use of the digestate. The practical implementation and site-specific conditions of biogas plants can lead to significant differences between life cycle impacts. Therefore, we emphasise the importance of site-specific LCA studies for reliable impact assessments. In addition, we suggest the incorporation of stakeholder interviews to support LCA at different phases and better implementation of life cycle thinking in policy design.