A modular framework to assess biological resource utilization impacts (BIORIM)

Abstract

The strong influence of biological processes and site conditions, the large diversity in management, compositional changes of agricultural produce, and the circularity of processes challenge the assessment of environmental impacts of the bioeconomy. This paper introduces a novel sustainability assessment and material flow model to study biological resource utilization impacts (BIORIM) which aims to address these challenges. The model represents important bioeconomic production systems (e.g. arable land, dairy farm, biogas plant) and considers input properties, production parameters such as site conditions or management, and different emission factors when calculating products and emissions. For this reason, the functions that represent the conversion processes need to be executed in the correct order when analysing larger production networks. The model keeps full track of mass, carbon and nitrogen flows, and therefore allows assessing how much is lost during processing, ending up in the produce and is recycled. The modelling approach is illustrated at the example of a dairy farm where dairy manure is used as an organic fertilizer for fodder crop production in the following year. This is compared to a scenario that includes a biogas plant. The comparison of manure storage to biogas production reveals that this change does not only affects direct emissions. Biogas production leads to higher carbon losses and thus negatively affects the humus balance. The manure storage, on the other hand, leads to higher nitrogen losses, which result in a lower fertilization value of the manure, and therefore a higher amount of mineral fertilizer is required in the following year. Together with the emission savings from the energy production, this results in a lower global warming effect of the biogas scenario. The study shows that it is important to consider the interplay of processes when assessing impacts of bioeconomic production systems.