LCA based methodology for spatial and temporal variation of climate impactfrom biobased energy

Spatial variation in global warming potential (GWP) reduction compared with diesel of using the grass-based biogas system, without fossil fuel substitution. Colours indicate site-specific GWP reduction. Background indicates the soil pH, where a darker shade indicates lower pH. The white dashed line represents the municipality border.

Background

One strategy to limit global warming is to phase out fossil products and replace them with bio-based alternatives. In this transition, it is important to study the impact ofthe bio-based products and how to optimise the systems. Life Cycle Assessment (LCA) is a suitable methodology to study these impacts since the methodology comprehends the whole life cycle of the studied item. The spatial effects due to soil types, initialcarbon content, transport distances etc have in previous studies been of major importance. LCA does, however, rarely include the spatial and temporal variation of the impact and also rarely include soil processes such as soil C balance and soil N2O emissions are often roughly estimated.

Aims

The general aim of the thesis was to develop knowledge about the climate impact and mitigation potential of grass-based biogas systems. Another aim was to develop a model combining agro-ecosystem modelling with life cycle assessment methodology and also considering spatial and temporal variations.

Approaches

LCA methodology was combined agro-ecosystem model DNDC to include soil processes and their variations over time and space. The developed method was used to assess the climate impact and eutrophication of grass-based biogas production in Uppsala municipality, Sweden. The grass for the biogas production was assumed to be cultivated on fallow land in the studied region. In total, more than 1000 sites with different properties were included in the analysis. In this study, the whole life cycle was included, from cradle to grave. The results showed large variation in the impact between different locations, depending on weather conditions, soil properties, transport distances etc. The analysed grass-based biogas reduced climate impact significantly compared to the reference system.

Keywords

Life Cycle Assessment (LCA), Soil carbon sequestration, Soil N2O emissions, DNDC model, Bio-methane, Digestate, Greenhouse gas emissions, Perennial cropping systems.

Links

Link to published article ”Regional variation in climate impact of grass-based biogas production: A Swedish case study”

Project leaders

Johan Nilsson, Per-Anders Hansson, SLU

Other project members

Cecilia Sundberg, Pernilla Tidåker, Kajsa Henrysson, SLU; BrianGrant, WardSmith, Ottawa RDC, Canada

Other funding agencies

Parts of a Phd work in this area was co-funded from the NJ-faculty at SLU