Life cycle assessment of first-generation biofuels using a nitrogen crop model

Area of Science:

• Agricultural Science
• Environmental Science
• Chemical Engineering

Background:

• Life Cycle Assessment (LCA) is crucial for evaluating biofuel sustainability.
• Traditional LCA methods often use generic emission factors, overlooking site-specific impacts.
• Nitrogen (N) losses from soil, particularly nitrous oxide (N₂O), significantly contribute to the global warming potential (GWP) of biofuels.

Purpose of the Study:

• To develop and apply an integrated LCA approach incorporating a semi-empirical model for crop production.
• To assess the site-specific environmental impacts of biodiesel (from rapeseed) and bioethanol (from wheat) in the Basque Country.
• To improve the estimation of N losses (N₂O, NO₃, NH₃) and their contribution to LCA impact categories at a local scale.

Main Methods:

• Integration of a new semi-empirical crop model into a Life Cycle Assessment (LCA).
• System expansion method to account for co-products.
• Analysis of environmental impacts including non-renewable energy use, GWP, acidification, eutrophication, and land competition.
• Uncertainty analysis focusing on soil N₂O emissions.

Main Results:

• Biofuels (biodiesel from rapeseed, bioethanol from wheat) reduce non-renewable energy use (-55%) and GWP (-40%) compared to fossil fuels.
• Significant increase in eutrophication potential (42 times higher) due to biofuel production.
• Site-specific climate and fertilizer management introduce variability in LCA results.
• Soil N₂O emissions are a major contributor to GWP, with significant uncertainty in predictions.

Conclusions:

• The novel LCA approach enhances the accuracy of biofuel impact assessment by considering local conditions.
• Accounting for site-specific factors, especially N losses, is critical for reliable biofuel sustainability evaluations.
• Improved modeling reduces uncertainty, providing a clearer picture of biofuel viability compared to fossil fuels.