Life cycle assessment of bioethanol from wheat and sugar beet discussing environmental impacts of multiple concepts of co-product processing in the context of the European Renewable Energy Directive

ABSTRACT

The environmental performance of biofuels is often assessed comparing multiple feedstocks while implications of different co-product processing options are neglected. This study presents a life cycle assessment of several co-product processing concepts of wheat- and sugar beet-based ethanol production in Germany. Inventory data are first-hand industry data presenting state-of-the-art plants. The methodology defined by the Renewable Energy Directive (RED) is applied. The cradle-to-gate investigation shows that the co-production of fodder results in lowest impacts allocated to ethanol: 37 g CO₂-eq. per MJ of ethanol from sugar beets. Total impacts are lower in case of beet-based ethanol in impact categories which are dominated by emissions from cultivation, such as eutrophication and acidification. Biogas co-production results in lowest total emissions but in higher emissions allocated to ethanol. A sensitivity analysis shows how certain assumptions, such as using a different energy carrier, grain drying, etc., influence these results. Results indicate that the environmental impacts of different co-product processing concepts differ. Consequently, special attention should be given to this aspect when the environmental impacts of biofuels are compared. It is furthermore advised to apply a method accounting for the utility and benefits of co-products when allocating emissions, as opposed to RED methodology.

KEYWORDS:

• Bioethanol
• life cycle assessment
• co-product processing
• Renewable Energy Directive

Acknowledgements

This work has been accomplished in the course of a research project assessing sustainability aspects of biofuel production and utilization. I. Klenk and S. Lengert are acknowledged for providing technical description of processes and data.

Financial and competing interests disclosure

The project is financed by CropEnergies AG. CropEnergies AG provided data on several ethanol production concepts discussed in this study. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. No writing assistance was utilized.