Counting the cost of carbon in bioenergy systems: sources of variation and hidden pitfalls when comparing life cycle assessments

Abstract

Energy from biomass is renewable and capable of providing heat, power or liquid fuels. Life cycle assessments of these renewable fuels have often shown positive energy balances and GHG savings, relative to fossil fuels. There are, however, large variations between studies and not all are positive, leading to recent reports questioning the long-term sustainability of bioenergy. Using a systematic review of life cycle assessments relevant to feedstocks grown in a temperate climate (three for heat and power and eight for liquid biofuels) we have defined these sources of variation, highlighting areas of uncertainty and priorities for future research. In addition, we have explored the challenges in comparing bioenergy and biofuels production chains and their fossil fuel equivalents and demonstrated how this can be done in a fair and consistent manner.

Acknowledgements

Thanks go to Niels Jungbluth at ESU-services Ltd. for providing data from the RENEW project on second generation biodiesel production, and thanks to Steve Ryder for assisting with the data analysis and to Hazel Smith for commenting on a earlier version of this manuscript.

Financial & competing interests disclosure

The authors’ research is supported by the UK Energy Research Centre funded by Engineering and Physical Sciences Research Council, the Natural Environment Research Council and the Economic and Social Research Council in the UK. G Taylor also acknowledges funding from the Carbo-BioCrop consortium of the NERC (NE/H010716/1), ‘Land Based Renewables’ research theme that is part of the Living With Environmental Change research program of the UK. 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 apart from those disclosed. No writing assistance was utilized in the production of this manuscript.