Environmental sustainability of biofuels: a review

Abstract

Biofuels are being promoted as a low-carbon alternative to fossil fuels as they could help to reduce greenhouse gas (GHG) emissions and the related climate change impact from transport. However, there are also concerns that their wider deployment could lead to unintended environmental consequences. Numerous life cycle assessment (LCA) studies have considered the climate change and other environmental impacts of biofuels. However, their findings are often conflicting, with a wide variation in the estimates. Thus, the aim of this paper is to review and analyse the latest available evidence to provide a greater clarity and understanding of the environmental impacts of different liquid biofuels. It is evident from the review that the outcomes of LCA studies are highly situational and dependent on many factors, including the type of feedstock, production routes, data variations and methodological choices. Despite this, the existing evidence suggests that, if no land-use change (LUC) is involved, first-generation biofuels can—on average—have lower GHG emissions than fossil fuels, but the reductions for most feedstocks are insufficient to meet the GHG savings required by the EU Renewable Energy Directive (RED). However, second-generation biofuels have, in general, a greater potential to reduce the emissions, provided there is no LUC. Third-generation biofuels do not represent a feasible option at present state of development as their GHG emissions are higher than those from fossil fuels. As also discussed in the paper, several studies show that reductions in GHG emissions from biofuels are achieved at the expense of other impacts, such as acidification, eutrophication, water footprint and biodiversity loss. The paper also investigates the key methodological aspects and sources of uncertainty in the LCA of biofuels and provides recommendations to address these issues.

Considering sustainability thresholds for BECCS in IPCC and biodiversity assessments

“…Current biomass for bioenergy is in many cases related to acidification, eutrophication, water footprint, and biodiversity loss (Jeswani et al, 2020). Deforestation of greater than the current levels (average of 0.26 Mkm 2 between 2014 and 2019; NYDF Assessment Partners, 2019) to expand plantations and/or energy crops for bioenergy would be incompatible with sustainability targets, including climate protection (the biophysical effect and forgone sequestration of deforesting tropical forests would largely offset any potential gains).…”

Copper molybdate synthesized by sonochemistry route at room temperature as an efficient solid catalyst for esterification of oleic acid

“…In general, biofuels are obtained via transesterification reactions from animal fats or vegetable oils and fatty acid esterification [7] . Thus, biofuels combustion provides high energy efficiency with less emission of greenhouse gases [8] . However, due to the esterification or transesterification reactions' energy barrier, catalysts have been a viable alternative to increase the reaction speed and the conversion percentage of the final product [9] .…”

More sustainable vegetable oil: balancing productivity with carbon storage opportunities

“…Oil palm plantation land area still appears to be growing in SE Asia, and the world production of soybean, rapeseed and sunflower is forecast to continue to grow at a rate of around 1.5% per year 13 . Whilst the use of vegetable oil for biofuel production has fallen out of favour due to sustainability concerns 16,25,26,27 , the demand for used cooking oil as a fuel source is expected to rise significantly 28 . However, despite this being seen as a highly sustainable source of transport fuel compared to first generation biofuel or fossil alternatives 29,30,31 , recent reports suggest that it could in fact be linked to deforestation and thus an additional source of currently under-considered GHG emissions 28,32 .…”