The current debate over biofuels produced from food crops has pinned a lot of hope on “2nd-generation biofuels” produced from crop and forest residues and from non-food energy crops. This IEA report, produced jointly with IEA Bioenergy, examines the current state-of-the-art and the challenges for 2nd-generation biofuel technologies. It evaluates their costs and considers policies to support their development and deployment.
It is increasingly understood that 1st-generation biofuels produced primarily from food crops are limited in their ability to achieve targets for oil-product substitution, climate change mitigation and economic growth. Their sustainable production is under review, as is the possibility of creating undue competition for land and water used for food and fiber production. A possible exception that appears to meet many of the acceptable criteria is ethanol produced from sugar cane.
The cumulative impacts of these concerns have increased the interest in developing biofuels produced from non-food biomass. These “2nd-generation biofuels” could avoid many of the concerns facing 1st-generation biofuels and potentially offer greater cost reduction potential in the longer term.
Our recent IEA report looks at the technical challenges facing 2nd-generation biofuels, evaluates their costs and examines related current policies to support their development and deployment. The potential for production of more advanced biofuels is also discussed. Policy recommendations are given as to how these constraints to commercial deployment might best be overcome in the future.
While most analyses continue to indicate that 1st-generation biofuels show a net benefit in terms of GHG emissions reduction and energy balance, they also have several drawbacks. Current concerns for many, but not all, of the 1st-generation biofuels are that they:
- contribute to higher food prices due to competition with food crops;
- are an expensive option for energy security taking into account total production costs excluding government grants and subsidies;
- provide only limited GHG reduction benefits (with the exception of sugarcane ethanol, Fig. 1) and at relatively high costs in terms of $/tonne of carbon dioxide ($/t CO2) avoided;
- do not meet their claimed environmental benefits because the biomass feedstock may not always be produced sustainably;
- are accelerating deforestation (with other potentially indirect land use effects also to be accounted for);
- potentially have a negative impact on biodiversity; and
- compete for scarce water resources in some regions.
Figure 1. Well-to-wheel emission changes for a range of 1st- and 2nd-generation biofuels (excluding land use change) compared with gasoline or mineral diesel. Source: OECD, 2008 based on IEA and UNEP analysis of 60 published life-cycle analysis studies giving either ranges (shown by the bars) or specific data (shown by the dots).
Additional uncertainty has also recently been raised about GHG savings if indirect land use change is taken into account.
Second Generation Biofuels
Many of the problems associated with 1st-generation biofuels can be addressed by the production of biofuels manufactured from agricultural and forest residues and from non-food crop feedstocks. Where the ligno-cellulosic feedstock is to be produced from specialist energy crops grown on arable land, several concerns remain over competing land use, although energy yields (in terms of GJ/ha) are likely to be higher than if crops grown for 1st-generation biofuels (and co-products) are produced on the same land. In addition poorer quality land could possibly be utilized.
Given the current investments being made to gain improvements in technology, some expectations have arisen that, in the near future, these biofuels will reach full commercialization. This would allow much greater volumes to be produced at the same time as avoiding many of the drawbacks of 1st-generation biofuels. However, from this IEA analysis, it is expected that, at least in the near to medium-term, the biofuel industry will grow only at a steady rate and encompass both 1st- and 2nd-generation technologies that meet agreed environmental, sustainability and economic policy goals.
The transition to an integrated 1st- and 2nd generation biofuel landscape is therefore most likely to encompass the next one to two decades, as the infrastructure and experiences gained from deploying and using 1st-generation biofuels is transferred to support and guide 2nd-generation biofuel development.
Authors: R. Sims, M. Taylor, J. Saddler and W. Mabee