Biofuels sustainable

Hall CA, Dale BE, Pimentel D. (2011) Seeking to understand the reasons for different energy return on investment (EROI) estimates for biofuels. Sustainability, 3 2413-2432. 

American public support has turned its attention to third-generation biofuels (eg, biomass/cellulose based biofuels), sustaining numerous projects. Excise tax credits ( 1.00/gallon biodiesel tax credit for producers or blenders of pure biodiesel and biodiesel from biomass) and import tariffs are mainly used as instmments for biofuels support across States (U.S. Department of Energy, 2015). The support policy for biofuels in the United States tends to apply low tariffs on imported biofuels commodities. Tariffs on ethanol are, for example, the equivalent of 1.2—2.5% from countries outside NAFTA. Blending practices are also notably applied to favor the reexport of biofuel commodities, in particular to the European Union. 

Bracco, S., 2015. Effectiveness of EU biofuels sustainability criteria in the context of land acquisitions in Africa. Renewables and Sustainable Energy Reviews 50, 130—143. 

The key question is how to measure biofuel sustainability in such a complex system with a diversity of feedstock, a large number of biofuel pathways, and variations on specific interests of the stakeholders. The answer lies within the establishment of environmental and other indicators, which enable the assessing of the sustainability of different types of bioenergy systems. The indicators should, however, apply to both large installations and local sites, and also should be useful to diverse stakeholders (McBride et al., 2011). 

Several studies have been recently conducted with efforts to fiuther improve the current status of biofuel sustainability certification. Gnansounou (2011) proposed a logic-based model for the sustainability assessment of biofuels. The proposed model uses a hierarchical stracture to link multiple factors from the more specific variables to the most general one, sustainability performance. The study proposed 7 general and 20 specific indicators for assessing the social, economic, and environmental performance of a biofuel supply chain. 

Another important aspect to be examined related to biofuels production is its environmental sustainability. It is not always easy to assess the ecological footprint of biofuels, as they involve many factors that are linked in a complex way. In 2008, a roundtable for sustainable biofuels set 12 criteria (partially updated in 2011) for the evaluation of biofuel sustainability ... 

In 2009, the US Environmental Protection Agency (EPA) proposed some modifications to the RFS called RFS2. Although it has not been signed into law yet, the RFS2 contains a lot of very strict provisions in order to improve the sustainability of biofuels. Moreover, it provides a detailed regulation for next-generation biofuels and defines other measures in order to improve biofuel sustainability. 

Silva Lora, E.E., Escobar Palacio, J.C., Rocha, M.H., Grillo Reno, M.L., Venturini, O.J., del Olmo, O.A., 2011. Issues to consider, existing tools and constraints in biofuels sustainability assessments. Energy 36, 2097—2110. 

Biofuels rely on organic feedstocks such as plant oil, food wastes and trees but their larger scale and rapid exploitation to meet government targets is stressing large areas of land and associated systems such as water, food production and recreation. A truly sustainable future for biofuels and other eco-system exploitation for industrial value requires a better understanding and more quantitative assessment of a number of critical issues ... 

The assessment of the sustainability of the cultivation of energy crops includes the input and recycling of nutrients, the application of pesticides, the water-use efficiency, the consumption of fossil fuels and the balance of soil carbon. The aim is to recycle the nutrients, which is simple in the case of anaerobic digestion by applying the digestate to the field. If crops are combusted many of the minerals can be returned via the ash. In the case of liquid biofuels, exported nutrients are lost and have to be replaced. The application of pesticides, mainly herbicides, can often be reduced in comparison to food production, but the energy yield per hectare might be reduced if the share of weeds exceeds certain thresholds. Water use efficiency,... 

Hill J (2007) Environmental costs and benefits of transportation biofuel production from food- and I i gnocc11 u I osc-based energy crops A review. Agron Sustain Dev 27 1-12. doi 10.1051/ agro 2007006... 

Land availability may not be a major problem, but land use issues need to be coordinated. The long-term production of biofuels in substantial quantities will require a number of changes. Grain surpluses will not provide sufficient feedstocks for the fuel quantities needed. Producers will need to switch to short-rotation woody plants and herbaceous grasses, these feedstocks can sustain biofuel production in long-term, substantial... 

Doornbosch, R. and Steenblik, R. (2007). Biofuels Is the Cure Worse Than the Disease Paris OECD, General Secretariat. OECD Round Table on Sustainable Development SG/SD/RT(2007) 3. 

Worldwatch Institute (2007). Biofuels for Transport Global Potential and Implications for Sustainable Agriculture and Energy in the 21st Century. Earthscan Publications, Ltd. 

In 2003, the European Biofuels Directive (CEU, 2007 EC, 2003) was enacted. It sets an indicative target of a 2% market share for biofuels in 2005, a 5.75% share in 2010 and a 10% share in 2020 for road transport related to the energy content of the fuel. It has to be noted, however, that biofuel mandates are increasingly being scrutinised from a sustainability perspective and the targets in the EU are currently being reconsidered. 

The alternative fuels and drive systems available only seem to be viable on the mass market, if the oil price stays above 60 to 70 /bbl for a sustained period. Oil prices peaked above 140 /bbl in summer 2008 and many experts believe that stable oil prices over 100 /bbl could be reached in the next one or two decades. The higher the market prices of fossil fuels, the more competitive low-carbon alternatives will become The principal choice here is between biofuels, electricity and hydrogen, provided that they are produced either from low/zero-carbon feedstock or that the C02 generated during their production is captured and stored. But higher priced conventional oil resources, on the other hand, can also be replaced by high-carbon alternatives such as oil sands, oil shale or synthetic fuels from coal and gas. 

Fig. 1.12 Fully integrated agro-biofuel-biomaterial-biopower cycle for sustainable technologies (From A. J. Ragauskas et al., Science, 311,484 (2006). Reprinted with permission from AAAS [7]).

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