Outlook for advanced biofuels

Abstract

Modern use of biomass can play an important role in a sustainable energy supply. Biomass abounds in most parts of the world and substantial amounts could be produced at low costs. Motor biofuels seem a sensible application of biomass: they are among the few sustainable alternatives to the transportation sector and can address many of the problems associated with mineral oil. Many biofuels are conceivable. Biodiesel (from oil crops) and ethanol from sugar beets or grains are already used in practice. However, these traditional biofuels have severe disadvantages in land use, costs, and potential to reduce CO2 emissions. Sugar cane ethanol and advanced biofuels that are produced from lignocellulose biomass via gasification-synthesis or via hydrolysis-fermentation have much better perspectives.

Based on the possibilities to apply fuels in the present transportation sector, the implementation ease at short and middle term, the ultimate attractiveness (e.g. fuel economy in fuel cell cars), possibilities for process scale-up, and expected economic performance on the long-term, four attractive biofuels are selected for further analysis: methanol, hydrogen, Fischer-Tropsch (FT) diesel and ethanol. Previous studies in the biofuels field, and on these four fuels in particular, did not yield comparable results, and did not give insight in the further improvement potential by the use of advanced future conversion technologies, application of large scale, process optimisation and electricity co-production.

The four candidate fuels are globally analysed in the same way. Existing and developing production technologies were studied. Concepts were developed that incorporated new and improved technologies, and had potential low cost or high energy efficiency. The models directly yielded the plant energy balance and flow dimensions that could be used for the economic calculations. An important input parameter to the calculations is the feedstock costs. To supply biomass from production areas to energy importing regions, long distance international transport is necessary, implying additional logistics, costs, energy consumption and material losses compared to local utilisation. International bioenergy trade is found to be possible against low costs and modest energy loss.

In the long term (2030) methanol and hydrogen could be produced at 9 €/GJHHV. Ethanol and FT diesel are more expensive (11 and 13 €/GJHHV). These numbers are above the current gasoline production costs that ranged from 3 to 7 and diesel from 2 to 7 €/GJHHV in the last ten years. The uncertainties in the biofuels production costs of the four named biofuels is 15 – 30 %, this is small when considering the large uncertainty in future (2030) gasoline/diesel prices.

Fuels from lignocellulose crops and sugarcane are found to have better prospects for the costs of driving, and the potential and costs of CO2 emission reduction, than traditional biofuels. Eventually, gasification based processes give a broader flexibility in fuel choice than hydrolysis fermentation. Methanol, dimethylether (DME) and Fischer-Tropsch diesel are fuels that could gradually be introduced as blends with gasoline and diesel, and hardly require infrastructure adaptations. Sugar/starch derived ethanol blends with gasoline and rapeseed derived biodiesel with diesel may remain the most popular (and important) biofuels until 2010. Ethanol-gasoline blends could facilitate development of better ethanol processes, and the introduction of neat ethanol vehicles later. biodiesel does not have such advantages. On longer term, hydrogen, methanol and DME are the most suitable in a transition to fuel cell vehicles, if that would be desirable. The eventual shift to hydrogen then requires concurrent development of new infrastructure and FCV introduction.