NSF releases report on next-generation hydrocarbon biofuels; finds large potential

Sunday, March 2, 2008
Posted in Biofuels | Tagged Biofuels

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The National Science Foundation (NSF) of the United States has published an extensive roadmap for the production of next generation hydrocarbon biofuels derived from lignocellulosic biomass that are close analogs for their petroleum-derived hydrocarbon counterparts. Whereas the U.S. has made a significant investment in technologies focusing on breaking the biological barriers to biofuels, principally cellulosic ethanol, this is only one of many biofuel production pathways. There has not been a commensurate investment in the research needed to break the chemical barriers to make bio-based hydrocarbon fuels. According to the roadmap, chemical pathways hold many advantages over bioconversion of biomass into cellulosic alcohols and can generate a much wider range of fuels that can replace gasoline, diesel, and jet fuel (schematic, click to enlarge).

The comprehensive report entitled Breaking the Chemical and Engineering Barriers to Lignocellulosic Biofuels: Next Generation Hydrocarbon Biorefineries [*.pdf 8.8Mb] is one of the outcomes of a workshop on the topic held last June with more than 70 leading biofuels scientists and engineers from America’s leading laboratories and research organisations. The workshop was sponsored by NSF, the U.S. Department of Energy (DOE) and the American Chemical Society; it was chaired by George W. Huber, University of Massachusetts-Amherst.

Focusing on next-generation hydrocarbon liquid biofuels based on chemical conversion technologies similar to those found in the petrochemical industry, the study finds them to have many important advantages:

First, green hydrocarbon fuels are essentially the same as those currently derived from petroleum, except that they are made from biomass. Therefore, it will not be necessary to modify existing infrastructure (e.g. pipelines, engines) and hydrocarbon biorefining processes can be tied into the fuel production systems of existing petroleum refineries.
Second, biomass-based hydrocarbon fuels are energy equivalent to fuels derived from petroleum. In contrast to the lower energy density of E85 flex fuel, there will be no penalty in gas mileage with biomass-based hydrocarbon fuels.
Third, hydrocarbons produced from lignocellulosic biomass are immiscible in water; they self-separate, which eliminates the need for an expensive, energy-consuming distillation step.
Fourth, biomassbased hydrocarbon fuels are produced at high temperatures, which allows for faster conversion reactions in smaller reactors. Thus, processing units can be placed close to the biomass source or even transported on truck trailers.
Fifth, the amount of water needed for processing hydrocarbon fuels from biomass can be greatly reduced, compared with the dilute sugar solutions to which enzymes are constrained. This is because organic or heterogeneous catalysts work well in concentrated water solutions or even in the absence of water if ionic liquids are used.
Finally, heterogeneous catalysts are inherently recyclable. So they can be used over the course of months and even years, which significantly reduces costs compared to biological catalysts. The elimination of energy-intensive distillation, the higher reaction rates, and the much smaller process footprints can also lead to lower biofuel costs than are possible using currently available biological pathways for producing cellulosic ethanol.

According to the study, advances in agriculture and biotechnology have made it possible to inexpensively produce lignocellulosic biomass at costs that are significantly lower - about $15 per barrel of oil energy equivalent - than crude oil [note, this cost was calculated with at oil prices of $80 pb].

Availability of domestic lignocellulosic biomass is not a limitation to making the U.S. oil independent. In fact, non-food biomass, including trees, grasses and agricultural residues, constitutes more than 80% of the total biomass in the U.S. Significant amounts of lignocellulosic biomass can thus be sustainably produced on US agriculture and forestry land with an energy content of 60% of the current US petroleum consumption.

However, the key bottleneck for lignocellulosic-derived biofuels is the current lack of technology for the efficient conversion of this large biomass resource into liquid fuels. The report therefor illuminates the principal technological barriers and the underlying scientific limitations associated with efficient processing of biomass resources into finished hydrocarbon fuels.

It identifies the basic research needs and opportunities in catalytic chemistry and materials science that underpin biomass conversion and fuel utilization, with a focus on new, emerging and scientifically challenging areas that have the potential for significant impact.

The report focuses on six primary areas:

According to the scientists, the benefits of moving toward fuel from lignocellulosic biomass sources will yield valuable benefits for national security, the economy, and the environment.

These benefits can be summarised as follows:

National Security Benefits of Biofuels: Achieving independence from foreign oil, and thereby making the country less vulnerable to political instability in the oil producing regions of the Middle East, is perhaps our foremost energy issue. America’s oil consumption accounts for approximately 25 percent of the global total, yet America holds only 3 percent of the world’s known oil reserves. Roughly 60% of the 319 billion gallons of petroleum consumed in the U.S. annually is imported, with about 13% (~42 billion gallons) coming from Persian Gulf countries.

The United States primarily imports crude oil but also imports petroleum products including gasoline, aviation fuel, and fuel oil. A concerted effort to develop the chemical and engineering methods for costeffective production of biomass-derived alternatives to conventional transportation fuels could significantly reduce our dependence on foreign oil.

Economic Benefits of Biofuels: According to the U.S. Council on Competitiveness, energy security and sustainability are key U.S. competitiveness issues because of the direct impact they have on the productivity of U.S. companies and the standard of living of all Americans. A vibrant lignocellulosic biofuels industry would create a large amount of high paying domestic jobs in the agricultural, forest management, and oil/chemical industries.

The U.S. Bureau of Labor Statistics (BLS) has stated that production workers in chemical manufacturing, which would be similar to those in a biorefinery, earn more money ($820 weekly) than in all other manufacturing sectors ($659/week). The BLS has further stated that the median hourly wages in 2004 were more than $19/hour for plant operators, maintenance and repair workers, chemical technicians, and chemical equipment operators and tenders. Thus, jobs created in the biofuel industry are likely to be good-paying jobs for skilled workers.

Because of the variable nature of biomass resources, small-scale, geographically localized plants are likely to be prevalent in the biofuels production industry. In contrast to fossil fuels, the quantity of biomass is not confined to certain localities and the resource cost of biomass is much lower than that of crude oil. Therefore, conversion to fuels or fuel precursors must be done on a local level to eliminate the expense of transporting low-cost biomass, which would likely limit biomass harvest to a radius of 50-75 miles around the conversion plant; such a plant would produce the liquid fuel equivalent of 10,000-20,000 barrels of oil/day.�

Distributed production of fuels from domestically grown biomass would reduce infrastructure vulnerability by not consolidating all extraction and production activities in single geographic area. This paradigm of distributed production will create good jobs in biorefineries and may offer the opportunity to found new bio-based industries that will benefit rural economies across the nation.

Biofuels and Food: Biofuels can and should be produced sustainably with food and animal feed as co-products. Ethical and moral questions arise when edible biomass products are converted into biofuels. Therefore, conversion of non-edible biomass is the preferred strategy for long-term, large-scale biofuels production in the U.S. However, the economics are currently more favorable for conversion of edible biomass (e.g. corn starch, soybeans) into fuels due to their chemical structure, which can be more efficiently processed.

Therefore, it is important to continue developing technologies for the cost-effective conversion of non-edible lignocellulosic biomass into fuels. Agricultural practices in the U.S. and other industrialized countries are very advanced, and most industrialized regions produce more than enough food for domestic consumption.

Farmers do not pick the crops based on how efficiently they produce edible food products. Instead farmers’ goals are to grow crops that maximize their income, even though more efficient crops can be grown. Therefore, to the extent that bioenergy crops can be produced economically and dependably command a good price, they can provide farmers another market for their products, which could improve the economic situation of agricultural communities.

Environmental Benefits of Biofuels: One of the biggest benefits of biofuels is the associated reduction in net emissions of CO2. The release of CO2 into the atmosphere is directly related to an increase in temperatures worldwide. According to a landmark report released by the United Nation’s Intergovernmental Panel on Climate Change (IPCC), an international body comprised of representatives from 113 world governments,”Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.” The IPCC report further states that burning fossil fuels is one of global warming’s main drivers.

Projections of rising sea levels and more frequent episodes of severe weather have prompted policy makers and the general public to demand action to stabilize atmospheric CO2 concentrations. Over the long term, stabilizing CO2 concentrations in the atmosphere means reducing emissions close to zero. Fossil fuel combustion releases CO2 into the atmosphere. While the biofuels combustion also releases CO2, it is consumed during subsequent biomass re-growth. Thus, biofuels made from lignocellulosic biomass can be carbon-neutral transportation fuels if efficient processes for biomass conversion are developed (i.e. the amount of CO2 produced during fuel production and combustion is equal to the amount of CO2 consumed by the biomass during its growth).

References:
National Science Foundation: Breaking the Chemical and Engineering Barriers to Lignocellulosic Biofuels: Next Generation Hydrocarbon Biorefineries [*.pdf 8.8Mb], Ed. George W. Huber, University of Massachusetts Amherst. National Science Foundation. Chemical, Bioengineering, Environmental, and Transport Systems Division. Washington DC, 2008.

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