Advances in genetics, biotechnology, process chemistry, and engineering are leading to a new manufacturing concept for converting renewable biomass to valuable fuels and products, generally referred to as “the biorefinery.” The integration of crops as a source of raw material and energy with biorefinery manufacturing technologies offers the potential for the development of materials and sustainable power that will lead to a new manufacturing paradigm.

In an integrated biorefinery, high-value chemicals (e.g., fragrances, flavorings) would be extracted first. Then the plant polysaccharides and lignin would be processed into “value-added” chemicals, building blocks for synthetic products and fuels. The residue from that process may undergo further processing (e.g., to produce syngas), the objective being to reduce the amount of intractable waste at the end of the process. The development of integrated biorefineries would also influence research in plant science and genetics, both to increase yield and to produce a more easily processed feedstock.

A summary of information about the future of biorefineries, which appeared in a review article in Science, represents a consensus from a joint workshop in April 2005 involving the Georgia Institute of Technology, Imperial College of London, and ORNL. Among the authors are Brian Davison and Jonathan Mielenz (Biosciences Division) and Timothy Tschaplinski (Environmental Sciences Division).The authors cite a number of available, environmentally friendly chemical processes that could be used in a biorefinery as well as the challenges that remain to bring the concept into practice. They also note that the first generation of biorefineries is already appearing.

A. J. Ragauskas, C. K. Williams, B. H. Davison, G. Britovsek, J. Cairney, C. A. Eckert, J. Frederick, J. P. Hallett, D. Leak, C. L. Liotta, J. R. Mielenz, R. Murphy, R. Templer, and T. Tschaplinski. “The path forward for biofuels and biomaterials,” Science 311 (5760): 484–89 (2006).

Cellulose is the most abundant renewable natural resource, and the production of biobased products and bioenergy from less costly renewable lignocellulose is important for sustainable development. A reduction in the production costs of cellulase enzymes, improvements in their performance, and an increase in sugar yields are all vital to reducing the processing costs of biorefineries. Improvements in specific cellulase activities for noncomplexed cellulase mixtures can be implemented through cellulase engineering based on either directed evolution or rational design for each cellulase component enzyme and on the reconstitution of cellulase components.

Rhodopseudomonas palustris is a versatile, widely distributed bacterium whose genome has recently been completed and annotated. Among bacteria, R. palustris is exceptional in its metabolic versatility. It can obtain energy from both light and organic compounds, it can grow aerobically or anaerobically, and it can degrade structurally diverse compounds under both aerobic and anaerobic conditions. R. palustris also produces hydrogen gas as a by-product of nitrogen fixation, making it a potential biofuel producer, and it has the potential to act as a greenhouse gas sink by converting carbon dioxide into cell mass. Because most of its metabolic states can easily be attained in laboratory settings, R. palustris is an ideal model for the study of diverse metabolic modes and their control within a single organism.

A research team including research staff in the Chemical Sciences and Biosciences divisions is experimenting with R. palustris with the long-term goal of obtaining a comprehensive understanding of its diverse metabolic states. As a starting point, the team set out to determine the baseline proteome of a wild-type strain of R. palustris under phototrophic and chemotrophic growth conditions. From the resulting dataset, a variety of biological studies can be performed to understand the microbe’s life processes and metabolic diversity. The team has created the ORNL Rhodopseudomonas palustris Proteome Study Website (http://compbio.ornl.gov/rpal_proteome), a much-needed open-access repository for R. palustris data, and plan to make it a powerful and user-friendly site. It is expected to be one of the largest ongoing public resources to date, one that will provide truly open access to proteome results.

N. C. VerBerkmoes, M. B. Shah, P. K. Lankford, D. A. Pelletier, M. B. Strader, D. L. Tabb, W. H. McDonald, J. W. Barton, G. B. Hurst, L. Hauser, B. H. Davison, J. T. Beatty, C. S. Harwood, F. R. Tabita, R. L. Hettich, and F. W. Larimer. “Determination and comparison of the baseline proteomes of the versatile microbe Rhodopseudomonas palustris under its major metabolic states,” Journal of Proteome Research 5 (2): 287–98 (2006).

A team of researchers that included members of the Environmental Sciences and Biosciences divisions conducted a “biostimulation” study at the Environmental Remediation Sciences Program Field Research Center on the Oak Ridge Reservation. The research was motivated by the likelihood that metal- and sulfate-reducing bacteria could be stimulated in the subsurface to enhance the reduction of redox-sensitive metals and radionuclides, thereby immobilizing them in situ. An aboveground processing facility was used for the removal of high concentrations of nitrate, metals, and perchloroethylene.

The team was able to achieve the “maximum contaminant limit” determined by the U.S. Environmental Protection Agency for uranium in drinking water (< 0.03 mg/L) in situ in the highly contaminated uranium- and nitrate-rich system by stimulating subsurface microorganisms. Both field and laboratory investigations confirmed that metal-reducing Geobacter spp. and sulfate-reducing Desulfovibrio spp. were stimulated by additions of ethanol (an electron donor) and that they were most likely significant contributors to the reduction of dissolved uranium. The team found that the prescribed groundwater uranium concentrations could be maintained and that solid-phase uranium remains stable under anaerobic conditions for 1 to 2 years.

The research will have a significant impact on the Oak Ridge Reservation Groundwater Strategy (DOE/OR/01-2069&D2), which describes a watershed-based strategy for making decisions about groundwater remediation on the Oak Ridge Reservation.

W. M. Wu, J. Carley, S. Caroll, O. Cirpka, M. W. Fields, M. Fienen, M. E. Gentile, T. Gentry, M. A. Ginder-Vogel, R. F. Hickey, B. Gu, J. Luo, T. L. Mehlhorn, J. Nyman, H. Yan, D. B. Watson, J. Zhou, S. E. Fendorf, P. Kitanidis, P. M. Jardine, and C. S. Criddle.

“Pilot-scale in situ bioremediation of uranium in a highly contaminated aquifer II: Reduction of U(VI) and geochemical control of U(VI) bioavailability,” Environmental Science and Technology 40 (12): 3986–95 (2006).

Brian Spalding and David Watson, in the Environmental Sciences Division, have devised a generic, nondestructive technique for determining the persistence of contaminants immobilized on soils and sediments. It offers the capability to conveniently and cost-effectively test large numbers of soils and soil treatments for contaminant release and uptake under actual field environmental conditions.

The two researchers fabricated “permeable environmental leaching capsules” (PELCAPs) by casting a polyacrylamide matrix into small (~ 5 cm3), water-permeable cylinders that contain radioisotope-spiked soil. As a proof of principle, they used soils labeled with either 85Sr or 134Cs and leached the PELCAPs in both laboratory tests and in situ by continuously exposing them to groundwater and stream water at two field sites on the Oak Ridge Reservation.

Groups of PELCAPs were retrieved, assayed nondestructively for radioisotopes, and then reinstalled repeatedly over a 6-month period. PELCAPs that contained no soil readily leached both 85Sr and 134Cs into laboratory extractants, the groundwater, and the surface water. PELCAPs containing thermally treated soil retained both of the isotopes in laboratory sequential extractions as well as in field tests. PELCAPs containing untreated soil readily leached more than 90% of 85Sr but less than 1% of 134Cs at both field sites. Soils were retained in the PELCAPs and maintained their cation-exchange capacities during the exposure period.

B. P. Spalding and S. C. Brooks. “Permeable environmental leaching capsules (PELCAPs) for in situ evaluation of contaminant immobilization in soil,” Environmental Science and Technology 39: 8912–18 (2005).

Efforts to enhance terrestrial organic carbon sequestration have traditionally focused on aboveground biomass and surface soils. An unexplored potential exists in thick lower horizons of widespread, mature soils, and a multiple-scale approach may be necessary to assess the propensity of deep subsoils to sequester organic carbon in situ. A research team that included staff from the Environmental Sciences Division studied the fate and transport of dissolved organic carbon within a highly weathered soil, involving spatial scales from the laboratory to the landscape.

The team’s objectives were to interpret processes observed at various scales and to provide an improved understanding of the mechanisms that control the mobility and sequestration of dissolved organic carbon in deep subsoils within humid climatic regimes. Their multiple-scale approach involved laboratory batch and soil columns (0.2 × 1.0 m), an in situ pedon (2 × 2 × 3 m), a well-instrumented subsurface facility on a subwatershed (0.47 ha), and ephemeral and perennial stream discharge at the landscape scale (38.4 ha).

The laboratory-scale experiments confirmed that the lower soil horizons tend to accumulate dissolved organic carbon but that preferential fracture flow tends to limit sequestration. Intermediate-scale experiments demonstrated the beneficial effects of carbon diffusion into soil micropores. Field- and landscape-scale studies demonstrated the coupled hydrological, geochemical, and microbiological mechanisms that limit the sequestration of dissolved organic carbon and their sensitivity to local environmental conditions.

P. M. Jardine, M. A. Mayes, J. R. Tarver, P. J. Hanson, P. J. Mulholland, G. V. Wilson, and J. F. McCarthy. “Exploring vadose zone flow and transport of dissolved organic carbon at multiple scales in humid regimes, ” Vadose Zone Journal 5: 140–52 (2005).

Most of the aircraft fuel used by the U.S. Air Force is consumed in high-payload aircraft such as cargo planes (C130Hs) and bombers (B-52s), which are expected to be heavily used into the middle of the twenty-first century, for example, for fighting wars and for humanitarian aid missions. The fixed-wing aircraft can produce significant amounts of gaseous and particulate emissions that are deposited directly into the atmosphere, contributing to changes on both local and global scales in air composition, air quality, radiation balance, and possibly the life cycle of clouds. However, the fate and transport of the gases and ultrafine particulates that are the dominant species in the aircraft exhaust are not well understood at present because current methods are not suitable for measuring them.

An ongoing project led by ORNL and involving the Wright- Patterson Air Force Research Laboratory, the U.S. Environmental Protection Agency, and industrial partners sought a reliable means for quantifying exhaust emissions from military aircraft. Observations from the field measurements of a C130H cargo plane in 2005 revealed that the particulate matter was dominated by soot and sulfate. The researchers also determined that for reactive aerosol chemistry and turbulent flow mixing in the exhaust plume, far-field measurements (15 m behind the exhaust) would not provide information that would enable direct identification and quantification of individual aircraft emissions. Extractive sampling by using a nitrogen-gas-driven dilution probe effectively quenches aerosol growth at the probe tip, yielding a reliable means for quantitative determination of aircraft emissions at present. Infrared visualization and on-line chemical measurements (by remote sensing and extractive methods) of the exhaust plume from a B-52 aircraft reveal complex turbulent reactive flow patterns as a function of engine power settings. The data are helping scientists improve their understanding of chemical transformation of the emitted materials and design better measurement strategies for future emissions science research.

M.-D. Cheng. The FY 2006 Annual Report on Characterization of B-52 Aircraft Engine Emissions for SERDP, in review (2006).

M.-D. Cheng, E. Corporan, M. DeWitt, C. Spicer, M. Holdren, K. Cowen, B. Harris, R. Shores, R. Hashmonay, R. Kaganan, J. M. Storey, and J. E. Parks II. “Probing emissions of military cargo aircraft: description of a Joint Field Measurement Program,” Journal of the Air and Waste Management Association, submitted (August 2006).

Chinese climate records obtained through a bilateral research agreement between the U.S. DOE and the China Meteorological Administration reveal that much of China has experienced significant decreases in cloud cover over the last half of the twentieth century. This conclusion is supported by analysis of the observed frequency of cloud-free and overcast skies. From 1954 to 2001, total cloud cover and low cloud cover over China have decreased by 0.88% and 0.33% per decade, respectively, while cloud-free days have increased by 0.60% per decade, and overcast days have decreased by 0.78% per decade. Records of cloud amount are especially important in understanding climate change; it would be expected that the decreasing cloud amount would increase surface radiation; however, the opposite was found over most of China. Both solar radiation and pan evaporation (which gives an indication of the combined effects of temperature, humidity, solar radiation, and wind) have decreased over most of China. Annual mean solar radiation has decreased by 3.1 W/m2 per decade, and annual mean pan evaporation has decreased by 39 mm per decade.

Combining these results with findings of previous studies, the researchers postulate that an increasing human-made aerosol burden (mainly SO2) has produced a fog-like haze over much of China and that the haze has increasingly reflected and absorbed solar radiation and thus has resulted in less solar radiation reaching the surface, despite concurrent decreasing trends in cloud amount and increasing trends in cloud-free sky.

Y. Qian, D. P. Kaiser, L. R. Leung, and M. Xu. “More frequent cloud-free sky and less surface solar radiation in China from 1955–2000,” Geophysical Research Letters 33: L01812 (2006).

It is well known that forest soils exhibit a natural increase in the abundance of 13C with soil depth, but the mechanisms causing changes in the isotopic composition of carbon through the soil profile are unclear. Some researchers have speculated that the changes are related to carbon turnover times. A better understanding of soil carbon turnover is fundamental to terrestrial carbon-sequestration strategies for mitigating future increases in atmospheric CO₂.

Recent research by Charles Garten and Paul Hanson in the Environmental Sciences Division has produced estimates of forest soil carbon turnover times and has demonstrated their association with 13C enrichment factors (a measure of change in carbon isotope composition with soil depth). This research represents the first empirical confirmation of an inferred link between soil 13C enrichment factors and soil carbon dynamics and relates the values to environmental variables and major soil carbon pools. This new work shows that environmental factors, soil carbon partitioning, and vertical changes in 13C:12C soil ratios are interrelated and that measurements of carbon isotope ratios are a potential indicator of carbon dynamics in undisturbed forest soils.

C. T. Garten, Jr., and P. J. Hanson. “Measured forest soil C stocks and estimated turnover times along an elevation gradient,” Geoderma (2006), doi:10.1016/j.geoderma.2006.03.049.

C. T, Garten, Jr. “Relationships among forest soil C isotopic composition, partitioning, and turnover times,” Canadian Journal of Forest Research 36: 2157–67 (2006).

Observed increases in the concentrations of atmospheric CO2 are expected to continue, leading to continued increases in near-surface air temperatures. As temperatures change, so too will the amount of energy required for heating and cooling buildings, with fossil fuel emissions increasing as a result. A team of researchers led by Stan Hadley (Engineering Science and Technology Division) and David Erickson (Computer Science and Mathematics Division) melded the results of detailed climate and energy economics models and ran simulations for the United States for the years 2000 through 2025. “Business-as-usual” climate model simulations for the period were used to drive a detailed numerical economics model based on a low-temperature (1.2°C) and a high-temperature (3.4°C) response to CO₂ doubling.

The researchers found that energy for heating in the low temperature- change scenario was relatively consistent in the end years of the simulation but that it continued to decline in the high-temperature-change scenario, making projected net energy use in the high-temperature case slightly lower than in the low-temperature case by 2025. In northern regions, the net energy requirements would be lower because the climate would be warmer, but southern and western regions of the United States would experience increases in energy use as air-conditioning needs increased with rising temperatures. As a whole, increases in carbon emissions from higher air-conditioning needs would more than offset decreases in carbon emissions from reduced heating needs.

S. Hadley, D. J. Erickson III, J. Hernandez, C. Broniak and T. J. Blasing. “Responses of energy use to climate change: A climate modeling study,” Geophysical Research Letters 33 (17): L17703 (2006).

Climate change predictions from models are highly dependent on assumptions about feedback between the biosphere and the atmosphere. One critical feedback occurs if carbon uptake by the biosphere, its net primary productivity (NPP), increases in response to the fossil-fuel-driven increase in atmospheric CO₂, thereby slowing the rate of increase in atmospheric CO₂.

A research team led by R. J. Norby (Environmental Sciences Division) analyzed the response of NPP to elevated CO₂ (~550 ppm) in four free-air CO₂ enrichment (FACE) experiments in forest stands. The research showed that the response of forest NPP to elevated CO₂ is consistent across a broad range of productivity, with a stimulation at the median of 23 ±2%. The surprising consistency of response across diverse FACE sites provides a benchmark to evaluate predictions of ecosystem and global models and allows researchers to focus (1) on unresolved questions about carbon partitioning and retention and (2) on spatial variation in NPP response caused by the availability of other growth-limiting resources.

R. J. Norby, E. H. DeLucia, B. Gielen, C. Calfapietra, C. P. Giardina, J. S. King, J. Ledford, H. R. McCarthy, D. J. P. Moore, R. Ceulemans, P. De Angelis, A. C. Finzi, D. F. Karnosky, M. E. Kubiske, M. Lukac, K. S. Pregitzer, G. E. Scarascia-Mugnozza, W. H. Schlesinger, and R. Oren. “Forest response to elevated CO₂ is conserved across a broad range of productivity,” Proceedings of the National Academy of Sciences 102: 18052–56 (2005).

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