There is a strong societal need to evaluate and understand the sustainability of biofuels, especially because of the significant increases in production mandated by many countries, including the United States. Sustainability will be a strong factor in the regulatory environment and investments in biofuels. Biomass feedstock production is an important contributor to environmental, social, and economic impacts from biofuels. This study presents a systems approach where the agricultural, energy, and environmental sectors are considered as components of a single system, and environmental liabilities are used as recoverable resources for biomass feedstock production. We focus on efficient use of land and water resources. We conducted a spatial analysis evaluating marginal land and degraded water resources to improve feedstock productivity with concomitant environmental restoration for the state of Nebraska. Results indicate that utilizing marginal land resources such as riparian and roadway buffer strips, brownfield sites, and marginal agricultural land could produce enough feedstocks to meet a maximum of 22% of the energy requirements of the state compared to the current supply of 2%. Degraded water resources such as nitrate-contaminated groundwater and wastewater were evaluated as sources of nutrients and water to improve feedstock productivity. Spatial overlap between degraded water and marginal land resources was found to be as high as 96% and could maintain sustainable feedstock production on marginal lands. Other benefits of implementing this strategy include feedstock intensification to decrease biomass transportation costs, restoration of contaminated water resources, and mitigation of greenhouse gas emissions.

Efforts to achieve the decomposition of carbon tetrachloride through anaerobic and aerobic bioremediation and chemical transformation have met with limited success because of the conditions required and the formation of hazardous intermediates. Recently, particles of zero-valent iron (ZVI) have been used with limited success for in situ remediation of carbon tetrachloride. We studied a modified microparticulate product that combines controlled-release carbon with ZVI for stimulation of in situ chemical reduction of persistent organic compounds in groundwater. With this product, a number of physical, chemical, and microbiological processes were combined to create very strongly reducing conditions that stimulate rapid, complete dechlorination of organic solvents. In principle, the organic component of ZVI microparticles is nutrient rich and hydrophilic and has high surface area capable of supporting the growth of bacteria in the groundwater environment. In our experiments, we found that as the bacteria grew, oxygen was consumed, and the redox potential decreased to values reaching -600 mV. The small modified ZVI particles provide substantial reactive surface area that, in these conditions, directly stimulates chemical dechlorination and cleanup of the contaminated area without accumulation of undesirable breakdown products. The objective of this work was to evaluate the effectiveness of ZVI microparticles in reducing carbon tetrachloride under laboratory and field conditions. Changes in concentrations and in chemical and physical parameters were monitored to determine the role of the organic products in the reductive dechlorination reaction. Laboratory and field studies are presented.

Cores were collected from Late Cretaceous and Early Tertiary rocks in the Piceance Basin of western Colorado, USA, to investigate the origins of subsurface microorganisms under geological conditions likely to constrain microbial transport and survival. The sampled strata from 856–862, 1996–1997 and 2091–2096 m recorded peak paleotemperatures of 120–145°C from 40–5 million years ago, while present temperatures range from 43 to 85°C. Cores were analyzed for culturable anaerobic bacteria (Fe(III)‐ and Mn(IV)‐reducing bacteria, fermenters, sulfate reducers, nitrate reducers and methanogens), ester‐linked phospholipid fatty acid and selected enzyme and physiological activities. Measurable but low biomass (total phospholipid fatty acid) and anaerobic bacteria, primarily Fe(III) reducers and fermenters, were present in samples from the 856–862 m core. Cores from greater depths yielded only a single positive enrichment and lower biomass values. Methanogens and sulfate reducers were not detected in any of the samples nor were bacteria that could grow with methane and any added electron acceptors. 16S rRNA genes cloned from products of PCR amplification of DNA extracted from an 858 m, 65°C, Fe(III)‐reducing enrichment were most closely related to bacteria in the genus Desulfotomaculum, Gram‐positive, spore‐forming sulfate‐reducing bacteria. Assuming the maximum temperatures would have eliminated any entrained bacteria, these anaerobic microorganisms likely migrated into the shallower Wasatch formation within the last 5 million years. However, the deepest stratum sampled was hydrologically isolated and lacked any indication of microbial colonization by all biological measures. Hydrologic connection to the surface, high maximum temperatures and the presence of fractures are probably the primary factors that control distribution of microorganisms in these deep rock environments.

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