Utilization of biomass in the U.S. for the production of ethanol fuel as a gasoline replacement—I terrestrial resource potential

With relatively minor adjustments in the agricultural sector, large additional amounts of starch derived from feed corn, surplus and distressed grain, and set-aside land could presently be used for ethanol production. The quantity of ethanol that could be produced would be sufficient to replace anywhere from 5 to 27 per cent (5.5–30 billion gallons) of present gasoline requirements. Thus, the ethanol requirement for total gasohol use (10 per cent) in the U.S. could be met in the short period of time required for facility construction with no evident impact on food production. Increased supplies of ethanol will make feasible the introduction of ethanol fueled engines. High-yield sugar crops planted on new acreage could provide an additional 10 billion gal. of ethanol by the year 2000; conversion of the waste biomass from this crop to ethanol could also add substantially to this amount. Utilization of novel cellulose conversion technology can provide fermentable sugars from municipal wastes, agricultural and forest wastes, and ultimately, highly productive silvicultural operations. The wastes alone could yield over 36 billion gal. of 192° PR ethanol-fuel by the year 2000. Fast-growing woody species from silviculture are expected to yield a conservative average of 10 over-dry tons per acre per yr, convertible to 710 gal. of ethanol in a process that has 37 per cent yield. Advantages over sugar/starch crops include year-round harvesting, and use of marginal acreage. Commercial forest land presently suitable for silviculture is about 100 million acres in large tracts plus 200 million acres in small private tracts. The potential additional yield of ethanol from lignocellulosic biomass appears to be well in excess of liquid fuel requirements of an enhanced efficiency transport sector in the U.S. at present mileage demands. No conflict with food production would be necessary.     

Energy consumption analysis of integrated flowsheets for production of fuel ethanol from lignocellulosic biomass

Fuel ethanol is considered one of the most important renewable fuels due to the economic and environmental benefits of its use. Lignocellulosic biomass is the most promising feedstock for producing bioethanol due to its global availability and to the energy gain that can be obtained when non-fermentable materials from biomass are used for cogeneration of heat and power. In this work, several process configurations for fuel ethanol production from lignocellulosic biomass were studied through process simulation using Aspen Plus. Some flowsheets considering the possibilities of reaction–reaction integration were taken into account among the studied process routes. The flowsheet variants were analyzed from the energy point of view utilizing as comparison criterion the energy consumption needed to produce 1 L of anhydrous ethanol. Simultaneous saccharification and cofermentation process with water recycling showed the best results accounting an energy consumption of 41.96 MJ/L EtOH. If pervaporation is used as dehydration method instead of azeotropic distillation, further energy savings can be obtained. In addition, energy balance was estimated using the results from the simulation and literature data. A net energy value of 17.65–18.93 MJ/L EtOH was calculated indicating the energy efficiency of the lignocellulosic ethanol.     

Meeting U.S. liquid transport fuel needs with a nuclear hydrogen biomass system

The two major energy challenges for the United States are replacing crude oil in our transportation system and eliminating greenhouse gas emissions. A domestic-source greenhouse-gas-neutral nuclear hydrogen biomass system to replace oil in the transportation sector is described. Some parts of the transportation system can be electrified with electricity supplied by nuclear energy sources that do not emit significant quantities of greenhouse gases. Other components of the transportation system require liquid fuels. Biomass can be converted to greenhouse-gas-neutral liquid fuels; however, the conversion of biomass-to-liquid fuels is energy intensive. There is insufficient biomass to meet U.S. liquid fuel demands and provide the energy required to process the biomass-to-liquid fuels. With the use of nuclear energy to provide heat, electricity, and hydrogen for the processing of biomass-to-liquid fuels, the liquid fuel production per unit of biomass is dramatically increased, and the available biomass could meet U.S. liquid fuel requirements.     

Investigation of a novel & integrated simulation model for hydrogen production from lignocellulosic biomass

Process simulation and modeling works are very important to determine novel design and operation conditions. In this study; hydrogen production from synthesis gas obtained by gasification of lignocellulosic biomass is investigated. The main motivation of this work is to understand how biomass is converted to hydrogen rich synthesis gas and its environmentally friendly impact. Hydrogen market development in several energy production units such as fuel cells is another motivation to realize these kinds of activities. The initial results can help to contribute to the literature and widen our experience on utilization of the CO₂ neutral biomass sources and gasification technology which can develop the design of hydrogen production processes. The raw syngas is obtained via staged gasification of biomass, using bubbling fluidized bed technology with secondary agents; then it is cleaned, its hydrocarbon content is reformed, CO content is shifted (WGS) and finally H₂ content is separated by the PSA (Pressure Swing Adsorption) unit. According to the preliminary results of the ASPEN HYSYS conceptual process simulation model; the composition of hydrogen rich gas (0.62% H₂O, 38.83% H₂, 1.65% CO, 26.13% CO₂, 0.08% CH₄, and 32.69% N₂) has been determined. The first simulation results show that the hydrogen purity of the product gas after PSA unit is 99.999% approximately. The mass lower heating value (LHV_mass) of the product gas before PSA unit is expected to be about 4500 kJ/kg and the overall fuel processor efficiency has been calculated as ～93%.     

Chemicals from biomass—the U.S. prospects for the turn of the century

Historically, chemicals from biomass have been and are expected to be economical in three major areas: byproducts, specialty items and polymers. Assessments of producing major chemicals from biomass in a processing plant based on the available conversion techniques indicate that they are not economically attractive, with the possible exception of conversion to ammonia and ethanol. The deterrents are the heavy capital investments, dependability of raw material supply and transportation costs for large plants, lack of operation experience, inadaptability to market variations, and competition from petroleum and coal. More importantly, it is also shown that even if chemicals from biomass were economical today, the resultant savings in petroleum would be far less than those achieved through other options available for the utilization of biomass as fuel and structural material. Thus, it is concluded that near-term research and development must be toward improved conversion processes, recovery of valuable products from waste streams at existing plants, more efficient use of biomass for energy and more efficient production of superior material products.     

Alkali-stable cellulase from a halophilic isolate,Gracilibacillus sp. SK1 and its application in lignocellulosic saccharification for ethanol production

A halophilic strain SK1 showing cellulolytic activity was isolated from Yuncheng Salt Lake, and was identified as the genus of Gracilibacillus by 16S rRNA gene sequence analysis. Cellulase production was strongly influenced by the salinity of culture medium with maximal level in the presence of 10% NaCl. Substrate specificity test indicated the crude cellulase was a multi-component enzyme system, showing a combined activity of endoglucanase, exoglucanase and β-glucosidase. Zymogram analysis indicated six different endoglucanases were secreted by this strain. The crude enzyme was highly active and stable over broad ranges of temperature (40–70 °C), pH (6.0–10.0) and NaCl concentration (7.5–17.5%), with an optimum at 60 °C, pH 8.0 and 12.5% NaCl, which showed excellent thermostable, alkali-stable and halostable properties. Moreover, it displayed high stability in the presence of hydrophobic organic solvents. Saccharification of corn stover and rice straw by the cellulase resulted in respective yields of 0.678 and 0.502 g g⁻¹ dry substrate of reducing sugars. The enzymatic hydrolysates of corn stover were then used as the substrate for ethanol production by Saccharomyces cerevisiae. The yield of ethanol was 0.186 g g⁻¹ dry substrate, and the efficiency of reducing sugars conversion to ethanol was about 52.8%, which suggested the prospects of the crude enzyme from Gracilibacillus sp. SK1 in application for bio-ethanol production.     

Spatial heterogeneity of factors determining ethanol production site selection in the U.S., 2000-2007

Bivariate probit regression and spatial clustering methods analyze investment activity of ethanol plants at the county level for the contiguous 48 United States from 2000-2007. Infrastructure, product and input markets, fiscal policy of local communities, and state and federal incentives determined the location of ethanol plants. The ability to supply feedstock and the absence of previously established ethanol plants dominated the distribution of site selection. Other factors, such as access to railroads or navigable rivers, product markets, lower wages, producer credit and excise tax incentives, and methyl tertiary-butyl ether bans provided some counties comparative advantage with respect to attracting ethanol plants.     

Integration properties of disaggregated solar,geothermal and biomass energy consumption in the U.S.

This paper investigates the integration properties of disaggregated solar, geothermal and biomass energy consumption in the U.S. The analysis is performed for the 1989–2009 period and covers all sectors which use these types of energy, i.e., transportation, residence, industrial, electric power and commercial. The results suggest that there are differences in the order of integration depending on both the type of energy and the sector involved. Moreover, the inclusion of structural breaks traced from the regulatory changes for these energy types seem to affect the order of integration for each series.     

Potential availability of urban wood biomass in Michigan: Implications for energy production,carbon sequestration and sustainable forest management in the U.S.A.

Tree and wood biomass from urban areas is a potentially large, underutilized resource viewed in the broader social context of biomass production and utilization. Here, data and analysis from a regional study in a 13-county area of Michigan, U.S.A. are combined with data and analysis from several other studies to examine this potential. The results suggest that urban trees and wood waste offer a modest amount of biomass that could contribute significantly more to regional and national bio-economies than it does at present. Better utilization of biomass from urban trees and wood waste could offer new sources of locally generated wood products and bio-based fuels for power and heat generation, reduce fossil fuel consumption, reduce waste disposal costs and reduce pressure on forests. Although wood biomass generally constitutes a “carbon-neutral” fuel, burning rather than burying urban wood waste may not have a net positive effect on reducing atmospheric CO₂ levels, because it may reduce a significant long term carbon storage pool. Using urban wood residues for wood products may provide the best balance of economic and environmental values for utilization.     

Biomass production and bioconversion to both fuel and food employing solar energy technology—An alternative to conventional farming and the conversion of food to fuel

A bioconversion process for the conversion of high yield biomass to both fuel and food is discussed. Attention has been directed toward the diversion of farm land for the production of a crop such as corn for subsequent conversion to liquid fuel; the bioconversion process is reviewed as an alternative. The premise of this process involves growing biomass at optimum crop yield. The biomass is converted to synthesis gas and then bioconverted to single cell protein and methanol fuel. Supporting references, background and preliminary engineering economics are provided.     

Shallow subsurface temperature surveys in the basin and range province—II. Ground temperatures in the upsal hogback geothermal area, West-Central Nevada, U.S.A.

Numerous temperature surveys at a depth of 1 m were made in 1973–1985 in the Upsal Hogback and Soda Lakes geothermal areas in west-central Nevada. Whereas the surveys effectively delineated temperature at depth and heat flow within the relatively intense Soda Lakes thermal anomaly, they were not effective at the diffuse Upsal Hogback anomaly, where several perturbing factors that affect shallow subsurface temperatures are exceedingly variable. Albedo is the most important factor in the Upsal Hogback area, even at a depth of 30 m. All possible perturbing factors should be considered when designing a shallow temperature-based prospecting scheme.     

Review of consumption trends and public policies promoting woody biomass as an energy feedstock in the U.S.

A review of the four main wood energy sectors in the U.S. was conducted to explore historic trends and the impact of alternative energy prices and public policies on wood energy consumption. High oil prices have triggered the adoption of government regulation and financial incentives to promote greater use of wood energy over the last four decades. However, the amount of wood energy consumed in the U.S. industrial sector was driven mainly by the output of the pulp and paper products industry and not by energy prices or any particular public policy incentive. Residential consumption of wood energy was positively correlated with competing energy prices. Public policies seem to have had a greater impact on wood energy consumption in the electric power sector and over the last four decades have concentrated on promoting biopower with a recent shift to liquid cellulosic biofuels. High oil prices and a series of public policies such as tax credits, loans, grants, and renewable energy standards have resulted in higher consumption of wood energy from 2004 to 2009 in the residential, electric power and commercial sectors by an estimated 5, 2, and less than 1 percent annually, respectively. The impact of new federal programs such as the Biomass Crop Assistance Program remains to be observed. Continuation of public incentives and preferential regulations for renewable energy appears to be necessary for a steady increase in U.S. wood energy consumption.     

Energetic and economic feasibility associated with the production,processing, and conversion of beef tallow to a substitute diesel fuel

This study investigates the resource availability, energetic efficiency, and economic feasibility of converting edible and inedible beef tallow into biodiesel, a substitute diesel fuel.A resource assessment of edible and inedible beef tallow generation in the United States was performed for the period of 1997–2001. At that time, an average of more than 1.8 Mt (4 billion pounds) of edible and inedible tallow were generated each year in the 11 largest commercial cattle slaughtering states, which would equate to more than 2.08 GL (551 million gallons) of biodiesel (∼1% of the total US distillate consumption).Tallow is a by-product of our meat production and processing system, which complicates its energy and economic analysis. Although tallow is available in significant quantities at relatively low cost, it is not intentionally produced as a feedstock for biodiesel. Because of this uncertainty, energetic (energy ratio) and economic (production cost per gallon) feasibilities were estimated for three different system boundaries: (1) conversion of tallow by a continuous-flow transesterification process only with co-product (glycerin) credit, (2) rendering plant operations plus tallow transesterification, and (3) growth and maintenance of the beef animal from conception through rendering and transesterification. Energy ratios varied from 17.29 to 0.81 within the three system boundaries based on various assignments of the co-product energy credit for glycerin.Cost-sensitivity analyses were performed to determine the effect of feedstock cost and by-product (glycerin) credit on biodiesel cost. Feedstock cost had the greatest impact, while by-product credit effect was minimal. Cost of production ranged from $0.22 to $0.63 L⁻¹ ($0.82–$2.38 gallon⁻¹) produced.     

Perspectives for the direct firing of biomass as a supplementary fuel in combined cycle power plants

An analysis of the performance of a gas turbine–steam turbine combined cycle with supplementary firing has been carried out. Natural gas is fired in the main combustor of the cycle, whereas biomass fuel is considered as the supplementary fuel. Although, supplementary firing is found to reduce the overall cycle efficiency, the low cost of biomass and the CO₂‐neutral attribute of its combustion reduce the specific fuel cost and specific CO₂ emission. The effects of pressure and temperature ratios of the topping cycle and main steam conditions of the bottoming cycle on the performance parameters of the combined cycle have been studied at different degrees of supplementary firing. The topping cycle temperature ratio is found to be the most critical parameter and its low value gives substantial advantages in lowering the fuel cost and CO₂ emission. Marginal advantages are also achieved at higher pressure ratio and better bottoming cycle main steam conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

Use of ash-free “Hyper-coal” as a fuel for a direct carbon fuel cell with solid oxide electrolyte

“Hyper-coal”, produced by the Kobe Steel Company, was investigated by analytical and physico-chemical methods to consider its potential usability as a fuel for a direct carbon fuel cell with solid oxide electrolyte (DC-SOFC). The performed tests showed that DC-SOFCs fed with this processed fossil coal were characterized by stable operation with reasonable current and power densities. The performance of the fuel cells can be improved by using iron as a catalyst for the anodic reaction and by the choice of appropriate working conditions.