28 Februar 2011

Evaluating a Biomass Refinery

Detailed environmental evaluations consider alternatives and the effect of developing a cellulosic ethanol plant with a power generation component

The Abengoa Bioenergy Biorefinery of Kansas (ABBK) in Hugoton, Kansas, would be one of the first commercial-scale cellulosic biorefineries in the United States and offers an opportunity to demonstrate a powerful renewable energy source that could reduce the nation’s dependency on oil.

Abengoa Bioenergy responded to a call from the U.S. Department of Energy (DOE) to submit an application to build a commercial-scale demonstration facility using biomass. The bioenergy firm was selected via an extensive merit review process to build a biomass-to-ethanol and biomass-to-energy production biorefinery that would use a combination of biomass feedstocks (such as corn stover, wheat straw and, potentially, energy crops like switchgrass) to produce ethanol and to generate sufficient electricity to power the facility and supply excess electricity to the regional power grid.

However, approval of the ABBK facility is dependent upon viable financing and the findings of the recently completed comprehensive environmental impact evaluation.

Environmental Impact Statement
The proposed biorefinery project site comprises approximately 810 acres of row-cropped agricultural land. The biorefinery facilities would sit on 385 acres, while the remaining 425 acres would remain agricultural and act as a buffer between the biorefinery and the city of Hugoton.

Construction of the biorefinery would take approximately 18 months and would require infrastructure improvements, such as site roads, a 1.5-mile-long electrical transmission line and railroad spur. Temporary utility connections would include electricity, cable, telephone and a nonpotable water line. Temporary potable water and sanitary facilities would be provided onsite until construction of permanent, onsite facilities.

The DOE is required to comply with the National Environmental Policy Act (NEPA) to evaluate potential environmental impacts associated with proposed projects. For this project, DOE determined that an environmental impact statement (EIS) would be required since no EIS had ever been conducted on this type of facility and several potentially significant impacts affecting the quality of the human environment were associated with this project.

The DOE contracted an EIS team consisting of Jason Associates Corp., a U.S. DOE NEPA contractor; Kleinfelder, a nationwide project management and engineering firm; and technical consultants Ageiss, Battelle and Lechel and Associates to perform the environmental impact analysis. The definition of project alternatives was a key factor in the initial development of EIS analyses.

Action and Reaction
At the outset of the program, the DOE’s EIS team established three development alternatives: Proposed Action, Action Alternative and No-Action Alternative.

Under the Proposed Action, the biorefinery would process approximately 2,500 dry short tons per day of feedstock obtained from producers within 50 miles of the biorefinery project site. In addition, it would produce up to 19 million gallons of denatured ethanol per year and have an electrical capacity of 125 MW, of which 75 MW would be sold to the regional grid.

The Action Alternative assumes the biorefinery does not produce excess electricity for sale to the regional grid, while the No-Action Alternative assumes the biorefinery would not be constructed.

The EIS evaluated the potential direct, indirect, and cumulative environmental impacts to land use, air quality, greenhouse gas emissions, water resources, wastes and biological habitat from the construction, operation, and decommissioning of the biorefinery under the Proposed Action and Action Alternative scenarios.

In addition, the EIS addressed socioeconomics, cultural factors, health and safety, transportation, environmental justice, aesthetics, accidents/sabotage and the strategies to mitigate potential related issues.

Development Benefits
Whether the Proposed Action or Action Alternative was implemented, the EIS team found that the construction and operation of the integrated biorefinery would result in some beneficial changes to the environment and community.

For instance, the biorefinery is expected to employ up to 230 to 260 workers (Action Alternative and Proposed Action, respectively) during the peak of construction and would employ from 34 to 43 workers during the expected 30 years of operations. This would result in an annual infusion of earnings into the regional economy of about $16 to $16.6 million a year during construction and $3.5 to $4.4 million a year during operations. This does not include the sale of biomass for facility feedstock and the resulting infusion of income to suppliers.

Under the Proposed Action, the biorefinery would produce electricity via a high-pressure, steam-condensing turbine generator. Biomass boilers would be used to produce steam. Steam would be used for ethanol production processes and electricity production. The DOE estimated that during normal biorefinery operations, the co-generation component of the facility would provide 75 MW of electrical power to the regional transmission grid.

The projected additional power from the biorefinery would represent about 5.8 percent of the production capacity in the western-central region of Kansas, but only about 0.18 percent of current summer demand in the Southwest Power Pool. The DOE projected that there will be a continued demand for the electrical power that would be generated by the biorefinery under the Proposed Action, even if that production is only a minor portion of the regional demand.

Although the biorefinery would be a source of greenhouse gas emissions, operation of the biorefinery would provide a net reduction in greenhouse gas emissions when considering the emissions produced during the lifecycle of ethanol production and use relative to the lifecycle of gasoline production and use. To determine the level of greenhouse gas reduction from the Proposed Action, the DOE used the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model. The GREET model examines “well-to-wheel” fuel lifecycles by considering factors such as producing raw materials for fuels, refining the raw materials into fuels, and using the fuel in vehicles.

The biorefinery would reduce greenhouse gas emissions not only by producing a fuel that displaces gasoline, but also by producing power that displaces electricity from other electricity-generating sources. The GREET model combines these reductions and other factors into a single metric to express the net effect on lifecycle greenhouse gas emissions relative to a baseline scenario in which the biorefinery is not built.

The metric used to express lifecycle effects on greenhouse gas emissions is the relative percent reduction calculated by comparing (a) the quantity of greenhouse gas emissions (grams of carbon dioxide equivalent per mile) under a range of scenarios with (b) a baseline in which the biorefinery is not built and passenger vehicles use 100 percent conventional or reformulated gasoline.

In using the GREET model to make these comparisons, the DOE accounted for energy consumed by and exported by the biorefinery; biomass-generated electricity exported to the grid was applied to the total energy balance of the biorefinery as an “energy credit” (approximately 42 kilowatt-hours per gallon of ethanol). The DOE assumed that the exported energy would replace electricity that would have been produced by the average U.S. mix, approximately 70 percent or more of which is from fossil energy sources. Results of calculations, presented below, with percentage reductions that exceed 100 percent, reflect the relatively large “negative” contribution of the energy credit.

GHG Comparisons
The GREET model was used to compare greenhouse gas emissions from three scenarios with the baseline scenario: (1) vehicles fueled only by ethanol, (2) vehicles fueled by 85 percent ethanol and 15 percent gasoline (E85) and (3) vehicles fueled by 10 percent ethanol and 90 percent gasoline (E10). Based on the GREET model, the Proposed Action under the first scenario would result in a 340 percent reduction in greenhouse gas emissions compared with the gasoline-only baseline. The reductions in greenhouse gas emissions are due largely to the emissions “credit” for the electricity being exported to the grid. The exported biopower would replace electricity that would have been produced largely through coal, nuclear and natural gas.

Thus, the greenhouse gas emissions credit is essentially equal to the difference between the greenhouse gases from producing biomass-based electricity and greenhouse gases from electricity produced via coal, natural gas and nuclear. Because the majority of the electricity the biorefinery would produce would be exported rather than used for biorefinery operations, the greenhouse gases displaced by the biorefinery would be larger than the greenhouse gases emitted by biorefinery operations. This causes a decrease in greenhouse gas that exceeds 100 percent.

As a comparison, if only enough electricity were produced to run the biorefinery (none sold to the grid), the percent reduction under the Proposed Action would be 69 percent as compared with the gasoline-only baseline. In the second scenario (E85), the DOE estimated a 329 percent reduction in greenhouse gas emissions, again primarily due to the emissions credit. As a comparison, without the export of electricity to the grid, the percent reduction in greenhouse gas under the second scenario would be 62 percent. In the third scenario (E10), the DOE estimated a 29 percent reduction in greenhouse gas emissions could be achieved relative to the gasoline-only baseline.

In terms of water resources, the biorefinery project would actually decrease groundwater use at the site. Under the Proposed Action, the biorefinery facility would require up to 2,950 acre-feet of groundwater per year from eight wells. That is about 4,290 acre-feet less than the currently permitted annual volume for those wells. The Action Alternative scenario would require up to 850 acre-feet per year from three wells, which is 1,500 acre-feet less than the currently permitted annual volume.

Impacts of Increased Activity
In general, the EIS team found that adverse impacts of constructing and operating the biorefinery would be small. For example, the DOE does not anticipate that there would be substantial changes in land use practices in the region surrounding the biorefinery project site. There would be no need to convert marginal cropland or lands in the Conserve Reserve Program to meet the biomass demand of the biorefinery.

Many of the adverse impacts that could occur, especially those resulting from construction, would be temporary and local. Under the Proposed Action and Action Alternative, there would be a significant increase in truck and rail traffic into and from the Hugoton area. Transportation statistics indicate there would be an increase in traffic fatalities associated with these shipments and the commuting of workers.

Potential strategies being considered to mitigate traffic accidents include staggering workforce schedules to minimize road congestion and developing safety-based criteria to be used, in part, to select motor carriers.

The DOE is considering noise mitigation strategies, including maximizing the use of rail for shipments to and from the project site to reduce truck traffic.

Waste Disposal
The 18-month construction of the biorefinery facility would generate up to 78 tons per day of solid waste. In addition, if ash from the solid biomass boilers (up to 350 tons per day under the Proposed Action) was not sold as a soil nutrient replacement, it could require disposal at permitted solid waste disposal facilities.

However, the Stevens County landfill does not have adequate capacity to receive the generated construction ash/wastes and maintain its existing permit, which is limited to 20 tons per day. Revising that permit would be expensive.

The strategy is to split the waste streams among permitted landfills and transfer stations within 35 miles of the biorefinery project site, though permission for disposal would be required from those facilities.

The EIS team recommended that Abengoa develop and implement a contingency plan for alternative beneficial uses of the fly ash in the event a significant percentage of the material is not used by biomass producers as soil amendment.

Funding Fundamentals
Based in part on the analyses in the Abengoa Biorefinery Project EIS, the U.S. DOE will decide whether to provide funding to support:

(1) Final design, construction, and startup of the biorefinery project as proposed by Abengoa Bioenergy (the Proposed Action);

(2) Final design, construction, and startup of the biorefinery project for all elements of the facility as proposed by Abengoa, at a reduced ethanol production level using synthetic gas and without the portion dedicated to generating electricity for commercial sale (the Action Alternative); or

(3) Proposed Action or Action Alternative, contingent on the implementation of environmental mitigation measures, which would be determined based on the environmental impact analysis in this EIS.

If the DOE decides to provide federal funding, it would negotiate an agreement with Abengoa Bioenergy to provide up to $71 million, subject to annual appropriations, of the total anticipated cost of approximately $685 million (2009 dollars). The Record of Decision (ROD) was anticipated before the end of the 2010 calendar year. The complete FEIS can be viewed on the US DOE NEPA Web site at http://www.nepa.energy.gov.

Source: Renewable Energy World.com, 2011-02-28.


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