A 10-year US Department of Energy-sponsored research program designed to evaluate and develop switchgrass ( Panicum virgatum ), a native perennial warm-season grass, as a dedicated energy crop is reviewed. The programmatic objectives were to identify the best varieties and management practices to optimize productivity, while developing an understanding of the basis for long-term improvement of switchgrass through breeding and sustainable production in conventional agroecosystems. This research has reduced the projected production cost of switchgrass by about 25% ($8–9 Mg −1 ) through yield increases of about 50% achieved through selection of the best regionally adapted varieties; through optimizing cutting frequency and timing; and by reducing the level (by about 40%) and timing of nitrogen fertilization. Breeding research has made further gains in productivity of switchgrass that exceed the historical rate of yield improvement of corn. Studies of soil carbon storage under switchgrass indicate significant carbon sequestration will occur in soils that will improve soil productivity and nutrient cycling and can substantially augment greenhouse gas reductions associated with substituting renewable energy for fossil energy. Collaborative research with industry has included fuel production and handling in power production, herbicide testing and licensing, release of new cultivars, and genetic modifications for chemical coproduct enhancement. Economically based life cycle analyses based on this research suggest that switchgrass produced for energy will compete favorably both as an agricultural crop and as fuel for industry.

Development of switchgrass (Panicum virgatum) as a bioenergy feedstock in the United States.

Switchgrass (Panicum virgatum L.)—a perennial, warm-season (C4) species—evolved across North America into multiple, divergent populations. The resulting natural variation within the species presents considerable morphological diversity and a wide range of adaptation. The species was adopted as a crop—initially as a forage—only in the last 50 yr. Its potential uses have recently been expanded to include biofuels. Management of switchgrass for biofuels is informed by an understanding of the plant's biology. Successful establishment requires attention to seed dormancy and weed control as well as proper depth and date of planting. The plant's growth rate is closely tied to temperature, but timing of reproductive development is linked to photoperiod. Accordingly, the period of vegetative growth can be extended by planting lower-latitude cultivars at higher latitudes. This strategy may provide a yield advantage, but cold tolerance can become limiting. Switchgrass is thrifty in its use of applied N; it appears a...

The Biology and Agronomy of Switchgrass for Biofuels

https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2754&context=facpub

Biomass-coal co-combustion: opportunity for affordable renewable energy

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1076&context=biosysengfacpub

Switchgrass for Bioethanol and Other Value-Added Applications: A Review

Historical development of the chemical industry.- Chemical process safety: Safe practices and accident prevention.- Managing an emergency preparedness program.- Applied statistical methods.- Green engineering: Integration of green chemistry, pollution prevention, and risk based considerations.- Industrial catalysis: A practical guide.- Environmental chemical determinations.- Nanotechnology: Principles and applications.- Nanostructured materials: Industrial Applications.- Synthetic organic chemicals.- Chemistry in the pharmaceutical industry.- Manufactured textile fibers.- Dye application, manufacture of dyes and dye intermediates.- Chemistry of structural adhesives: Epoxy, urethane, and acrylic adhesives.- Synthetic resins and plastics.- Rubber.- The agrochemical industry.- Petroleum and its products.- Coal technology for power, liquid fuels and chemicals.- Natural gas.- The nuclear industry.- Synthetic nitrogen products.- Phosphorus and phosphates.- Fertilizers.- Sulfur and sulfuric acid.- Salt, chlor-alkali, and related heavy chemicals.- Industrial gases.- Wood and wood products.- Pigments, paints, polymer coatings, lacquers and printing inks.- Industrial biotechnology: Discovery to delivery.- Industrial enzymes and biocatalysis.- Industrial production of therapeutic proteins: Cell lines, cell culture and purification.- Biomass utilization.- Animal and vegetable fats, oils and waxes.- Sugar and other sweeteners.- Soap, fatty acids, and synthetic detergents.- Chemical explosives.- Electrochemical energy storage: Applications, processes, and trends.

Handbook of Industrial Chemistry and Biotechnology

Tests were conducted in June 1992 at Georgia Power Company's plant Hammond Unit 1 to evaluate the impact of cofiring wood waste with pulverized coal on plant performance. Hammond 1 is a 100 MW Babcock and Wilcox (B & W) unit fueled by pulverized coal. Over a three day period, 11 full load performance tests were conducted, five with coal and six with wood/coal mixture. A total of 125 tonnes (140 tons) (as received, 19% moisture) was burned, the wood waste a mixture of sawdust and ground tree trimming waste. Wood percentage in the fuel ranged between 9.7 and 13.5%, with an average for the cofire tests of 11.5% (all percentages by weight). At medium and high O2 levels, boiler efficiency with wood cofiring was within 0.2-0.4% of boiler efficiency with coal alone. Mill fineness was slightly affected, as the wood particles did not grind as small as the coal particles. Coal particles experienced only a minimal effect due to the presence of the wood. Mill power increased with wood cofiring. Opacity was observed to increase with wood cofiring, the cause of which is presently under investigation. NOx emissions with wood were about the same or slightly less than with coal firing. Sulfur emissions theoretically should have been 6–7% lower with wood cofiring. This decrease was not observed because of fluctuations in the coal sulfur content.

Southern company tests of wood/coal cofiring in pulverized coal units

A study is under way to evaluate the feasibility, costs, and benefits of co-milling and direct injection cofiring of switchgrass with coal as a potential renewable energy source. Switchgrass is an American native prairie grass, ideally adapted to the eastern United States. The grass is highly productive, requires little fertilization and herbicide, and can be grown on marginal land. There are four phases in the study, which look at (1) farm production issues, (2) pilot co-milling, (3) pilot combustion tests, and (4) full-scale demonstration. To date, good data have been obtained on farm production costs and field processing and handling issues. Pilot-scale milling tests and combustion tests of blends of switchgrass with coal have been successfully completed, and a full-scale demonstration of direct pneumatic injection of switchgrass for co-firing in a pulverized coal boiler is planned for the spring of 2001.

Switchgrass cofiring: pilot scale and field evaluation.

Evaluation of Switchgrass as a Co-Firing Fuel In the Southeast

Switchgrass was co-fired with coal in an industrial scale boiler to investigate the co-firing effects on boiler performance and pollutant emissions. Comparing with firing coal alone, co-firing with switchgrass slightly lowered boiler efficiency by 0.6 to 1% under full-load and low-load conditions, respectively. Net carbon dioxide and SO2 emissions were reduced with co-firing. Nitrogen oxides (NOx) emissions were similar with co-firing to firing coal alone under both high and low loading amounts of switchgrass. Varying the nitrogen content by changing switchgrass type and harvest time revealed no significant effect on NOx emission in the range of tested conditions.

Doug Boylan

Papers

Southern company tests of wood/coal cofiring in pulverized coal units

Switchgrass cofiring: pilot scale and field evaluation.

Evaluation of Switchgrass as a Co-Firing Fuel In the Southeast

Co-firing switchgrass in a 60-megawatt pulverized coal-fired boiler: Effects on combustion behavior and pollutant emissions