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Abstract Life cycle inventory models of greenhouse gas emissions from biofuel production have become tightly integrated into government mandates and other policies to encourage biofuel production. Current models do not include life cycle impacts of biomass storage or reflect current literature on emissions from soil and biomass decomposition. In this study, the GREET model framework was used to determine net greenhouse gas emissions during ethanol production from corn and switchgrass via three biomass storage systems: wet ensiling of whole corn, and indoor and outdoor dry bale storage of corn stover and switchgrass. Dry matter losses during storage were estimated from the literature and used to modify GREET inventory analysis. Results showed that biomass stability is a key parameter affecting fuel production per farmed hectare and life cycle greenhouse gas emissions. Corn silage may generate 5358 L/ha of ethanol at 26.5 g CO2 eq/MJ, relative to 5654 L/ha at 52.3 g CO2 eq/MJ from combined corn stover and conventional grain corn ethanol production, or 3919 L/ha at 21.3 g CO2 eq/MJ from switchgrass. Dry matter losses can increase net emissions by 3–25% (ensiling), 5–53% (bales outdoors), or 1–12% (bales indoors), decreasing the net GHG reduction of ethanol over gasoline by up to 10.9%. Greater understanding of biomass storage losses and greenhouse gas fluxes during storage is necessary to accurately assess biomass storage options to ensure that the design of biomass supply logistics systems meet GHG reduction mandates for biofuel production.

Abstract Biomass is a key variable for crop monitoring and for assessing carbon stocks and bioenergy potential. This study aimed to develop an allometric model for predicting the dry leaf biomass of sisal, an agave plant with crassulacean acid metabolism grown for fibre production in the tropics and subtropics and whose biomass can be utilised as a feedstock to produce biogas through anaerobic digestion. The allometric model was used to estimate leaf biomass and productivity across different stand ages in a sisal plantation in semi-arid region in south-east Kenya (annual rainfall 611 mm and temperature 24.9 °C). Based on a sample of 38 leaves, the best predictor for biomass was leaf maximum width and plant height used as a combined variable in a log-log regression model (cross-validated R2 = 0.96 and root-mean-square error = 7.69 g). The mean productivity in nine 26- to 36-month-old plots was 11.1 Mg ha−1 yr−1, which could potentially yield approximately 3000 m3 CH4 ha−1 yr−1. The leaf biomass in 55 field plots (400 m2 in area) ranged from 2.7 to 42.7 Mg ha−1, with mean at 13.5 Mg ha−1, which equals to 6.3 Mg C ha−1. The yielded allometric equations can be utilised for predicting the leaf biomass of sisal in similar agro-ecological zones. The estimates on plantation biomass can be used in assessing the role of sisal plantations as a regional carbon storage. In addition, the results provide reference on the productivity of agave and crassulacean acid metabolism in semi-arid regions of East Africa, where such reports are few.

Abstract Limited information is available regarding biomass production potential of long-term (>5- yr-old) switchgrass (Panicum virgatum L.) stands. Variables of interest in biomass production systems include cultivar selection, site/environment effects, and the impacts of fertility and harvest management on productivity and stand life. We studied biomass production of two upland and two lowland cultivars under two different managements at eight sites in the upper southeastern USA during 1999–2001. (Sites had been planted in 1992 and continuously managed for biomass production.) Switchgrass plots under lower-input management received 50 kg N ha−1 yr−1 and were harvested once, at the end of the season. Plots under higher-input management received 100 kg N ha−1 (in two applications) and were harvested twice, in midsummer and at the end of the season. Management effects on yield, N removal, and stand density were evaluated. Annual biomass production across years, sites, cultivars, and managements averaged 14.2 Mg ha−1. Across years and sites, a large (28%) yield response to increased inputs was observed for upland cultivars; but the potential value of higher-input management for lowland cultivars was masked overall by large site×management interactions. Nitrogen removal was greater under the higher-input system largely due to greater N concentrations in the midsummer harvests. Management recommendations (cultivar, fertilization, and harvest frequency), ideally, should be site and cultivar dependent, given the variable responses reported here.

Abstract Weyerhaeuser Company is committed to being a responsible steward of the environmental quality and economic value of the forests we manage. Weyerhaeuser's regional Forest Councils have developed specific resource strategies for forest products, water quality, wildlife habitat, soil productivity and aesthetics. The sustainable site productivity or soil productivity strategy is as follows: “We protect soil stability and ensure long-term soil productivity by: (1) using equipment and practices appropriate to the soil, topography and weather to minimize erosion and harmful soil disturbance, and (2) using forestry practices and technology to retain organic matter and soil nutrients.” The elements of the Weyerhaeuser reliable processes used to achieve this strategy in the Northwest, U.S.A. include (1) a research database; (2) common goals and standards leading to management guidelines; (3) education, training and teaming across the organization; (4) implementation of Best Management Practices (BMPs); (5) monitoring of performance and (6) adaptive experimentation. This is not a static process—continuous improvement is a design element in the process. Guidelines and BMPs have been developed to minimize detrimental soil disturbance. This was accomplished by having (1) a strategic database on soil disturbance impacts; (2) a classification system that describes soil disturbance classes; (3) a soil operability risk rating system that rates soils on their susceptibility to compaction and puddling; and (4) a close working relationship between R and D and operations to develop BMPs. Steps are being taken to develop organic matter management guides for various soil groups and a soil nutrient risk-rating system. These combined with fertilizer guides will lead to practices that conserve and strive to maintain organic matter and soil nutrients. Education and training of employees is an important step in implementing the guides and BMPs. Operational practices are monitored to assess performance against specified standards. Identification of knowledge gaps lead to additional research and operational adaptive trials. Based on new research information, operational experiences and monitoring feedback. BMPs will be continuously improved to meet Weyerhaeuser's sustainable site productivity strategy.

Perennial energy crop development is just starting in Poland and there are great expectations on this sector to make a substantial contribution to the achievement of renewable energy targets defined in the European Union (EU) directive 28/2009/EC. Insights into the economics of energy crop production may lead to a better understanding of the dynamics of developments in the field. This work addresses current and future economics of willow, Miscanthus and triticale (a whole crop) production for energy use in Poland. The economics of energy crops is set next to that of common cereal production for grain. Potential cost reductions of energy crops in the future are investigated with regard to the hypothetical impact of scale effect, as well as the combined effect of scale and technology developments. Results indicate that for the assumed biomass prices applied, willow is profitable while Miscanthus and triticale generate loss. The volatility of cereal market prices is found to significantly affect the competitiveness of energy crops compared to grain production. Willow and Miscanthus are produced with lower costs compared to triticale. Furthermore, the economics of perennials are less susceptible to changes in agricultural inputs prices compared to annual crops. For the first farmers to cultivate energy crops, the costs are high, however, there are large opportunities for cost reduction due to the economics of scale and technology developments. With the expected increase in biomass market demand and biomass prices, energy crops should be profitably produced in the future. (C) 2011 Elsevier Ltd. All rights reserved. (Less)

An analysis of the potential land base for energy crops in the conterminous United States has identified 158.6 million ha that can grow short-rotation woody crops (SRWC) and herbaceous energy crops (HEC) without irrigation. Of this land, 145.3 million ha is currently used for agriculture as either cropland or pastureland, but agricultural land needs are anticipated to decline in the future. Both SRWC and HEC may be suitable crops for surplus cropland. Of the capable land base, 91.1 million ha is suitable for SRWC, and 131.1 million ha is suitable for HEC. Suitability is based on an assumption that the land must be capable of energy crop yields of at least 11.2 Mg ha −1 yr−1 with current technology. Most of this suitable land is in the North Central, South Central and Southeastern regions of the United States, although present predictions suggest that future cropland surpluses will occur largely in the Great Plains and Mountain regions of the United States. This paper defines the land suitable for energy crop production and estimates the yield potential of that land. Analyses of the relative economics of energy crop and alternative agricultural land uses will be required before the land base potentially available for energy crop production can be defined.

The combustion of perennial grass biomass to generate electricity may be a promising renewable energy option. Switchgrass (Panicum virgatum) grown as a biofuel has the potential to provide a cash crop for farmers and quality nesting cover for grassland birds. In southwestern Wisconsin (near lat. 42°52′, long. 90°08′), we investigated the impact of an August harvest of switchgrass for bioenergy on community composition and abundance of Wisconsin grassland bird species of management concern. Harvesting the switchgrass in August resulted in changes in vegetation structure and bird species composition the following nesting season. In harvested transects, residual vegetation was shorter and the litter layer was reduced in the year following harvest. Grassland bird species that preferred vegetation of short to moderate height and low to moderate density were found in harvested areas. Unharvested areas provided tall, dense vegetation structure that was especially attractive to tall-grass bird species, such as sedge wren (Cistothorus platensis) and Henslow's sparrow (Ammodramus henslowii). When considering wildlife habitat value in harvest management of switchgrass for biofuel, leaving some fields unharvested each year would be a good compromise, providing some habitat for a larger number of grassland bird species of management concern than if all fields were harvested annually. In areas where most idle grassland habitat present on the landscape is tallgrass, harvest of switchgrass for biofuel has the potential to increase the local diversity of grassland birds.

Abstract Rice husk generated as a by-product of rice processing is an important energy resource. The availability of this resource in India has been assessed and the technologies for exploitation of its energy potential in rice processing industry discussed. Nomographs have been developed for estimation of the husk required to meet the energy demand of parboiling, drying and milling operations. The unit cost of electricity using rice husk gasifier-based power generation systems has been calculated and its financial feasibility assessed in comparison with utility-supplied and diesel-generated electricity. With the cost and efficiency data assumed here, the unit cost of electricity produced by rice husk gasifier-dual fuel engine-generator system varies between Rs 2/kWh and Rs 7/kWh. (Note: 35 Rs approximates to $US 1.)

Abstract Short-rotation woody crops in the southeastern United States will make a significant contribution to the growing renewable energy supply over the 21st century; however, there are few studies that investigate how species selection may affect water yield. Here we assessed the impact of species selection on annual and seasonal water budgets in unvegetated plots and late-rotation 14–15-year-old intensively managed loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) stands in South Carolina USA. We found that while annual aboveground net primary productivity and bioenergy produced was similar between species, sweetgum transpiration was 53% higher than loblolly pine annually and 92% greater during the growing season. Canopy interception was 10.5% of annual precipitation and was not significantly different between the two species. Soil evaporation was less than 1.3% of annual precipitation and did not differ between species, but was 26% of precipitation in unvegetated plots. Annual water yield was 69% lower for sweetgum than loblolly pine, with water yield to precipitation ratios of 0.13 and 0.39 for sweetgum and loblolly pine, respectively. If planted at a large scale, the high transpiration and low water yield in sweetgum could result in declines in downstream water availability relative to loblolly pine by the end of the growing season when storage in groundwater, streams, and water supply reservoirs are typically at their lowest. Our results suggest that species selection is of critical importance when establishing forest plantations for woody bioenergy production due to potential impacts on downstream water yield.