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Leaf growth of hybrid poplar following exposure to elevated CO2 总被引:1,自引:1,他引:0
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Energy crops: current status and future prospects 总被引:3,自引:0,他引:3
RALPH E. H. SIMS ASTLEY HASTINGS† BERNHARD SCHLAMADINGER‡ GAIL TAYLOR§ PETE SMITH† 《Global Change Biology》2006,12(11):2054-2076
Energy crops currently contribute a relatively small proportion to the total energy produced from biomass each year, but the proportion is set to grow over the next few decades. This paper reviews the current status of energy crops and their conversion technologies, assesses their potential to contribute to global energy demand and climate mitigation over the next few decades, and examines the future prospects. Previous estimates have suggested a technical potential for energy crops of~400 EJ yr?1 by 2050. In a new analysis based on energy crop areas for each of the IPCC SRES scenarios in 2025 (as projected by the IMAGE 2.2 integrated assessment model), more conservative dry matter and energy yield estimates and an assessment of the impact on non‐CO2 greenhouse gases were used to estimate the realistically achievable potential for energy crops by 2025 to be between 2 and 22 EJ yr?1, which will offset~100–2070 Mt CO2‐eq. yr?1. These results suggest that additional production of energy crops alone is not sufficient to reduce emissions to meet a 550 μmol mol?1 atmospheric CO2 stabilization trajectory, but is sufficient to form an important component in a portfolio of climate mitigation measures, as well as to provide a significant sustainable energy resource to displace fossil fuel resources. Realizing the potential of energy crops will necessitate optimizing the dry matter and energy yield of these crops per area of land through the latest biotechnological routes, with or without the need for genetic modification. In future, the co‐benefits of bioenergy production will need to be optimized and methods will need to be developed to extract and refine high‐value products from the feedstock before it is used for energy production. 相似文献
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Tests for no treatment effect in randomized clinical trials 总被引:1,自引:0,他引:1
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SYNOPSIS. Some birds can fly for more than 1000 kilometers withoutfeeding. Are these distances compatible with the fuel reservesand the power requirements that flying birds are thought tohave? The fuel for flight is primarily fat, which can make up50% of the total body mass of a bird prior to a long distanceflight. As the bird uses up fuel during the flight and becomeslighter, the power requirements of flight probably decrease.However, a constant power requirement can be assumed throughoutthe flight without introducing serious errors into the estimateof maximum flight distance at a given flight speed. Variousmethods that have been used to estimate the power requirementsof flight are reviewed. Estimates based on indirect calorimetryindicate that the maximum flight distances of birds, when agiven proportion of body mass is used as fuel, are directlyproportional to body mass raised to the 0.227 power. Calculatedvalues of range suggest that birds have small margins of safelyin long, over-water flights unless they are aided by winds orvertical air currents. 相似文献