Bioenergy potential of the United States constrained by satellite observations of existing productivity

United States (U.S.) energy policy includes an expectation that bioenergy will be a substantial future energy source. In particular, the Energy Independence and Security Act of 2007 (EISA) aims to increase annual U.S. biofuel (secondary bioenergy) production by more than 3-fold, from 40 to 136 billion liters ethanol, which implies an even larger increase in biomass demand (primary energy), from roughly 2.9 to 7.4 EJ yr(-1). However, our understanding of many of the factors used to establish such energy targets is far from complete, introducing significgant uncertainty into the feasibility of current estimates of bioenergy potential. Here, we utilized satellite-derived net primary productivity (NPP) data-measured for every 1 km(2) of the 7.2 million km(2) of vegetated land in the conterminous U.S.-to estimate primary bioenergy potential (PBP). Our results indicate that PBP of the conterminous U.S. ranges from roughly 5.9 to 22.2 EJ yr(-1), depending on land use. The low end of this range represents the potential when harvesting residues only, while the high end would require an annual biomass harvest over an area more than three times current U.S. agricultural extent. While EISA energy targets are theoretically achievable, we show that meeting these targets utilizing current technology would require either an 80% displacement of current crop harvest or the conversion of 60% of rangeland productivity. Accordingly, realistically constrained estimates of bioenergy potential are critical for effective incorporation of bioenergy into the national energy portfolio.     

Energy balance and emissions associated with biochar sequestration and pyrolysis bioenergy production

The implications for greenhouse gas emissions of optimizing a slow pyrolysis-based bioenergy system for biochar and energy production rather than solely for energy production were assessed. Scenarios for feedstock production were examined using a life-cycle approach. We considered both purpose grown bioenergy crops (BEC) and the use of crop wastes (CW) as feedstocks. The BEC scenarios involved a change from growing winter wheat to purpose grown miscanthus, switchgrass, and corn as bioenergy crops. The CW scenarios consider both corn stover and winter wheat straw as feedstocks. Our findings show that the avoided emissions are between 2 and 5 times greater when biochar is applied to agricultural land (2--19 Mg CO2 ha(-1) y(-1)) than used solely for fossil energy offsets. 41--64% of these emission reductions are related to the retention of C in biochar, the rest to offsetting fossil fuel use for energy, fertilizer savings, and avoided soil emissions other than CO2. Despite a reduction in energy output of approximately 30% where the slow pyrolysis technology is optimized to produce biochar for land application, the energy produced per unit energy input at 2--7 MJ/MJ is greater than that of comparable technologies such as ethanol from corn. The C emissions per MWh of electricity production range from 91-360 kg CO2 MWh(-1), before accounting for C offset due to the use of biochar are considerably below the lifecycle emissions associated with fossil fuel use for electricity generation (600-900 kg CO2 MWh(-1)). Low-temperature slow pyrolysis offers an energetically efficient strategy for bioenergy production, and the land application of biochar reduces greenhouse emissions to a greater extent than when the biochar is used to offset fossil fuel emissions.     

A biorefinery for mobility?

Biofuels are considered as a carbon neutral alternative to hydrocarbons in the transport sector and this approach has triggered concerns about the impact the production of biofuels might have on land usage. Another option that might also lead to reduced emissions in the transport sector is electricity based on renewable energy sources such as biomass. Below, we assess the benefits and drawbacks of the joint production of ethanol and electricity in a sugar cane based refinery, and the use of both energy forms in privately owned automobiles. In this analysis, we have considered technology for energy production that is currently available and cost competitive. The results show that the amount of land that is required to power our current automobile use needs is less than what is typically stated. According to our results that are based on 2010 values, 2 million ha of land are sufficient to power the Brazilian automobile fleet, 25 million ha are enough to satisfy the needs of the U.S. fleet, and 67 million ha are sufficient to cover the global autofuel requirements. When minor efficiency gains are considered, 19 million ha will be enough to satisfy the fuel needs of the U.S. fleet in 2030, whereas land required to supply the Brazilian and global fleet remain basically unchanged. Our analysis shows that the harvested energy density of sugar cane is 306 GJ/ha/yr, which is 1.7 times the value usually reported in the literature for biofuels. As a result, taking advantage of the primary energy potential of sugar cane, only 4% of the world's available cropland area would be sufficient to produce fuels that would power the global car fleet.     

Carbon consequences and agricultural implications of growing biofuel crops on marginal agricultural lands in China

Using marginal agricultural lands to grow energy crops for biofuel feedstocks is a promising option to meet the biofuel needs in populous China without causing further food shortages or environmental problems. Here we quantify the effects of growing switchgrass and Miscanthus on Chinese marginal agricultural lands on biomass production and carbon emissions with a global-scale biogeochemical model. We find that the national net primary production (NPP) of these two biofuel crops are 622 and 1546 g C m(-2) yr(-1), respectively, whereas the NPP of food crops is about 600 g C m(-2) yr(-1) in China. The net carbon sink over the 47 Mha of marginal agricultural lands across China is 2.1 Tg C yr(-1) for switchgrass and 5.0 Tg C yr(-1) for Miscanthus. Soil organic carbon is estimated to be 10 kg C m(-2) in both biofuel ecosystems, which is equal to the soil carbon levels of grasslands in China. In order to reach the goal of 12.5 billion liters of bioethanol in 2020 using crop biomass as biofuel feedstocks, 7.9-8.0 Mha corn grain, 4.3-6.1 Mha switchgrass, or 1.4-2.0 Mha Miscanthus will be needed. Miscanthus has tremendous potential to meet future biofuel needs, and to benefit CO(2) mitigation in China.     

Global land acquisition: neo-colonialism or development opportunity?

Increasingly, developing nations which are land rich are sanctioning the sale or transfer of user rights of large tracts of farmland for foreign investment. While this issue is of relatively recent origin, caused in large measure by the recent global food crisis and related to desires by food importing countries to have greater control over their food supply, the impact on food security could be very significant. Because of the newness of the matter, most of the available evidence is found outside traditional academic literature. Poor, smallholder farmers without formal land titles currently occupy much of the land sold in these transactions, threatening the internal food security of the lessor state. Factors driving the global acquisition of land include development aid shortfalls, the global food crisis, the burgeoning middle class in middle- and high-income nations, and the increasing acceptance of biofuels as a viable alternative source of fuel by governments of these nations. The risks associated with the global acquisition of land on food security of the seller country are manifold. This article reviews the current literature available on the subject and makes policy suggestions for equitable investment and benefit-sharing for all stakeholders. Opportunities and risks abound but if the risks are mitigated, then the global acquisition of land has the potential to be an unparalleled development opportunity for lessor states.     

Wanted: institutions for balancing global food and energy markets

The increasing demand for biomass for energy use is further escalating existing food security risks. Managing these risks is a task for global institutions. These should ensure timely investment in the world’s capacity for producing biomass and balance the use of this biomass for foods and for non-foods. To achieve this, institutional arrangements for global food markets must fulfil two important goals: reduce the short-term price instability of food markets and prevent a structural scarcity of food in the long term. This paper analyses how agro-food markets, energy markets and biofuel markets are currently regulated. As this regulation is ill-suited to manage food price instabilities and balance food and non-food use of biomass, new institutions need to be put in place. A coordinated system of global commodity management — not unlike the Commodity Control Organization proposed by Keynes for the post-WWII era — is proposed to deal with these coming challenges.     

The effect of climate change on the water and food nexus in China

A country level food security approach called PODIUMSim model was applied in this paper to analyse the likely food surplus/deficit in China in the years 2030 and 2050 based on population growth and irrigation area development scenarios. PODIUMSim is an interactive policy planning and scenario analysis tool, which explores the trade-offs and future demands on water resources at a national scale. Changes in precipitation and evapotranspiration estimated from climate models are used to represent climate change. A decision support tool for stochastic analysis called @RISK was used to perform stochastic analysis on future water availability and water demand. Without climate change the results indicate that total grain demand in China would increase from 427 million tons in 2000 to 609 million tons by 2030 and 714 million tons by 2050 while the total grain production was 400 million tons in 2000 and would increase to 521 million tons and 629 million tons in 2030 and 2050, respectively. There was a 27 million ton grain deficit in the year 2000 and there would be an 88 million ton and 85 million ton grain deficit in 2030 and 2050, respectively, under medium population growth and irrigation area development scenarios. To meet the total food demand in 2030 and 2050 in the high population growth scenario, 107.8 and 104.7 million ha of gross irrigated area need to be reached respectively, which requires 48% and 73% of surface water and groundwater irrigation efficiencies in the year 2030 and 49% and 75% of surface water and groundwater irrigation efficiencies in the year 2050, subject to the constraint of irrigation water use being between 400 and 420 billion m³, as set by the Chinese government. Achieving these gains in both gross irrigated area and irrigation efficiency at the country levels is a formidable task, requiring further intensification of land and water use. To meet the total food, domestic and industrial demand, the total water production will have to increase from 564 billion m³ in 2000 to 600 and 615 billion m³ in 2030 and 2050, respectively. In addition, climate change will have significant impacts on future water availability and irrigation water demand. Under climate change (precipitation increased by 3% and evapotranspiration increased by 0.03 mm day⁻¹) in 2030, the surface water availability would decrease from 951 billion m³ to 914 billion m³ and groundwater availability would decrease from 383 billion m³ to 378 billion m³. To cope with the impacts from climate change, some mitigation measures such as investing in drought resistant crops, expanding water storage schemes, and increasing irrigation water use efficiencies should be adopted.     

Economic approach to assess the forest carbon implications of biomass energy

There is widespread concern that biomass energy policy that promotes forests as a supply source will cause net carbon emissions. Most of the analyses that have been done to date, however, are biological, ignoring the effects of market adaptations through substitution, net imports, and timber investments. This paper uses a dynamic model of forest and land use management to estimate the impact of United States energy policies that emphasize the utilization of forest biomass on global timber production and carbon stocks over the next 50 years. We show that when market factors are included in the analysis, expanded demand for biomass energy increases timber prices and harvests, but reduces net global carbon emissions because higher wood prices lead to new investments in forest stocks. Estimates are sensitive to assumptions about whether harvest residues and new forestland can be used for biomass energy and the demand for biomass. Restricting biomass energy to being sourced only from roundwood on existing forestland can transform the policy from a net sink to a net source of emissions. These results illustrate the importance of capturing market adjustments and a large geographic scope when measuring the carbon implications of biomass energy policies.     

Resource-conserving agriculture increases yields in developing countries

Despite great recent progress, hunger and poverty remain widespread and agriculturally driven environmental damage is widely prevalent. The idea of agricultural sustainability centers on the need to develop technologies and practices that do not have adverse effects on environmental goods and services, and that lead to improvements in food productivity. Here we show the extent to which 286 recent interventions in 57 poor countries covering 37 M ha (3% of the cultivated area in developing countries) have increased productivity on 12.6 M farms while improving the supply of critical environmental services. The average crop yield increase was 79% (geometric mean 64%). All crops showed water use efficiency gains, with the highest improvement in rainfed crops. Potential carbon sequestered amounted to an average of 0.35 t C ha(-1) y(-1). If a quarter of the total area under these farming systems adopted sustainability enhancing practices, we estimate global sequestration could be 0.1 Gt C y(-1). Of projects with pesticide data, 77% resulted in a decline in pesticide use by 71% while yields grew by 42%. Although it is uncertain whether these approaches can meet future food needs, there are grounds for cautious optimism, particularly as poor farm households benefit more from their adoption.     

Agriculture, food and the environment

The United Nations Conference on Environment and Development alerted the world to the hazards presumptive if the planet's natural resources of land, water, air, energy and biological organisms are not protected and utilised more conservatively. UNCED declared two urgent research priorities: global climate change and genetic diversity. Excessive use of fossil fuels and a resultant atmospheric pollution forebodes higher temperatures at the earth's surface. The consequences for agriculture are unpredictable. Alternative sources of energy are described: electric motors with high-capacity batteries and high energy fly-wheels; solar-thermal and photovoltaic systems of power generation. Global population will rise to at least 8 billion (1 BILLION = 10⁹) by 2025, a rate of growth demanding an annual increase of 3% in agricultural production. The principles of sustainable production in relation to land and water management, genetic diversity among crop species, and food science and technology are discussed. Among the many thousand crop genotypes in the international germ plasm banks, more is known about agronomic characters than about functional properties relevant to food processing. Transgenic modifications broaden the spectrum of pest resistance in crops, but too little is known of the nutritional implications. Biotechnological advances, demands for non-polluting waste disposal, consumer concerns for food safety, the need to provide food security for a global population changing in age and income distribution, offer exciting challenges to all food scientists and technologists.     

Using land to mitigate climate change: hitting the target, recognizing the trade-offs

Land can be used in several ways to mitigate climate change, but especially under changing environmental conditions there may be implications for food prices. Using an integrated global system model, we explore the roles that these land-use options can play in a global mitigation strategy to stabilize Earth's average temperature within 2 °C of the preindustrial level and their impacts on agriculture. We show that an ambitious global Energy-Only climate policy that includes biofuels would likely not achieve the 2 °C target. A thought-experiment where the world ideally prices land carbon fluxes combined with biofuels (Energy+Land policy) gets the world much closer. Land could become a large net carbon sink of about 178 Pg C over the 21st century with price incentives in the Energy+Land scenario. With land carbon pricing but without biofuels (a No-Biofuel scenario) the carbon sink is nearly identical to the case with biofuels, but emissions from energy are somewhat higher, thereby results in more warming. Absent such incentives, land is either a much smaller net carbon sink (+37 Pg C - Energy-Only policy) or a net source (-21 Pg C - No-Policy). The significant trade-off with this integrated land-use approach is that prices for agricultural products rise substantially because of mitigation costs borne by the sector and higher land prices. Share of income spent on food for wealthier regions continues to fall, but for the poorest regions, higher food prices lead to a rising share of income spent on food.     

Soils for Sustaining Global Food Production

ABSTRACT: Soil is commonly described as the mantle or the skin covering the landmass of planet Earth. Soils perform 6 main functions (biomass production, water quality maintenance, biological habitat, physical infrastructure support, raw materials for human use, and maintaining cultural heritage) and a soil is evaluated by its ability to perform one or more of these functions. The ability of the land to feed and clothe people and to maintain ecological functions is being impeded by demographics. The global land area that is generally free of constraints for most agricultural uses is about 12.6%. Agricultural land, however, is unequally spread around the globe with a larger portion in the temperate countries of the world. In addition to poorer land quality in tropical regions, land degradation is also well entrenched, thus aggravating food security. There are 11.9 million km² of such lands and about 1.4 billion people are involved and most of these areas are in the developing countries. Countries of the developing parts of the world have to make a conscious decision to better manage their land resources. The paradigm shift that poorer countries need to make to sustain food production is to implement holistic and sustainable land management programs by adopting technologies that have already been validated in other parts of the world.     

The energetics of British agriculture

An analysis is presented firstly of the biological energetics of UK agriculture in which the ultimate yield of edible food is related to primary plant production and solar radiation incidence. Secondly, the industrial energetics of British agriculture are dealt with in which agriculture is regarded as an industry in which the input is of materials which have required, for their production, energy as fossil fuel and the output is again edible food. The results show that primary plant output is 0.18% of solar radiation receipt and of this 12% is recovered as human food. This meets 57% of the requirements of the population for dietary energy and the labour of one man supports the dietary requirement of 48 people. UK agriculture accounts for 3.9% of the total UK primary fuel consumption and the farm gate output relative to total fossil fuel input is 0.6 : 1 while the edible food output is 0.3 : 1. The results of the analysis are discussed taking both a short term and long term view.     

乳清蛋白的市场与应用

<正> 一、美国乳业及乳清粉行业近况 1.美国乳业近况在过去的二十年中,美国奶牛的存栏量总体呈下降趋势,但牛奶产量却稳步攀升,在2008年达到了860亿升。牛奶单产的不断提升得益于基因技术的不断进步、动物营养的不断改善以及养殖操作技术的不断改进。今年,美国奶牛的存栏量及牛奶的产量与2008年相比有所下降,这主要是由国内外市场的需求减少所造成的。在经济危机的影响下,美国奶牛养殖的损失较为严重,奶农纷纷减少了奶牛养殖数量。未来,美国经济的复苏直接     

Acute View Transport biofuels: Can they help limiting climate change without an upward impact on food prices?

Comprehensive life cycle assessments show that current transport biofuels often do worse than conventional fossil transport fuels as to the emission of greenhouse gases. Biofuels from microalgae grown with present technology and lignocellulosic biofuels from current arable land or land that is to be deforested are unlikely to do better regarding the emission of greenhouse gases than fossil transport fuels. When crops characterized by relatively low fossil fuel inputs and relatively high biomass yields are grown on abandoned agricultural and marginal soils which currently sequester little carbon, cropping for transport biofuels may help in limiting climate change without an impact on food prices. For such cropping one probably has to go beyond the market mechanism. Worldwide, there is some scope for the use of harvest residues in biofuel production. However, European arable soils show on average large losses of soil carbon and this rather favors increased addition of such residues to soils. Received: November 17, 2008; accepted: December 3, 2008     

我国能源植物概况与能源型甘蔗斑茅后代前景展望

随着工业化的迅猛发展,能源危机已经成为全球所面临的急需解决的难题。生物质能源是目前开发潜力最大的可再生能源,已成为世界许多国家未来经济发展的主要动力之一。目前,虽然以粮食为原料的第1代生物质能源已在许多国家产业化生产,但基于粮食安全因素考虑,在中国无法实施。而开发以木质纤维素为原料的第2代生物质能源是当前研究热点。能源型甘蔗斑茅后代是甘蔗和斑茅的杂交后代,不但富含糖分的蔗汁可用于直接生产乙醇,同时具有生物量大,生物适应性强的特点,是一种潜力巨大的能源作物。近年来,随着甘蔗和斑茅杂交技术的瓶颈突破、分子育种鉴定和染色体核型分析技术的成熟,选育能源型斑茅蔗作为新型能源植物,可能成为未来生物质能发展的一个重要突破。     

Can we improve global food security? A socio-economic and political perspective

Ensuring global food security for a growing population remains a major challenge. This is especially true against the background of increasing food prices paired with growing income levels and changing demand patterns in the developing world. At the same time, climate change and the occurrence of more frequent and extreme natural disasters increase the vulnerability of rural farm households, negatively affecting agricultural production. Given the many dimensions of food security, no simple solution can be found. Promoting productivity of farming and increasing the efficiency of the food marketing system are effective measures contributing to rural development in developing countries. Policy reforms in agriculture and beyond help to reduce distortions and change consumers’ awareness with respect to food waste and resource use inefficiencies related to human diets. What is new in this context is the increasing link of agriculture with other sectors such as the energy and the financial markets. This calls for further research as additional pressure is being put on the global food system.     

Grain reserves and food security in the Middle East and North Africa

Aggregate stocks of major grains declined to minimal feasible levels in 2007–2008, due to high global income growth and biofuel mandates. Given these minimal stocks, prices were very sensitive to shocks, such as the Australian drought, and biofuel demand boosts due to the oil price spike. The effects of these shocks were magnified by a sequence of trade restrictions by key exporters to protect vulnerable consumers. Beginning in the ‘thin’ global rice market in the fall of 2007, these turned market anxiety into panic. Recognizing the unreliability of imports, vulnerable countries, including some in the Middle East and North Africa (MENA), are now considering investing in strategic reserves, pursuing self sufficiency and acquiring foreign land to ensure grain supplies for domestic consumption. The associated expense and negative incentive effects on national reserves may be acceptable if they have quantitative targets related to the needs of the most vulnerable, for distribution only in emergencies. In many MENA countries, heavy subsidies on grain consumption for both rich and poor reduce the stabilizing response of consumption to price, and increase reserves needed to ensure food security. Accumulation of stocks is a more efficient strategy than pursuit of self-sufficiency in most MENA countries, as they have no comparative advantage in expanding agriculture, given restricted water supplies. Acquisition of foreign lands leaves food supplies exposed to sovereign risk and other supply chain problems beyond importers’ control. MENA countries could cooperate and so smooth much of the risk posed by fluctuations in their own harvests.     

碳捕集、封存与利用技术研究进展

二氧化碳(CO2)是一种温室气体,被认为是导致全球温度升高(也称为全球变暖)的主要因素.到2040年,全球能源需求预计将比2019年增长30％,而化石燃料仍将是满足这些需求的主要能源(预计占比74％),其直接燃烧所排放的CO2量也将持续增长.目前全球CO2总利用量低于2亿吨/年,与每年320亿吨以上的CO2排放量相比,...     

Management of tropospheric ozone by reducing methane emissions

Background concentrations of tropospheric ozone are increasing and are sensitive to methane emissions, yet methane mitigation is currently considered only for climate change. Methane control is shown here to be viable for ozone management. Identified global abatement measures can reduce approximately 10% of anthropogenic methane emissions at a cost-savings, decreasing surface ozone by 0.4-0.7 ppb. Methane controls produce ozone reductions that are widespread globally and are realized gradually (approximately 12 yr). In contrast, controls on nitrogen oxides (NOx) and nonmethane volatile organic compounds (NMVOCs) target high-ozone episodes in polluted regions and affect ozone rapidly but have a smaller climate benefit. A coarse estimate of the monetized global benefits of ozone reductions for agriculture, forestry, and human health (neglecting ozone mortality) justifies reducing approximately 17% of global anthropogenic methane emissions. If implemented, these controls would decrease ozone by -1 ppb and radiative forcing by approximately 0.12 W m(-2). We also find that climate-motivated methane reductions have air quality-related ancillary benefits comparable to those for CO2. Air quality planning should consider reducing methane emissions alongside NOx and NMVOCs, and because the benefits of methane controls are shared internationally, industrialized nations should consider emphasizing methane in the further development of climate change or ozone policies.