Life cycle assessment of renewable diesel production from lignocellulosic biomass

Purpose

Governments around the world encourage the use of biofuels through fuel standard policies that require the addition of renewable diesel in diesel fuel from fossil fuels. Environmental impact studies of the conversion of biomass to renewable diesel have been conducted, and life cycle assessments (LCA) of the conversion of lignocellulosic biomass to hydrogenation-derived renewable diesel (HDRD) are limited, especially for countries with cold climates like Canada.

Methods

In this study, an LCA was conducted on converting lignocellulosic biomass to HDRD by estimating the well-to-wheel greenhouse gas (GHG) emissions and fossil fuel energy input of the production of biomass and its conversion to HDRD. The approach to conduct this LCA includes defining the goal and scope, compiling a life cycle inventory, conducting a life cycle impact assessment, and executing a life cycle interpretation. All GHG emissions and fossil fuel energy inputs were based on a fast pyrolysis plant capacity of 2000 dry tonnes biomass/day. A functional unit of 1 MJ of HDRD produced was adopted as a common unit for data inputs of the life cycle inventory. To interpret the results, a sensitivity analysis was performed to measure the impact of variables involved, and an uncertainty analysis was performed to assess the confidence of the results.

Results and discussion

The GHG emissions of three feedstocks studied—whole tree (i.e., chips from cutting the whole tree), forest residues (i.e., chips from branches and tops generated from logging operations), and agricultural residues (i.e., straw from wheat and barley)—range from 35.4 to 42.3 g CO_2,eq/MJ of HDRD (i.e., lowest for agricultural residue- and highest for forest residue-based HDRD); this is 53.4–61.1 % lower than fossil-based diesel. The net energy ratios range from 1.55 to 1.90 MJ/MJ (i.e., lowest for forest residue- and highest for agricultural residue-based HDRD) for HDRD production. The difference in results among feedstocks is due to differing energy requirements to harvest and pretreat biomass. The energy-intensive hydroprocessing stage is responsible for most of the GHG emissions produced for the entire conversion pathway.

Conclusions

Comparing feedstocks showed the significance of the efficiency in the equipment used and the physical properties of biomass in the production of HDRD. The overall results show the importance of efficiency at the hydroprocessing stage. These findings indicate significant GHG mitigation benefits for the oil refining industry using available lignocellulosic biomass to produce HDRD for transportation fuel.

     

Potential agronomic options for energy-efficient sugar beet-based bioethanol production in northern Japan

Sugar beet (Beta vulgaris L. subsp. vulgaris) is deemed to be one of the most promising bioethanol feedstock crops in northern Japan. To establish viable sugar beet‐based bioethanol production systems, energy‐efficient protocols in sugar beet cultivation are being intensively sought. On this basis, the effects of alternative agronomic practices for sugar beet production on total energy inputs (from fuels and agricultural materials during cultivation and transportation) and ethanol yields (estimated from sugar yields) were assessed in terms of (i) direct drilling, (ii) reduced tillage (no moldboard plowing), (iii) no‐fungicide application, (iv) using a high‐yielding beet genotype, (v) delayed harvesting and (vi) root+crown harvesting. Compared with the conventional sugar beet production system used in the Tokachi region of Hokkaido, northern Japan, which makes use of transplants, direct drilling and no‐fungicide application contributed to reduced energy inputs from raising seedlings and fungicides, respectively, but sugar (or ethanol) yields were also reduced by these practices, to a greater equivalent extent than the reductions in energy inputs. Consequently, direct drilling (6.84 MJ L^?1) and no‐fungicide application (7.78 MJ L^?1) worsened the energy efficiency (total energy inputs to produce 1 L of ethanol), compared with conventional sugar beet production practices (5.82 MJ L^?1). Sugar yields under conventional plow‐based tillage and reduced tillage practices were similar, but total energy inputs were reduced as a result of reduced fuel consumption from not plowing. Hence, reduced tillage showed improved energy efficiency (5.36 MJ L^?1). The energy efficiency was also improved by using a high‐yielding genotype (5.23 MJ L^?1) and root+crown harvesting (5.21 MJ L^?1). For these practices, no major changes in total energy inputs were noted, but sugar yields were consistently increased. Neither total energy inputs nor ethanol yields were affected by extending the vegetative growing period by delaying harvesting.     

Variation of energy flow and greenhouse gas emissions in vineyards located in Natura 2000 sites

A combination of agro-environmental indicators and energy analysis of a production system, such as vineyards located in Natura 2000 sites, for which little is known, may be a useful tool to decide best farm management practices with low greenhouse gas emissions. In randomly selected vineyards at six sites of Natura 2000 network in Cyprus, we evaluated the energy flow and the greenhouse gas emissions. Hierarchical cluster analysis using production coefficients and a topographic variable (altitude) was used to detect clusters of the studied vineyards. Three groups were revealed. Group 1 (eight vineyards) with the lowest energy inputs, followed by Group 2 (three vineyards) with intermediate inputs and Group 3 (three vineyards) with the highest energy inputs. Altitude, fertilizers, labour, fuel and transportation had the greatest contribution on cluster formation. Non-parametric comparisons concerning 28 indicators showed that ten indicators (total energy inputs, renewable and non-renewable energy inputs, fruit energy outputs, shoot energy outputs, total energy outputs, fruit production, CO₂, CH₄, and N₂O) were significantly higher in high energy input vineyards (Group 3) and three (energy use for renewable inputs, energy productivity and energy fruit efficiency) in low energy input vineyards (Group 1). Five indicators (energy use for fuel, transportation and non-renewable inputs, and energy efficiency for (shoot + fruit) outputs and renewable energy inputs) were significantly lower in Group 3 and two (intensity and non-renewable energy consumption) in Group 1. Similarities and/or dissimilarities among vineyards in Natura 2000 sites were related to altitude, production coefficients and local farming practices. These mixed results stress the importance of taking both local management indicators and vineyard topography into consideration when developing future agri-environment schemes, and suggest that local–regional interactions may affect Natura 2000 sites services and functions. It is important that EU agricultural policies are complemented by national–regional interventions in order to regulate the fragile balance between Natura 2000 sites and agriculture, reducing non-renewable energy inputs as percent of total energy inputs.     

黄土高原沟壑区粮食生产中的生态成本

以黄土高原沟壑区的陕西省长武县为研究对象,应用生态学和经济学方法,对粮食生产生态成本进行了初步研究.结果表明： 2008年该区粮食生产生态损失总价值相当于当年种植业总产值的7.2%;小麦和玉米生态成本已分别达到2.42和2.12元·kg^-1,而出售单价分别为1.70和1.28元·kg^-1,高成本低收益的情况对该区域生态经济可持续发展产生不利影响;利用灰色关联对粮食生产生态成本中各因素进行分析,单位产量、播种面积和农业机械费用是影响生态成本的重要因素,化肥费用和有机肥费用对其影响不大;在当前生产力水平下,适当加大科学技术投入水平,提高粮食产量,扩大家庭种植规模,可以降低生产单位粮食的生态成本.     

农田合理投能区域与最优投能配比的研究

研究表明,农田代辅助能投入有一个合理的投区域,在该区域内增加水肥投能可增加产出能和产投比,总产出能的合理投能区域大于产投比的合理投能区域;低产农田的合理投区域大小高产农田,通过人工辅助能的增加,可能低产农田与高产农田一样达到作物的最高产量水。在合理投能区域内存在水分投 效线和肥料投入高效线,在两条线上相应的水分和肥料投入效益最高;也存在最优投能配比线和最优经济投入配比线,在两条线上的水肥投入,其能     

中国小麦燃料乙醇的能量收益

分析了燃料乙醇能量收益问题提出的背景,国外有关燃料乙醇能量收益研究的最新进展及国内研究现状,采用全生命周期分析方法,计算了小麦燃料乙醇净能量值和能量产投比,对中国小麦燃料乙醇的能量收益进行了评价。主要结论有:如不考虑副产品能量价值,旧工艺和新工艺的NEV分别为-17022MJ/t燃料乙醇和-11778MJ/t燃料乙醇,R值分别是0.64和0.72;如考虑副产品能量价值,旧工艺和新工艺的NEV值分别为2271MJ/t燃料乙醇和11249MJ/t燃料乙醇,R值分别是1.05和1.27,从能源经济性角度看,旧工艺和新工艺的能量收益已是正效益,且新工艺的能量收益显著提高;与美国玉米燃料乙醇生产相比,如考虑副产品能量价值,新工艺和美国玉米燃料乙醇的NEV分别为11249MJ/t燃料乙醇和7457MJ/t燃料乙醇,R值分别是1.27和1.34。由于小麦转化率要低于玉米,因而小麦燃料乙醇的R值会低于玉米燃料乙醇。中国小麦燃料乙醇生产(新工艺)NEV大于美国玉米燃料乙醇的原因在于:中国小麦燃料乙醇副产品综合利用水平(23027MJ/t燃料乙醇)已明显优于美国玉米燃料乙醇(5078MJ/t燃料乙醇)。     

An emergy evaluation of the sustainability of Chinese crop production system during 2000–2010

Crop production systems are the basis of human survival and development because they can produce grain and industrial raw materials. As one of the largest agricultural countries in the world, the sustainability of China's crop production system is being concerned widely with its economic development and increasing population. This study adopted emergy analysis to explore the comprehensive performance of this system. A set of emergy based indicator system was used to investigate its economic benefit, environmental pressure and sustainability from 2000 to 2010. The study results show that the purchased nonrenewable input makes the largest contribution to the total input (average value 60.73% of the total input), which mainly derived from agricultural mechanic equipments and chemical fertilizer; on the average, beans has the largest share (20.20%) to the total emergy output, next from rape seed (18.36%), then from peanuts (15.85%), fruits (15.74%), wheat (8.26%), rice (8.07%), corn (7.66%) and cotton (4.60%) accordingly, and the other four categories crops just have a contribution of 1.28%; the production efficiency of China's crop production system has been raised by 11.54% with decrease of the indicator unit emergy value of product (UEVP) from 1.82E09 sej/g to 1.61E09 sej/g, the dependence of this system on economic market has increased by 24.92% with growth of the indicator EIR from 6.22 to 7.77, its economic benefit has been reduced by 0.59% with decline of the indicator EYR from 1.69 to 1.68, and its environmental loading has raised by 57.89% with growth of the indicator ELR from 1.33 to 2.10; the sustainability of China's crop production system is reduced by 37.01% with decrease of the index ESI from 1.27 to 0.80, during this study period. Based on these study results, the following measures should be emphasized in future, including raising the efficiency of purchased non-renewable resources (especially agricultural mechanical equipments and chemical fertilizer), using other methods of cultivation inherently more sustainable (e.g. replacing chemical fertilizer with organic fertilizer, recycling organic wastes, biological control of agricultural pests, use of local renewable energy, and more), strengthening supervision of the related industrial processes and further promoting agricultural environmental protection.     

氮肥运筹对晚播冬小麦氮素和干物质积累与转运的影响

氮素平衡对干物质积累与分配的影响是农业生态系统研究的重要内容,在保障产量前提下减少氮肥施用量可减少环境污染与温室气体排放。以晚播冬小麦为研究对象,设置4个施氮量水平:0 kg/hm2(N0)、168.75 kg/hm2(N1)、225 kg/hm2(N2)、281.25 kg/hm2(N3),每个施氮量水平下设置2个追氮时期处理:拔节期(S1)、拔节期+开花期(S2),研究了氮肥运筹对晚播冬小麦氮素和干物质积累与转运及氮肥利用率的影响。结果表明:拔节期追施氮肥(S1)条件下,在225 kg/hm2(N2)基础上增施25%氮肥(N3)对开花期氮素积累总量和营养器官氮素转运量无显著影响;拔节期+开花期追施氮肥(S2)条件下,随施氮量增加,开花期氮素积累总量和花后营养器官氮素转运量升高;S2较S1显著提高成熟期籽粒及营养器官氮素积累量、花后籽粒氮素积累量及其对籽粒氮素积累的贡献率。同一施氮量条件下,S2较S1提高了成熟期的干物质积累量、开花至成熟阶段干物质积累强度和花后籽粒干物质积累量。同一追氮时期条件下,籽粒产量N2与N3无显著差异,氮肥偏生产力随施氮量增加而降低;同一施氮量条件下,S2较S1提高了晚播冬小麦的籽粒产量和氮肥吸收利用率。拔节期+开花期追施氮肥,总施氮量225kg/hm2为有利于实现晚播冬小麦高产和高效的最优氮肥运筹模式。     

Emergy synthesis of a combined food and energy production system compared to a conventional wheat (Triticum aestivum) production system

It is a major challenge to produce food and energy sustainably for the ever increasing world population as today's conventional food production and energy needs are met by the fossil based resources, causing enormous environmental load. A novel, combined food and energy (CFE) agro-ecosystem, was designed for sustainable production of food, fodder and energy without chemical inputs (fertiliser, herbicide and fungicide). The objective was an emergy synthesis of the CFE system compared to a conventional wheat (Triticum aestivum) production system to assess resource use efficiency. The emergy indices, used to assess the environmental performance and sustainability, exhibited contrasting differences between the two production systems in terms of outputs (Y), total emergy use, solar transformity, relative use of local renewable resources, environmental loading ratio (ELR), emergy yield ratio (EYR) and emergy sustainability index (ESI). The Y in the CFE consisted of grain, straw, fodder and woodchip production of 4020, 3580, 6100 and 10,000 kg/ha/yr respectively whereas Y in the conventional wheat consisted of 7250 and 3770 kg grain and straw/ha/yr respectively. The Y in the CFE was 81% (2.80E+11 J/ha/yr) higher with 13.5 times (6.40E+03 seJ/J) lower solar transformity compared to the Y (1.54E+11 J/ha/yr) and solar transformity (8.63E+04 seJ/J) in the conventional wheat, exhibiting highly resource intensive production in conventional wheat. The local renewables constituted 19.2% and 2.6% of the total emergy input in the CFE and the conventional wheat respectively with a corresponding lower ELR (4.21) and 22.5% higher EYR (1.26) in CFE compared to conventional wheat. CFE was more reliant on local renewable emergy flows and compatible with the local environment with higher ESI (0.30) compared to conventional wheat (0.03), where 64.5% of the total emergy input constituted chemical inputs. The study demonstrated that the innovative agro-ecosystem, exemplified by CFE, is considerably less resource demanding and more amenable to sustainable production, whether defined in terms of outputs, solar transformity, relative use of local renewable resources, EYR, ELR or ESI.     

Regional variations in life cycle greenhouse gas emissions of canola‐derived jet fuel produced in western Canada

This study investigates the life cycle GHG emissions of jet fuel produced via the hydroprocessed esters and fatty acids (HEFA) pathway from canola grown in western Canada, with a focus on characterizing regional influences on emissions. We examine the effects of geographic variations in soil type, agricultural inputs, farming practices, and direct land use changes on life cycle GHG emissions. We utilize GREET 2016 but replace default feedstock production inputs with geographically representative data for canola production across eight western Canadian regions (representing 99% of Canada's canola production) and replace the default conversion process with data from a novel process model previously developed in ASPEN in our research group wherein oil extraction is integrated with the HEFA‐based fuel production process. Although canola production inputs and yields vary across the regions, resulting life cycle GHG emissions are similar if effects of land use and land management changes (LMC) are not included; 44–48 g CO₂e/MJ for the eight regions (45%–50% reduction compared to petroleum jet fuel). Results are considerably more variable, 16–58 g CO₂e/MJ, when including effects of land use and LMC directly related to conversion of lands from other uses to canola production (34%–82% reduction compared to petroleum jet fuel). We establish the main sources of emissions in the life cycle of canola jet fuel (N‐fertilizer and related emissions, fuel production), identify that substantially higher emissions may occur when using feedstock sourced from regions where conversion of forested land to cropland had occurred, and identify benefits of less intense tillage practices and increased use of summerfallow land. The methods and findings are relevant in jurisdictions internationally that are incorporating GHG emissions reductions from aviation fuels in a low carbon fuel market or legislating carbon intensity reduction requirements.     

Agronomic improvements can make future cereal systems in South Asia far more productive and result in a lower environmental footprint

South Asian countries will have to double their food production by 2050 while using resources more efficiently and minimizing environmental problems. Transformative management approaches and technology solutions will be required in the major grain‐producing areas that provide the basis for future food and nutrition security. This study was conducted in four locations representing major food production systems of densely populated regions of South Asia. Novel production‐scale research platforms were established to assess and optimize three futuristic cropping systems and management scenarios (S2, S3, S4) in comparison with current management (S1). With best agronomic management practices (BMPs), including conservation agriculture (CA) and cropping system diversification, the productivity of rice‐ and wheat‐based cropping systems of South Asia increased substantially, whereas the global warming potential intensity (GWPi) decreased. Positive economic returns and less use of water, labor, nitrogen, and fossil fuel energy per unit food produced were achieved. In comparison with S1, S4, in which BMPs, CA and crop diversification were implemented in the most integrated manner, achieved 54% higher grain energy yield with a 104% increase in economic returns, 35% lower total water input, and a 43% lower GWPi. Conservation agriculture practices were most suitable for intensifying as well as diversifying wheat–rice rotations, but less so for rice–rice systems. This finding also highlights the need for characterizing areas suitable for CA and subsequent technology targeting. A comprehensive baseline dataset generated in this study will allow the prediction of extending benefits to a larger scale.     

Life cycle assessment of biofuels from Jatropha curcas in West Africa: a field study

In recent years, liquid biofuels for transport have benefited from significant political support due to their potential role in curbing climate change and reducing our dependence on fossil fuels. They may also participate to rural development by providing new markets for agricultural production. However, the growth of energy crops has raised concerns due to their high consumption of conventional fuels, fertilizers and pesticides, their impacts on ecosystems and their competition for arable land with food crops. Low-input species such as Jatropha curcas , a perennial, inedible crop well adapted to semiarid regions, has received much interest as a new alternative for biofuel production, minimizing adverse effects on the environment and food supply. Here, we used life-cycle assessment to quantify the benefits of J. curcas biofuel production in West Africa in terms of greenhouse gas emissions and fossil energy use, compared with fossil diesel fuel and other biofuels. Biodiesel from J. curcas has a much higher performance than current biofuels, relative to oil-derived diesel fuels. Under West Africa conditions, J. curcas biodiesel allows a 72% saving in greenhouse gas emissions compared with conventional diesel fuel, and its energy yield (the ratio of biodiesel energy output to fossil energy input) is 4.7. J. curcas production studied is eco-compatible for the impacts under consideration and fits into the context of sustainable development.     

Spatial and Temporal Variations of Crop Fertilization and Soil Fertility in the Loess Plateau in China from the 1970s to the 2000s

Increased fertilizer input in agricultural systems during the last few decades has resulted in large yield increases, but also in environmental problems. We used data from published papers and a soil testing and fertilization project in Shaanxi province during the years 2005 to 2009 to analyze chemical fertilizer inputs and yields of wheat (Triticum aestivum L.) and maize (Zea mays L.) on the farmers'' level, and soil fertility change from the 1970s to the 2000s in the Loess Plateau in China. The results showed that in different regions of the province, chemical fertilizer NPK inputs and yields of wheat and maize increased. With regard to soil nutrient balance, N and P gradually changed from deficit to surplus levels, while K deficiency became more severe. In addition, soil organic matter, total nitrogen, alkali-hydrolysis nitrogen, available phosphorus and available potassium increased during the same period. The PFP of N, NP and NPK on wheat and maize all decreased from the 1970s to the 2000s as a whole. With the increase in N fertilizer inputs, both soil total nitrogen and alkali-hydrolysis nitrogen increased; P fertilizer increased soil available phosphorus and K fertilizer increased soil available potassium. At the same time, soil organic matter, total nitrogen, alkali-hydrolysis nitrogen, available phosphorus and available potassium all had positive impacts on crop yields. In order to promote food safety and environmental protection, fertilizer requirements should be assessed at the farmers'' level. In many cases, farmers should be encouraged to reduce nitrogen and phosphate fertilizer inputs significantly, but increase potassium fertilizer and organic manure on cereal crops as a whole.     

Seventeenth century organic agriculture in China: II. Energy flows through an agroecosystem in Jiaxing region

The energy flows in a seventeenth century agroecosystem in Jiaxing region of eastern China were analyzed on the basis of historical data. The agroecosystem included cropping, mulberry-silkworm, livestock, and fishing systems. In terms of energy, the agroecosystem was sustainable. Human labor provided all the power with inputs of about 3700 hr per hectare of farmland. Most or 70% of the labor was expended in the cropping system. Human and animal manure provided most of the nutrients for crop and mulberry production. About two-thirds of the total manure was used in crop production and one-third in the mulberry plantations. The only fossil energy input was a few hand tools. Approximately 55% of the grain was consumed directly by local residents, about one-third of the grain was used to make an alcohol drink and produce distillers'grains, which was fed to pigs, and only 2% of the grains were exported outside the agroecosystem. About two-thirds of the harvested crop residues were used as household fuel, while the remainder was returned to the field as an organic fertilizer. Pork accounted for 85% and silk cocoons 14% of the total animal products produced. Even though the agroecosystem was generally sustainable in terms of energy, the major environmental problem was that two-thirds of the harvested crop residues were used for household fuel. This reduced nutrient cycling in the system. Insufficient land was available to produce fuelwood;thus, crop residues were the primary source of fuel for the people.     

不同产量水平旱地冬小麦品种干物质累积和转移的差异分析

旱地小麦高产栽培中品种起着重要作用,研究不同产量水平旱地冬小麦品种干物质累积和转移的差异,对黄土高原旱区作物高产稳产有重要意义。以9个旱地冬小麦品种为材料,通过田间试验研究了不同产量水平旱地冬小麦品种的生物量、花前花后干物质累积量、干物质转移量、转移率及转移干物质对籽粒的贡献率、叶面积、SPAD值以及光合速率的差异。结果表明,不同小麦品种的生物量、花前花后干物质累积量、干物质转移量、转移率及转移干物质对籽粒的贡献率均存在明显差异。与不施肥相比,高、中、低3个产量水平小麦品种在低养分投入时,成熟期生物量分别提高29%,22%和6%,高水平时分别提高46%,39%和23%,高产品种的生物量及其对养分投入的敏感程度明显高于低产品种。不同品种的花后干物质累积量随养分投入水平提高而增加,但花前营养器官中储存物质的转移量、转移率和对籽粒的贡献率却明显随之下降。功能叶(旗叶)在灌浆期高、中、低3个产量水平品种的SPAD值在低养分投入条件下分别为20.7、17.5和13.7;高养分投入时,分别为35、26.1和16.8。高产品种西农88的光合速率为6.0μmolCO.2m-.2s-1),中产和低产品种的平均光合速率分别为4.3μmolCO.2m-.2s-1和4.0μmolCO.2m-.2s-1,高产品种功能叶(旗叶)在灌浆期能保持较高的SPAD值和光合速率,因而花后能生产较多的干物质,但其花前干物质转移量、转移率及转移干物质对籽粒的贡献率均没有明显优势。可见,花后较高的叶绿素水平、光合速率和干物质累积是旱地小麦品种高产的重要原因。选择优良品种,采取合理的栽培措施,特别是通过养分调控保持花后具较高的干物质累积量是西北旱地进一步提高冬小麦产量的重要途径。     

红壤丘陵区粮食生产的生态成本

人类的生产活动必然对资源与环境造成影响,以红壤丘陵区的湖南省祁阳县为研究对象,应用经济学和生态学方法,对粮食生产中的生态成本进行了研究。结果表明:2008年该区粮食生产生态损失总价值相当于当年农业总产值的4.85%;早、中、晚稻生态成本已分别达到3.18、2.44、3.02元/kg,而出售单价分别为1.76、1.90、1.84元/kg,高成本低收益的情况对该区域的可持续发展产生着不利影响;在当前生产力水平条件下,适度提高化肥、农药、农业机械、农膜、劳动力的投入,提高水稻产量,扩大家庭种植规模,可降低生产单位水稻的生态成本。     

中国四川旱坡地植物篱农作系统能流特征

关于农业生态系统能流特征的研究很多,但关于植物篱农作系统能流特征的研究很少。在四川盆地雨养丘陵农区,2/3的耕地土壤侵蚀严重,为了控制土壤侵蚀和提高耕地生产力,该区域大量栽种了植物篱。该研究通过了解作物与植物篱之间的能流交付作用,通过系统能量投入水平提高与结构优化,建立环境友好的农作系统,最终实现坡地农业的可持续。通过两年田间小区试验,详细记录所有劳力投入、化肥投入、农药投入、农事管理活动以及落叶的数量并折算为标准能量单位。作物收获后所有生物产量的能量根据其各部分的转换值折算为标准能量。系统能流特征及效率通过统计分析完成。通过研究主要获得了以下3个结论:1)“作物-植物篱”系统产出能和输入能的数量和结构变化主要受植物篱子系统类型的影响。与大面积旱坡地传统农作物生产系统比较,植物篱农作系统能有效提高系统光能利用率、人工输入能效率,耕地单位面积总产出能也会增加,坡度越大,相对增幅亦越大;由于能极显著减少无机能施入量,这有利于降低化肥农药使用量,减少对环境的污染和破坏。2)“作物-果树类植物篱”系统输入能总量和有机能输入量大幅度增加,因此有利于优化输入能结构,促进坡地生态系统良性循环和集约高效农业发展。3)“作物-草本植物篱”系统人工辅助能的输入量大幅度下降,由于它所需投入能少,有机能耗和无机能耗均低,人工输入能效率很高而生物产量也较高,并且它们提高了与其间作的其它作物的能量产投比,因此提升了整个系统能量产投比率;由于保水固土的生态功能显著,使它能在四川广大山地、丘陵区退耕还林还草工程中发挥重要作用。     

Emergy and end-point impact assessment of agricultural and food production in the United States: A supply chain-linked Ecologically-based Life Cycle Assessment

The concept of tracing the ecologically-based life cycle impacts of agricultural and food industries (AFIs) has become a topic of interest worldwide due to their critical association with the climate change, water and land footprint, and food security. In this study, an in-depth analysis of ecological resource consumption, atmospheric emissions, land and water footprints of 54 agricultural and food industries in the U.S. were examined extensively. Initially, the supply-chain linked ecological life cycle assessment was performed with Ecologically-based Life Cycle Assessment (Eco-LCA) tool. Then, the results of life cycle inventory were used to assess the mid and end-point impacts by using the ReCiPe approach. Thirdly, ecological performance assessment was performed using well-known metrics, including loading and renewability ratios and eco-efficiency analysis. As a novel comprehensive approach, the integrated framework that consists of the Eco-LCA, ReCiPe and linear programming-based ecological performance assessment is of importance to have an overall understanding about the extent of impacts related to agricultural and food production activities across the U.S. Results indicated that grain farming, dairy food, and animal production-related sectors were found to have the greatest shares in both environmental and ecological impact categories as well as endpoint impacts on human health, ecosystem and resources. In terms of climate change, animal (except poultry) slaughtering, rendering, and processing (ASRP), cattle ranching and farming (CRF), fertilizer manufacturing (FM), grain farming (GF), fluid milk and butter manufacturing (FMBM) were found to be the top five dominant industries in climate change impacts accounting for about 60% share of the total impact.     

广西中粮20万吨/年木薯燃料乙醇净能量分析

广西中粮20万吨/年木薯燃料乙醇装置建成后经历多次工艺改造,为了评估广西装置的能量投入/产出,利用国内已有的全生命周期模型进行了净能量分析。计算结果表明,广西装置的净能量为9.56 MJ/L乙醇。其中乙醇转化环节的能量投入占总能量投入的51.3%,而其中精馏工序仅蒸汽消耗即占乙醇转化总能耗的61.5%。副产品提供的能量可补偿5.03 MJ/L乙醇。因此,原料的综合利用是广西装置提高能源利用效率的重要措施,精馏工序的节能改造对净能量具有重要影响。最后展望了木薯燃料乙醇的发展前景。