北京市居民食物消费碳足迹

碳足迹作为一种评价碳排放影响的全新测度方法,已被用来衡量人类活动对大气环境和气候变化的影响。食物是人类的首要消费品,其消费的碳足迹反应维持一个区域人口的基本食物需求的碳排放以及对气候变化的影响。在碳足迹理论和模型的基础上,根据北京市食物的供应和消费现状情况,利用生命周期法(Life cycle analysis LCA),计算和分析了北京市居民食物消费的碳足迹。得到北京市居民食消费碳足迹为476.8×104t,约占北京市总碳足迹的6%,人均碳足迹为310.0kgCO2/人,占北京市家庭消费碳排放的23.3%,只占北京市能源消费人均碳排放量的5.96%,反映了居民食物消费对全球气候变化造成的影响有限。食物消费碳足迹最大的为粮食,其次为瓜果蔬菜豆类,总共占到65%以上,而在食物生命周期过程中,食物的再加工炊事过程碳排放最大,超过50%,合理减少食物加工炊事过程中碳排放将是减少食物消费碳排放的重要途径之一。其次为化肥农药施用,占到23.23%,减少食物生产过程中化肥农药使用,提高化肥农药的使用效率,或者进行生态农业尽量不使用化肥农药,北京市每年可减少135.1×104t CO2排放,人均87.84kgCO2/人,是有效的减排途径之一。     

基于土地利用变化的四川省碳排放与碳足迹效应及时空格局

土地利用变化的碳排放与碳足迹研究对了解人类活动对生态环境的扰动程度及其机理、制定有效的碳排放政策具有重要意义。采用1990—2010年四川省能源消费数据和土地利用数据,通过构建碳排放模型、碳足迹及其压力指数模型,对研究区20年来土地利用的碳排放及碳足迹进行了定量分析。结果表明:(1)土地利用变化的碳排放和能源消费碳的足迹呈显著增加趋势。碳排放增加5407.839×10~4t,增长率达143%;能源消费的碳足迹增加1566.622×10~4hm~2,四川全省的生态赤字达1563.598×10~4hm~2。(2)建设用地和林地分别为四川省最大的碳源与碳汇。20年间建设用地的碳排放增加5407.072×10~4t,增长率达126.27%,占碳排放总量的88%以上;林地的碳汇减少10.351×10~4t,但仍占四川省碳汇的96%以上。(3)土地利用碳排放、碳足迹和生态赤字存在明显区域差异。成都平原区碳排放、碳足迹压力最大,生态赤字严重,西部高山高原区和盆周山区碳排放、碳足迹最小,未出现生态赤字;成都、德阳、资阳和内江等地的碳排放、碳足迹压力最大,生态赤字最严重,甘孜、阿坝等地的碳排放、碳足迹最小,未出现生态赤字。(4)土地利用结构与碳排放、碳足迹存在一定的相互关系,趋高的碳源、碳汇比导致土地利用的碳源效应远大于碳汇效应。因此,四川省减排的重点应该在保持或增加现有的林地的同时,主要以降低建设用地的碳排放、碳足迹为主。     

基于生命周期评价的上海市水稻生产的碳足迹

碳足迹是指由企业、组织或个人引起的碳排放的集合。参照PAS2050规范并结合生命周期评价方法对上海市水稻生产进行了碳足迹评估。结果表明:(1)目前上海市水稻生产的碳排放为11.8114 t CO2e/hm2,折合每吨水稻生产周期的碳足迹为1.2321 t CO2e;(2)稻田温室气体排放是水稻生产最主要的碳排放源,每吨水稻生产的总排放量为0.9507 t CO2e,占水稻生产全部碳排放的77.1%,其中甲烷(CH4)又是最主要的温室气体,对稻田温室气体碳排放的贡献率高达96.6%;(3)化学肥料的施用是第二大碳排放源,每吨水稻生产的总排放量为0.2044 t CO2e,占水稻生产总碳排放的16.5%,其中N最高,排放量为0.1159 t CO2e。因此,上海低碳水稻生产的关键在降低稻田甲烷的排放,另外可通过提高氮肥利用效率,减少氮肥施用等方法减少种植过程中碳排放。     

不同规模餐馆食物浪费及其氮足迹——以北京市为例

餐饮食物浪费的普遍性和严重性已得到了社会各界的关注。通过实证研究的方法对餐饮消费中食物浪费问题进行了研究,并从食物全供应链的视角,对比分析了不同规模餐馆食物浪费的氮足迹及其环境影响。研究表明:北京市餐饮食物浪费人均浪费量为74.39g/人次,其含氮量为1.24g/人次,约占总浪费量的2%。北京市餐饮食物浪费所引起总的氮排放量为16.37 g/人次,其中有1.24g/人次的氮排放来自于食物的直接浪费,其余15.13g/人次氮排放来自于食物生产过程。北京市餐饮食物浪费的氮足迹为0.22g N/g,即每浪费1g的食物,就会有0.22 g的氮排放到环境中。对比不同规模餐馆的食物浪费情况可知,大型餐馆的人均浪费量最高,有99.38g/人次,其氮排放量也相应最大,为22.53g/人次;中型餐馆和小型餐馆的食物浪费人均量及N排放量依次减少,而快餐的最低,仅为北京市整体平均水平的1/3。     

旅游风景区旅游交通系统碳足迹评估——以南岳衡山为例

随着全国各地旅游业的蓬勃发展,旅游风景区内碳排放总量不断攀升,严重影响了旅游业的可持续发展。选择南岳衡山旅游风景区为典型案例区,运用生命周期评价理论,构建了南岳风景区旅游交通系统碳足迹计算模型。结果表明:①从总量来看,不同类型交通方式的碳足迹情况相差甚远。公路旅游交通对旅游景区的环境威胁最大,碳足迹总量是索道旅游交通的2.6倍,人行道旅游交通的46.1倍;②从阶段构成来看,公路和索道旅游交通系统运营使用阶段碳足迹占整个生命周期的大部分,所占比率分别为79%和96%.而人行道旅游交通系统中建造施工和运营后期阶段能源消耗比较大;③从来源构成来看,在使用期内公路旅游交通的碳足迹比重最大,约占碳足迹总量的71%,其次是索道旅游交通占27%,人行道旅游交通仅占2%。研究结果有利于实现旅游风景区低碳旅游发展目标,为旅游风景区节能减排提供理论支撑。     

全球电力碳足迹及其当量因子测算

电力碳足迹旨在测度发电过程中所引起的生命周期CO2排放水平.本研究从地球碳循环的角度入手,在综合大量研究数据的基础上,针对不同电力来源的碳排放特征,结合地表覆被的碳吸收能力,分类测算了全球平均电力碳足迹当量(即单位电力消费量所产生的生命周期碳足迹),并实证分析了2000-2008年全球电力碳足迹的构成及变化.结果表明:煤炭类火电(以下简称煤电)、石油类火电、天然气类火电、水电和核电的全球平均碳足迹当量分别为131.3×10-6、95.8×10-6、56.6×10-6、38.8×10-6、1.9×10-6 hm2·(kW·h)-1,火电特别是煤电的环境影响显著大于水电和核电;2000-2008年,全球电力碳足迹由730.7×106 hm2增至1101.8×106 hm2,其中火电占比由60.0％增至68.1％,煤炭取代石油成为火电碳足迹的主要构成部分,而水电和核电占比则分别降至30.7％、1.3％;全球电力结构总体趋于劣化,平均碳排放系数由265.8×10-3kg·(kW· h)-1增至315.4×10-3 kg·(kW·h)-1,火电特别是煤电在很大程度上决定着电力碳排放的强度与规模.     

基于生命周期的松通高速公路碳排放估算

基于车辆的交通量预测数据和不同类型车辆的 CO2 排放因子, 定量估算了松通高速公路生命周期中运营阶段的碳排放量, 鉴于之前的研究成果 , 进而估算了高速公路整个生命周期中的碳排放量。结果表明 , 松通高速公路每年车辆的 CO2 排放量为 19.69 万 t, 排放量在车型分配上以大型车居多 , 占总量的 50.6%; 在燃油类型分配上以柴油车居多 , 占总量的 55.5%。松通高速公路在 30 年的生命周期中将共排放 658.09 万 tCO2, 其中运营阶段车辆排放 590.7 万tCO2, 占总量的 89.8%; 筑路建材生产、公路建造、公路养护和废弃拆除 4 个阶段共排放 67.39 万 tCO2, 占总量的 10.2%。     

城市能源利用碳足迹分析——以厦门市为例

城市能源利用碳足迹分析综合考虑直接与间接碳排放,对于深度分析碳排放的本质过程、制定科学全面的碳减排计划具有重要意义。以厦门市为研究案例,应用碳足迹的混合分析方法,对厦门市2009年能源利用碳足迹进行了分析,除了包括传统研究中的城市能源终端利用产生的直接碳排放,还计算了跨界交通和城市主要消耗物质的内含能引起的间接碳排放。研究结果表明:(1)城市边界内的工业、交通、商业等部门的能源消耗产生的直接碳排放(即层次1和层次2)只占到总碳足迹的64%,而一直被忽略的跨界交通和城市主要消耗物质的内含能引起的间接碳排放(层次3)占到36%;(2)在直接碳排放中,工业部门的碳排放贡献率最大,占到直接碳排放的55%,其中化工行业带来的碳排放占到工业部门的25%;(3)在间接碳排放中,跨界交通引起的碳排放占间接碳排放的27%,其中长途道路运输贡献率最大,占跨界交通碳排放的38%;主要材料内含能碳排放占间接碳排的73%,其中燃料的内含能碳排放占总内含能的份额最大,达51%。;(4)从人均碳足迹角度比较,厦门市人均碳足迹和丹佛市的人均直接碳排(层次1+层次2)分别为5.74 t CO2e/人、18.9 t CO2e/人,包含3个层次的人均碳足迹分别为9.01 tCO2e/人、25.3 t CO2e/人,其中跨界交通引起的碳排放均占总碳足迹的10%左右,主要材料的内含能引起的碳排放分别占到总碳足迹的26%、15%;通过国内外典型城市不同层次碳足迹比较可见厦门还是相对低碳的,但有个显著的特点是主要消耗物质的内含碳排放比例较高,这在一定程度上说明了发展中国家城市消耗更多的基础材料,进一步证明了传统核算中忽略的第3层次碳排放核算与管理的重要性。     

基于生命周期方法的城市绿地生态环境负面影响评估

城市绿地在施工建设以及后续的管理养护工作中所产生的生态环境负面影响往往被人们忽视。本研究以天津市城市绿地为对象，通过实地调研收集数据，采用生命周期评价方法，分析比较了城市绿地乔木层、灌木层以及草本层在建设阶段和管养阶段各环节的生命周期环境影响。结果表明：在50年生命周期内，单位面积乔木层、灌木层和草本层的环境影响综合指数分别为5.51×10³、8.75×10³和1.60×10³。城市绿地最主要环境影响类型是淡水毒性和土壤毒性，分别占总环境影响的73.12%和26.65%。病虫害防治为城市绿地环境影响的主要贡献环节，贡献率高达99.33%。与农林业相比，城市绿地的管养环境影响指数处于中高水平。因此，城市绿地所造成的生态环境负面影响不可忽视。研究结果可以为城市建设低碳生态型绿地以及科学化管养提供参考依据。     

有机与常规培肥模式生产水稻的碳足迹

为明确不同施肥模式对水稻生产碳足迹的影响,采取田间动态监测与室内分析相结合的方式,应用生命周期碳足迹的评价方法,研究了施用化肥(CF)、猪粪(ZM)、牛粪(NM)、鸡粪(JM)对稻田系统碳排放、碳增汇、水稻生产碳足迹及单位产量碳足迹的影响。结果表明:水稻种植过程中温室气体的排放是水稻生产碳排放的主要来源,与CF处理相比,施用有机肥可增加稻田碳排放,ZM、NM和JM处理分别增加34%、30%和65%,各处理均以稻田CO_2排放贡献最大;施用有机肥处理的环境正效应高于施用化肥处理,ZM、NM和JM处理碳增汇分别是CF处理的3.3、3.8和2.9倍,可相应抵消76%、92%和55%的碳排放;施用不同有机肥对水稻生产碳足迹影响不一,但与CF处理相比均可降低单位产量的碳足迹,ZM、NM和JM处理分别降低了55%、83%和22%。综合考虑畜禽粪污处理、肥料生产与管理以及水稻种植各环节的碳排放与稻谷产量情况,有机培肥有利于降低水稻单位产量碳足迹,其中以施用牛粪处理效果最佳。     

Livestock greenhouse gas emissions and mitigation potential in Europe

The livestock sector contributes considerably to global greenhouse gas emissions (GHG). Here, for the year 2007 we examined GHG emissions in the EU27 livestock sector and estimated GHG emissions from production and consumption of livestock products; including imports, exports and wastage. We also reviewed available mitigation options and estimated their potential. The focus of this review is on the beef and dairy sector since these contribute 60% of all livestock production emissions. Particular attention is paid to the role of land use and land use change (LULUC) and carbon sequestration in grasslands. GHG emissions of all livestock products amount to between 630 and 863 Mt CO₂e, or 12–17% of total EU27 GHG emissions in 2007. The highest emissions aside from production, originate from LULUC, followed by emissions from wasted food. The total GHG mitigation potential from the livestock sector in Europe is between 101 and 377 Mt CO₂e equivalent to between 12 and 61% of total EU27 livestock sector emissions in 2007. A reduction in food waste and consumption of livestock products linked with reduced production, are the most effective mitigation options, and if encouraged, would also deliver environmental and human health benefits. Production of beef and dairy on grassland, as opposed to intensive grain fed production, can be associated with a reduction in GHG emissions depending on actual LULUC emissions. This could be promoted on rough grazing land where appropriate.     

Greenhouse Gas Emission Estimates of U.S. Dietary Choices and Food Loss

Dietary behavioral choices have a strong effect on the environmental impact associated with the food system. Here, we consider the greenhouse gas (GHG) emissions associated with production of food that is lost at the retail and consumer level, as well as the potential effects on GHG emissions of a shift to dietary recommendations. Calculations are based on the U.S. Department of Agriculture's (USDA) food availability data set and literature meta‐analysis of emission factors for various food types. Food losses contribute 1.4 kilograms (kg) carbon dioxide equivalents (CO₂‐eq) capita^?1day^?1 (28%) to the overall carbon footprint of the average U.S. diet; in total, this is equivalent to the emissions of 33 million average passenger vehicles annually. Whereas beef accounts for only 4% of the retail food supply by weight, it represents 36% of the diet‐related GHG emissions. An iso‐caloric shift from the current average U.S. diet to USDA dietary recommendations could result in a 12% increase in diet‐related GHG emissions, whereas a shift that includes a decrease in caloric intake, based on the needs of the population (assuming moderate activity), results in a small (1%) decrease in diet‐related GHG emissions. These findings emphasize the need to consider environmental costs of food production in formulating recommended food patterns.     

The impacts of Japanese food losses and food waste on global natural resources and greenhouse gas emissions

Japan depends heavily on imports for its food supply. Since 2000, the food self‐sufficiency ratio has remained approximately 40% on a caloric basis. Japanese food wastage (i.e., food losses and food waste) is estimated to have been 6.42 million tonnes (50 kg per capita of wastage) in 2012. These values indicate that food wastage leads to wasted natural resources and excessive greenhouse gas (GHG) emissions both in Japan and in countries that export to Japan. This study estimates Japanese food wastage by food item to evaluate impacts on land and water resources and global GHG emissions during the processing, distribution, and consumption phases of the food supply chain while also considering the feed crops needed for livestock production. Despite uncertainties due to data limitations, in 2012, 1.23 million hectares of harvested land were used to produce food that was eventually wasted, and 413 million m³ of water resources were wasted due to Japanese food wastage in agricultural production. Furthermore, unnecessary GHG emissions were 3.51 million tonnes of CO₂ eq. in agricultural production and 0.49 million tonnes of CO₂ eq. in international transportation. The outcomes of the present study can be used to develop countermeasures to food wastage in industrializing Asian countries where food imports are projected to increase and food wastage issues in the consumption stage are expected to become as serious as they currently are in Japan.     

Environmental and resource burdens associated with world biofuel production out to 2050: footprint components from carbon emissions and land use to waste arisings and water consumption

Environmental or ‘ecological’ footprints have been widely used in recent years as indicators of resource consumption and waste absorption presented in terms of biologically productive land area [in global hectares (gha)] required per capita with prevailing technology. In contrast, ‘carbon footprints’ are the amount of carbon (or carbon dioxide equivalent) emissions for such activities in units of mass or weight (like kilograms per functional unit), but can be translated into a component of the environmental footprint (on a gha basis). The carbon and environmental footprints associated with the world production of liquid biofuels have been computed for the period 2010–2050. Estimates of future global biofuel production were adopted from the 2011 International Energy Agency (IEA) ‘technology roadmap’ for transport biofuels. This suggests that, although first generation biofuels will dominate the market up to 2020, advanced or second generation biofuels might constitute some 75% of biofuel production by 2050. The overall environmental footprint was estimated to be 0.29 billion (bn) gha in 2010 and is likely to grow to around 2.57 bn gha by 2050. It was then disaggregated into various components: bioproductive land, built land, carbon emissions, embodied energy, materials and waste, transport, and water consumption. This component‐based approach has enabled the examination of the Manufactured and Natural Capital elements of the ‘four capitals’ model of sustainability quite broadly, along with specific issues (such as the linkages associated with the so‐called energy–land–water nexus). Bioproductive land use was found to exhibit the largest footprint component (a 48% share in 2050), followed by the carbon footprint (23%), embodied energy (16%), and then the water footprint (9%). Footprint components related to built land, transport and waste arisings were all found to account for an insignificant proportion to the overall environmental footprint, together amounting to only about 2%     

Water,land and carbon footprints of sheep and chicken meat produced in Tunisia under different farming systems

Meat production puts larger demands on water and land and results in larger greenhouse gas emissions than alternative forms of food. This study uses footprint indicators, the water, land and carbon footprint, to assess natural resources use and greenhouse gas emissions for sheep and chicken meat produced in Tunisia in different farming systems in the period 1996–2005. Tunisia is a water-scarce country with large areas of pasture for sheep production. Poultry production is relatively large and based on imported feed. The farming systems considered are: the industrial system for chicken, and the agro-pastoral system using cereal crop-residues, the agro-pastoral system using barley and the pastoral system using barley for sheep. Chicken meat has a smaller water footprint (6030 litre/kg), land footprint (9 m²/kg) and carbon footprint (3 CO₂-eq/kg) than sheep meat (with an average water footprint of 18900 litre/kg, land footprint of 57 m²/kg, and carbon footprint of 28 CO₂-eq/kg). For sheep meat, the agro-pastoral system using cereal crop-residues is the production system with smallest water and land footprints, but the highest carbon footprint. The pastoral system using barley has larger water and land footprints than the agro-pastoral system using barley, but comparable carbon footprint.     

春玉米-晚稻与早稻-晚稻种植模式碳足迹比较

量化作物生产的碳足迹有助于为农业生态系统温室气体减排提供理论依据。利用生命周期法研究了我国南方地区稻田春玉米-晚稻水旱轮作种植模式和早稻-晚稻连作种植模式下粮食生产的碳足迹,并定量分析粮食生产过程中各种碳排放源的相对贡献。结果表明,与早稻-晚稻的连作模式相比,春玉米-晚稻轮作模式的单位面积碳排放降低了6724 kg CO₂-eq/hm²,单位产量的碳足迹降低了0.56 kg CO₂-eq/kg。春玉米比早稻少排放6228 kg CO₂-eq/hm²;与早稻-晚稻模式中晚稻碳排放相比,春玉米-晚稻轮作模式晚稻碳排放降低了497 kg CO₂-eq/hm²。早稻-晚稻种植模式的碳足迹主要来源于甲烷（CH₄）,其碳排放为9776 kg CO₂-eq/hm²（54.8%）,氮肥生产和施用的碳排放为2871 kg CO₂-eq/hm²（16.1%）,灌溉电力消耗的碳排放2849 kg CO₂-eq/hm²（16.0%）。春玉米-晚稻轮作模式的碳足迹主要来源于CH₄的碳排放4442 kg CO₂-eq/hm²（39.9%）,氮肥生产和施用的碳排放2871 kg CO₂-eq/hm²（25.8%）,灌溉电力消耗的碳排放1508 kg CO₂-eq/hm²（13.6%）。该模式中晚稻的碳足迹组成情况与春玉米-晚稻模式的碳足迹相似。但是,对于春玉米而言,其碳足迹主要来源氮肥生产和施用的碳排放1436 CO₂-eq/hm²（50.1%）,氧化亚氮（N₂O）的碳排放为579 kg CO₂-eq/hm²（20.2%）,CH₄的碳排放为378 CO₂-eq/hm²（13.2%）。同时,相比于早稻-晚稻中晚稻的产量（6333 kg/hm²）,春玉米-晚稻轮作模式下的晚稻产量（7270 kg/hm²）提高了14.8%。因此,引入春玉米-晚稻轮作模式有利于提升稻田生产力,降低稻田连作系统碳排放和碳足迹。     

The Greenhouse Gas Footprint of China's Food System: An Analysis of Recent Trends and Future Scenarios

Food chain systems (FCSs), which begin in agricultural production and end in consumption and waste disposal, play a significant role in China's rising greenhouse gas (GHG) emissions. This article uses scenario analysis to show China's potential trajectories to a low‐carbon FCS. Between 1996 and 2010, the GHG footprint of China's FCSs increased from 1,308 to 1,618 megatonnes of carbon dioxide equivalent (Mt CO₂‐eq), although the emissions intensity of all food categories, except for aquatic food, recorded steep declines. We project three scenarios to 2050 based on historical trends and plausible shifts in policies and environmental conditions: reference scenario; technology improvement scenario; and low GHG emissions scenario. The reference scenario is based on existing trends and exhibits a large growth in GHG emissions, increasing from 1,585 Mt CO₂‐eq in 2010 to 2,505 Mt CO₂‐eq in 2050. In the technology improvement scenario, emissions growth is driven by rising food demand, but that growth will be counterbalanced by gains in agricultural technology, causing GHG emissions to fall to 1,413 Mt CO₂‐eq by 2050. Combining technology improvement with the shift to healthier dietary patterns, GHG emissions in the low GHG emissions scenario will decline to 946 Mt CO₂‐eq in 2050, a drop of 41.5% compared with the level in 2010. We argue that these are realistic projections and are indeed indicative of China's overall strategy for low‐carbon development. Improving agricultural technology and shifting to a more balanced diet could significantly reduce the GHG footprint of China's FCSs. Furthermore, the transition to a low‐carbon FCS has potential cobenefits for land sustainability and public health.