城乡居民食物氮足迹估算及其动态分析——以北京市为例

氮足迹作为一种评价氮排放影响的新兴测度方法,已被用来衡量人类活动造成的环境影响。食物消费是城市营养元素流动的重要环节,其产生的氮足迹反映了维持一个城市人口的基本食物需求所导致的活性氮排放以及对周边环境的影响。以北京市为例,基于N-Calculator模型的基础上,估算了1980—2012年居民食物氮足迹,分析其变化特点及其与经济社会因素之间的关系。结果表明:北京市居民人均食物氮足迹变化与食物消费量变化趋势相似,城镇居民氮足迹呈持续增长后渐趋平稳,在14.69—22.58 kg(N)/a之间波动,平均为17.78 kg(N)/a,接近发达国家水平;农村居民氮足迹呈小幅减少趋势,在10.81—15.28kg(N)/a之间波动,平均为12.72 kg(N)/a。其中,高氮含量食物在城乡居民人均食物氮足迹中所占比例都有所增加,以肉类为主的荤食比例分别由27%和10%上升至41%和31%;以奶类为主的副食比例由7%和1%上升至18%和13%。城镇居民食物氮足迹与人均可支配收入呈正相关,与恩格尔系数和平均家庭人口数呈负相关,而农村居民食物氮足迹与各因子的相关关系则与前者相反。此外,北京市食物氮足迹总体呈增长趋势,年均增加约8066 t(N)/a。城镇居民当前的饮食消费模式不利于减缓北京区域食物氮足迹高通量的剧增趋势,更多的农村及外来人口进入城镇将加速区域氮足迹增长。食物氮足迹的估算能为居民改变高氮消费模式提供参考,进而促进城市的低氮发展。     

政策对城市餐饮业食物浪费变化特征的影响分析-以拉萨市为例

基于拉萨市3次餐饮食物消费调研数据（2011年、2013年和2015年）,以拉萨市餐饮食物浪费特征为主线,对比分析了政策出台前后拉萨市餐饮食物浪费特征变化,揭示了政策因素对减少拉萨餐饮业食物浪费的干预效果及影响机制。研究结果显示：政策因素在很大程度上遏制了餐饮食物浪费,干预效果明显。与政策出台前相比（2011年）,除蛋类浪费以外,2013年和2015年拉萨市餐饮食物浪费总量、动物食品浪费总量以及植物食品浪费总量均显著下降,其中,拉萨市餐饮浪费在2015年较2013年基础之上食物浪费总量和植物食品浪费总量表现出显著差异,动物食品浪费总量为表现出显著差异,但是仍呈现出进一步降低。不同规模餐饮业食物浪费结果显示,政策对餐饮食物浪费的干预效果主要表现在大、中型餐馆;尤其是大型餐馆,食物浪费总量、动物食品浪费总量以及植物食品浪费总量均显著下降。小型餐馆干预效果不明显,食物浪费数量与政策出台以前相比甚至有所增加,这可能受到除政策以外其它因素的影响。可见,大、中型餐馆减少食物浪费潜力较大,未来应该加强大中型餐馆食物浪费研究,探索影响食物浪费的因素,引导我国城镇餐饮业实现可持续发展。     

城市餐饮业食物浪费碳足迹——以北京市为例

食物浪费及其造成的环境影响已成为全球广泛关注的热点。无论从生命周期还是碳足迹的视角来看,食物浪费意味着生产、运输、加工与储存这些被浪费掉的食物过程中所投入的各种资源的浪费以及不必要的温室气体排放。以北京市餐饮食物浪费问题为切入点,在通过问卷调查和称重方法对餐饮食物浪费状况进行调查的基础上,将整个食物生命周期各供应链环节相应的温室气体排放纳入考量,估算了北京市餐饮食物浪费的碳排放量。研究结果表明:北京市餐饮食物浪费总量为39.86×10~4t/a。其中,蔬菜类浪费量最高,约占浪费总量的43.16%,其次为肉类和主食类,分别占食物浪费总量的20.59%和16.66%。北京市餐饮食物浪费所产生的总碳足迹为192.51×10~4—208.52×10~4t CO_2eq。其中,农业生产阶段的碳排放量最大为99.34×10~4t CO2eq,占食物浪费总碳足迹的47.64%。其次是消费阶段的碳足迹77.96×10~4t CO_2eq,占食物浪费总碳足迹的37.39%,再次是餐厨垃圾处理阶段的碳足迹28.54×104tCO2eq,占食物浪费总碳足迹的13.68%。这些不同供应链环节的碳排放比例,为透视食物浪费所带来的环境影响提供了新的认知,也为遏制食物浪费提供了科学的理论依据。     

典型移民城市食物氮足迹估算分析——以深圳市为例

城市食物源氮消费产生的环境排放是全国氮污染的重要源头,城市食物氮足迹评估可反映维持城市人口基本食物需求的活性氮排放以及对周边环境的潜在影响。以典型移民城市深圳市为例,基于改进N-Calculator模型的基础上,估算了2010-2015年间因城市人口流动导致的城市食物氮足迹变化,并分析其时空异质性及其与城市化间的关系。结果表明：深圳市不同类型城市居民食物氮足迹不一致,其中常住户籍居民人均食物氮足迹从14.63 kg N a^-1增加至15.17 kg N a^-1,高于非户籍居民食物氮足迹13.09 kg N a^-1,其主要体现在瓜果、肉类、水产品等食物消费上。总体上,深圳城市食物氮足迹呈增长趋势,5年增幅11.50%,增幅最大为常住户籍居民食物氮足迹,但目前深圳非户籍居民的食物消费主导着城市食物氮足迹。深圳城市内部区域食物氮足迹呈高度空间异质性与聚集性,各区域增长量差异明显,街道尺度城市食物氮足迹增长热点主要分布在城市的西部沿海区域,部分热点区域单位增长量数量级比肩区级尺度单位的增长量,城市区域食物氮足迹与人口城市化的关联性不明显,但与经济城市化存在一定的关联性。当前城市移民落户趋势及居民高氮饮食倾向不利于城市氮足迹的削减,减少食物生产上游活性氮流失为深圳市贯彻粤港澳大湾区协同可持续发展的关键。     

三种控释肥在赤红壤中的氧化亚氮排放

采用静态箱收集和对比法,研究了无作物种植条件下包膜与否对高氮、均衡及高钾3种氮磷钾配比复合肥在华南赤红壤发育的菜园土中氧化亚氮(N2O)排放情况.结果表明:肥料氮磷钾配比不同,N2O排放量差异显著,3种类型复合肥N2O累积排放量表现为均衡型≥高氮型＞高钾型;同一类型复合肥,包膜控释能显著降低N2O排放量,包膜控释高氮、均衡及高钾型复合肥N2O排放总量分别为不包膜复合肥N2O排放量的34.4％、30.5％和89.3％;与不包膜相比,复合肥包膜能降低肥料在土壤中的N2O日排放通量,滞后和削减N2O排放高峰,减少土壤氮素损失以及由N2O排放造成的全球增温潜势.     

紫色土菜地生态系统土壤N2O排放及其主要影响因素

应用静态箱/气相色谱法对种菜历史超过20a的紫色土菜地进行了一年N2O排放的定位观测, 分析了菜地N2O排放特征及施氮、土壤温度、土壤湿度和蔬菜参与对N2O排放的影响. 结果表明, 紫色土菜地生态系统在不施氮和施氮（N150kg?hm-2）情况下N2O平均排放通量为50.713.3和168.437.3g?m-2?h-1, N2O排放系数为1.86%. 菜地生态系统N2O排放强度高于当地粮食作物农田,其主要原因在于菜地较高的养分水平和频繁的施肥、浇水等田间管理措施. 从菜地N2O排放总量的季节分配来看, 有64%的N2O排放量来自于土壤水热条件较好的夏秋季蔬菜生长期, 冬春季蔬菜生长期N2O排放量较少, 仅占34%. 因此, 土壤水热条件不同是造成菜地N2O排放量季节分配差异的重要原因. 氮肥对增加N2O排放的效应因蔬菜生育期内单位时间施肥强度不同而异, 蔬菜生育期越短, 施氮对增加N2O排放的效应越明显.不施氮和常规施氮菜地N2O排放通量与地下5cm处土壤温度呈显著的正相关, 但不种蔬菜的空地两者之间的关系不显著, 并且常规施氮菜地土壤温度（T）对N2O排放通量（F）的影响可用指数方程F＝11.465e0.032T（R＝0.26, p<0.01）表示. 土壤湿度对菜地N2O排放的影响存在阈值效应, 当土壤含水空隙率（WFPS）介于60%-75％时更易引发N2O高排放. 因此, 依据蔬菜生育期特点, 结合土壤水分状况调节施肥量与施肥时间可能会减少菜地N2O排放.     

北京市消耗食物生态足迹距离

以北京市消耗食物生态足迹的距离为研究核心。结果表明2008年至2012年,北京的生态足迹距离、人均生态足迹和生态足迹总里程总体呈现逐年增长趋势:生态足迹距离增大到676.75 km,增长19.3%;人均生态足迹距离增加到18.42万km,增长54%;生态足迹总里程增加了1倍强,达到56亿t km。北京市的食物生态足迹距离不断扩大,并涵盖了全国大部分地区,北京城市化的生态成本上升。所消耗各类食物的生态足迹距离从大到小分别为水果类、蔬菜或粮油类、肉蛋类和水产类。蔬菜类和水果类的生态足迹距离存在明显的季节波动,且冬春季节远高于夏秋季节。从转移生态承载力来源地的视角,直线距离越远、占据市场份额越大的地区,对北京市消耗食物生态足迹距离的贡献率越高。     

日光温室番茄-西瓜轮作系统不同水氮处理氨挥发特征

为探究黄土高原地区日光温室果蔬栽培中氨挥发特征,在陕西省杨凌区选择当地典型的日光温室,设置4个不同的水氮处理,采用密闭式间歇抽气法监测番茄-西瓜轮作季的氨挥发特征.结果表明: 日光温室栽培土壤氮素转化快,施氮处理施肥后第1～2天氨挥发出现峰值,氨挥发峰值为0.26～2.02 kg N·hm^-2·d^-1,7 d左右各处理氨挥发通量相近;施氮处理间氨累积排放量无显著差异;相同施氮量条件下,降低灌溉量氨累积排放量两季平均增加了46.7%;不同种植季氨平均排放通量和累积排放量均表现为西瓜季高于番茄季,西瓜季高温促进了氨排放;土壤铵态氮含量、土壤孔隙含水量、0～5 cm地温和温室气温均对氨排放通量有极显著影响,而土壤pH值与氨挥发通量呈显著负相关关系.不同种植季氨挥发通量和累积排放量存在差异,降低施氮量可减少氨排放,相同施氮量条件下降低灌溉量增加了氨排放.     

施氮对桉树人工林生长季土壤温室气体通量的影响

施肥是维持短期轮伐人工林生产量的重要手段,为了提高肥料利用效率,缓释氮肥逐渐成为广泛采用的氮肥种类。评估缓释肥施用对人工林生长季土壤温室气体通量的影响对于全面评估人工林施肥的环境效应具有重要意义。以我国南方广泛种植的桉树林为对象,采用野外控制实验研究了4种施氮处理(对照CK:0 kg/hm2;低氮L:84.2 kg/hm2;中氮M:166.8 kg/hm2;高氮H:333.7 kg/hm2)对土壤-大气界面3种温室气体(CO2、N2O和CH4)通量的影响,结果表明:(1)4种施氮水平下CO2排放通量、N2O排放通量和CH4吸收通量分别为276.84—342.84 mg m-2h-1、17.64—375.34μg m-2h-1和29.65—39.70μg m-2h-1;施氮显著促进了N2O的排放(P0.01),高氮处理显著增加CO2排放和显著减少CH4吸收(P0.05),且CO2排放通量与CH4吸收通量随着施氮量的增加分别呈现增加和减少的趋势;(2)生长季CO2和N2O排放呈现显著正相关(P0.01),CO2排放和CH4吸收呈现显著负相关(P0.05),N2O排放和CH4吸收呈现显著负相关(P0.01);(3)土壤温度和土壤水分是影响CO2、N2O排放通量和CH4吸收通量的主要环境因素。结果表明:施用缓释肥显著增加了桉树林生长季土壤N2O排放量,且高氮处理还显著促进CO2排放和显著抑制CH4吸收,上述研究结果可为人工林缓释肥对土壤温室气体通量评估提供参数。     

黄淮海平原河北省范围内农田土壤二氧化碳和氧化亚氮排放量的估算

以黄淮海平原河北省范围内的农田土壤为研究对象,通过与田间实际观测数据进行比较发现,DNDC模型能够较好地反映农田土壤温室气体CO2和N2O的排放通量,可以用来模拟估算农田土壤CO2和N2O的排放通量.根据模型估算,2003年河北省111个县市农业土壤CO2排放量约3.758×106tC,各县市总的N2O排放量40.345×106kgN.全省释放的CO2和N2O中有40%左右来自冬小麦/夏玉米地.因此,减少该地区农业土壤CO2和N2O排放量的措施,应集中用于排放量高的县市和这些地区的冬小麦/夏玉米地,进行大范围的普遍减排可能收效甚微,并且没有必要.     

Development of a Climate Choice meal concept for restaurants based on carbon footprinting

Purpose

Significant reductions in greenhouse gas emissions from food production and consumption can be made at the level of individual diet. Together with the food and beverage sector, consumers could play a significant role by making informed choices that benefit the environment and their own health. Communicating information on carbon footprints to consumers is challenging and should be made very simple, yet reliable. This sector is showing interest in using eco-design tools to decrease climate change impacts of their meals.

Methods

A long-term concept for communicating information on carbon footprints associated with meals was developed in Finland. The criteria for a Climate Choice meal were created through stakeholder dialogue, and three restaurant operators piloted the concept in 25 restaurants. In addition to climate change impacts, possibilities to include other sustainability criteria were reviewed. The concept was based on simplified carbon footprinting of raw material production and processing of ingredients for 105 commonly selected lunches. The carbon footprint calculations allowed the development of the Climate Choice meal concept, its criteria, and piloting the concept. Based on experiences from restaurants and consumers from the pilot phase, final criteria were developed.

Results and discussion

The Climate Choice meal concept was created using two alternative climate criteria: one for immediate implementation and another for future implementation, in cases where carbon footprinting is feasible for restaurants. The criteria for immediate implementation include a list of mainly plant-based ingredients with low carbon footprint. Regarding future criteria, it should be made easy enough for restaurants to estimate the carbon footprints of their meals, allowing labeling of meals when their carbon footprints are at least 25 % smaller than for an average meal. In addition to the two climate criteria, Climate Choice meals need to follow Finnish public catering nutritional recommendations, taking into account that fish species on the Red List of WWF’s Finnish seafood guide are prohibited.

Conclusions

To promote climate-friendly eating, a long-term concept rather than a short-term campaign is needed. There is interest among consumers and restaurants for information on food carbon footprints and sustainability. Lunch is regarded as a good opportunity for consumers to learn about climate-friendly eating. The main challenges are to produce sufficiently reliable background data and to raise consumer and the food and beverage sector interest and understanding of carbon footprints associated with food.

     

湖北省不同花生轮作种植体系碳氮足迹

明确作物生产过程的主要碳氮排放环节,可为不同花生轮作种植体系实现高产高效与低碳氮排放的协同效益提供有效参考。本研究对湖北省黄冈市油菜-花生轮作、小麦-花生轮作、花生单作3种种植模式生产过程的农资投入和田间管理措施等进行实地调查,核算该3种种植模式的碳足迹和氮足迹。结果表明: 油菜-花生轮作较小麦-花生轮作单位面积碳排放降低7.8%、单位净现值碳排放降低36.9%、单位面积氮排放降低12.5%、单位净现值氮排放降低41.9%;油菜-花生轮作较花生单作单位净现值碳排放和氮排放分别降低19.6%和30.8%;油菜-花生轮作净收益是小麦-花生轮作的1.4倍、花生单作的2.4倍。表明油菜-花生轮作可实现高产高效与低碳氮排放的协同效益,有利于油料作物的绿色高质高效生产。     

Modelling,assessing, and ranking public procurement options for a climate-friendly catering service

Purpose

Several scientific papers and technical reports have discussed the role of green public procurement in the food sector. Different strategies for the restoration sector have been identified. However, there is not yet a common understanding of which policies could be the most efficient in reducing the global warming potential of the public restoration service. This paper assesses a set of procurement policies, ranking them according to their potential to reduce the greenhouse gas emissions of public catering.

Methods

Eleven relevant green public procurement policies were identified from the literature. These are discussed in the context of a case study of the school catering service in the city of Turin (Italy). Initially, a life cycle approach is applied to a baseline scenario of the collective restoration system of the city, to quantify the quantity of greenhouse gases produced by the entire catering service (including all stages from the production of food to the management of waste from kitchens and canteens). Afterwards, the 11 policies were applied to the baseline scenario so that the potential improvement achieved by each policy could be quantified.

Results and discussion

The baseline scenario resulted in 1.67 kgCO₂eq per average meal. The production of food dominates the global warming potential of the full service, being responsible for about 78% of the greenhouse gas emissions. Among the selected policies, a change in diet was the most effective (leading to a 32% reduction of the CO₂eq emissions), followed by the adoption of improved food production practices (11% reduction) and the purchasing of certified green electricity (6% reduction).

Conclusions

The proposed method allows the assessment of procurement policies in the catering service by applying a simplified life cycle approach that considers all the stages of the process. Public authorities and other stakeholders could benefit from basing their decisions upon scientific evidence and avoiding the prioritisation of policies based on personal opinions or weak evidence. Uncertainties and areas for improvement in the method have been also identified for future investigation.

     

减氮施肥对春玉米-晚稻生产系统碳足迹的影响

随着对气候变化和粮食安全的的日益认识,低碳农业引起了人们的广泛关注.低碳农业的研究需要综合考虑作物产量和温室气体排放,改进氮肥管理可能有助于减缓作物生产系统的温室气体排放,同时实现对作物稳产甚至高产的需求.本试验利用生命周期法研究了不同施氮量(150、225、300 kg N·hm^-2)对春玉米-晚稻轮作系统碳足迹的影响.结果表明: 随着氮肥用量增加,两季作物生产过程中温室气体和碳足迹增加.在春玉米生产过程中,氮肥生产和施用引起的温室气体排放对碳足迹贡献最大,占36.2%～50.2%;而在晚稻生产中,甲烷的排放贡献最大,占42.8%～48.0%,并且随氮肥用量增加甲烷排放增加.当氮肥施用量减少25%(225 kg N·hm^-2)和50%(150 kg N·hm^-2)时,春玉米生产的温室气体排放分别下降了21.9%和44.3%,碳足迹分别下降了20.3%和39.1%;晚稻生产的温室气体排放分别下降了12.3%和20.4%,碳足迹分别降低了13.7%和16.7%.氮肥减量对春玉米产量无显著影响,而晚稻产量在225 kg N·hm^-2施肥量下最高.因此,春玉米氮肥用量降低至150 kg N·hm^-2和晚稻氮肥用量降低至225 kg N·hm^-2不仅能够保持作物高产,而且还能大幅度降低作物系统的碳足迹.     

Food Consumption and Nutrient Flows: Nitrogen in Sweden Since the 1870s

Changes in food consumption and related processes have a significant impact on the flow of nitrogen in the environment. This study identifies both flows within the system and emissions to the hydrosphere and atmosphere. A case study of an average inhabitant of the city of Linköping, Sweden, covers the years 1870, 1900, 1950, and 2000 and includes changes in food consumption and processing, agricultural production, and organic waste handling practices. Emissions to the hydrosphere from organic waste handling increased from 0.57 kilograms of nitrogen per capita per year (kg N/cap per year) to 3.1 kg N/cap per year, whereas the total flow of nitrogen to waste deposits grew from a negligible amount to 1.7 kg N/cap per year. The largest flow of nitrogen during the entire period came from fodder. The input of chemical fertilizer rose gradually to a high level of 15 kg N/cap per year in the year 2000. The total load per capita disposed of to the environment decreased during these 130 years by about 30%.     

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%     

Meat meal in the diet of the early-weaned pig. I. A comparison of meat meal and soya bean meal

Seventy-two pigs, initially weighing 4–5 kg, were fed on wheat-based diets supplemented with soya bean meal and/or meat meal in two experiments each of 4 weeks' duration.In the first experiment, 0, 25, 50 or 100% replacement of soya bean meal protein supplement with meat meal was associated with a linear decrease in weight gains (341-280 g/d), a linear increase in feed conversion ratios (1.64–2.35) and a linear decrease in apparent digestibility of dry matter (80.1–73.4%). There was no change in the apparent digestibility of nitrogen.In the second experiment, bone meal was added to provide 0.80, 1.55 and 3.05% calcium in diets in which the protein supplements were either soya bean meal or meat meal. The addition of bone meal to the diets containing soya bean meal did not affect the performance of the pigs, but it caused a linear decrease in the apparent digestibility of dry matter, nitrogen and calcium. The addition of bone meal to the diet containing meat meal reduced the feed intakes of the pigs from 617 to 516 g/d and the weight gains from 414 to 324 g/d.Weight gains of pigs were similar when their diets contained soya bean meal or meat meal as the protein supplement in the second experiment when the calcium content of the diets was 0.8%. The meat meal included in the diet was manufactured from soft offal.