中国农作物生产碳足迹及其空间分布特征

基于中国1993—2013年的农业统计数据,采用生命周期评价、重心模型以及GIS等方法分析农作物生产碳排放及碳足迹的时序变化、碳足迹重心的移动轨迹、碳排放和碳足迹的空间分布特征以及影响碳排放的主导因素.结果表明: 研究期间,中国农作物生产碳排放量(GHGe)、单位播种面积碳足迹(CFs)和单位耕地面积碳足迹(CFc)均显著增加,而单位产量碳足迹(CFy)和单位产值碳足迹(CFv)显著减少.CFs重心一直分布在河南,且逐渐移向西南;CFc重心位于湖北或河南,并向西北方向移动;CFy重心位于陕西或河南,且整体移向东南;CFv重心始终在河南,并逐渐移向西南.GHGe和碳足迹存在显著的省域差异,GHGe具有南北低、中部高的特点,CFs是东西两翼高、中间低,CFc高值区主要集中在中部及东部沿海省份,CFy在西北-东南方向上表现为“高-低-高”,CFv在西北-东南方向上则是由高走低.农业生产过程中不同投入占农作物碳足迹的比例以化肥最为突出,化肥投入构成中以氮肥和复合肥所占比例较大.通过分析GHGe与各影响因素的关联度,得出化肥尤其是磷肥和氮肥、灌溉以及农田N₂O排放是导致GHGe显著增加的主导因素,并据此提出发展低碳农业的对策建议.     

全球温室气体排放概况

全球温室气体排放概况曹志平（中国农业大学资源与环境学院生态系,北京１０００９４）ＩｎｔｒｏｄｕｃｔｉｏｎｏｆＧｌｏｂａｌＥｍｉｓｓｉｏｎｓｏｆＧｒｅｅｎｈｏｕｓｅＧａｓ．ＣａｏＺｈｉｐｉｎｇ（ＣｏｌｅｇｅｏｆＲｅｓｏｕｒｃｅｓａｎｄＥｎｖｉｒｏｎｍ...     

山东省小麦-夏直播花生种植体系碳足迹

明确小麦-夏直播花生(W-P)种植体系的主要碳排放环节,可为采取有效措施实现该体系高产与低碳排放的协同效益提供参考.本文依据全生命周期方法,构建碳足迹模型,并核算了山东省W-P种植体系生命周期碳排放.结果表明:山东省W-P种植体系的净收益较小麦-玉米(W-M)种植体系高71.2%~88.3%;W-P种植体系的单位面积碳排放达6977.9~8018.5 kg·hm^-2,较W-M种植体系高6.2%,但单位净产值的碳排放为每元0.23~0.28kg CO_2-eq,较W-M种植体系低37.4%~44.1%.综合2种种植体系的净收益和单位净产值碳排放发现,W-P种植体系可以实现高产出与低碳排放的协同效益,符合优化供给、提质增效、农民增收的农业供给侧结构性改革目标.     

中国农业系统近40年温室气体排放核算

基于排放因子法构建了包含种植业和牲畜养殖业的农业系统温室气体排放核算体系,系统核算了1980-2020年我国全国尺度上的农业系统温室气体排放总量和变化趋势,并在区县级尺度下对1980、2000、2011年的中国农业系统的温室气体排放量进行核算,对比不同阶段农业系统温室气体排放变化的时空异质性规律。研究发现：1980-2020年我国农业系统温室气体排放量呈波动增长趋势,增长了近46%。CH₄是农业系统排放贡献最大的温室气体,占总排放量的47.33%。我国农业系统温室气体排放与不同地区农业生产方式有关,CH₄排放量高的地区主要位于我国主要水稻产区以及旱地作物产区。CO₂排放量高的地区主要位于东北、西北等地区以及华东地区。N₂O排放量较高地区主要位于西北的主要畜牧养殖地区,以及我国农业经济发展水平高的中南部地区。研究有助于揭示我国农业温室气体排放的动态特征,现状规律,以及空间差异性特征,从农业减排角度为实现双碳目标提供科学参考。     

The potential of Miscanthus to sequester carbon in soils: comparing field measurements in Carlow,Ireland to model predictions

Growing bioenergy crops such as Miscanthus has the potential to mitigate atmospheric carbon dioxide emissions by the replacement of fossil fuels and by storing carbon (C) in the soil due to land use change. Here we compare direct measurements of soil organic C fractions made in Carlow (Ireland) to model predictions made by RothC and a cohort model. Our results show that when Miscanthus is grown on land previously under arable agriculture, the soil organic C will increase to a level above that of native pasture, as Miscanthus organic material is shown to have a slow decomposition rate. In addition we demonstrate that for measured organic C, fractions of different lability are similar to the C pools used in RothC. Using the model predictions from RothC and Miscanthus yields from MISCANFOR, we predict that in Ireland, changing the land use from arable to Miscanthus plantations has the potential to store between 2 and 3 Mg C ha^?1 y^?1 depending on the crop yield and the initial soil organic C level.     

Impact of Power Generation Mix on Life Cycle Assessment and Carbon Footprint Greenhouse Gas Results

The mix of electricity consumed in any stage in the life cycle of a product, process, or industrial sector has a significant effect on the associated inventory of emissions and environmental impacts because of large differences in the power generation method used. Fossil‐fuel‐fired or nuclear‐centralized steam generators; large‐scale and small‐scale hydroelectric power; and renewable options, such as geothermal, wind, and solar power, each have a unique set of issues that can change the results of a life cycle assessment. This article shows greenhouse gas emissions estimates for electricity purchase for different scenarios using U.S. average electricity mix, state mixes, state mixes including imports, and a sector‐specific mix to show how different these results can be. We find that greenhouse gases for certain sectors and scenarios can change by more than 100%. Knowing this, practitioners should exercise caution or at least account for the uncertainty associated with mix choice.     

河北省小麦白粉病发生气象等级动态预警

根据河北省4县2001—2010年小麦白粉病病情和逐日气象资料,采用因子膨化、秩相关分析、通径分析、Bayes准则、模糊数学(Fuzzy)和广义回归神经网络(GRNN)等方法,筛选影响小麦白粉病发生的关键期和关键因子,建立了小麦白粉病发生气象等级指标模型、基于Bayes准则的Fuzzy模型和基于Fuzzy模型的GRNN模型。结果表明:影响河北4县小麦白粉病发生气象等级的关键因子是前三候至当候的平均温度、前三候至当候的降水量、前三候至当候的降雨系数和前一候的小麦白粉病实际发生等级;3种预警模型具有层层递进的关系,预报准确率基于Fuzzy模型的GRNN模型基于Bayes准则的Fuzzy模型指标模型,并均超过了85%,可以用于对候尺度小麦白粉病发生等级进行中短期预报。     

Greenhouse Gas Emissions Quantification and Reduction Efforts in a Rural Municipality

The present article aims to determine the current carbon footprint (CF) of Zernez, a Swiss mountain village, and to identify reduction potentials of greenhouse gas (GHG) emissions. For this purpose, material and energy flows were assessed mainly based on detailed household surveys, interviews, and energy bills, but also by means of other information sources, for example, national statistics, traffic censuses, and literature values. To set up the GHG balance, special attention was paid to the consistent definition of system boundaries by adopting two fundamentally different perspectives: purely geographical accounting (PGA) and the consumption‐based footprint (CBF) method. Each of these two perspectives total approximately 10 tonnes of carbon dioxide equivalents per capita per year. The PGA revealed that 70% of the direct emissions in Zernez are caused by agricultural activities, whereas no consumption area dominated the consumption‐induced CF. For the identification of targeted measures, both perspectives were considered in a complementary manner. The building stock and its underlying energy supply system showed a GHG reduction potential of 80%. The building sector was thus detected as a reasonable first step for the municipality to adopt GHG mitigation strategies. In the case of Zernez, building‐stock‐related measures are predicted to decrease the current CF by 13% (CBF) and 17% (PGA), respectively.     

Energy Use and Greenhouse Gas Emissions of Air‐Source Heat Pump and Innovative Ground‐Source Air Heat Pump in a Cold Climate

This article compares climate impacts of two heat‐pump systems for domestic heating, that is, energy consumption for space heating of a residential building. Using a life cycle approach, the study compared the energy use and greenhouse gas (GHG) emissions of direct electric heating, a conventional air‐source heat pump, and a novel ground‐source air heat pump innovated by a citizen user, to assess whether such user innovation holds benefit. The energy use of the heat pumps was modeled at six temperature intervals based on duration curves of outdoor temperature. Additionally, two heat pump end‐of‐life scenarios were analyzed. Probabilistic uncertainty analysis was applied using a Monte Carlo simulation. The results indicated that, in ideal conditions, that is, assuming perfect air mixing, the conventional air‐source heat pump's emissions were over 40% lower and the ground‐air heat pump's emissions over 70% lower than in the case of direct electric heating. Although proper handling of the refrigerant is important, total leakage from the retirement of the heat‐pump appliance would increase GHG emissions by just 10%. According to the sensitivity analysis, the most influential input parameters are the emission factor related to electricity and the amount of electricity used for heating.     

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。     

Effect of Change of Forest Carbon Storage on Net Carbon Dioxide Balance of Wood Use for Energy in Japan

This study analyzed the net carbon dioxide (CO₂) emission reductions between 2005 and 2050 by using wood for energy under various scenarios of forest management and energy conversion technology in Japan, considering both CO₂ emission reductions from replacement of fossil fuels and changes in carbon storage in forests. According to our model, wood production for energy results in a significant reduction of carbon storage levels in forests (by 46% to 77% in 2050 from the 2005 level). Thus, the net CO₂ emission reduction when wood is used for energy becomes drastically smaller. Conventional tree production for energy increases net CO₂ emissions relative to preserving forests, but fast‐growing tree production may reduce net CO₂ emissions more than preserving forests does. When wood from fast‐growing trees is used to generate electricity with gas turbines, displacing natural gas, the net CO₂ emission reduction from the combination of fast‐growing trees and electricity generation with gas turbines is about 58% of the CO₂ emission reduction from electricity generation from gas turbines alone in 2050, and an energy conversion efficiency of around 20% or more is required to obtain net reductions over the entire period until 2050. When wood is used to produce bioethanol, displacing gasoline, net reductions are realized after 2030, provided that heat energy is recovered from residues from ethanol production. These results show the importance of considering the change in carbon storage when estimating the net CO₂ emission reduction effect of the wood use for energy.     

农田生态系统碳足迹时空变化——以河南省为例

农田生态系统是陆地生态系统的重要组成部分,起着碳源和碳汇的双重作用,对维持整个生态系统碳平衡具有重要意义.本文基于ArcGIS 10.1、SPSS 20.0、Sigmaplot 12.5等分析平台,以农田生态系统为研究对象,构建农田生态系统碳足迹模型,分析2005—2014年河南省农田生态系统碳排放、碳吸收和碳足迹及三者之间的关系.结果表明: 2005—2014年,研究区碳排放年平均增长率为2.7%,其中因化肥施用引起的碳排放量占总碳排放量的比例最高,占66.2%,且化肥的使用强度为890.38 kg·hm^-2,远高于发达国家公认的安全警戒线225 kg·hm^-2.河南省农田生态系统的碳总储量整体呈逐年上升趋势,其中,小麦的碳吸收比例最高,占总吸收量的60%,水稻的碳吸收增速最快,为7.9%.河南省农田生态系统存在碳生态盈余,且农田生态系统碳足迹总体呈现不断增加趋势,农田生态系统碳足迹占同期生产性土地面积(耕地)的平均比例为5.7%.研究区碳排放、碳吸收、碳足迹的空间变化较为一致,均呈现东南多、西北少的空间分布规律,且地区差异及变化幅度差异较大是三者的最主要外部特征.     

Environmental footprinting of hospitals: Organizational life cycle assessment of a Canadian hospital

Healthcare is a critical and complex service sector with direct and indirect greenhouse gas (GHG) emissions amounting to 5%–10% of the national total in developed economies like Canada and the United States. Along with a growing, albeit sporadic, set of life cycle assessment (LCA) (and “carbon footprinting”) studies of specific medical products and procedures, there is growing interest in “environmental footprinting” of hospitals. In this article, we advance this rapidly evolving area through a comprehensive organizational LCA of a 40-bed hospital in British Columbia, Canada, in its 2019 fiscal year. Our results indicate that the total environmental footprint of the hospital includes, among other things, global warming potential of 3500–5000 t CO₂ eq. (with 95% confidence). “Hotspots” in this footprint are attributable to energy and water use (and wastewater released), releases of anesthetic gases (which are potent GHGs), and the upstream production of the thousands of materials, chemicals, pharmaceuticals, and other products used in the hospital. The generalizability and comparability of these results are limited by inconsistencies across the few environmental footprinting studies of hospitals conducted to date. Nonetheless, our novel methodological approach, in which we compiled new LCA data for 200 goods and services used in healthcare—strategically selected to statistically represent the 2927 unique products in the hospital's “supply-chains”—has broad applicability in healthcare and beyond.     

The Concept of City Carbon Maps: A Case Study of Melbourne,Australia

Cities are thought to be associated with most of humanity's consumption of natural resources and impacts on the environment. Cities not only constitute major centers of economic activity, knowledge, innovation, and governance—they are also said to be linked to approximately 70% to 80% of global carbon dioxide emissions. This makes cities primary agents of change in a resource‐ and carbon‐constraint world. In order to set meaningful targets, design successful policies, and implement effective mitigation strategies, it is important that greenhouse gas (GHG) emissions accounting for cities is accurate, comparable, comprehensive, and complete. Despite recent developments in the standardization of city GHG accounting, there is still a lack of consistent guidelines regarding out‐of‐boundary emissions, thus hampering efforts to identify mitigation priorities and responsibilities. We introduce a new conceptual framework—based on environmental input‐output analysis—that allows for a consistent and complete reconciliation of direct and indirect GHG emissions from a city. The “city carbon map” shows local, regional, national, and global origins and destinations of flows of embodied emissions. We test the carbon map concept by applying it to the greater metropolitan area of Melbourne, Australia. We discuss the results and limitations of the approach in the light of possible mitigation strategies and policies by different urban stakeholders.     

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.     

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.