Forest carbon accounting methods and the consequences of forest bioenergy for national greenhouse gas emissions inventories

While bioenergy plays a key role in strategies for increasing renewable energy deployment, studies assessing greenhouse gas (GHG) emissions from forest bioenergy systems have identified a potential trade-off of the system with forest carbon stocks. Of particular importance to national GHG inventories is how trade-offs between forest carbon stocks and bioenergy production are accounted for within the Agriculture, Forestry and Other Land Use (AFOLU) sector under current and future international climate change mitigation agreements. Through a case study of electricity produced using wood pellets from harvested forest stands in Ontario, Canada, this study assesses the implications of forest carbon accounting approaches on net emissions attributable to pellets produced for domestic use or export. Particular emphasis is placed on the forest management reference level (FMRL) method, as it will be employed by most Annex I nations in the next Kyoto Protocol Commitment Period. While bioenergy production is found to reduce forest carbon sequestration, under the FMRL approach this trade-off may not be accounted for and thus not incur an accountable AFOLU-related emission, provided that total forest harvest remains at or below that defined under the FMRL baseline. In contrast, accounting for forest carbon trade-offs associated with harvest for bioenergy results in an increase in net GHG emissions (AFOLU and life cycle emissions) lasting 37 or 90 years (if displacing coal or natural gas combined cycle generation, respectively). AFOLU emissions calculated using the Gross-Net approach are dominated by legacy effects of past management and natural disturbance, indicating near-term net forest carbon increase but longer-term reduction in forest carbon stocks. Export of wood pellets to EU markets does not greatly affect the total life cycle GHG emissions of wood pellets. However, pellet exporting countries risk creating a considerable GHG emissions burden, as they are responsible for AFOLU and bioenergy production emissions but do not receive credit for pellets displacing fossil fuel-related GHG emissions. Countries producing bioenergy from forest biomass, whether for domestic use or for export, should carefully consider potential implications of alternate forest carbon accounting methods to ensure that potential bioenergy pathways can contribute to GHG emissions reduction targets.     

Review of greenhouse gas emissions from crop production systems and fertilizer management effects

Fertilizer nitrogen (N) use is expanding globally to satisfy food, fiber, and fuel demands of a growing world population. Fertilizer consumers are being asked to improve N use efficiency through better management in their fields, to protect water resources and to minimize greenhouse gas (GHG) emissions, while sustaining soil resources and providing a healthy economy. A review of the available science on the effects of N source, rate, timing, and placement, in combination with other cropping and tillage practices, on GHG emissions was conducted. Implementation of intensive crop management practices, using principles of ecological intensification to enhance efficient and effective nutrient uptake while achieving high yields, was identified as a principal way to achieve reductions in GHG emissions while meeting production demands. Many studies identified through the review involved measurements of GHG emissions over several weeks to a few months, which greatly limit the ability to accurately determine system-level management effects on net global warming potential. The current science indicates: (1) appropriate fertilizer N use helps increase biomass production necessary to help restore and maintain soil organic carbon (SOC) levels; (2) best management practices (BMPs) for fertilizer N play a large role in minimizing residual soil nitrate, which helps lower the risk of increased nitrous oxide (N₂O) emissions; (3) tillage practices that reduce soil disturbance and maintain crop residue on the soil surface can increase SOC levels, but usually only if crop productivity is maintained or increased; (4) differences among fertilizer N sources in N₂O emissions depend on site- and weather-specific conditions; and (5) intensive crop management systems do not necessarily increase GHG emissions per unit of crop or food production; they can help spare natural areas from conversion to cropland and allow conversion of selected lands to forests for GHG mitigation, while supplying the world's need for food, fiber, and biofuel. Transfer of the information to fertilizer dealers, crop advisers, farmers, and agricultural and environmental authorities should lead to increased implementation of fertilizer BMPs, and help to reduce confusion over the role of fertilizer N on cropping system emissions of GHGs. Gaps in scientific understanding were identified and will require the collaborative attention of agronomists, soil scientists, ecologists, and environmental authorities in serving the immediate and long-term interests of the human population.     

氮肥管理措施对黑土玉米田温室气体排放的影响

采用静态箱-气相色谱法研究了不同氮肥管理措施(农民常规施肥、减氮20%、添加硝化抑制剂、施用控释肥)对黑土玉米田温室气体排放的影响.结果表明:黑土玉米田施肥(基肥和追肥)后1~3d出现N2O排放峰,施肥后16d内N2O排放量占生育期总排放量的28.8%~41.9%.减施氮肥20%显著降低土壤N2O排放,生育期内的N2O累积排放量减少了17.6%~46.1%,综合温室效应降低30.7%~67.8%,温室气体排放强度降低29.1%~67.0%.等氮量投入时,添加吡啶抑制剂土壤N2O排放量、综合温室效应和温室气体排放强度最低.玉米拔节~乳熟期出现了较强的土壤CO2排放,黑土玉米田是大气中CH4的一个较弱的“汇”,施氮和添加硝化抑制剂对黑土玉米田CO2排放和CH4吸收没有显著影响.添加硝化抑制剂和施用控释肥不影响玉米产量.在本试验条件下,减氮20%并添加吡啶抑制剂在保证玉米产量的同时, 减排增收效果优于其他施肥措施,适宜在黑土区玉米种植中推广使用.     

强还原与生物炭对土壤酶活性和温室气体排放的影响

本研究设置未修复对照(CK)、土壤强还原处理(RSD)、生物炭修复(BC)以及RSD与生物炭联合修复(RSD+BC),采用培养实验对比研究不同修复处理对设施蔬菜地土壤酶活性和温室气体(CO2和N2O)排放的影响.结果表明:相比CK,RSD和RSD+BC处理显著提高了β-葡萄糖苷酶(βG)、纤维二糖水解酶(CBH)、过氧...     

生物质炭与强还原处理对退化设施蔬菜地土壤温室气体排放的影响

生物质炭和土壤强还原处理（Reductive Soil Disinfestation, RSD）可以有效地修复退化设施蔬菜地土壤,但2种修复技术联用对土壤温室气体（CO₂、N₂O和CH₄）排放的影响研究报道较少.本研究采用室内培养实验,设置未修复土壤（CK）、生物质炭修复（BC）、RSD修复（RSD）和BC与RSD联合修复（BC+RSD）4个处理,35℃条件下培养15 d,研究BC与RSD单独以及联合修复对退化设施蔬菜地土壤温室气体排放和综合温室效应（Global Warming Potential, GWP）的影响.结果表明,与对照CK相比,BC处理土壤N₂O排放量显著下降了50.0%,但CO₂排放量和GWP均显著增加（p<0.05）;RSD和BC+RSD处理土壤CO₂、N₂O、CH₄排放量和GWP均大幅度增加.但与RSD处理相比,BC+RSD处理土壤N₂O排放量和GWP分别下降了71.0%和30.0%.相关分析表明,土壤CO₂、N₂O、CH₄排放量和GWP与可溶性有机碳（DOC）和铵态氮（NH₄⁺-N）显著正相关,与pH和硝态氮（NO₃^--N）显著负相关.可见,生物质炭可以减少退化设施蔬菜地RSD修复引起的GWP.     

微塑料污染和蚯蚓活动对黄棕壤温室气体排放的影响

为明确蚯蚓暴露于不同量聚丙烯（PP）微塑料后对土壤CO₂、N₂O排放的影响,采用湖北当阳橘园土壤,进行室内培养试验,设置了5个处理：对照（CK）、接种蚯蚓（E）、接种蚯蚓并添加低量聚丙烯（0.25%干土重m/m,M1+E）、接种蚯蚓并添加中量聚丙烯（2%干土重m/m,M2+E）和接种蚯蚓并添加高量聚丙烯（7%干土重m/m,M3+E）.结果表明：接种蚯蚓可以显著增加土壤CO₂、N₂O的排放,相比未接种蚯蚓（CK）处理,土壤的CO₂、N₂O累积排放量分别增加了4.17、1.79倍,且接种蚯蚓显著提高了土壤p H.而微塑料添加后显著降低了土壤CO₂、N₂O排放,其中,接种蚯蚓并添加高量微塑料对土壤的CO₂、N₂O排放抑制效果最明显,分别降低了16.99%、27.28%.微塑料的添加会显著降低蚯蚓生物量,低、中、高量微塑料处理下蚯蚓生物量损失值较仅接种蚯蚓增加了29%、48%、...     

Livestock-related greenhouse gas emissions: impacts and options for policy makers

Research shows that livestock account for a significant proportion of greenhouse gas (GHG) emissions and global consumption of livestock products is growing rapidly. This paper reviews the life cycle analysis (LCA) approach to quantifying these emissions and argues that, given the dynamic complexity of our food system, it offers a limited understanding of livestock's GHG impacts. It is argued that LCA's conclusions need rather to be considered within a broader conceptual framework that incorporates three key additional perspectives. The first is an understanding of the indirect second order effects of livestock production on land use change and associated CO₂ emissions. The second compares the opportunity cost of using land and resources to rear animals with their use for other food or non-food purposes. The third perspective is need—the paper considers how far people need livestock products at all. These perspectives are used as lenses through which to explore both the impacts of livestock production and the mitigation approaches that are being proposed. The discussion is then broadened to consider whether it is possible to substantially reduce livestock emissions through technological measures alone, or whether reductions in livestock consumption will additionally be required. The paper argues for policy strategies that explicitly combine GHG mitigation with measures to improve food security and concludes with suggestions for further research.     

不同耕作方式对稻田净增温潜势和温室气体强度的影响

免耕技术近年来在南方稻区被广泛推广应用,但该项技术是否有利于减缓稻田综合温室效应目前并不清楚.因此,本文以双季稻-紫云英为研究对象,利用静态箱-气相色谱法分别研究不同耕作方式对稻田CH4和N2O排放、双季稻产量、土壤固碳、稻田净综合增温潜势(GWP)和温室气体强度(GHGI)的影响.试验处理包括常规翻耕(CT)、旋耕(RT)和免耕(NT).结果表明,稻田周年CH4累积排放量为233.5~404.0kg·hm-2·a-1,NT和RT处理分别比CT增加73.1%和35.1%.晚稻生长季CH4排放量占周年CH4排放量的53.7%~66.5%,其中,晚稻移栽至烤田期间CH4累积排放通量占晚稻季排放总量的77.0%~81.3%.稻田N2O累积排放量为4.00~4.82 kg·hm-2·a-1(以N计),但各处理之间没有显著差异.稻田年固碳量为0.36~1.31 t·hm-2·a-1(以C计),其中,NT处理比CT和RT处理分别增加148.4%和261.0%.双季稻周年产量为15.2~17.1 t·hm-2,耕作方式对产量没有显著影响.稻田净GWP为5095.4~7788 kg·hm-2(以CO2当量计),其中,RT和NT处理分别比CT增加52.8%和32.2%.稻田GHGI为0.30~0.46 kg·kg-1(以每kg粮食产量产生的CO2当量计),其中,RT和NT处理分别显著高于CT处理50.1%和45.3%.综上所述,免耕在短期内会增加稻田温室效应,但可以促进土壤固碳量的显著增加,因此,其固碳减排的长期效应还有待观测.     

The holistic impact of integrated solid waste management on greenhouse gas emissions in Phuket

Continually increasing amounts of municipal solid waste (MSW) and the limited capacity of the existing waste management system in Phuket have led to the consideration of integrated waste management system (IWMS). Life cycle assessment (LCA) was employed to compare the greenhouse gas emissions expressed as global warming potential (GWP) of the existing waste management system (the base scenario) and other three IWMSs for Phuket MSW. Besides incineration and landfilling, the proposed scenarios include 30% source separation for recycling (scenario 2), anaerobic digestion (scenario 3) and both (scenario 4).The functional unit is set as 1 t of Phuket MSW treated. Results from the impact assessment of the base scenario shows that the net GWP is 1006 kg CO₂ equivalent. Landfilling contributes to the highest potentials of this impact. The results from a holistic comparison show that scenario 4 is the best option among all the scenarios, contributing GWP of 415 kg CO₂ eq., whereas the base scenario is the worst. The emission of greenhouse gas from landfilling is reduced by the introduction of landfill gas recovery and utilization for electricity production. By assumption, 50% recovery of landfill gas leads to the GWP reduction around 58% by total GWP of landfilling and 36% by the net GWP of the whole system in the base scenario. The study suggests that a policy that promotes source separation should be pursued, preferably combined with the application of landfill gas recovery for electricity. Policy promoting recycling is favorable over anaerobic digestion in the situation that both treatment systems could not be established at the same time. The major conclusion from the study is that results from the LCA can support Phuket Municipality for decision-making with respect to planning and optimizing IWMS. It can benefit other municipalities or policy makers to apply in their waste management projects.     

城市污泥堆肥对土壤温室气体排放的短期影响

采用田间试验,施用2种城市污泥堆肥（含生物质炭和不含生物质炭）,通过静态暗箱-气相色谱法研究污泥堆肥土地利用过程温室气体排放特征,探讨施用污泥堆肥的短期影响作用.结果表明,在观测时间内,N₂O排放主要集中在前3周,约占总排放量的87.9%~95.6%.N₂O排放量均随污泥堆肥施用量的增加而增加（P<0.05）,裸地N₂O排放量高于种植作物处理.施用含生物质炭污泥堆肥能减少土壤N₂O排放,且随着施用量的增加,N₂O减少量越大（P<0.05）.CH₄排放量较低,在试验前期和后期主要为负,总体表现为吸收CH₄.各处理吸收CH₄主要集中在第18d以后,其CH₄吸收量占总吸收量的52.1%~66.7%.施用含生物质炭污泥堆肥处理CH₄吸收量比不含生物质炭污泥堆肥处理低35.2%~62.2%,同时,裸地CH₄吸收量明显高于种植作物处理（P<0.05）.CO₂排放也主要集中在18d以后,约占排放总量的50.5%~61.8%.种植作物能促进CO₂的排放,种植作物处理是裸地的1.34~1.57倍.在观测时间内,污泥堆肥土地利用是CH₄的弱吸收汇,是N₂O和CO₂的排放源,施加污泥堆肥能显著增加土壤N₂O和CO₂的排放.施用生物质炭污泥堆肥短期内能够减少温室气体总排放量,温室气体减排量达到20.41%~62.51%.     

黄土及其他添加物对猪粪贮存过程氨气和温室气体排放的影响

畜禽粪肥在贮存阶段养分损失严重,是CO_2、CH_4、NH_3和N_2O等大气污染物的重要排放来源.本文采用室内培养方法,研究了添加黄土、秸秆、生物炭和膨润土对猪粪贮存过程中氨气及温室气体排放的影响.结果表明,添加10%用量的生物炭和膨润土处理的CO_2累积排放量与不添加任何添加物的猪粪对照相比分别降低了15.4%和20.9%,N_2O累积排放量分别降低了19.8%和37.6%.添加膨润土处理的NH_3损失量显著增加,但添加生物炭和膨润土处理的综合温室效应与猪粪对照相比均显著降低.添加10%秸秆处理的CH_4和NH_3累积排放量分别较猪粪对照降低了56.8%和95.8%,但其综合温室效应与对照相比差异不显著.模拟黄土垫圈过程添加黄土处理的氨气及温室气体累积排放量均显著降低,综合温室效应显著低于其他处理(p0.05).可见,黄土垫圈是保蓄粪肥碳、氮养分的有效措施,猪粪贮存阶段添加少量生物炭、膨润土对于减少粪肥综合温室效应具有积极作用.     

浅层淹水条件下不同施肥处理对黑土温室气体排放的影响

以东北黑土区长期耕作土壤为对象,通过室内培养试验研究了浅层淹水条件下不同施肥处理对黑土温室气体排放的影响.结果表明,浅层淹水条件下,与不施肥对照处理相比,单施氮肥处理对土壤CO₂排放没有显著影响,氮肥配施猪粪或者秸秆则显著促进了CO₂的排放,使得CO₂排放速率提高了一个数量级,氮肥配施秸秆处理的CO₂排放量最高.浅层淹水条件下,与不施肥对照处理相比,施用氮肥显著促进了土壤N₂O的排放.而与单施氮肥处理相比,氮肥配施猪粪和秸秆则显著抑制了N₂O的排放,表现为土壤对N₂O的微量吸收,氮肥配施秸秆处理的N₂O吸收量相对较高.浅层淹水条件下施用氮肥抑制了土壤CH₄的排放,而与单施氮肥处理相比,氮肥配施猪粪或者秸秆则促进了土壤CH₄的排放.     

人工湿地温室气体排放研究进展与减污降碳优化

全球气候变暖问题越来越受到重视,随着人工湿地广泛应用于水处理,人工湿地温室气体排放也受到关注。采用文献计量学方法,筛选分析了Web of Science（WoS）核心数据库中人工湿地温室气体排放相关文献,聚类统计了其中216篇研究文献关键词,总结了主要研究方向及进展。结果表明：1）人工湿地温室气体排放研究相关文献数量于2003年开始逐年增加,文献被引频次同样逐年上升;主要研究热点关键词聚类为四大研究方向,即基质和曝气对温室气体排放的影响、植物对温室气体排放的影响、一氧化二氮（N₂O）产生及去除路径、甲烷（CH₄）产生及去除路径。2）人工湿地基质种类及配置均会影响人工湿地温室气体排放;而曝气可改变人工湿地内部氧化还原条件导致温室气体排放发生变化;植物能够减少人工湿地温室气体排放总量,且不同植物因通气组织及生物量的差异引起人工湿地温室气体排放差异。3）人工湿地N₂O产生于硝化/反硝化、厌氧氨氧化、硝酸盐异化还原成铵等多条路径,但N₂O去除路径仅有反硝化;人工湿地CH₄产生于有机物厌氧氧化过程,其去除则包括好氧氧化和厌氧氧化2条路径。基于上述综述,提出人工湿地工艺/运行方式优选、内部配置优化、外部条件强化等方面的优化模式,并提出未来需深入研究人工湿地内部N₂O 及CH₄ 转化机制,优化调控人工湿地温室气体排放,以实现人工湿地减污降碳。

     

Reduction of urban heat island and associated greenhouse gas emissions

Mitigation and Adaptation Strategies for Global Change - The reduction of urban heat island (UHI) and carbon emission is of great importance for thermal environment of urban residential areas. This...     

National and global greenhouse gas dynamics of different forest management and wood use scenarios: a model-based assessment

An increased use of wood products and an adequate management of forests can help to mitigate climate change. However, planning horizons and response time to changes in forest management are usually long and the respective GHG effects related to the use of wood depend on the availability of harvested wood. Therefore, an integral long-term strategic approach is required to formulate the most effective forest and wood management strategies for mitigating climate change.The greenhouse gas (GHG) dynamics related to the production, use and disposal of wood products are manifold and show a complex time pattern. On the one hand, wood products can be considered as a carbon pool, as is the forest itself. On the other hand, an increased use of wood can lead to the substitution of usually more energy-intense materials and to the substitution of fossil fuels when the thermal energy of wood is recovered. Country-specific import/export flows of wood products and their alternative products as well as their processing stage have to be considered if substitution effects are assessed on a national basis.We present an integral model-based approach to evaluate the GHG impacts of various forest management and wood use scenarios. Our approach allows us to analyse the complex temporal and spatial patterns of GHG emissions and removals including trade-offs of different forest management and wood use strategies. This study shows that the contributions of the forestry and timber sector to mitigate climate change can be optimized with the following key recommendations: (1) the maximum possible, sustainable increment should be generated in the forest, taking into account biodiversity conservation as well as the long-term preservation of soil quality and growth performance; (2) this increment should be harvested continuously; (3) the harvested wood should be processed in accordance with the principle of cascade use, i.e. first be used as a material as long as possible, preferably in structural components; (4) waste wood that is not suitable for further use should be used to generate energy. Political strategies to solely increase the use of wood as a biofuel cannot be considered efficient from a climate perspective; (5) forest management strategies to enhance carbon sinks in forests via reduced harvesting are not only ineffective because of a compensatory increase in fossil fuel consumption for the production of non-wooden products and thermal energy but also because of the Kyoto-“cap” that limits the accountability of GHG removals by sinks under Article 3.3 and 3.4, at least for the first commitment period; (6) the effect of substitution through the material and energy use of wood is more significant and sustained as compared with the stock effects in wood products, which tend towards new steady-state flow equilibria with no further increase of C stocks; (7) from a global perspective, the effect of material substitution exceeds that of energy recovery from wood. In the Swiss context, however, the energy recovery from wood generates a greater substitution effect than material substitution.     

Integrated scenario modelling of energy,greenhouse gas emissions and forestry

Preventing dangerous climate change requires actions on several sectors. Mitigation strategies have focused primarily on energy, because fossil fuels are the main source of global anthropogenic greenhouse gas emissions. Another important sector recently gaining more attention is the forest sector. Deforestation is responsible for approximately one fifth of the global emissions, while growing forests sequester and store significant amounts of carbon. Because energy and forest sectors and climate change are highly interlinked, their interactions need to be analysed in an integrated framework in order to better understand the consequences of different actions and policies, and find the most effective means to reduce emissions. This paper presents a model, which integrates energy use, forests and greenhouse gas emissions and describes the most important linkages between them. The model is applied for the case of Finland, where integrated analyses are of particular importance due to the abundant forest resources, major forest carbon sink and strong linkage with the energy sector. However, the results and their implications are discussed in a broader perspective. The results demonstrate how full integration of all net emissions into climate policy could increase the economic efficiency of climate change mitigation. Our numerical scenarios showed that enhancing forest carbon sinks would be a more cost-efficient mitigation strategy than using forests for bioenergy production, which would imply a lower sink. However, as forest carbon stock projections involve large uncertainties, their full integration to emission targets can introduce new and notable risks for mitigation strategies.     

冷凝水回流对堆肥腐熟度和污染气体排放影响

为探究堆肥过程中高温水蒸气携带的冷凝水回流对腐熟度及温室气体排放的影响,本文以猪粪和厨余垃圾为堆肥原料,在60L密闭好氧堆肥反应器中进行48d的高温好氧堆肥实验.结果表明,堆肥高温期产生的饱和水蒸汽因发酵罐封闭体系不能及时排出,会在发酵罐壁形成冷凝水回流入堆体中,整个堆肥过程冷凝水产率为物料湿重的18%.此外,回流冷凝水中主要成分为NH₄⁺-N(11.40g/L)、溶解性有机碳(6.3g/L)以及无机盐离子,具有较高的EC值(41.05mS/cm)和pH值(9.22),而较高的NH₄⁺-N含量使冷凝水回流处理的堆肥产品种子发芽指数(GI)略达到腐熟(71.4%),与排出处理相比GI下降了25.5%.同时,冷凝水回流使NH₃和CH₄排放量分别增加了55.2%的60.2%,但是CO₂和N₂O排放量分别降低了16.8%的34.8%.研究表明,冷凝水回流可降低17.8%总温室效应.本文建议堆肥过程将高温水蒸气冷凝排出,一...     

Estimation of greenhouse gas emissions in China and the abatement measures

The major emission sources of carbon dioxide, methane, nitrous oxide and CFCs in China have been identified, and the emission trends has been estimated. Besides fossil fuel combustion, human respiration and biomass burning are important sources. Some feasible abatement measures on energy conservation, afforestation and biomass recycling have been discussed.     

A high-definition spatially explicit modelling approach for national greenhouse gas emissions from industrial processes: reducing the errors and uncertainties in global emission modelling

Mitigation and Adaptation Strategies for Global Change - Industrial processes cause significant emissions of greenhouse gases (GHGs) to the atmosphere and, therefore, have high mitigation and...     

我国饮食结构变化对农业温室气体排放的影响

从食物消费端入手,研究饮食结构变化对农业温室气体排放的影响.研究显示我国食物消费呈现出动物性食物替代粮食消费的趋势,动物性食物的温室气体排放系数是植物性食物的7倍以上.1990~2010年人均食物消费相关的温室气体排放增长了39%,肉类消费已成为食物消费中最大的温室气体排放来源,且还将持续增长.当我国人均收入达到2010年美国水平时,世界平均肉类消费水平、高肉类消费水平、低肉类消费水平和营养均衡消费水平四种情景下,人均肉类消费的温室气体排放将比2010年分别增长47.8%、119.9%、4.8%、-29.6%.我国食物消费应当提倡在保障均衡营养摄入的前提下,适当减少肉类消费,达到温室气体减排、资源节约、污染减排的协同效应.