Managing the nitrogen cycle to reduce greenhouse gas emissions from crop production and biofuel expansion

Public policies are promoting biofuels as an alternative to fossil fuel consumption in order to mitigate greenhouse gas (GHG) emissions. However, the mitigation benefit can be at least partially compromised by emissions occurring during feedstock production. One of the key sources of GHG emissions from biofuel feedstock production, as well as conventional crops, is soil nitrous oxide (N₂O), which is largely driven by nitrogen (N) management. Our objective was to determine how much GHG emissions could be reduced by encouraging alternative N management practices through application of nitrification inhibitors and a cap on N fertilization. We used the US Renewable Fuel Standards (RFS2) as the basis for a case study to evaluate technical and economic drivers influencing the N management mitigation strategies. We estimated soil N₂O emissions using the DayCent ecosystem model and applied the US Forest and Agricultural Sector Optimization Model with Greenhouse Gases (FASOMGHG) to project GHG emissions for the agricultural sector, as influenced by biofuel scenarios and N management options. Relative to the current RSF2 policy with no N management interventions, results show decreases in N₂O emissions ranging from 3 to 4 % for the agricultural sector (5.5–6.5 million metric tonnes CO₂?eq.?year^?1; 1 million metric tonnes is equivalent to a Teragram) in response to a cap that reduces N fertilizer application and even larger reductions with application of nitrification inhibitors, ranging from 9 to 10 % (15.5–16.6 million tonnes CO₂?eq.?year^?1). The results demonstrate that climate and energy policies promoting biofuel production could consider options to manage the N cycle with alternative fertilization practices for the agricultural sector and likely enhance the mitigation of GHG emissions associated with biofuels.     

Forgotten carbon: indirect CO2 in greenhouse gas emission inventories

National governments that are Parties to the United Nations Framework Convention on Climate Change (UNFCCC) are required to submit greenhouse gas (GHG) inventories accounting for the emissions and removals occurring within their geographic territories. The Intergovernmental Panel on Climate Change (IPCC) provides inventory methodology guidance to the Parties of the UNFCCC. This methodology guidance, and national inventories based on it, omits carbon dioxide (CO₂) from the atmospheric oxidation of methane, carbon monoxide, and non-methane volatile organic compounds emissions that result from several source categories. The inclusion of this category of “indirect” CO₂ in GHG inventories increases global anthropogenic emissions (excluding land use and forestry) between 0.5 and 0.7%. However, the effect of inclusion on aggregate UNFCCC Annex I Party GHG emissions would be to reduce the growth of total emissions, from 1990 to 2004, by 0.2% points. The effect on the GHG emissions and emission trends of individual countries varies. The paper includes a methodology for calculating these emissions and discusses uncertainties. Indirect CO₂ is equally relevant for GHG inventories at other scales, such as global, regional, organizational, and facility. Similarly, project-based methodologies, such as those used under the Clean Development Mechanism, may need revising to account for indirect CO₂.     

Full accounting of the greenhouse gas budget in the forestry of China

Forest management to increase carbon (C) sinks and reduce C emissions and forest resource utilization to store C and substitute for fossil fuel have been identified as attractive mitigation strategies. However, the greenhouse gas (GHG) budget of carbon pools and sinks in China are not fully understood, and the forestry net C sink must be determined. The objective of this study was to analyze potential forest management mitigation strategies by evaluating the GHG emissions from forest management and resource utilization and clarify the forestry net C sink, and its driving factors in China via constructing C accounting and net mitigation of forestry methodology. The results indicated that the GHG emissions under forest management and resource utilization were 17.7 Tg Ce/year and offset 8.5% of biomass and products C sink and GHG mitigation from substitution effects from 2000 to 2014, resulting in a net C sink of 189.8 Tg Ce/year. Forest resource utilization contributed the most to the national forestry GHG emissions, whereas the main driving factor underlying regional GHG emissions varied. Afforestation dominated the GHG emissions in the southwest and northwest, whereas resource utilization contributed the most to GHG emissions in the north, northeast, east, and south. Furthermore, decreased wood production, improved product use efficiency, and forests developed for bioenergy represented important mitigation strategies and should be targeted implementation in different regions. Our study provided a forestry C accounting in China and indicated that simulations of these activities could provide novel insights for mitigation strategies and have implications for forest management in other countries.     

Accounting for time in Mitigating Global Warming through land-use change and forestry

Many proposed activities formitigating global warming in the land-use change and forestry(LUCF) sector differ from measures to avoid fossilfuel emissions because carbon (C) may be held out ofthe atmosphere only temporarily. In addition, thetiming of the effects is usually different. Many LUCFactivities alter C fluxes to and from the atmosphereseveral decades into the future, whereas fossil fuelemissions avoidance has immediate effects. Non-CO₂ greenhouse gases (GHGs), which are animportant part of emissions from deforestation inlow-latitude regions, also pose complications forcomparisons between fossil fuel and LUCF, since themechanism generally used to compare these gases(global warming potentials) assumes simultaneousemissions. A common numeraire is needed to expressglobal warming mitigation benefits of different kindsof projects, such as fossil fuel emissions reduction,C sequestration in forest plantations, avoideddeforestation by creating protected areas and throughpolicy changes to slow rates of land-use changes suchas clearing. Megagram (Mg)-year (also known as`ton-year') accounting provides a mechanism forexpressing the benefits of activities such as these ona consistent basis. One can calculate the atmosphericload of each GHG that will be present in each year,expressed as C in the form of CO₂ and itsinstantaneous impact equivalent contributed by othergases. The atmospheric load of CO₂-equivalent Cpresent over a time horizon is a possible indicator ofthe climatic impact of the emission that placed thisload in the atmosphere. Conversely, this index alsoprovides a measure of the benefit of notproducing the emission. One accounting methodcompares sequestered CO₂ in trees with theCO₂ that would be in the atmosphere had thesequestration project not been undertaken, whileanother method (used in this paper) compares theatmospheric load of C (or equivalent in non-CO₂GHGs) in both project and no-project scenarios.Time preference, expressed by means of a discount rateon C, can be applied to Mg-year equivalencecalculations to allow societal decisions regarding thevalue of time to be integrated into the system forcalculating global warming impacts and benefits. Giving a high value to time, either by raising thediscount rate or by shortening the time horizon,increases the value attributed to temporarysequestration (such as many forest plantationprojects). A high value for time also favorsmitigation measures that have rapid effects (such asslowing deforestation rates) as compared to measuresthat only affect emissions years in the future (suchas creating protected areas in countries with largeareas of remaining forest). Decisions on temporalissues will guide mitigation efforts towards optionsthat may or may not be desirable on the basis ofsocial and environmental effects in spheres other thanglobal warming. How sustainable development criteriaare incorporated into the approval and creditingsystems for activities under the Kyoto Protocol willdetermine the overall environmental and social impactsof pending decisions on temporal issues.     

Wood materials used as a means to reduce greenhouse gases (GHGs): An examination of wooden utility poles

There has been growing concern over the build-up of greenhouse gase(GHGs) in the atmosphere, particularly carbon dioxide (CO₂), as acause of global warming. The IPCC Third Assessment Report (2001) suggests two ways in which the choice of materials could berelevant. First, some materials, particularly wood, have the advantage thatthey continue to hold carbon (C)in their cells even after being convertedto products. The implications of this feature are well researched. Second,an area that is not well researched relates to the different energyrequirements for producing similar products made with different materials. Using the findings of recent research, this paper compares the energyrequirements and C emissions of manufacturing a product using wood withthat of other materials. The case study of utility poles demonstrates thepositive C and global warming consequences of the lower energyrequirements of wood in the U.S., compared to other materials such assteel or concrete. It demonstrates that GHG emissions associated withutility poles are a small but significant percent of total US annual emissions. Wood utility poles are associated with GHG emission reductions of 163Terragrams (Tg) of CO₂ when compared with steel poles. This isabout 2.8 percent of US annual GHG emissions, which are estimated atabout 5.28 Petragrams (Pg) of CO₂ annually. Thus, the use ofwooden utility poles rather than steel results in a small but significantreduction in total US emissions.     

Greenhouse gas emissions along a peat swamp forest degradation gradient in the Peruvian Amazon: soil moisture and palm roots effects

Tropical peatlands in the Peruvian Amazon exhibit high densities of Mauritia flexuosa palms, which are often cut instead of being climbed for collecting their fruits. This is an important type of forest degradation in the region that could lead to changes in the structure and composition of the forest, quality and quantity of inputs to the peat, soil properties, and greenhouse gas (GHG) fluxes. We studied peat and litterfall characteristics along a forest degradation gradient that included an intact site, a moderately degraded site, and a heavily degraded site. To understand underlying factors driving GHG emissions, we examined the response of in vitro soil microbial GHG emissions to soil moisture variation, and we tested the potential of pneumatophores to conduct GHGs in situ. The soil phosphorus and carbon content and carbon-to-nitrogen ratio as well as the litterfall nitrogen content and carbon-to-nitrogen ratio were significantly affected by forest degradation. Soils from the degraded sites consistently produced more carbon dioxide (CO₂) than soils from the intact site during in vitro incubations. The response of CO₂ production to changes in water-filled pore space (WFPS) followed a cubic polynomial relationship with maxima at 60–70% at the three sites. Methane (CH₄) was produced in limited amounts and exclusively under water-saturated conditions. There was no significant response of nitrous oxide (N₂O) emissions to WFPS variation. Lastly, the density of pneumatophore decreased drastically as the result of forest degradation and was positively correlated to in situ CH₄ emissions. We conclude that recurrent M. flexuosa harvesting could result in a significant increase of in situ CO₂ fluxes and a simultaneous decrease in CH₄ emissions via pneumatophores. These changes might alter long-term carbon and GHG balances of the peat, and the role of these ecosystems for climate change mitigation, which stresses the need for their protection.

     

Impacts of international trade on carbon flows of forest industry in Finland

Finland is a forested country with a large export oriented forest industry. In addition to domestic forest extraction, roundwood is imported, thus displacing the environmental impacts of harvests. In this paper, we analyse the international carbon flows of forest industries in Finland from a consumption-based perspective. Quantitative analyses are available on trade embedded emissions of CO₂ from fossil fuel combustion, and here we address in a similar way the impact of trade on the carbon budget of the forest products sector in Finland. Carbon flows through the forest industry system increased substantially between 1991 and 2005. We show that the annual carbon balance related to forests and forest industry system in Finland functioned as a sink in 1991, whereas in 2005 the system was a sink on a national level, but not on a global level. Through calculating the carbon content in traded forest industry products and emissions embodied in forest industry activities, we further show that the direct impacts of the forest industry in Finland are only a minor fraction of the total CO₂ emissions related to Finnish production. Nearly all of the emissions were caused due to production of exports. Yet, direct carbon dioxide emissions of the industrial production are reported to Finland in the production based inventories.     

Nitrogen fertilizer management for nitrous oxide (N<Subscript>2</Subscript>O) mitigation in intensive corn (Maize) production: an emissions reduction protocol for US Midwest agriculture

Nitrous oxide (N₂O) is a major greenhouse gas (GHG) product of intensive agriculture. Fertilizer nitrogen (N) rate is the best single predictor of N₂O emissions in row-crop agriculture in the US Midwest. We use this relationship to propose a transparent, scientifically robust protocol that can be utilized by developers of agricultural offset projects for generating fungible GHG emission reduction credits for the emerging US carbon cap and trade market. By coupling predicted N₂O flux with the recently developed maximum return to N (MRTN) approach for determining economically profitable N input rates for optimized crop yield, we provide the basis for incentivizing N₂O reductions without affecting yields. The protocol, if widely adopted, could reduce N₂O from fertilized row-crop agriculture by more than 50%. Although other management and environmental factors can influence N₂O emissions, fertilizer N rate can be viewed as a single unambiguous proxy—a transparent, tangible, and readily manageable commodity. Our protocol addresses baseline establishment, additionality, permanence, variability, and leakage, and provides for producers and other stakeholders the economic and environmental incentives necessary for adoption of agricultural N₂O reduction offset projects.     

Quantifying and managing regional greenhouse gas emissions：Waste sector of Daejeon, Korea

A credible accounting of national and regional inventories for the greenhouse gas （GHG） reduction has emerged as one of the most significant current discussions. This article assessed the regional GHG emissions by three categories of the waste sector in Daejeon Metropolitan City （DMC）, Korea, examined the potential for DMC to reduce GHG emission, and discussed the methodology modified from Intergovernmental Panel on Climate Change and Korea national guidelines. During the last five years, DMC＇s overall GHG emissions were 239 thousand tons C02 eq./year from eleven public environmental infrastructure facilities, with a population of 1.52 million. Of the three categories, solid waste treatment/disposal contributes 68%, whilst wastewater treatment and others contribute 22% and 10% respectively. Among GHG unit emissions per ton of waste treatment, the biggest contributor was waste incineration of 694 kg CO2 eq./ton, followed by waste disposal of 483 kg CO2 eq./ton, biological treatment of solid waste of 209 kg CO2 eq./ton, wastewater treatment of 0.241 kg CO2 eq./m3, and public water supplies of 0.067 kg CO2 eq./m3. Furthermore, it is suggested that the potential in reducing GHG emissions from landfill process can be as high as 47.5% by increasing landfill gas recovery up to 50%. Therefore, it is apparent that reduction strategies for the main contributors of GHG emissions should take precedence over minor contributors and lead to the best practice for managing GHGs abatement.     

Greenhouse gas mitigation and offset options for suckler cow farms: an economic comparison for the Swiss case

We assessed the economic suitability of 4 greenhouse gas (GHG) mitigation options and one GHG offset option for an improvement of the GHG balance of a representative Swiss suckler cow farm housing 35 Livestock units and cultivating 25 ha grassland. GHG emissions per kilogram meat in the economic optimum differ between the production systems and range from 18 to 21.9 kg CO₂-eq./kg meat. Only GHG offset by agroforestry systems showed the potential to significantly reduce these emissions. Depending on the production system agroforestry systems could reduce net GHG emissions by 66% to 7.3 kg CO₂-eq./kg meat in the most intensive system and by 100% in the most extensive system. In this calculation a carbon sequestration rate of 8 t CO₂/ha/year was assumed. The potential of a combination of the addition of lipids to the diet, a cover of the slurry tank and the application of nitrification inhibitors only had the potential to reduce GHG emissions by 12% thereby marginal abatement costs are increasing much faster than for agroforestry systems. A reduction of the GHG emissions to 7.5 kg CO₂-eq./kg meat—possible with agroforestry only—raised costs between 0.03 CHF/kg meat and 0.38 CHF/kg meat depending on the production system and the state of the system before the reduction. If GHG emissions were reduced maximally average costs ranged between 0.37 CHF/kg meat, if agroforestry had the potential to reduce net GHG emissions to 0 kg CO₂-eq., to 1.17 CHF/kg meat if also other options had to be applied.     

Emission inventory on company level: lessons from Russia

Developing a transparent,accurate greenhouse gas (GHG) emissionsinventory is the first step toward buildingan effective GHG management system. Todate, GHG inventories have been conductedprimarily at national levels. Theinternationally accepted inventorymethodology developed by theIntergovernmental Panel on Climate Change(IPCC) is oriented to countrywideinventories. The electricity company RAOUESR is the largest single corporateemitter of GHG in the Russian Federation. The company is responsible for about 1/3 ofRussia's CO₂ emissions; RAO's fossil fuelemissions are comparable to the fossil fuelemissions of the United Kingdom. The GHGinventory prepared by RAO is the first suchcorporate emissions inventory undertaken ina non-OECD country. In this article wepresent a detailed independent examinationof the methodology RAO applied for theinventory. We identify the most importantsources of uncertainty and we estimate theuncertainty. The main conclusion of theindependent review is that the methodologyutilized by RAO and the informationsupporting the methodology are reliable andpresent a reasonably accurate company-widepicture of RAO's CO₂ emissions. The shareof other greenhouse gases is negligiblysmall and we did not focus on this fractionof RAO's GHG emissions. As a next step, RAOmay wish to conduct more precisefacility-by-facility inventories in orderto create a robust GHG emission managementsystem.     

基于投入产出法的北京能源消耗温室气体排放清单分析

城市是一个巨大能源物资消耗体和温室气体排放体,相关研究受到广泛关注.本文以2007年为例基于投入产出法研究北京市能源消耗的温室气体排放量,计算得出CH4和N2O这两种常规温室气体排放量.结果表明,北京市2007年能源消耗温室气体排放量为3531.72万tCO2当量,其中CO2排放量为3514.40万t,CH4排放量为1734.32t,N2O排放量为435.83t.北京市工业部门仍然是主要的温室气体排放部门,其排放的温室气体占CO2总量的98.96%,CH4总量的88.48%和N2O总量的98.99%.不同最终使用部门中,政府部门消费产生的温室气体排放量超过总量的15%,高于城镇消费和农村消费之和;调出和出口部门的碳排放量超过总量的40%,所占比例最大.贸易中,隐含在调出和出口部门中温室气体排放量是隐含在调入和进口部门的十几倍.北京市不同行业的温室气体排放强度略优于全国水平.降低北京市温室气体排放量可从进一步优化产业结构,发挥科技减排的作用,提高不同产业的能源利用率等方面采取措施.     

A little REDD model to quickly compare possible baseline and policy scenarios for reducing emissions from deforestation and forest degradation

A simple model allows rapid comparison of typical baseline and policy scenarios which might be considered under international programs to avoid CO₂ emissions caused by forest clearing, such as REDD (Reducing Emissions from Deforestation and Forest Degradation). These tests of REDD policy scenarios can also include CO₂ stored in forest products. The value of avoided emissions can also be determined if expected carbon prices, constant or varying, are included. The paper discusses simple illustrative example comparisons as well as possible feedback effects within larger scale setting of CO₂ offset availability, CO₂ price and emissions reductions.     

Disaggregated greenhouse gas emission inventories from agriculture via a coupled economic-ecosystem model

Estimates of regional greenhouse gas emissions from agricultural systems are needed to evaluate possible mitigation strategies with respect to environmental effectiveness and economic feasibility. Therefore, in this study, we used the GIS-coupled economic-ecosystem model EFEM–DNDC to assess disaggregated regional greenhouse gas (GHG) emissions from typical livestock and crop production systems in the federal state of Baden-Württemberg, Southwest Germany. EFEM is an economic farm production model based on linear programming of typical agricultural production systems and simulates all relevant farm management processes and GHG emissions. DNDC is a process-oriented ecosystem model that describes the complete biogeochemical C and N cycle of agricultural soils, including all trace gases.Direct soil emissions were mainly related to N₂O, whereas CH₄ uptake had marginal influence (net soil C uptake or release was not considered). The simulated N₂O emissions appeared to be highly correlated to N fertilizer application (R² = 0.79). The emission factor for Baden-Württemberg was 0.97% of the applied N after excluding background emissions.Analysis of the production systems showed that total GHG emissions from crop based production systems were considerably lower (2.6–3.4 Mg CO₂ eq ha⁻¹) than from livestock based systems (5.2–5.3 Mg CO₂ eq ha⁻¹). Average production system GHG emissions for Baden-Württemberg were 4.5 Mg CO₂ eq ha⁻¹. Of the total 38% were derived from N₂O (direct and indirect soil emissions, and manure storage), 40% were from CH₄ (enteric fermentation and manure storage), and 22% were from CO₂ (mainly fertilizer production, gasoline, heating, and additional feed). The stocking rate was highly correlated (R² = 0.85) to the total production system GHG emissions and appears to be a useful indicator of regional emission levels.     

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.     

CO2 emission reduction for Japanese petrochemicals

Energy efficiency in the Japanese industry is one of the highest in the world. As a consequence, reduction of CO₂ emissions is considered to be difficult and costly. However little attention has been paid as of yet to changes related to so-called non-energy use of fossil fuels. The analysis in this paper suggests that a large number of options exist for emission reduction in the Japanese petrochemical industry. This includes the introduction of biomass feedstocks, the introduction of new catalytic production processes, and changes in waste handling. The use of bioplastics and the use of CO₂ feedstocks seem costly options for GHG emission reduction that should not be applied on the short term. Japanese GHG emissions can be reduced by 7.7% if the optimal set of emission mitigation options is applied. About 60 Mt emission reduction (4.9%) can be achieved by changes on the supply side, another 35 Mt emission reduction (2.8%) can be achieved by changes in waste management. While changes in waste management can be implemented before 2010, biomass introduction on the supply side will probably require a longer lead-time. About half of the emission reduction is cost–effective, but will require further technology development. The other half can be achieved at a cost level of 10,000 yen/t CO₂ (80 US$/t CO₂). The latter part is based on proven technology that is currently not cost–effective.     

Marginal costs of abating greenhouse gases in the global ruminant livestock sector

Livestock [inclusive of ruminant species, namely cattle (Bos Taurus and Bos indicus), sheep (Ovis aries), goats (Capra hircus), and buffaloes (Bubalus bubalis), and non-ruminant species, namely pigs (Sus scrofa domesticus) and chickens (Gallus domesticus)] are both affected by climate change and contribute as much as 14.5 % of global anthropogenic greenhouse gas (GHG) emissions, most of which is from ruminant animals (Gerber et al. 2013). This study aims to estimate the marginal costs of reducing GHG emissions for a selection of practices in the ruminant livestock sector (inclusive of the major ruminant species—cattle, sheep, and goats) globally. It advances on previous assessments by calculating marginal costs rather than commonly reported average costs of abatement and can thus provide insights about abatement responses at different carbon prices. We selected the most promising abatement options based on their effectiveness and feasibility. Improved grazing management and legume sowing are the main practices assessed in grazing systems. The urea (CO(NH₂)₂) treatment of crop straws is the main practice applied in mixed crop–livestock systems, while the feeding of dietary lipids and nitrates are confined to more intensive production systems. These practices were estimated to reduce emissions by up to 379 metric megatons of carbon dioxide (CO₂) equivalent emissions per year (MtCO₂-eq yr^?1). Two thirds of this reduction was estimated to be possible at a carbon price of 20 US dollars per metric ton of CO₂ equivalent emissions ($20 tCO₂-eq^?1). This study also provides strategic guidance as to where abatement efforts could be most cost effectively targeted. For example, improved grazing management was particularly cost effective in Latin America and Sub-Saharan Africa, while legume sowing appeared to work best in Western Europe and Latin America.     

The role of CH4 and N2O emission reductions in the cost-effective control of the greenhouse gas emissions from Finland

The reduction of carbon dioxide (CO₂) emissions may be quite expensive and it is necessary to consider reduction measures for other anthropogenic greenhouse gases, such as methane (CH₄) and nitrous oxide (N₂O) as well. Their contribution to the total GHG emission from Finland is about 15–20%. In Finland most of the CH₄ emissions are due to waste management, agriculture and burning processes. N₂O emissions originate from burning processes, agriculture, industry and atmospheric deposition of nitrogen. The cost-effective reduction of the Finnish GHG emissions has been studied with the EFOM-ENV model, which is a quasi-dynamic linear energy system optimisation model. The target function to be minimised is the total discounted cost for the modelled system. In this study the model has been expanded to cover all well-known anthropogenic CO₂, CH₄ and N₂O sources and reduction measures. The results indicate it is economic to reduce the emissions of CO₂, CH₄ and N₂O in Finland. It is profitable to exploit the economic reduction potential of CH₄ and N₂O, because then the abatement of CO₂ emissions does not need to be as extensive as when the reduction is aimed only at CO₂ emissions. The inclusion of CH₄ and N₂O decreases the annual reduction costs about 20% in the year 2010.     

城市废弃物处理温室气体排放研究:以厦门市为例

城市废弃物处理是城市人为活动产生温室气体的来源之一.参考IPCC国家温室气体清单指南2006推荐的方法建立了厦门市废弃物处理的温室气体排放计算模型,对厦门市2005～2010年废弃物处理的温室气体排放情况进行了估算,包括固体废弃物填埋、焚烧以及污水处理等过程.结果表明,2005年温室气体总排放量折合二氧化碳当量(CO2e)为406.3 kt,2010年温室气体总排放量(以CO2e计)达到704.6 kt,随着废水处理工艺的提高和城市生活垃圾量的迅速增长,主要排放源由废水处理转变为固体废弃物填埋.2005年填埋产生的温室气体排放占固体废弃物处理排放量的90%左右,2010年所占比例下降到75%.厦门市废水处理温室气体排放量2007年最高,以CO2e计达到325.5 kt,化学原料及化学品制造业从2005～2010年一直是厦门市CH4排放量最高的产业,占工业废水处理CH4排放总量的55%以上.     

Greenhouse gas emission factors for land use and land-use change in Southeast Asian peatlands

Tropical peat swamp forests, which are predominantly located in Southeast Asia (SEA) and play a prominent role as a global carbon store, are being intensively degraded and converted to agricultural lands and tree plantations. For national inventories, updated estimates of peat emissions of greenhouse gases (GHG) from land use (LU) and land-use change in the tropics are required. In this context, we reviewed the scientific literature and calculated emission factors of peat net emissions of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) in seven representative LU categories for SEA i.e. intact peat swamp forest, degraded forest (logged, drained and affected by fire), mixed croplands and shrublands, rice fields, oil palm, Acacia crassicarpa and sago palm plantations. Peat net CO₂ uptake from or emissions to the atmosphere were assessed using a mass balance approach. The balance included main peat C inputs through litterfall and root mortality and outputs via organic matter mineralization and dissolved organic carbon. Peat net CO₂ loss rate from degraded forest, croplands and shrublands, rice fields, oil palm, A. crassicarpa and sago palm plantations amounted to 19.4?±?9.4, 41.0?±?6.7, 25.6?±?11.5, 29.9?±?10.6, 71.8?±?12.7 and 5.2?±?5.1 Mg CO₂ ha^?1 y^?1, respectively. Total peat GHG losses amounted to 20.9?±?9.4, 43.8?±?6.8, 36.1?±?12.9, 30.4?±?10.6, 72?±?12.8 and 8.6?±?5.3 Mg CO₂-equivalent ha^?1 y^?1 in the same LU categories, respectively. A single land-clearing fire would result in additional emissions of 493.6?±?156.0 Mg CO₂-equivalent ha^?1.