The rumen and hindgut as source of ruminant methanogenesis

The advantage of ruminants is their ability to convert fibrous biomass to high quality protein for human nutrition purposes. Rumen fermentation, however, is always associated with the formation of methane — a very effective greenhouse gas. Hindgut fermentation differs from rumen fermentation by a substantially lower methane production and the presence of reductive acetogenesis or dissimilatory sulfate reduction. Sulfate reduction and methanogenesis seem to be mutually exclusive, while methanogenesis and reductive acetogenesis may occur simultaneously in the hindgut. Although acetogenic bacteria have been isolated from the bovine rumen, methanogenesis prevails in the forestomachs. The substitution of acetate for methane as a hydrogen sink in the rumen should increase energy yield for the animal and decrease methane emissions into the environment. Differences in the major hydrogen sinks in both microbial ecosystems are discussed and mainly related to differences in substrate availability and to the absence of protozoa in the hindgut.     

Reporting emissions of greenhouse gases in Canada

Non-carbon dioxide greenhouse gases are considered in Canada's National Report on Climate Change: Actions to Meet Commitments Under the United Nations Framework Convention on Climate Change. By including all major greenhouse gases and their anthropogenic sources and sinks using best available science, the Report provides a practical illustration of the comprehensive approach policy to implementing the Convention's requirements. In addition to carbon dioxide emissions from fossil fuel combustion, the Report includes information on other sources and sinks for carbon dioxide, and for methane and nitrous oxide. Other gases considered include polyflourocarbons, hydroflourocarbons, and the primary tropospheric ozone precursors, nitrogen oxides and volatile organic compounds. Current Global Warming Potential indices are used to compare and integrate the best estimates of climate change impacts of the major greenhouse gases. The presentation of emission data is intended to be transparent and comparable. The relative quality of the data for various gases and sources is indicated. The existence of environmental, economic, and other benefits to limiting emissions of all greenhouse gases, in addition to carbon dioxide, should be recognized. Continuing assessments and actions on non-carbon dioxide greenhouse gas emissions, both nationally and internationally, are suggested.     

Methane emission from naturally ventilated livestock buildings can be determined from gas concentration measurements

Determination of emission of contaminant gases as ammonia, methane, or laughing gas from natural ventilated livestock buildings with large opening is a challenge due to the large variations in gas concentration and air velocity in the openings. The close relation between calculated animal heat production and the carbon dioxide production from the animals have in several cases been utilized for estimation of the ventilation air exchange rate for the estimation of ammonia and greenhouse gas emissions. Using this method, the problem of the complicated air velocity and concentration distribution in the openings is avoided; however, there are still some important issues remained unanswered: (1) the precision of the estimations, (2) the requirement for the length of measuring periods, and (3) the required measuring point number and location. The purpose of this work was to investigate how estimated average gas emission and the precision of the estimation are influenced by different calculation procedures, measuring period length, measure point locations, measure point numbers, and criteria for excluding measuring data. The analyses were based on existing data from a 6-day measuring period in a naturally ventilated, 150 milking cow building. The results showed that the methane emission can be determined with much higher precision than ammonia or laughing gas emissions, and, for methane, relatively precise estimations can be based on measure periods as short as 3 h. This result makes it feasible to investigate the influence of feed composition on methane emission in a relative large number of operating cattle buildings and consequently it can support a development towards reduced greenhouse gas emission from cattle production.     

Methane Clathrate Outgassing and Anoxic Expansion in Southeast Asian Deeps Due to Global Warming

Numerous marine areas in SouthEast Asia are cold and deep enough to develop stable gas hydrates of greenhouse gases methane and carbon dioxide and of reducing agents such as hydrogen sulfide. In addition many of these deeps have low oxygen values below sill depths. Warming of such waters could:(1) destabilize existing gas hydrates (clathrates) flashing them into gas and(2) reduce the oxygen capacity of waters below the sill depth.Outgassing could increase the buoyancy, producing upwelling of potentially noxious deep waters into the photic zone and even to the surface where the greenhouse gases would be added to the atmosphere. We plotted the depth (pressure) and temperatures of SouthEast Asian deep basins on a clathrate phase diagram to determine their suceptibility to outgassing and upwelling using a creditable global warming scenario. In general, most of the Indonesian basins are too cold or too deep for any pre-existing clathrates to be destabilized by perceived global warming. However, the Sulu Basin of the Philippines and the Halmahera Basin in Indonesian waters have sill depths in the pycnocline shoal enough and temperatures warm enough potentially to support outgassing and upwelling of basin waters, if water temperatures were raised. The presence of gas hydrates has not been demonstrated in these deeps. Although generally associated with high latitudes, clathrates have been identified in tropical waters off Central America. Accordingly, the proximity of the SouthEast Asian deeps to land and their low oxygen content suggest that tropical plant debris could accumulate and provide sufficient organic matter to generate methane and/or hydrogen sulfide clathrates. Local fisheries initially could be affected adversely by upwelling of anoxic or near anoxic waters into the photic zone. However, in the long term, the anoxic effects would dissipate and the nutrients brought up by the upwelling could increase primary productivity. A major adverse affect would be the introduction of methane into the atmosphere, as that gas has about 20 times the warming potential of carbon dioxide.     

The Kyoto Protocol and non-CO2 Greenhouse Gases and Carbon Sinks

Many trace constituents other than carbon dioxide affect the radiative budget of the atmosphere. The existing international agreement to limit greenhouse gases, the Kyoto Protocol, includes carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF₆) and credit for some carbon sinks. We investigate technological options for reducing emissions of these gases and the economic implications of including other greenhouse gases and sinks in the climate change control policy. We conduct an integreated assessment of costs using the MIT Emissions Prediction and Policy Analysis (EPPA) model combined with estimates of abatement costs for non-CO₂ greenhouse gases and sinks. We find that failure to take advantage of the other gas and sink flexibility would nearly double aggregate Annex B costs. Including all the GHGs and sinks is actually cheaper than if only CO₂ had been included in the Protocol and their inclusion achieves greater overall abatement. There remains considerable uncertainty in these estimates, the magnitude of the savings depends heavily on reference projections of emissions, for example, but these uncertainties do not change the overall conclusion that non-CO₂ GHGs are an important part of a climate control policy.     

Greenhouse gas emissions from forestry,land-use changes,and agriculture in Tanzania

The purpose of the study was to identify and quantify anthropogenic sources and sinks of greenhouse gases from forestry, land-use changes and agriculture in Tanzania. The 1990 inventory revealed that, in the land-use sector, methane (CH₄) and carbon dioxide (CO₂) are the primary gases emitted. Enteric fermentation in livestock production systems is the largest source of CH₄. Although deforestation results in greenhouse gas emissions, the managed forests of Tanzania are a major CO₂ sink.     

Scientific aspects of the framework convention on climate change and national greenhouse gas inventories

Though the principles of the Earth's greenhouse effect have been known for well over a century, it is only recently that advances in climate research have indicated that significant and possibly costly climate change, due to growing emissions of greenhouse gases and their precursors by human activity, is a real possibility. Current estimates of the global human-related emissions of carbon dioxide, methane and nitrous oxide are presented, though many sources remain poorly known or understood. The compilation of national greenhouse inventories as required by the United Nations Framework Convention on Climate Change is likely in the longer term to help improve such global estimates, as long as comparable methodologies are used. The development of the IPCC Guidelines for National Greenhouse Gas Inventories is described, emphasizing the strategies employed to gain wide international participation.     

Assessing the impact of environmental regulation on pollution abatement and collaborative emissions reduction: Micro-evidence from Chinese industrial enterprises

Given the rapid industrialization and urbanization of China, environmental problems have gradually become major constraints that hinder its sustainable economic development. Moreover, China's pollution abatement and reduction of greenhouse gas emissions have been severely affected by pressures coming from domestic environmental appeals and international environmental diplomacy. By using integrated data from the Chinese Industrial Enterprise and the Chinese Enterprise Environmental Survey and Reporting databases, this study constructs comprehensive indicators of pollutant discharge intensity and carbon emissions index at the enterprise level and uses the panel fixed effect model, Kaya identity, and mediation effect model to assess the effects of environmental regulations on pollution abatement and collaborative emissions reduction from the micro-perspective. Results show that these regulations can abate the pollution emissions of Chinese industrial enterprises and verify the effectiveness of environmental policies. These regulations can also efficiently reduce the carbon dioxide emissions of enterprises through pollution abatement. In other words, environmental regulations facilitate a collaborative emissions reduction of pollutant and greenhouse gas emissions from enterprises. Such collaborative emissions reduction effect is also influenced by the energy structure and consumption of enterprises. This paper presents empirical evidence and policy basis for further improving China's environmental regulation policy system and achieving coordinated progress in China's economic development and environmental governance.     

Biotic landfill cover treatments for mitigating methane emissions

Landfill methane (CH₄) emissions have been cited as one ofthe anthropogenic gas releases that can and should be controlledto reduce global climate change. This article reviews recent research that identifies ways to enhance microbial consumptionof the gas in the aerobic portion of a landfill cover. Use of these methods can augment CH₄ emission reductions achievedby gas collection or provide a sole means to consume CH₄ atsmall landfills that do not have active gas collection systems.Field studies indicate that high levels of CH₄ removal can be achieved by optimizing natural soil microbial processes. Further, during biotic conversion, not all of the CH₄ carbonis converted to carbon dioxide (CO₂) gas and released to theatmosphere; some of it will be sequestered in microbial biomass.Because biotic covers can employ residuals from other municipalprocesses, financial benefits can also accrue from avoided costsfor residuals disposal.     

Resource recovery potential from secondary components of segregated municipal solid wastes

Fermentable components of municipal solid wastes (MSW) such as fruit and vegetable wastes (FVW), leaf litter, paddy straw, cane bagasse, cane trash and paper are generated in large quantities at various pockets of the city. These form potential feedstocks for decentralized biogas plants to be operated in the vicinity. We characterized the fermentation potential of six of the above MSW fractions for their suitability to be converted to biogas and anaerobic compost using the solid-state stratified bed (SSB) process in a laboratory study. FVW and leaf litter (paper mulberry leaves) decomposed almost completely while paddy straw, sugarcane trash, sugarcane bagasse and photocopying paper decomposed to a lower extent. In the SSB process between 50–60% of the biological methane potential (BMP) could be realized. Observations revealed that the SSB process needs to be adapted differently for each of the feedstocks to obtain a higher gas recovery. Bagasse produced the largest fraction of anaerobic compost (fermentation residue) and has the potential for reuse in many ways.     

基于区域环境空气质量和碳排放数据的减污降碳协同效果评估

化石燃料燃烧产生的温室气体与大气污染物具有同根同源性,但具体治理中减污降碳的协同效果尚不明确。以浙江省11个设区市为研究样本,对环境空气质量和二氧化碳(CO₂)排放数据进行分析研究,结果显示：2016—2020年浙江省环境空气质量持续改善,但CO₂排放总量仍处于增长阶段。11个设区城市PM_2.5年均浓度降幅在26%～41%之间,二氧化氮(NO₂)年均浓度下降趋势不明显,大部分城市呈现碳排放增加、NO₂浓度下降的特征,只有杭州和温州两市呈现碳排放总量和NO₂、PM_2.5浓度协同下降的趋势。因子相关性分析结果表明,各设区市呈现NO₂浓度与碳排放相关性较大、协同性强,PM_2.5浓度与碳排放相关性较小的特点。进一步通过减污降碳协同定量评价分析表明,浙江地区在环境空气质量改善和温室气体减排已表现出一定成效,但各设区市因产业结构、环境基础条件、协同程度等不同导致减污降碳综合绩效有明显差异。从源头减排实现...     

The GTP of Methane: Modeling Analysis of Temperature Impacts of Methane and Carbon Dioxide Reductions

The Global Temperature Potential (GTP) has recently been proposed as an alternative to the Global Warming Potential (GWP). Using two different Earth Models of Intermediate Complexity, we show that the solution to the 100-year sustained GTP for methane is significantly larger than the equivalent GWP due to the inclusion of future changes in greenhouse gas concentrations in the reference scenario and different atmospheric chemistry assumptions. This result suggests that methane reductions may be undervalued when using GWPs, but the policy implications depend on how the objectives of greenhouse gas policy are defined.     

Effectiveness of non-CO2 greenhouse gas emission reduction technologies

Non-CO₂ greenhouse gases, such as methane and nitrous oxide, can make a relevant contribution to the enhanced greenhouse effect, and hence emission reduction is desirable. In emission reduction inventories, both the magnitude of the emission reduction as well as the specific emission reduction costs should be determined. The current knowledge of the potential for and costs of reducing these emissions is still limited. Taking this into account, the following results can be obtained. Methane emissions can be considerably reduced from underground coal mining, oil production, natural gas operations, landfilling of waste, and wastewater treatment. Also emissions from enteric fermentation and animal manure can be reduced substantially. The total technical potential for methane emission reduction (given the present activity level) is estimated to be about one third. The economic potential, having net negative emission reduction costs, is estimated to be about half of this value. These reductions can be attained over a period of 10 – 20 years. The technical potential for the reduction of nitrous oxide emissions is currently estimated to be less than 10% Apart from the possibility of implementing existing techniques, there seems to be considerable room for developing techniques for more far-reaching emission reductions both for methane and nitrous oxide.     

生活垃圾填埋场覆盖膜破损及其环境影响

中国的垃圾填埋场目前多采用高密度聚乙烯膜(HDPE)进行覆盖,已建成的填埋场均存在不同程度覆盖膜破损现象。采用填埋气泄漏可视化检测技术对中国东部某大型生活垃圾填埋场开展覆盖膜完整性检测,揭示了覆盖膜破损特征及破损成因,明确了破损点泄漏量,评估了其温室效应影响,梳理了国内外填埋场覆盖层监管相关管理规定和措施。结果表明:尖锐物体应力损伤导致的破损是填埋场覆盖膜破损的主要类型,粗放施工、监管机制不足、维护管理不到位是造成填埋场覆盖膜破损的主要原因。破损点的甲烷泄漏量约为817.2 m³/d,约合每年向大气环境释放温室气体超过4 900 t CO₂-eq。完善填埋场污染控制标准和技术规范、加强填埋场覆盖膜完整性的监管,是控制填埋场温室气体排放和推进固废处置设施碳减排的重要举措。     

中国高精度温室气体排放清单编制研究进展

高精度温室气体排放清单是摸清区域碳排放来源、识别时空演变特征的数据基础,也是政府部门科学制定“减污降碳”策略、实现“双碳”目标的科技支撑。通过调研国内外组织机构、科研团队在高精度排放清单方面的成果,从核算范围、核算方法、时空化方法、评估与校验4个方面介绍了我国温室气体排放清单编制方法的研究进展。针对我国高精度温室气体排放清单研究区域分散、方法与格式不统一的问题,提出我国清单编制要逐步统筹本地化、精细化和动态化的发展建议。     

Carbon footprint: current methods of estimation

Increasing greenhouse gaseous concentration in the atmosphere is perturbing the environment to cause grievous global warming and associated consequences. Following the rule that only measurable is manageable, mensuration of greenhouse gas intensiveness of different products, bodies, and processes is going on worldwide, expressed as their carbon footprints. The methodologies for carbon footprint calculations are still evolving and it is emerging as an important tool for greenhouse gas management. The concept of carbon footprinting has permeated and is being commercialized in all the areas of life and economy, but there is little coherence in definitions and calculations of carbon footprints among the studies. There are disagreements in the selection of gases, and the order of emissions to be covered in footprint calculations. Standards of greenhouse gas accounting are the common resources used in footprint calculations, although there is no mandatory provision of footprint verification. Carbon footprinting is intended to be a tool to guide the relevant emission cuts and verifications, its standardization at international level are therefore necessary. Present review describes the prevailing carbon footprinting methods and raises the related issues.     

新疆农业碳减排管理经验初探

研究了美国国际集团(AIG)注资新疆昌吉玛纳斯等3县开展温室气体减排项目的推进过程.这是在中国成功开展的第一例农业温室气体自愿减排项目,该项目共减排温室气体21×104t CO2当量.主要通过农户沼气推广、沙漠防沙林种植、农业滴灌灌溉等项目,达到温室气体减排、节约能源、防沙造林、改善当地的生态环境、增加农民收入等目的....     

Micro-treatment options for components of organic fraction of MSW in residential areas

There is a growing interest in management of MSW through micro-treatment of organic fraction of municipal solid wastes (OFMSW) in many cities of India. The OFMSW fraction is high (>80%) in many pockets within South Indian cities like Bangalore, Chikkamagalur, etc. and is largely represented by vegetable, fruit, packing and garden wastes. Among these, the last three have shown problems for easy decomposition. Fruit wastes are characterized by a large pectin supported fraction that decomposes quickly to organic acids (becomes pulpy) that eventually slow down anaerobic and aerobic decomposition processes. Paper fraction (newsprint and photocopying paper) as well as paddy straw (packing), bagasse (from cane juice stalls) and tree leaf litter (typical garden waste and street sweepings) are found in reasonably large proportions in MSW. These decompose slowly due to poor nutrients or physical state. We have examined the suitability of these substrates for micro-composting in plastic bins by tracking decomposition pattern and physical changes. It was found that fruit wastes decompose rapidly to produce organic acids and large leachate fraction such that it may need to be mixed with leachate absorbing materials (dry wastes) for good composting. Leaf litter, paddy straw and bagasse decompose to the tune of 90, 68 and 60% VS and are suitable for composting micro-treatment. Paper fractions even when augmented with 10% leaf compost failed to show appreciable decomposition in 50 days. All these feedstocks were found to have good biological methane potential (BMP) and showed promise for conversion to biogas under a mixed feed operation. Suitability of this approach was verified by operating a plug-flow type anaerobic digester where only leaf litter gathered nearby (as street sweepings) was used as feedstock. Here only a third of the BMP was realized at this scale (0.18 m³ biogas/kg VS 0.55 m³/kg in BMP). We conclude that anaerobic digestion in plug-flow like digesters appear a more suitable micro-treatment option (2–10 kg VS/day) because in addition to compost it also produces biogas for domestic use nearby.     

Ground level volume mixing ratio of methane in a tropical coastal city

Urban regions are hotspots of greenhouse gas emissions which include CO₂, CH₄, N₂O, etc. Methane is a strong greenhouse gas which is produced from a number of sources including fossil fuel combustion, municipal waste, and sewage processing, etc. Ground level mixing ratio of methane in the tropical coastal city of Thiruvananthapuram in South India, during calm early morning period was measured. Measurements were done during both winter and summer seasons. Concentrations were significantly higher than global average value. Intra-city variation in ground level mixing ratio was also significant. Ground level methane concentration at Thiruvananthapuram urban area showed maximum value of 3.16 ppmV. Under stable atmospheric conditions in early morning, ground level mixing ratio of methane was 2.79 ppmV in winter and 2.54 ppmV during summer. The spatial distribution of methane concentration shows correlation with urban heat island.     

A Comprehensive Numerical Model Simulating Gas,Heat, and Moisture Transport in Sanitary Landfills and Methane Oxidation in Final Covers

A model to simulate gas, heat, and moisture transport through a sanitary landfill has been developed. The model not only considers the different processes that go on in a landfill but also the oxidation of methane in the final cover. The model was calibrated using published results and field data from a pilot scale landfill in Calgary. The model captures the physics of the different processes quite well. Simulations from the model show that waste permeability had a significant impact on the temperature, pressure distribution, and flux from a landfill. The presence of the final and intermediate covers enhanced the gas storage capacity of the landfill. Biodegradation of the waste was enhanced as the final cover minimized the atmospheric influences. In addition, the composition of landfill gas emitted to the atmosphere was significantly different from the composition of gas generated in landfill due to the presence of covers as some of the methane is oxidized to carbon dioxide. There was no significant benefit of using a final cover of higher depth. The presence and number of intermediate covers had an impact on gas flux and temperature distribution within a landfill.