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1.
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.  相似文献   

2.
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.  相似文献   

3.
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.  相似文献   

4.
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.  相似文献   

5.
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.  相似文献   

6.
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.  相似文献   

7.
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.  相似文献   

8.
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。  相似文献   

9.
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.  相似文献   

10.
Carbon footprint: current methods of estimation   总被引:5,自引:0,他引:5  
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.  相似文献   

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