Air Quality and Climate Change: Hard Choices

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This paper presents the results of a study conducted by Itron, Sustainable Conservation and Bowen & Associates for the Sacramento Municipal Utility District (SMUD) to investigate the status and costs of controls for reducing emissions of oxides of nitrogen (NOx) from small (100 to 300 kW) reciprocating engines operating on biogas from dairy digesters. During the course of the study, it became apparent that simultaneous environmental policies have created a fundamental “catch 22” situation for California’s biogas industry. On one hand, California air quality regulations require distributed generation (DG) technologies to achieve aggressive emission limits for control of oxides of nitrogen (NOx). At the same time, California’s Governor and Legislature have passed landmark legislation calling for GHG emissions to be reduced by twenty-five percent to 1990 levels by no later than 2020. A “catch 22” occurs because while DG technologies, particularly biogas fueled technologies, can play a key role in reducing GHG emissions, NOx control technologies needed to meet the required NOx levels have not matured to commercial readiness. This requires project developers to take substantial risks on both the financial and technical front without the likelihood of recouping their investments. The result creates an impasse that potentially deprives California not only of forward progress in reducing GHG emissions but forestalls significant interim NOx reductions that could otherwise be achieved. However, the situation highlights a problem that extends beyond California’s borders and the biogas industry: how to simultaneously achieve aggressive air quality targets while making significant reductions in greenhouse gas (GHG) emissions. This paper presents the findings of an investigation into proposed NOx emissions limits for biogas to energy applications and how those requirements interact with policies to reduce GHG emissions.

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  • News Article
  • Cite Count Icon 1
  • 10.1289/ehp.119-a384a
Scorecard Rates Emission Reductions of Hybrid Vehicles
  • Sep 1, 2011
  • Environmental Health Perspectives
  • David C Holzman

For all its cachet, you might think that hybrid drivetrain technology is inherently green. But only 13 of 34 hybrid vehicles assessed achieve better than a 25% reduction in greenhouse gas (GHG) emissions, and just 3 exceed a 40% reduction, according to an evaluation by the Union of Concerned Scientists (UCS).1 Moreover, reductions in GHG emissions do not necessarily correlate with reductions in other toxic emissions. Like any engine output–improving technology, hybrid technology can boost both fuel efficiency and power—but the more you boost one, the less you can boost the other. That dichotomy spurred the UCS to develop its “hybrid scorecard,” which rates each hybrid according to how well it lives up to its promise of reducing air pollution.2 All the vehicles were from model year 2011 except for one, the 2012 Infiniti M Hybrid. First the UCS scored each hybrid on how much it reduced its GHG emissions relative to its conventional counterpart, on a scale of zero (least reduction) to 10 (greatest reduction). These scores reflect the percentage in fuel efficiency gain. For example, the Toyota Prius gets 50 mpg3 compared with 28 mpg for the comparable Toyota Matrix. This represents a 44.0% reduction in GHG emissions, earning the Prius a GHG score of 9.4. At the bottom of the scale, the 21-mpg hybrid VW Touareg reduces GHG emissions only 10% over the 19-mpg conventional Toureg, for a score of 0.0. With a 46% improvement, the luxury Lincoln MKZ Hybrid had the greatest reduction over its conventional counterpart. The UCS also scored hybrids for absolute emissions (rather than relative to the conventional model) of air pollutants including particulate matter, carbon monoxide, hydrocarbons, and nitrogen oxides. These scores, on a scale of zero (dirtiest) to 10 (cleanest), are based on California certifications for tailpipe emissions. As the scorecard showed, a vehicle that emits less heat-trapping gases may not necessarily emit less of other air pollutants. For example, the Mercedes Benz S400 Hybrid scored 9 on air pollution reduction, alongside the Prius and the Lincoln MKZ, but only 1.3 on GHG emissions. HYBRID SCORECARD: Top 10 Nonluxury Hybrids by Total Environmental Improvement Score “Hybrid technology doesn’t add additional challenges [to reducing exhaust pollutants] that can’t be addressed through design of the vehicle’s emission controls,” says Don Anair, senior vehicles analyst at the UCS. “Numerous manufacturers of hybrids are meeting the lowest emissions levels. Hybrid manufacturers who aren’t delivering the lowest smog-forming emissions have chosen not to do so.” Each vehicle’s air pollution and GHG scores were averaged into a total “environmental improvement score,” again with the MKZ and the Prius leading the pack, and the Touareg scraping bottom. The UCS also scored “hybrid value” (the cost of reducing GHG emissions in dollars per percent reduction) and “forced features” (options you must buy with the hybrid whether you want them or not). HYBRID SCORECARD: Top 10 Luxury Hybrids by Total Environmental Improvement Score Luke Tonachel, vehicles analyst with the Natural Resources Defense Council, compliments the scorecard for illustrating that hybrid technology is not automatically green. He says, “We should improve the efficiency of all vehicles, and [hybrid technology] is just one technology that can get us there if applied with that goal in mind.” Nonetheless, Jamie Kitman, the New York bureau chief for Automobile Magazine, questions the wisdom of emphasizing percentage improvement in gas mileage rather than absolute miles per gallon. At 21 mpg, the hybrid Cadillac Escalade 4WD represents a 29% improvement over the 15-mpg conventional model, saving nearly 2 gallons per 100 miles. But the hybrid Escalade is still a gas guzzler, and Kitman says he wishes people would see through the marketing that encourages them to buy SUVs and “crossovers” rather than ordinary cars, which are more efficient than either. Says Anair, “The scorecard shows that automakers can pair hybrid technology with advanced emission controls to help tackle climate change while reducing the health impacts from breathing polluted air.” However, he adds, alluding to the stark variation in how much hybrid technology boosted fuel efficiency, “Not all automakers are delivering on the full promise of this technology.”

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  • Research Article
  • Cite Count Icon 13
  • 10.3390/en10101515
Life Cycle Energy Consumption and Greenhouse Gas Emissions Analysis of Natural Gas-Based Distributed Generation Projects in China
  • Oct 1, 2017
  • Energies
  • Hansi Liu + 3 more

In this paper, we used the life-cycle analysis (LCA) method to evaluate the energy consumption and greenhouse gas (GHG) emissions of natural gas (NG) distributed generation (DG) projects in China. We took the China Resources Snow Breweries (CRSB) NG DG project in Sichuan province of China as a base scenario and compared its life cycle energy consumption and GHG emissions performance against five further scenarios. We found the CRSB DG project (all energy input is NG) can reduce GHG emissions by 22%, but increase energy consumption by 12% relative to the scenario, using coal combined with grid electricity as an energy input. The LCA also indicated that the CRSB project can save 24% of energy and reduce GHG emissions by 48% relative to the all-coal scenario. The studied NG-based DG project presents major GHG emissions reduction advantages over the traditional centralized energy system. Moreover, this reduction of energy consumption and GHG emissions can be expanded if the extra electricity from the DG project can be supplied to the public grid. The action of combining renewable energy into the NG DG system can also strengthen the dual merit of energy conservation and GHG emissions reduction. The marginal CO2 abatement cost of the studied project is about 51 USD/ton CO2 equivalent, which is relatively low. Policymakers are recommended to support NG DG technology development and application in China and globally to boost NG utilization and control GHG emissions.

  • Research Article
  • Cite Count Icon 2
  • 10.1016/j.oneear.2021.11.008
Major US electric utility climate pledges have the potential to collectively reduce power sector emissions by one-third
  • Dec 1, 2021
  • One Earth
  • Diana Godlevskaya + 2 more

Major US electric utility climate pledges have the potential to collectively reduce power sector emissions by one-third

  • Research Article
  • Cite Count Icon 1
  • 10.55003/eth.410401
Assessing GHG Emission Reductions for Organization through the Installation of Solar PV Rooftop On-grid System
  • Dec 25, 2024
  • Engineering and Technology Horizons
  • Sommai Saramath + 1 more

The Earth's surface temperature is steadily increasing due to the accumulation of greenhouse gases, a phenomenon known as global warming. Human activities are the root cause of this significant global issue. Reducing greenhouse gas (GHG) emissions is one of the most critical actions in climate change mitigation. Organizations can engage in activities that promote change and reduce greenhouse gases by acknowledging the significance of addressing climate change. By reducing GHG emissions and promoting the use of renewable energy, organizations can begin to address environmental issues. Therefore, the purpose of this investigation is to assess the reduction of GHG emissions in an educational institution by substituting electricity consumption from the electrical grid with renewable energy in the form of a solar PV rooftop on-grid system. The School of Renewable Energy's GHG emissions were assessed, covering three scopes of GHG emissions activities: direct emissions, indirect emissions, and other indirect emissions. The organization's activity data were collected over a 12-month period. Without installing a solar panel system, the organization reported total GHG emissions of 310.40 tCO2e, relying solely on imported electricity for internal use. The highest GHG emissions were from Scope 2, amounting to 239.38 tCO2e, primarily due to electricity importation. Scope 3 had the second highest GHG emissions, totaling 65.76 tCO2e, resulting from employee commuting and the use of purchased goods such as paper and tap water. Scope 1 had the lowest GHG emissions at 5.26 tCO2e, produced by the combustion of diesel and gasoline in both stationary and mobile sources, as well as CH4 emissions from the septic tank. The percentage of GHG emissions from Scope 2 activities was 77.12%, which was considered to have a significant environmental impact and contribute to global warming. This was because 478,851 kWh of electricity were imported. The installation of on-grid solar cells for power generation reduced imported electricity to 113,120 kWh. Consequently, GHG emissions from Scope 2 decreased to 56.55 tCO2e, leading to an overall reduction in the organization's GHG emissions to 127.57 tCO2e. The organization's GHG emissions decreased by 182.83 tCO2e as a result of using alternative energy to generate electricity. This assessment can serve as a database for educational institutions and prepare the government to report greenhouse gas emissions. Furthermore, it can serve as carbon credits for trading and exchanging carbon with other organizations to offset GHG emissions from various activities. In addition, it endorses the government's goal of achieving carbon neutrality and net zero emissions in the future.

  • Abstract
  • Cite Count Icon 1
  • 10.1136/gutjnl-2024-bsg.18
O18 Reduction in carbon footprint though a patient-initiated follow-up (PIFU) inflammatory bowel disease pathway
  • Jun 1, 2024
  • Gut
  • Shaji Sebastian + 4 more

IntroductionRemote digitally-supported care can drive carbon emission reductions, as well as increase access to health and patient comfort. IBD Home®, incorporating a PIFU pathway, minimises face-to-face appointments and relocates testing...

  • Research Article
  • Cite Count Icon 26
  • 10.1016/j.sciaf.2023.e01843
Greenhouse gas (GHG) emissions reduction in the electricity sector: Implications of increasing renewable energy penetration in Ghana's electricity generation mix
  • Aug 5, 2023
  • Scientific African
  • Ebenezer Nyarko Kumi + 1 more

Greenhouse gas (GHG) emissions reduction in the electricity sector: Implications of increasing renewable energy penetration in Ghana's electricity generation mix

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  • Cite Count Icon 3
  • 10.3390/su9020182
The Role of Sustainability Resources of Large Greenhouse Gas Emitters: The Case of Corporations in Alberta, Canada
  • Jan 26, 2017
  • Sustainability
  • Marwa Hannouf + 1 more

With the global challenge of climate change, it becomes crucial to understand the factors that can guide carbon intensive companies to comply with environmental regulations through significant reductions in greenhouse gas (GHG) emissions. Using the natural-resource-based view, the argument in this paper is that focusing on sustainability-driven resources by companies is a way to meet environmental compliance and reduce GHG emissions while gaining differential competitive benefits. A specific analysis on Alberta case has discussed large GHG emitters’ environmental compliance mechanisms in the context of their sustainability resources. The aim is examining if large GHG emitters in Alberta related to corporations having sustainability resources are complying with the Specified Gas Emitters Regulation (SGER) reduction requirement through cleaner-production driven internal mechanisms. The paper examines the existence of the sustainability resources in the reporting companies related to large GHG emitters responsible for 86% of total GHG reported by facilities with emissions above the threshold of 100 kilotonnes of GHG per year under SGER in Alberta. Corporations are found not using their sustainability resource potential to achieve internal reductions in GHG emissions throughout their facilities. Thus, some recommendations are presented for Alberta case as well as for environmental regulations in other jurisdictions that can potentially help policy makers improve their climate change regulations and achieve their global targets and enable companies to gain competitive advantage while meeting GHG reduction compliance.

  • Research Article
  • Cite Count Icon 5
  • 10.1001/jama.2009.1955
Cap and Trade Legislation for Greenhouse Gas Emissions
  • Jan 6, 2010
  • JAMA
  • Christopher D Barr + 1 more

Legislation to cap and trade greenhouse gas (GHG) emissions was approved by a 219-212 vote of the United States House of Representatives on June 26, 2009. Cap and trade policy articulated in the American Clean Energy and Security (ACES) act of 2009 regulates GHGs including carbon dioxide, methane, nitrous oxide, sulfur hexafluoride, hydrofluorocarbons, perfluorocarbons and nitrogen trifluoride. Debate over the ACES act focused heavily on economic issues contrasted against concerns about climate change1. However, discussion largely ignored the potential for cap and trade legislation to contribute to reductions in levels of other harmful air pollutants, such as sulfur dioxide, particulate matter, and ozone precursors that share emission sources with GHGs. Under the bill, domestic GHG emissions are to be capped at 2005 annual levels, and reduced to 17% of those marks by 20502. The bill provides for an initial round of pollution permits to be made available, some free, others at auction. Subsequently, these permits can be bought and sold in the open market by organizations such as utility companies and manufacturing firms. A key provision in the ACES act requires the president to impose tariffs on countries that do not implement similar regulations on GHG emissions. While other potentially viable legislation, such as a tax on carbon emissions, has been proposed3, the current cap and trade legislation is the first bill to pass in either the House or Senate. The greenhouse gases regulated under the ACES act do not generally pose serious direct health risks. For example, nitrous oxide is used in dental procedures, and carbon dioxide is an ingredient in carbonated beverages. Other GHGs, like nitrogen trifluoride and sulfur hexafluoride, are not harmful at their current concentration levels, but can be hazardous to persons working with them if safety precautions are not taken. Instead, substantial human health benefits from cap and trade legislation could potentially come from reductions in ambient levels of harmful pollutants, such as particulate matter and ozone, that share emissions sources with GHGs. For example, 94% of CO2 emissions in the US result from combustion of fossil fuels, with electricity generation and transportation alone comprising nearly 70%. These are also the leading source of sulfur dioxide, fine particles having diameter small than 2.5 micrometers (PM2.5), and precursors to ozone such as mono-nitrogen oxides (NOx)4. While the time scale for potential impacts of cap and trade legislation on climate change and related health benefits is likely decades or centuries, ancillary air pollution mitigation could have immediate health benefits. In two nationwide epidemiological studies, daily levels of ambient ozone and PM2.5 have been linked to increased risk of cardiovascular and respiratory mortality5 and to increased risk of emergency hospital admissions, especially for heart failure6, respectively. Estimates of the potential health benefits attributable to reductions in harmful air pollutants resulting from mitigation of GHG emissions, at the city, region and national, have been substantial7. While US cap and trade legislation would likely reduce domestic air pollution levels, two caveats deserve consideration. First, methods for reducing GHG emissions typically reduce air pollution levels, but not always. This problem can be highlighted using airplanes as an example8. Two methods to reduce CO2 emissions from airplanes are to decrease aircraft weight or increase engine combustion temperatures. The former reduces both GHG and air pollution emissions, whereas the later reduces GHG emissions at the cost of increasing precursors to ozone. In the broader context of energy production, it is likely cap and trade legislation would drive a shift away from fossil fuel combustion to sources such as solar technology that produce much less air pollution. However, the exact technology development path is still uncertain. A second problem is the potential for domestic cap and trade legislation to transfer US emissions to newly industrialized nations. Countries facing lower production costs associated with looser regulations on GHG emissions would have an economic advantage over manufacturing industries in the US. However, increased air pollution from new manufacturing could be a key public health issue for developing regions, such as China's Pearl River delta, where air pollution levels are already much higher than standards in the US9. The economic and physical systems that would be affected by cap and trade legislation are extremely complex, and impacts on air pollution will have to be considered in a broad context. For example, while the absence of tariffs would likely push manufacturing, air pollution and related negative health effects to developing regions, those regions might experience health benefits associated with increased per capita income. The discussion is similarly complex in the physical domain. For example, some air pollutants, such as sulfate particulate matter, can contribute to short term climate cooling. Though still somewhat unclear, there is an emerging debate over the possibility that air pollution mitigation could actually exacerbate global warming in the short term10. While it faces potentially significant opposition and alteration in the Senate, the cap and trade bill recently passed in the House has progressed further through Congress than any other similar legislation. There is tremendous potential for legislation regulating GHG emissions, via cap and trade or other strategies, to simultaneously decrease emissions of harmful air pollutants and reduce morbidity and mortality attributable to cardiovascular and respiratory illness. Such improvements in public health have been linked to economic benefits from recovered workforce productivity8, and add important support for progress on cap and trade legislation versus delayed action.

  • Research Article
  • 10.2139/ssrn.1869356
Taking Stock of Strategies on Climate Change and the Way Forward: A Strategic Climate Change Framework for Australia
  • Jun 24, 2011
  • SSRN Electronic Journal
  • Ananda Wickramasinghe + 1 more

Taking Stock of Strategies on Climate Change and the Way Forward: A Strategic Climate Change Framework for Australia

  • Conference Article
  • 10.2523/iptc-17314-ms
Greenhouse Gas Emission Reduction and Tailgas Maximization at ORYXGTL
  • Jan 19, 2014
  • N Pon Saravanan + 1 more

ORYX GTL, a joint venture between shareholders Qatar Petroleum and Sasol Synfuels International, is a pioneering gas-to-liquids (GTL) facility that produces premium diesel fuel, naphtha and LPG. The objectives of this paper are related to Greenhouse Gas (GHG) management at ORYX GTL: it aims toidentify the various sources of GHGdescribe the methodology to quantify GHG emissionsidentify various opportunities to reduce GHG emissions, andprovides a case study on GHG emission reduction through utilization of tailgas as fuel in fired heaters. The paper is organized in two sections; the first section presents a brief overview of the ORYX GTL process, identifies the various GHG emission sources, quantifies the GHG emissions and describes the concepts and options to reduce GHG emissions. The second section describes a case study on the opportunity to optimize fired heaters to make use of tailgas and steps that can be taken to make use of these opportunities. A brief overview is also provided on projects executed by ORYX GTL to support the company's strategy of optimizing sustainability and stability by reducing GHG emissions. The major GHG emission sources from the ORYX GTL facility are broadly classified as combustion and flaring emissions. The GHG emissions at ORYX GTL are derived from estimates and calculations taking into account the composition of fuel streams, the energy content of the fuel, available measurement data, emission factors and mass balance approaches. It was found that flaring of tailgas contributes significantly to the release of GHG emissions from the ORYX GTL facility. The GHG reduction was achieved by making use of Advanced Process Control techniques, utilization of tailgas for fuel, and recovery of low pressure vent gases to use as fuel in process heaters. The use of tailgas as a fuel to fired heaters increased from 10% to 90–95% of total heat duty since start-up. The increase of tailgas as fuel resulted in the reduction of natural gas as fuel, improving the carbon efficiency of the plant and thus reduced the environmental impact. In 2012, a 23% reduction in GHG emissions was achieved compared to 2011 levels due to maximizing tailgas utilization as fuel and stable plant operations. The results from this study highlight that a further reduction of GHG emissions is achievable by focusing on plant stability and flare reduction projects. 1. Introduction The growing world energy demand for fossil fuels plays a key role in the continuous increase in GHG emissions into the atmosphere. According to the IPCC, atmospheric GHG concentrations will more than triple in the next 50 years compared to pre-industrial levels if no action is taken, posing climate change risks such as damage to natural ecosystems and more extreme weather conditions [1]. As global concerns intensify to reduce GHG emissions, there is a continuous increase in demand for ultra-clean fuels derived from natural gas. Gas-to-Liquids (GTL) technology converts natural gas into high performing, ultra-clean liquid fuels, as alternatives to the conventional refining of crude oil. In the past ten years, there have been technological advances in developing GTL technology on a larger scale, with several commercial scale plants commissioned. This new and emerging technology is expected to contribute a larger share of the world's gas-processing industry in the future [2, 3].

  • Research Article
  • Cite Count Icon 7
  • 10.1007/s11771-015-2598-3
Optimal scenario balance of reduction in costs and greenhouse gas emissions for municipal solid waste management
  • Mar 1, 2015
  • Journal of Central South University
  • Na Deng + 6 more

To reduce carbon intensity, an improved management method balancing the reduction in costs and greenhouse gas (GHG) emissions is required for Tianjin’s waste management system. Firstly, six objective functions, namely, cost minimization, GHG minimization, eco-efficiency minimization, cost maximization, GHG maximization and eco-efficiency maximization, are built and subjected to the same constraints with each objective function corresponding to one scenario. Secondly, GHG emissions and costs are derived from the waste flow of each scenario. Thirdly, the range of GHG emissions and costs of other potential scenarios are obtained and plotted through adjusting waste flow with infinitely possible step sizes according to the correlation among the above six scenarios. And the optimal scenario is determined based on this range. The results suggest the following conclusions. 1) The scenarios located on the border between scenario cost minimization and GHG minimization create an optimum curve, and scenario GHG minimization has the smallest eco-efficiency on the curve; 2) Simple pursuit of eco-efficiency minimization using fractional programming may be unreasonable; 3) Balancing GHG emissions from incineration and landfills benefits Tianjin’s waste management system as it reduces GHG emissions and costs.

  • Research Article
  • Cite Count Icon 47
  • 10.1016/j.jclepro.2017.03.032
Cost-effectiveness analysis of inducing green vehicles to achieve deep reductions in greenhouse gas emissions in New Zealand
  • Mar 6, 2017
  • Journal of Cleaner Production
  • Ehsan Shafiei + 2 more

Cost-effectiveness analysis of inducing green vehicles to achieve deep reductions in greenhouse gas emissions in New Zealand

  • Book Chapter
  • Cite Count Icon 9
  • 10.1108/s0895-993520210000028002
Coalitions that Clash: California's Climate Leadership and the Perpetuation of Environmental Inequality
  • Jul 19, 2021
  • Joshua A Basseches + 2 more

At a time when the US federal government failed to act on climate change, California's success as a subnational climate policy leader has been widely celebrated. However, California's landmark climate law drove a wedge between two segments of the state's environmental community. On one side was a coalition of “market-oriented” environmental social movement organizations (SMOs), who allied with private corporations to advance market-friendly climate policy. On the other side was a coalition of “justice-oriented” environmental SMOs, who viewed capitalist markets as the problem and sought climate policy that would mitigate the uneven distribution of environmental harms within the state. The social movement literature is not well equipped to understand this case, in which coalitional politics helped one environmental social movement succeed in its policy objectives at the expense of another. In this chapter, we draw on legislative and regulatory texts, archival material, and interviews with relevant political actors to compare the policymaking influence of each of these coalitions, and we argue that the composition of the two coalitions is the key to understanding why one was more successful than the other. At the same time, we point out the justice-oriented coalition's growing power, as market-oriented SMOs seek to preserve their legitimacy.

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  • Cite Count Icon 23
  • 10.5194/bg-11-2287-2014
Trade-offs between high yields and greenhouse gas emissions in irrigation wheat cropland in China
  • Apr 24, 2014
  • Biogeosciences
  • Z L Cui + 5 more

Abstract. Although the concept of producing higher yields with reduced greenhouse gas (GHG) emissions is a goal that attracts increasing public and scientific attention, the trade-off between high yields and GHG emissions in intensive agricultural production is not well understood. Here, we hypothesize that there exists a mechanistic relationship between wheat grain yield and GHG emission, and that could be transformed into better agronomic management. A total 33 sites of on-farm experiments were investigated to evaluate the relationship between grain yield and GHG emissions using two systems (conventional practice, CP; high-yielding systems, HY) of intensive winter wheat (Triticum aestivum L.) in China. Furthermore, we discussed the potential to produce higher yields with lower GHG emissions based on a survey of 2938 farmers. Compared to the CP system, grain yield was 39% (2352 kg ha−1) higher in the HY system, while GHG emissions increased by only 10%, and GHG emission intensity was reduced by 21%. The current intensive winter wheat system with farmers' practice had a median yield and maximum GHG emission rate of 6050 kg ha−1 and 4783 kg CO2 eq ha−1, respectively; however, this system can be transformed to maintain yields while reducing GHG emissions by 26% (6077 kg ha−1, and 3555 kg CO2 eq ha−1). Further, the HY system was found to increase grain yield by 39% with a simultaneous reduction in GHG emissions by 18% (8429 kg ha−1, and 3905 kg CO2 eq ha−1, respectively). In the future, we suggest moving the trade-off relationships and calculations from grain yield and GHG emissions to new measures of productivity and environmental protection using innovative management technologies.

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  • Research Article
  • Cite Count Icon 80
  • 10.1051/agro/2009031
Greenhouse gases and ammonia emissions from organic mixed crop-dairy systems: a critical review of mitigation options
  • Apr 1, 2010
  • Agronomy for Sustainable Development
  • S M Novak + 1 more

Dairy production systems represent a significant source of air pollutants such as greenhouse gases (GHG), that increase global warming, and ammonia (NH3), that leads to eutrophication and acidification of natural ecosystems. Greenhouse gases and ammonia are emitted both by conventional and organic dairy systems. Several studies have already been conducted to design practices that reduce greenhouse gas and ammonia emissions from dairy systems. However, those studies did not consider options specifically applied to organic farming, as well as the multiple trade-offs occurring between these air pollutants. This article reviews agricultural practices that mitigate greenhouse gas and ammonia emissions. Those practices can be applied to the most common organic dairy systems in northern Europe such as organic mixed crop-dairy systems. The following major points of mitigation options for animal production, crop production and grasslands are discussed. Animal production: the most promising options for reducing greenhouse gas emissions at the livestock management level involve either the improvement of animal production through dietary changes and genetic improvement or the reduction of the replacement rate. The control of the protein intake of animals is an effective means to reduce gaseous emissions of nitrogen, but it is difficult to implement in organic dairy farming systems. Considering the manure handling chain, mitigation options involve housing, storage and application. For housing, an increase in the amounts of straw used for bedding reduces NH3 emissions, while the limitation of CH4 emissions from deep litter is achieved by avoiding anaerobic conditions. During the storage of solid manure, composting could be an efficient mitigation option, depending on its management. Addition of straw to solid manure was shown to reduce CH4 and N2O emissions from the manure heaps. During the storage of liquid manure, emptying the slurry store before late spring is an efficient mitigation option to limit both CH4 and NH3 emissions. Addition of a wooden cover also reduces these emissions more efficiently than a natural surface crust alone, but may increase N2O emissions. Anaerobic digestion is the most promising way to reduce the overall greenhouse gas emissions from storage and land spreading, without increasing NH3 emissions. At the application stage, NH3 emissions may be reduced by spreading manure during the coolest part of the day, incorporating it quickly and in narrow bands. Crop production: the mitigation options for crop production focus on limiting CO2 and N2O emissions. The introduction of perennial crops or temporary leys of longer duration are promising options to limit CO2 emissions by storing carbon in plants or soils. Reduced tillage or no tillage as well as the incorporation of crop residues also favour carbon sequestration in soils, but these practices may enhance N2O emissions. Besides, the improvement of crop N-use efficiency through effective management of manure and slurry, by growing catch crops or by delaying the ploughing of leys, is of prime importance to reduce N2O emissions. Grassland: concerning grassland and grazing management, permanent conversion from arable to grassland provides high soil carbon sequestration while increasing or decreasing the livestock density seems not to be an appropriate mitigation option. From the study of the multiple interrelations between gases and between farm compartments, the following mitigation options are advised for organic mixed crop-dairy systems: (1) actions for increasing energy efficiency or fuel savings because they are beneficial in any case, (2) techniques improving efficiency of N management at field and farm levels because they affect not only N2O and NH3 emissions, but also nitrate leaching, and (3) biogas production through anaerobic digestion of manure because it is a promising efficient method to mitigate greenhouse gas emissions, even if the profitability of this expensive investment needs to be carefully studied. Finally, the way the farmer implements the mitigation options, i.e. his practices, will be a determining factor in the reduction of greenhouse gas and NH3 emissions.

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