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Aircraft Engines Emissions

Definition of the problem

Aircraft engines produce emissions that are similar to other emissions resulting from fossil fuel combustion. However, aircraft emissions are unusual in that a significant proportion is emitted at altitude.

These emissions give rise to important environmental concerns regarding their global impact and their effect on local air quality at ground level

Environmental Trends

Environmental report

Environmental Trends

Every three years, CAEP develops an analysis of environmental trends in aviation to include: Aircraft Emissions that affect the Global Climate; Aircraft Noise; and Aircraft Emissions that affect Local Air Quality (LAQ). CAEP uses the latest input data and related assumptions to assess the present and future impact and trends of aircraft noise and aircraft engine emissions. During the CAEP/10 meeting, CAEP developed an updated set of trends and it was recommended that these be the basis for decision-making on matters related to the environment during the 39th ICAO Assembly. Further information on the Environmental Trends in Aviation to 2050 can be found in Chapter 1 of this Environmental Report.

https://www.icao.int/environmental-protection/Documents/ICAO%20Environmental%20Report%202016.pdf

CAEP & LAQ

CAEP & LAQ

CAEP 10 CO2 Emissions Standards

Local Air Quality

Local Air Quality - Overview

Since the late 1970s ICAO has been developing measures to reduce the impact of aircraft emissions on Local Air Quality (LAQ). These measures focus on the effects of aircraft engine emissions released below 3,000 feet (915 metres) and emissions from airport sources, such as airport traffic, ground service equipment, and de-icing operations. One of the principal results arising from the work of ICAO is the development of the ICAO Standards and Recommended Practices (SARPs) on engine emissions contained in Volume II of Annex 16 to the Convention on International Civil Aviation (the “Chicago Convention”) and related guidance material and technical documentation. These SARPs aim to address potential adverse effects of air pollutants on LAQ, primarily pertaining to human health and welfare. Among other issues, these provisions address: liquid fuel venting, smoke, and the main gaseous exhaust emissions from jet engines, namely; hydrocarbons (HC), oxides of nitrogen (NOx), and carbon monoxide (CO). Specifically, the Annex 16 engine emissions Standards set limits on the amounts of gaseous emissions and smoke allowable in the exhaust of most civil aircraft engine types.

WHITE PAPER ON AIR QUALITY AVIATION IMPACTS ON AIR QUALITY: STATE OF THE SCIENCE

Aircraft produce emissions that react in the atmosphere to form pollutants that impact air quality. These emissions have long been regulated through standards for aircraft engines for oxides of nitrogen (NOx), carbon monoxide (CO), unburned hydrocarbons (UHC), and smoke, via a Smoke Number (SN). New standards are being developed for non-volatile particulate matter (nvPM). Much is understood about how these and other emissions affect air quality in airports and in the regions around them. Ongoing research efforts are extending that understanding through better measurements and modelling. Work on PM is directed at developing the new nvPM standard, and increasing the available data on aircraft engine PM emissions. Alternative fuels have the potential to reduce PM emissions significantly. Emissions inventories are developed to calculate the contributions of all emissions to the ambient burden of pollutant concentrations that, in turn, are used to estimate the impacts on air quality and human health. Aircraft emissions at cruise altitude can also propagate back to affect local and regional air quality, and estimates of this contribution and the associated uncertainties have been calculated.

NEW AND IMPROVED LAQ MODELS FOR ASSESSMENT OF AIRCRAFT ENGINE EMISSIONS AND AIR POLLUTION IN AND AROUND AIRPORTS

Complex Model PolEmiCa

PolEmiCa is still under development, and future enhancements to this model will have two important objectives: to improve the jet/wake transportation modelling by CFD codes, and to verify the modelling results against measurement data collected at various airports.

Further improvements to dispersion calculations are expected, based on the use of more accurate engine emission data which is expected to come from the use of aircraft engines operating under real airport conditions, as power thrust and other operating conditions, such as weather have an impact on the emission parameters. For example, the NOx emissions factor shows variations of up to 25% when compared with the value for Standard Atmosphere (air temperature 15ºC) for temperatures as low as -20ºC, or as high as 30 ºC.

NEW PARTICULATE MATTER STANDARD FOR AIRCRAFT GAS TURBINE ENGINES

Particulate matter (PM) emissions from aircraft gas turbine engines are known to adversely impact both health and climate. The proposed new particulate matter standard for aircraft gas turbine engines is an important development that will lead to an overall reduction of the PM emissions and associated impacts. This new standard is a critical milestone that contributes to ICAO’s strategic objective to minimize the adverse environmental effects of civil aviation activities.

At the engine exhaust source of an aircraft, particulate emissions mainly consist of ultrafine soot or black carbon emissions. Such particles are called “non-volatile” (nvPM). They are present at high temperatures in engine exhaust and they do not change in mass or number as they mix and dilute in the exhaust plume behind an aircraft. The geometric mean diameter of these particles is extremely small and ranges roughly from 15nm to 60nm (0.06 Microns).

Additionally, gaseous emissions from engines can also condense to produce new particles (i.e. volatile particulate matter – vPM), or coat the emitted soot particles. Other gaseous species react chemically with ambient chemical constituents in the atmosphere to produce the so-called secondary particulate matter. Volatile particulate matter is dependent on precursor emissions, which are controlled by gaseous emission certification and the fuel composition (e.g. sulfur content).

The new ICAO standard is an attempt to control the ultrafine non-volatile particulate matter emissions.

FROM SMOKE TO NANOPARTICLES: INTERNATIONAL MEASUREMENT CAMPAIGNS FOR THE ESTABLISHMENT OF A NEW nvPM REGULATION

Particle emissions of civil aviation aero engines have been the focus of much scientific research prior to the establishment of the new non-volatile particulate matter (nvPM) standard. Examples of such research efforts include the NASA campaigns APEX and AAFEX1 and the DLR PartEmis2 studies. The latter resulted in the EASA supported Studying, sAmpling and Measuring of aircraft ParticuLate Emissions (SAMPLE) studies3, which drew the attention of regulatory agencies to sampling and measurement issues associated with a new standard (Figure 1). Developing a standard requires the collaboration of scientists, engineers, regulatory agencies, and instrument and engine manufacturers in an international and multi-institutional effort. The Society of Automotive Engineering (SAE) International E-31 Aircraft Exhaust Emissions Measurement Committee played an essential role by elaborating the measurement and calibration procedures in the aerospace information report “Procedure for the Continuous Sampling and Measurement of Non-Volatile Particle Emissions from Aircraft Turbine Engines” (AIR 6241)4. The applicability of the developed procedures was tested in numerous field campaigns, which are the main focus of this article.

Innovation and metrics

Innovation & Metrics

Using Metrics to interpret Emissions

Using Metrics to Interpret Aviation Emissions

Piers Forster & Kathryn Emmerson, University of Leeds

Malte Meinshausen, Sarah Raper & Michiel Schaeffer, Manchester Metropolitain University

Helen Rogers & Olivier Dessens, University of Cambridge

The study is focused on understanding uncertainties in the possible application of an aviation emission multiplier. Three uncertainties examined:

1) the effects of the NOX pulse and the resulting radiative forcing;

2) the role of realistic background scenarios of both background and aviation emissions;

3) how timeframes affect the choice of multipliers.

2C Emissions Pathway

Shipping and aviation emissions in the context of a 2°C emission pathway

David S. Lee,

Ling Lim,

Bethan Owen

Shipping and aviation represented around 3.2% and 2.1% respectively of global CO2 emissions in the mid-2000s. A wide range of projections and scenarios shows that both sectors are likely to grow over the coming decades with a resultant increase in CO2 emissions by 2050, despite mitigation efforts through technology, operations, and usage of low-carbon fuels. Here, a typical emission pathway that will limit global mean surface temperatures to no more than a 2°C increase by 2100 over pre-industrial temperatures is taken from prior work. This 2°C emission pathway makes no assumptions over the contributions of either the shipping or aviation sectors or of any particular nations’ efforts. It merely shows what the overall global emission reduction trend must be to reach the 2°C target. If current projections of emissions from shipping and aviation to 2050 are placed in the context of such an overall global 2°C emissions reduction pathway, then shipping might contribute between approximately 6% and 18% of median permissible total CO2-equivalent emissions in 2050 to meet the pathway, and aviation might contribute between approximately 4% and 15% of median total CO2- equivalent emissions, and the two sectors together might contribute between approximately 10% and 32% of total median CO2-equivalent emissions in 2050.

IPCC

Fifth Assessment Report

After the Kyoto Protocol directed parties in Annex I to pursue international aviation GHG emission limitation/reduction working through the International Civil Aviation Organization (ICAO) (Petersen, 2008), member states are working together with the industry towards voluntarily improving technologies, increasing the efficient use of airport infrastructure and aircraft, and adopting appropriate economic measures (ICAO, 2007b; ICAO, 2010a).

Emissions

In 2010, ICAO adopted global aspirational goals for the international aviation sector to improve fuel efficiency by an average of 2% per annum until 2050 and to keep its global net carbon emissions from 2020 at the same level (ICAO, 2010b). These goals exceed the assumptions made in many scenarios (Mayor and Tol, 2010).

Chapter 8

Transport

Climate Change 2014

The transport sector is a key enabler of economic activity and social

connectivity. It supports national and international trade and a large

global industry has evolved around it. Its greenhouse gas (GHG) emissions

are driven by the ever-increasing demand for mobility and movement

of goods. Together, the road, aviation, waterborne, and rail transport

sub-sectors currently produce almost one quarter of total global energy-related CO2 emissions [Section 8.1]. Emissions have more than

doubled since 1970 to reach 7.0 Gt CO2eq by 2010 with about 80% of

this increase coming from road vehicles. Black carbon and other aerosols,

also emitted during combustion of diesel and marine oil fuels, are

relatively short-lived radiative forcers compared with carbon dioxide

and their reduction is emerging as a key strategy for mitigation [8.2].

EIBIS Project

Emissions and Impacts of supersonic BIzjets on the atmoSphere (EIBIS)

Rubén Rodríguez De León & David Lee

Manchester Metropolitan University

Piers Forster

University of Leeds

The EIBIS project aimed to assess the climatic impact of the potential introduction of a fleet of Supersonic Business Jets (SSBJs) by analyzing the changes in the atmospheric radiation fields linked to the injection of water vapour and ozone (from NOx emissions) into the stratosphere as well as their associated induced cloud cover. This assessment is important to industry and policymakers in evaluating the potential environmental acceptability of such a fleet.

nvPM Checklist

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