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GLOBE - CO2 Emission

The GLOBE project team is determined to reduce emission of carbon dioxide in relation to the project. After detailed analysis, two workshops and seminars have been rescheduled, and the team has managed to cut a number of flights related to the project for 16. Our colleague Tamara Pejovic of Imperial College London has calculated the reduction of carbon dioxide emission achieved. Note that this small exercise was carried out to demonstrate that considerable reduction of carbon dioxide emission could be easily achieved by sensible planning of events related to the project.

Tamara is currently working on the project which will identify the possible impacts of climate change for UK aviation and the feedback mechanisms involved. This research is concerned with the possible impacts of climate change on UK aviation and the feedback mechanisms associated with it. Through this new approach, it will identify how changes in the climate will affect UK air transport and how those effects will sequentially influence the ways in which aviation contributes to further climate change. Additionally, it will identify the sensitivities of the mechanisms through which aviation contributes to climate change and identify the most significant ones for the UK region. The research will explore the climate impacts associated with the continuing growth in UK air transport, considering factors such as increased airspace congestion and increased use of regional airports. In addition, the research will analyze and propose policy options to mitigate the impact of air transport on climate change. This work will complement ongoing work by the research team which combines atmospheric data analysis and air traffic simulations to evaluate policies to mitigate the climate impacts of aviation.

Contact: Tamara Pejovic Tamara.pejovic@imperial.ac.uk

Evaluating the Potential For CO2 Emission Reduction in Relation to the GLOBE Project

by Tamara Pejovic

Abstract

The GLOBE project team was determined to minimise the negative impact of the project to the environment by reducing emission of carbon dioxide (CO2) in relation to the project. After detailed analysis, two workshops and seminars have been rescheduled, and the team has managed to cut a number of flights related to the project for 22. The reduction of CO2 emission achieved (5.41 tonnes) is calculated using Reorganized Air Traffic Control Mathematical Simulator (RAMS Plus) software by taking into account factors such as: aircraft type, average number of passengers on the flight, duration and the distance, and actual aircraft fuel burn rates for different modes of flight.

Introduction

An Environmental Impact Assessment (EIA) is an assessment of the likely human environmental health impact, risk to ecological health, and changes to nature's services that a project may have. The purpose of the assessment is to ensure that decision-makers consider environmental impacts before deciding whether to proceed with new projects.

The EIA Directive on Environmental Impact Assessment of the effects of projects on the environment was introduced in 1985 and was amended in 1997. The directive was amended again in 2003 following the 1998 signature by the EU of the Aarhus Convention on public participation in environmental matters. The issue was enlarged to the assessment of plans and programmes by the so called SEA-Directive in 2001 which is now in force (Glasson, Therivel & Chadwick, 2005).

One of the possible ways to calculate impact of this Project on the environment was to calculate its CO2 aviation related emissions and by that its impact on climate change and local air quality. Project's aviation CO2 emissions are taken as an adequate measure since CO2 is one of the main causes of climate change and air transport is the fastest growing source (IPCC, 1999). CO2 is, theoretically, the easiest indicator of environmental performance of a flight to consider, as emissions to the atmosphere are proportional to fuel consumption and their impacts are independent of the location or time of emission, making it possible to compare emissions and impacts from aviation CO2 with that from other transport modes and from non-transport sources.

At the moment however, the academic institutions are not obliged to take into account the environmental impact of their research projects. This small case study will help to start appreciating the importance of CO2 emission related to the pan European research projects.

Methodology

In order to analyse fuel burn use and hence CO2 emissions the RAMS Plus is used. The RAMS model simulates the four dimensional profile of each flight. As a detailed flight profile is obtained, describing the operation of the aircraft at each of these points throughout the flight, the fuel burn for each element of the journey can be calculated. This allows calculation of the emitted CO2.

The RAMS Plus Simulation Model

The RAMS Simulator Tool is a fast-time discrete-event simulation software package providing functionality for the study and analysis of airspace structures, ATC systems and future ATC concepts. The RAMS can be used to evaluate the impacts on flight profiles and on controller workload of changes in air traffic procedures. It is a fast time simulator designed for analysis of airspace and ATM procedures (ISA, 2006).

Flight Trajectories

For each combination of route and aircraft type, the flight trajectory is calculated using the RAMS Plus simulation model. As an event-based air traffic simulator, the model returns time, altitude and location data for each aircraft at each point along the flight trajectory where there is interaction with air traffic control, including changes in altitude or bearing and transitions between air traffic control sectors. The calculations take into account the performance characteristics of each aircraft, defined using the Eurocontrol Base of Aircraft Data (BADA) (Eurocontrol, 2004).

These output event data are used as the start and end points of the flight segments which together describe the flight trajectory. The requested cruise altitude for the flight is set to match that of a base flight on the route in the traffic sample or to the maximum operating cruise altitude for the aircraft type, where this is lower.

For the purposes of this estimate, it is assumed that all aircraft follow a great circle route between the selected airports. This allows an idealized, 'best case' scenario to be considered. CO2 emissions from air traffic control (ATC) delays or diversions in flight are not included, nor are adjustments for wind.

CO2 Aviation Emissions Calculations

Air traffic as a source of combustion emissions varies with respect to the type of fuel which is being used, the location (altitude) of the exhaust gases, the types and the efficiency of the engines, and the length of the flight. Emissions come from jet kerosene and aviation gasoline which are used as fuel on aircraft.

The fuel burn, and hence CO2 emissions, are attributed to different modes of the flight (see Figure 1), with each using fuel at different rates. Emissions occur during:

  • The Landing and Take Off cycle (LTO) which includes all activities near the airport that take place below the altitude of 3000 feet (1000 m). This consists of taxi-out, take-off and climb out, and at the end of the flight, the landing approach and taxi-in.
  • The Climb, Cruise and Descent cycle (CCD) which is defined as all activities that take place at altitudes above 3000 feet (1000 m).
flight-phases-of-an-aircraft

Figure 1. Flight Phases of an Aircraft

Besides the combustion of fuel in the LTO and CCD activities, fuelling and fuel handling in general, maintenance of aircraft engines and emergency fuel dumping to avoid accidents are emission sources. These emissions are, however, not included in this analysis. Also, CO2 emissions from surface access to airports were not within the scope of this estimate.

To permit calculation of the total fuel burn of flights, fuel burn rates from the performance tables of the BADA Revision 3.6 data were incorporated into RAMS. Flight speed and rate of climb/descent were also defined according to the BADA performance tables (Eurocontrol, 2004).

CO2 emissions are calculated using a two level approach. From the RAMS output files it was possible to calculate CCD cycle CO2 emissions using total fuel burn. Combustion of one kilogram of fuel yields approximately 3.15 kilograms of CO2 gas. CO2 emissions are therefore 3.15 times the mass of fuel burned. Fuel burn for the flight trajectory above 3000ft is calculated using rates specific to each aircraft for each altitude and mode of flight from the BADA. For the LTO cycle and emissions below 3000 ft, offline calculations were necessary. LTO movements below 3000ft are assumed to follow the International Civil Aviation Organization defined standard LTO cycle and a fixed fuel burn total for each aircraft for this section of flight is assumed (Rypdal, 2000). Overall, CO2 calculations were based on the following equation:

Emissions = LTO Emissions + CCD Emissions

Discussion

Since the objective of the Project was to minimise its environmental impact, 23 direct flights were cut from the initial planned schedule by reorganising Project activities. CO2 emission calculations related to the Project activities were performed for two different scenarios. First scenario took into consideration initially planned flights (90), while the second scenario contained actual, reduced number of flights (68). For all flights within scenarios, aircraft type was chosen according to the current airline schedule for a given planned or actual route.

As explained in previous section, summarising emissions for LTO and CCD cycles it was possible to get values for total CO2 emissions for each simulated flight. After calculating total flight's CO2 emissions, next step was to calculate emissions per passenger on board. Calculations are performed according to aircraft number of seats and average load factor. Load factors (percentage of seats occupied) are taken to be 65.5 percent for the short haul domestic and 65.7 percent for continental European routes (Association of European Airlines, 2004).

The total CO2 emissions saving related to the Project are shown in Table below.

 
Total CO2 Emissions (t)
Total CO2 per Passenger (t)
Planned
560.36
19.43
Actual
514.93
14.02
Savings
45.43
5.41

Table 1. Planned and Actual GLOBE Air Traffic CO2 Emissions

Conclusion

There is no direct line from Belgrade to Porto, therefore by organising two seminars at the same time Project have minimised the negative environmental impact of the GLOBE for 5.41 tonnes of CO2. This is the estimate of the Project's CO2 aviation related emissions took into account factors such as: aircraft type, average number of passengers on the flight, duration and the distance, and actual aircraft fuel burn rates for different modes of flight .

Reference

  • Association of European Airlines (2004). Summary of Traffic and Airlines Results. From http://www.aea.be/aeawebsite/datafiles/STAR_SS/STAR-05.pdf.
  • Eurocontrol (2004). Aircraft Performance Summary Tables for the Base of Aircraft Data (BADA), Revision 3.6, EEC Note 12/04, From http://eurocontrol.int/eec/gallery/content/public/
    documents/EEC_notes/2004/EEC_note_2004_12.pdf
  • Glasson, J.. Therivel, R., Chadwick, A. (2005). Introduction to Environmental Impact Assessment, Routledge, London
  • IPCC (1999). Aviation and the Global Atmosphere. A Special Report of IPCC Working Groups I and III in collaboration with the Scientific Assessment panel to the Montreal Protocol on Substances that Deplete the Ozone Layer, J. E. Penner, D. H. Lister, D. J. Griggs, D. J. Dokken and M. McFarland (eds). Cambridge University Press, UK.
  • ISA (2006). RAMS Plus User Manual, Release 5.26, ISA Software Ltd.
  • Rypdal, K. (2000). Aircraft Emissions in Background Papers IPCC Expert Meetings on Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories. From http://www.ipcc-nggip.iges.or.jp/public/gp/bgp/2_5_Aircraft.pdf.
GLOBE: Good Practice Guidelines and Legislation Reform on Interdisciplinary Postgraduate Studies in Built Environment Engineering

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