The impact of aviation on the environment is growing, especially in regions where air travel is increasing rapidly. The contribution of aircraft to carbon dioxide production, and its influence on the environment, is reasonably well understood. However, other significant influences – such as those due to contrails and NOx (which leads to production of tropospheric ozone) – are more complex and the implications for aircraft manufacturers, operators and regulators are not yet well understood.

A previous PhD produced a new 4-dimensional fuel burn and emissions inventory from the civil aviation fleet over a period of seven years. This was used as input to a global chemistry transport model (CTM) in order to evaluate the impact of current global aircraft NOx emissions on atmospheric composition as well as the concentration and global spatial distribution of tropospheric NOx and O3. An operational mitigation strategy was also conducted, involving replacement of turbofan aircraft by turboprops on short-haul missions – due to their lower contribution to tropospheric ozone. Numerous findings concerning regional and global atmospheric chemistry effects of NOx production were generated, including shifts in geographical distribution.

The impact of NOx emissions depends strongly on background levels and hence on geographic location, particularly at lower altitudes: a global study does not reveal these geographic dependencies. The new PhD will complement previous work, using a trajectory transport model to compare overall NOx-related effects for missions from different airports. The locations chosen will be representative of background NOx and atmospheric conditions in various parts of the world. The studies will incorporate a selection of aircraft design and operational scenarios.

A further aspect of the study will be to evaluate use of biofuels in certain phases of flight, aimed at minimising changes in global warming potential. Biofuels have shown certain benefits in this respect; however, there are substantial difficulties in producing them in sufficient quantities to replace fossil fuels – hence the proposal to carry both types of fuel, using them selectively at altitudes to target overall emissions reduction.

The PhD will extend previous work on an aircraft performance model and resulting emissions inventory, and include application to a CTM to focus on regional and local impacts of NOx. A photochemical transport analysis of indicative civil air transport missions will be developed; estimates on the relative influence of individual routes or flights, and aircraft types, may also be considered. The objective is to understand the impact of NOx emissions in relation to geographic and operational scenarios, as well as aircraft/engine design parameters and fuel types.

It is expected that the PhD candidate will interact with Airbus in Bristol, to ensure access to realistic scenarios and intended outcomes.

Candidate requirements: Applicants should have or expect at least a high 2:1-level degree in a relevant chemistry or engineering degree, preferably at the Masters level.

Funding: EPSRC. Starting stipend (tax free) per annum is the EPSRC stipend of £13,863. Industry collaboration will be sought, which could potentially lead to a top-up to this amount. Additional resources will be available for research expenses, such as conference visits.

Contacts: Prof. Dudley Shallcross (D.E.Shallcross<στο>bristol.ac.uk) Prof. Mark Lowenberg  (M.Lowenberg<στο>bristol.ac.uk)