Life cycle assessment in aviation: Focus on climate change damage to human health

Life cycle assessment (LCA) is a tool for quantifying and analyzing environmental impacts from a product or system's whole life cycle perspective. It addresses multiple environmental issues from anthropogenic emissions and resource consumption and can be used to identify the environmental hot spots in any stage of a product´s life cycle, such as manufacturing or operation, or to compare the environmental performances of different systems. In the impact assessment phase of LCA, impacts on human health are quantified. In this PhD work, the first part of the thesis identifies environmental hot spots in the civil aviation sector. The second part develops mathematical factors in the form of damage and characterization factors to quantify the impacts on human health from climate change and applies the framework to civil aviation´s annual CO₂ emissions.

Chapter 1 The demand for air travel is expected to quadruple by 2050 compared to 2020. While the sector’s growth benefits users and aircraft producers, it poses challenges regarding aviation emissions and their environmental impact. Civil aviation contributes to various environmental problems, like climate change, air pollution or resource depletion. In the context of aviation’s environmental problems and climate change, this PhD aims i) to investigate the main findings of past LCA studies applied to the aviation sector, ii) to provide comprehensive recommendations to ensure a robust application of LCA in aviation, and iii) to expand further the impact assessment framework by developing a characterization model for damage to human health from climate change due to heat and cold.

Chapter 2 To meet the first two objectives, a comprehensive critical literature review was performed on LCA applications in the aviation sector. The aviation manufacturing sector was screened to identify environmental hotspots. With regard to the latter, a specific case study of aircraft rotor blades was performed, showing the potential benefits of recycling manufacturing waste in the form of titanium alloy chips. Based on these studies, we provided comprehensive recommendations to LCA practitioners, developers and decision-makers in the aviation sector.

Chapter 3 To address the third objective, a new framework was developed to quantify direct damage to human health from temperature changes due to heat and cold. The model is spatially differentiated for 166 countries and additionally differentiates four RCP climate scenarios (2.6, 4.0, 6.5, 8.5), two time periods (2040-2059, 2080-2099) and an adaptation scenario, with a resulting damage metric expressed in disability adjustment life years lost [DALY/℃.y]. Our resulting characterization factors show an increase by a factor of up to 3, depending on modelling value choices, compared to currently used characterization factors in the impact assessment method, ReCiPe2016. Characterization factors directly connecting GHG emissions with damage to human health can be used for LCA applications and can complement existing pathways when assessing climate change damage to human health.

Chapter 4 The developed characterization factors can also be used beyond LCA applications, e.g., as a tool in global and local mitigation and adaptation strategies against climate change. We apply our factors to quantify the impact of global and civil aviation´s CO₂ consumption-based emissions on human health. These modelling outputs, in providing more robust factors for climate change damages, can support applications of LCA in the civil aviation sector, such as adopting long-term perspectives on future environmental and social targets and estimating more comprehensively the magnitude of environmental impacts caused by the sector’s activities.

Chapters 5 and 6 summarize work done in the PhD thesis and outline future research needs in climate change damage modelling related to the development and refinement of endpoint characterization factors to sufficiently cover all the potential impacts of climate change. The renewed and improved method set out in this PhD thesis makes it possible to present potential damage from CO₂ emissions in terms of the loss of healthy life years for any system or product. Given the spatial differentiation of global and aviation impacts on human health in respect of who pollutes and who suffers, the research contributes to the discussion of whether information on potential damage can be used to narrow the inequality gap in climate change damage distributions globally.