International Industrial Ecology Day 2021
Uncertainty and variability in carbon footprint of hydrogen-powered aviation
Abstract
The civil aviation industry is responding to considerable pressure to reduce its carbon footprint through a variety of mechanisms, chiefly technological innovation and carbon offsets. One proposal that has resurged in popularity is the use of hydrogen as an aviation fuel. Recently, Airbus revealed three Zero-E (“zero-emission”) concept aircrafts, intended to run on liquid hydrogen (LH2) combustion supplemented with hydrogen fuel cells starting in 2035.While there are several pathways to create hydrogen using renewable energy, currently around three-quarters of dedicated hydrogen production is from natural gas and nearly one-quarter from coal, with oil and electricity comprising a minute fraction. In this work, we focus on the comparison of the well-to-wake (WTWa) potential environmental impacts of aircraft powered by combustion of LH2 produced by a variety of feedstocks with aircraft powered by the combustion of conventional jet fuel.
As many aspects of this product system are not yet mature, there is inherent uncertainty and variability to capture. Some uncertain variables pertain to future production and combustion efficiencies, or the probability of climate impacts from emissions at different altitudes. There is also variability in the type of feedstock, the aircraft model, passenger occupancy, and flight distance. Further, LCA practitioners can elect how to allocate credit, to consider near-term climate forcers, and to include infrastructure. Enhanced methods are needed to facilitate the incorporation of discrete variables into LCA.
The GREET 2020 model is modified to run a Monte Carlo simulation with nearly 500 continuous and discrete variables and a range of fuels and aircrafts. Initial comparisons are made between the WTWa performance. Sensitivity analyses were performed using regression analysis. The climate impact of contrail cirrus produced by combustion of various aviation fuels is a key driver of uncertainty, and the inclusion of infrastructure for renewable electrolysis matters in comparison with conventional fuels.
Author(s)
| Name | Affiliation |
|---|---|
| T. Reed Miller | University of Maine |
| Edgar Hertwich | NTNU - Norwegian University of Science and Technology |
| Marian Chertow | Yale University |