As climate impacts worsen, novel technologies to draw down atmospheric carbon are gaining attention. One such approach is ocean-based carbon dioxide removal (OCDR). However, the potential environmental side-effects of large-scale OCDR deployment remain understudied. Here, we present a systematic literature review of the life cycle assessments (LCAs) of OCDR approaches. We find that current OCDR LCAs have a limited scope, often overlook environmental impacts beyond global warming, and that LCA as a method is currently limited in capturing aquatic impacts. We provide several recommendations for future work, such as using a functional unit of storing atmospheric carbon over a specified time horizon and in a specified medium, performing cradle-to-grave analysis, including more (marine) environmental impacts, and estimating uncertainties. We also emphasise the need to develop the LCA methodology further for better assessing marine environment impacts.

Hybrid-electric aircraft represent a promising solution for the urgent need to decarbonize short-haul flights and bolster aviation sustainability. Nevertheless, the realization of hybrid-electric aircraft demands rigorous environmental impact analysis, given the substantial investments, time, and research required for technology development. This study offers a comprehensive life cycle inventory spanning the years 2030, 2040, and 2050 for both conventional and hybrid-electric aircraft configurations. Our inventory datasets are meticulously constructed through a systematic approach, ensuring data harmonization by drawing upon scientific literature, industry expertise, and primary data sources. This extensive dataset encompasses all pertinent systems necessary to model the environmental footprint of flights covering distances ranging from 200 to 600 nautical miles, utilizing a 50-passenger aircraft with the ATR42 as a reference model. Additionally, we furnish supplemental data for end-of-life considerations and uncertainty analysis. The systems under examination include the airframe, powertrain, power electronics and drives, batteries, fuel cells, hydrogen onboard storage, airport infrastructure, and battery charging stations. Notably, the carbon footprint of conventional aircraft aligns with data from the ecoinvent v3.8 database; however, our provided datasets are more than tenfold more detailed and incorporate a forward-looking perspective. These meticulously curated life cycle inventories can be amalgamated to simulate the potential environmental ramifications of conventional aircraft powered by kerosene or alternative aviation fuels, hybrid-electric aircraft utilizing battery technology, and hybrid-electric aircraft employing hydrogen as a fuel in conjunction with batteries. In this context, our findings play a pivotal role in nurturing the development of technology roadmaps that prioritize environmental sustainability within the realm of regional aviation.

The aviation sector contributes to environmental problems like climate change, resource depletion, and air pollution. We perform a systematic literature review of life cycle assessment studies to map the environmental impacts in the sector and provide methodological recommendations. The sector is divided into cross-cutting systems, namely aircraft, fuel and propulsion systems, and airports. Our review results confirm the sector's focus on climate change impacts. The mitigation strategies rely mostly on reducing CO₂ emissions during aircraft operations, like implementing sustainable aviation fuels and prospective technologies or decreasing aircraft weight with lightweight components. We use review analyses to identify and discuss knowledge gaps, such as the assessment of noise impacts or non-CO₂ flight emissions. Finally, aviation-specific recommendations are provided to LCA practitioners and aviation stakeholders with respect to data transparency and harmonization of results. Research needs, such as the development of characterization factors, are recommended to developers of life cycle impact assessment methods.