Future ships need to operate with low or possibly zero greenhouse gas (GHG) emissions while ensuring low influence on other environmental impacts and that the operation is economically feasible. This study conducts a life-cycle evaluation of potential decarbonization solutions involving selected energy carriers (electrolytic hydrogen, electro-ammonia, electro-methanol, and electricity) in different propulsion system setups (engines, fuel cells, and carbon capture technologies) in terms of environmental impact and costs. The results of the study show that the assessed decarbonization options are promising measures to reduce maritime GHG emissions with low-carbon-intensive electricity. The same order of GHG reduction is shown to be possible independent of the propulsion system and energy carrier used onboard. However, the carbon abatement cost ranges from 300 to 550 €/tCO₂eq, and there is a trade-off with environmental impacts such as human toxicity (cancer and non-cancer effects) and freshwater ecotoxicity mainly linked with the wind infrastructure used for electricity production. Electro-ammonia in fuel cells is indicated to be effective in terms of the carbon abatement cost followed by the so-called HyMethShip concept. The higher abatement cost of all options compared to current options indicates that major incentives and policy measures are required to promote the introduction of alternative fuel and propulsion systems.

The global shipping industry is under increasing scrutiny for its contribution to greenhouse gas emissions, and it is a challenge to find sustainable and cost-efficient solutions to meet new and stringent climate reduction targets. This study uses life cycle assessment and life cycle costing to evaluate five main decarbonization strategies to reduce climate impact from ships: uptake of e-fuels, blue-fuels, biofuels, battery electric propulsion, and onboard carbon capture technology. The environmental impact, the economic performance, and the total costs of abating carbon emissions of a total of 23 decarbonization pathways are investigated. The life cycle assessment and life cycle costing are performed on prospective scenarios considering three ship types: bulk carrier, container ship, and cruise ship, and incorporate future development uncertainties. The results show that electro-fuels in the form of e-ammonia, e-methanol, and e-liquid hydrogen in fuel cells offer the highest climate mitigation potential of more than 85% compared to the use of marine gas oil in internal combustion engines. Biofuel options have a reduction potential of up to 78%, while blue-fuel and onboard carbon capture have lower climate reduction potentials of up to 62% and 56%, respectively. Bio-methanol has the most promising cost outlook with a carbon abatement cost of around 100€ per tCO_2eq. Onboard carbon capture technologies have a carbon abatement cost of around 150–190 € per tCO_2eq. While they can serve as a short-term transitional solution, they have a higher environmental impact and offer limited potential for climate mitigation. E-Ammonia appears as one of the most cost-effective solutions among e-fuels. Development of policy measures and investments in renewable energy infrastructure are necessary for the growth of e-fuels production, as affordable and renewable electricity is vital for the viability of e-fuels in shipping. The uncertainty and sensitivity analysis show the influence of primary energy sources on carbon abatement costs which will be key to understand the effectiveness of policies and to develop strategies to support the shipping industry's transition to a sustainable future.

Energy efficiency (EE) improvement is one of the most crucial elements in the decarbonization of industry. EE potential within industries largely remains untapped due to the lack of information regarding potential EE measures (EEM), knowledge regarding energy use, and due to the existence of some inconsistencies in the evaluation of energy use. Classification of energy end-using processes would increase the understanding of energy use, which in turn would increase the detection and deployment of EEMs. The study presents a novel taxonomy with hierarchical levels for energy end-use in manufacturing operations for the engineering industry, analyzes processes in terms of energy end-use (EEU) and CO₂ emissions, and scrutinizes energy performance indicators (EnPIs), as well as proposing potential new EnPIs that are suitable for the engineering industry. Even though the study has been conducted with a focus on the Swedish engineering industry, the study may be generalizable to the engineering industry beyond Sweden.

Shipping is a transnational sector competing for energy on a global market and needs effective policies to decarbonize. Here we assess energy transitions under different shipping policies using a sector-coupled global energy system model and connected life-cycle environmental impacts. We find that postponed International Maritime Organization’s ‘net-zero framework’ could increase biofuel use in shipping to 40% by 2050 but might fall short of net-zero targets, which require broader adoption of low-carbon fuels. A combined levy and global fuel standards mechanism accelerates low-carbon fuel adoption, achieving 60% of ammonia penetration as marine fuel. Ammonia emerges as most cost-effective fuel under cross-sectoral competition for several assessed policies, whereas electrification is preferred for vessels with daily bunkering possibilities. To reach global climate targets, ammonia from bioenergy with carbon capture (yielding negative emissions) and e-ammonia are found potentially crucial for shipping. However, this transition risks increasing other environmental impacts, including land use and mineral resource depletion.