Research and analysis

Environmental impacts of alternative fuels: summary

Published 5 August 2026

Applies to England

1. Chief Scientist’s Group report summary

This project examined the potential environmental impacts of ten alternatives to petroleum-based fossil fuels. The alternative fuels in scope included e-Diesel, green ammonia, e-methane, and specific production routes for biomethane, synthetic kerosene, and sustainable aviation fuels. This summary of available knowledge will help provide the Environment Agency and others with evidence to regulate these fuels, support their deployment, and avoid or mitigate unintended consequences.

1.1 Background

To achieve net zero in the transport, industrial and manufacturing sectors, alternative fuels are expected to at least partially replace conventional fossil fuels. Alternative fuels could have environmental and public health impacts during their production and use. Incidents like fires, spills or leaks can also affect the environment. This project identified and reviewed alternative fuels and production pathways likely to be used in the United Kingdom (UK) by 2050, evaluated their potential impacts on the environment and human health, and examined their incident management requirements.

1.2 Approach

This study summarised the available scientific and grey literature about the deployment trajectories, process steps in production pathways, and physical and chemical properties of ten alternative fuels. It then identified potential pollutants which could be produced and assessed their risks to human health. Finally, it compared the physical and chemical properties of alternative fuels to conventional fossil fuels, identifying where existing incident management practices may no longer be appropriate.

1.3 Results

The state of the development of each fuel generation technology varies. None of the production pathways covered in this study have been deployed at significant commercial scale in the UK, although several plants are at the design stage. Alternative fuel deployment is expected to increase considerably before 2040.

Environmental impacts will depend on the exact production process used to generate each fuel. Fuels and fuel production pathways which were more mature, and more likely to be deployed in the UK by 2040 were chosen for this study. However, despite being the most mature production pathways, detailed evidence was sometimes sparse given the novelty of the methods involved. It was also acknowledged that even more novel and proprietary methods could instead be used. Common environmental impacts included:

• water abstraction demand for cooling, gasification or cleaning
• generation of dust or fine particles during biomass preparation
• fugitive emissions to air
• leakage of compounds such as catalysts or water-soluble compounds into water

Existing incident management guidance from the Health and Safety Executive for ammonia and methane remain relevant for ammonia, e-methane and biomethane. Alternative forms of diesel and kerosene (for example, sustainable aviation fuel) have similar physical and chemical properties to fossil fuels, meaning that existing incident management techniques will likely remain relevant. However, there was limited information available on the physical and chemical properties of some alternative fuels. For all fuels, effective wastewater management, as well as stringent regulatory compliance, are needed to protect water quality and prevent contamination.

1.4 Conclusions

The deployment of alternative fuels is expected to increase before 2040. All fuels studied are likely to have impacts to air or water, with fewer impacts to land. While there is potential for impacts on human health, current evidence is limited and more research is needed to better understand and quantify these risks. As scale-up of alternative fuels continues, this information will help the Environment Agency to mitigate environmental impacts through its regulation and management of sites and processes.

1.5 Publication details

This summary relates to information from the following output:

• Report: SC240039/R
• Title: Environmental impacts of alternative fuels
• Science manager: Helen Brooks, Chief Scientist’s Group
• Research Contractor: Judith Bates, Ricardo

This project was commissioned by the Environment Agency’s Chief Scientist’s Group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.

Enquiries: research@environment-agency.gov.uk.

© Environment Agency