Plastic Free Mersey – a cross-sector approach to tackling plastic pollution

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Tackling Plastic Pollution: The Plastic Free Mersey Project
The River Mersey can be a place of beauty, but like many urban rivers it suffers from plastic pollution. The Plastic Free Mersey project is leading the charge in combatting plastic pollution in the River Mersey and its tributaries in north-western England. This flagship collaborative initiative brings together a diverse coalition of environmental NGOs, plastics industry businesses, waste management organisations, academics, and local communities to address one of the region’s most pressing environmental challenges. Together, we’re striving to identify and implement lasting solutions to reduce plastic waste that will not only improve the Mersey catchment but also serve as a model for rivers in the UK and around the world.

Here, environmental charities Thames21 and Mersey Rivers Trust, who lead the Plastic Free Mersey project, explore the benefits and achievements of the project.

Our shared aims
At the core of the Plastic Free Mersey project are several clear, collective aims:
• Achieve significant reductions in plastic litter and waste in and around the River Mersey and its tributaries.
• Characterise and quantify litter on riverbanks through citizen science surveys, helping us to understand the extent of the problem.
• Improve our understanding of the sources of plastic waste and develop practical, effective solutions to reduce pollution.
• Establish a collaborative model that can be replicated in other river systems across the globe.

The issue of plastic litter in the River Mersey
The Mersey catchment was selected for this flagship project due to its long-standing issue with macroplastic pollution. Macroplastics are plastic materials greater than 5 mm in diameter and they pose a significant threat to both the environment (e.g. wildlife) and human health.

The origins of plastic pollution in the River Mersey date back to their introduction in England at the turn of the 20th century, but the scale of pollution has increased over time, particularly since the 1970s with the expansion of single-use plastics for consumer products. We now have a persistent plastic pollution problem in most of our rivers. Contributing factors include littering, overflowing waste bins, fly-tipping, and sewer overflows, all of which regularly introduce plastics into the Mersey catchment rivers.

The impact of macroplastic pollution is twofold. First, it directly harms aquatic wildlife, causing injury through, for example, entanglement and ingestion. Second, plastics break down and degrade over time into microplastics, which are harmful to both wildlife and human health. The full extent of the threat posed by microplastics (and the even smaller nanoplastics) is still under investigation, but it is clear that action must be taken to reduce plastic waste in our rivers by following the prevention and precautionary principles.

Citizen science: Empowering local communities
One of the key strengths of the Plastic Free Mersey project is the involvement of local volunteers, trained as citizen scientists. These volunteers collect data through scientifically accredited surveys, through which we estimate the relative abundance and distribution of plastic litter along the riverbanks of the Mersey and its tributaries.

Since November 2021, volunteers have been working hard to gather vital data to evidence plastic pollution in our waterways. These site assessments include Tier 1, Tier 2 and Tier 3 surveys. Tier 1 surveys are qualitative assessments of site locations to identify areas that can be monitored safely and provide an indication of ‘green’, ‘yellow’, ‘amber’, and ‘red’ levels of litter. This then leads on to Tier 2 and Tier 3 surveys wherein the litter is categorised into 28 different types by trained volunteers, with the majority of the categories being plastic waste. Tier 2 surveys follow a 5- minute walking route upon an agreed stretch of inaccessible river channel (e.g. due to mudflats or steep sides) wherein volunteers record the identity and quantity of litter items they see on either side of the walking path. In Tier 3 surveys, volunteers categorise and remove litter items in two separate 60m2 areas on riverbanks. In Tier 2 and Tier 3, alongside recording the litter data, volunteers provide information on environmental factors, such as weather conditions, estimated river flow and width, and potential litter sources like sewer overflows, to better understand the origins of the plastic pollution.

Figure 1. A graphic representation of how to set up a Tier 3 survey section. Where necessary, other dimension variations were permitted to create a 60m2 section of riverbank (e.g., 15 x 4m). Drawing by Bea Asquith.

Citizen science surveys play a crucial role in identifying the potential sources of plastic waste, which enables our Thames21-Mersey Rivers Trust team to propose effective solutions to reduce overall pollution in the catchment. By involving the local community, we are not only gathering important data, but also empowering citizens to take part in the movement for cleaner rivers.

Figure 2. Map of Tier 2 and Tier 3 locations across the Mersey Catchment. Tier 2 locations are indicated by blue markers and Tier 3 locations are indicated by black markers.

Implementing Change: Turning Data into Action
The project’s interim Plastic Free Mersey Citizen Science Report, which was released in December 2024, highlights the ongoing progress made toward our shared goals whilst outlining the key findings from the data collected by our Citizen Scientists.
Since November 2021, we have trained more than 50 volunteers in our three PFM survey methods; the 32 active volunteers have conducted more than 200 surveys across just over 30 sites in the Mersey Catchment. As of January 2025, in combined Tier 2 and Tier 3 locations almost 9,500 litter items have been recorded, with over 8,000 in Tier 3 locations. On average, over 80% of this litter is made from or contains plastic.

Figure 3. Top ten litter items found across all Tier 2 and Tier 3 sites in the Mersey Catchment. Item categories are grouped into items made only of plastics (blue), items containing plastics (purple) and items containing no plastic (yellow). Error bars indicate a 95% confidence interval.
Figure 4. Average number of litter items found during Tier 3 surveys across different rivers and brooks. Data for each river comes from one site, aside from the Alt (two sites), the Bollin (two sites) and the Mersey (seven sites). Error bars indicate a 95% confidence interval.
Figure 5. Mean percentage (%) of plastic items by site in each river. Error bars indicate a 95% confidence interval.

The data collected from our citizen scientists is analysed and used to inform recommendations that can be implemented at local, regional, and national levels. These recommendations aim to make a tangible difference in reducing plastic pollution and include:
• Supporting the introduction of a Deposit Return Scheme (DRS) for beverage containers (including glass), encouraging recycling and reducing waste, education through community and school outreach along with creative intervention strategies like the implementation of humorous/engaging anti-littering signage to reduce littering.
• Proposing that water companies invest more in sewerage infrastructure to prevent overflows that contribute to river pollution as well as the replacement of wet wipes with truly biodegradable options.
• Suggesting that local authorities install more bins at locations where litter is prevalent, with more closed-top bins and better provision for cigarette butt disposal as well as an improvement of bin design, visibility, and placement to support easier waste disposal.
• Developing a community toolkit for volunteers, empowering individuals to take action and campaign for positive change in their own communities.

These recommendations are just the beginning, and the data collected will continue to shape our strategy moving forward, within this project and/or in other projects at environmental charities Thames21 and Mersey Rivers Trust. By seeking to implement the above changes, we aim to create a cleaner, safer environment for both wildlife and people in the Mersey catchment and beyond.

A global model for change
The Plastic Free Mersey project is not only about cleaning up the River Mersey; it is about creating a model of cross-sectoral collaboration and change that can be replicated in other rivers and communities in the UK and around the world. By demonstrating the power of citizen science, cross-sector partnerships, and evidence-based decision-making, we have been inspiring local residents and stakeholders to seriously tackle plastic pollution.

By collaborating with our partners RECOUP, British Plastics Federation, INEOS/INOVYN, LyondellBasell and Peel NRE, we have learnt their industry challenges, and they have learnt our NGOs’ challenges towards our respective goals. The project team has benefited from articulate discussions around the plastic waste hierarchy, different types of recycling (e.g. mechanical and chemical), and the circular economy we can all strive for. Although plastics are a very useful and versatile material, their ubiquitous presence as waste in the natural environment has become unsustainable at the global scale. Therefore, single-use plastics should be ideally replaced with other products and/or with refill systems, whenever these represent an overall more environmentally sustainable option. Plastic Free Mersey has been recently focusing on changing behaviours around littering and waste disposal through education and engagement sessions in various schools in the catchment with 9 sessions in 9 schools with just over 300 students run so far.

The challenge of plastic pollution may seem daunting, but with the efforts of passionate volunteers, community organisations, and experts working together, we are proving that real change is possible. A total of 187 volunteers participated in 18 litter picks in 2021-2024 and have removed ~3 tonnes of litter from riverbanks alongside the removal of items from our citizen scientists.
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If you want to get involved, become a citizen scientist, or learn more about our work, visit our project webpage at https://www.thames21.org.uk/plastic-free-mersey/ or follow us on social media for the latest updates. Join us in making the Mersey and rivers everywhere, a cleaner, healthier place for future generations. Together, we can make a difference!

Written by Thames21’s Aidan Hubbard and Mersey Rivers Trust’s John Sanders.