From milk to growing media: protein fibre offers high-nutrient peat-free option for growers

A novel fibre made from waste milk protein is gaining traction as a high-nutrient option to help growers go peat-free – just when they need it most.

Valued for its moisture retention, aeration and crop performance, peat remains a cornerstone of horticulture, with over 2.2 million m³ used in the UK in 2020, and 44 million m³ extracted each year across Europe, primarily as a growing media. But with the depletion of natural peat resources being a major ecological concern, the UK government has set ambitious targets to phase out peat use by 2030. 

Since 2021 there has been a 741,000 m³ reduction in peat use year-on-year, prompting the growth in alternatives such as coir, bark and mushrooms. While these have grown in industry share, stakeholders have warned that some crops struggle with yields on peat-free mixes. In response, growers are calling for blends that can match peat’s performance whilst having higher ecological credentials.

Agri-tech start-up Grouse Fibre is aiming to provide producers with one such option. The Gloucestershire-based company utilises waste milk, initially in powdered form, which is dissolved into a solution and run through specialised machinery to produce a ‘protein yarn’ that becomes a nutrient-rich, high-performing fibre. 

According to Dr Tom O’Haire, founder and CEO, Grouse Fibre’s protein fibres can complement other peat-free solutions such as bark or coir, which would benefit from additional nitrogen content, absorption capacity and binding strength.

“Our fibre has high nitrogen content and it’s also very good at holding moisture and retaining water. So as an ingredient in growing media, we think there’s some advantages there,” he says. 

Building the evidence base for peat-free growing media

Grouse Fibre is one of the latest cohort of promising agricultural innovators receiving funding and mentoring support from SHAKE Climate Change, a funding and support programme led by Rothamsted Research in partnership with renowned research institutions and innovation funders.

The backing will allow the company to move beyond qualitative insights into how growers use the novel media, towards collecting hard data that could ultimately bring the product to a broader market.

“We’re doing trials in Scotland with commodity crops — radishes, cosmos and tomatoes — which have shown some really promising germination results versus standard peat-based grow media,” says O’Haire.

So far, interest has mainly come from growers who have already gone peat-free but are struggling to find optimal mixes for their products.

As well as the work with specialist growers in Scotland, Grouse Fibre is also working with forestry partners and Cumbria Wildflowers, a company involved in growing plants for peatland restoration. 

“They’ve been telling us about their challenges, and how they need ingredients that can help protect against drought and limit moss growth, and we think our fibres can help on those scores,” says O’Haire. 

When it comes to sourcing waste milk, the company is aiming high, hoping to approach brands like large dairy processors to gain access to their protein by-products. However, milk alone won’t suffice if the product is to play a serious role in horticulture. 

“The dairy side would only take us so far. There is a limit on how much of this we can make in the UK and even globally,” says O’Haire. “Where it becomes interesting is when we start looking at other proteins, like soy and nutmeal, which are more abundant than dairy protein,” he explains.

“We think this could help displace tens of millions of cubic metres of peat in professional horticulture, which would require fibre production in the order of kilotons per year.”

Scaling peat-free alternatives

With support from SHAKE Climate Change, Grouse Fibre is now investing in new equipment, initiating third-party validation, and building technical capacity – bringing more agronomy expertise into the team.

And with the goal of making a splash in the peat-free market, Grouse Fibre’s data collection mission is now underway. The company is working to align with more growers who are committed to peat-free mixes and may be willing to participate in trials. “We have been largely dependent on external grants, and that means we’ve had to be quite careful in our ambition,” says O’Haire.

“This injection of capital from SHAKE means we’ll be able to go to customers with more confidence that we have the bandwidth to produce kilos for their trials, whether that’s a controlled environment trial over the winter, or a polytunnel trial between spring and summer.”

Ultimately, success depends on scale. As well as struggles with water retention and nutrients, one current barrier to wider adoption of peat-free products is their higher costs. The global organic substrates market is projected to grow from $6 billion (£4.4bn) in 2025 to $8.13 billion (£6bn) in 2030, but only offering an option that delivers an optimal growing environment at the right price point is likely to attract investors in future-proof agricultural products. 

“We need to go from producing hundreds of grams per trial to kilos, and that will really enhance our ability to scale our fibre and lower costs, as well as do more meaningful testing,” O’Haire says. “We hope that both of those things will feed into a seed funding round in late 2026 or early 2027, which would be in the order of £750,000 to a £1 million.”

To find out more about the SHAKE Climate Change support programme, visit shakeclimate.org

This article is published as part of Farming Future Food’s Industry Insights series, which is supported by sector partners. The FFF editorial team maintains full independence over content.

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