SLG has established a new biofoam division to help make the fullest possible use of the hides it sources, and to confirm its status as a single, vertically integrated supplier of seating solutions.

Scottish Leather Group (SLG) is expanding its production of BioPRO, the protein-based foam it launched in 2025. The specialist aviation leather part of the group, Muirhead, was the first to supply customers with the new foam for use in seats on aircraft. It has described the new product as naturally fire-resistant, a quality it achieves thanks to the protein-based content. The biofoam is made from hydrolysed collagen, which comes from the hides the group uses for leather production. This development earned Scottish Leather Group a nomination in one of the categories at the 2025 Earthshot Prize, a sustainable innovation competition that awards funding of £1 million to winners in each of five categories. To earn a nomination is an important accolade.

Now the group’s specialist automotive leather division, Bridge of Weir, has begun offering BioPRO as seating foam to customers in the car industry, which include Aston Martin, McLaren, JLR and Polestar. It says the product will provide a lower-impact alternative to traditional automotive seating foam, which is mostly developed from polyurethane (PU). Group chief commercial officer, James Muirhead, says that, for decades, Bridge of Weir has been an enthusiastic supporter of its automotive partners as they work to reduce the environmental impact of their interiors. SLG calculates carbon intensity at 8 kilos of CO2-equivalent per kilo of finished leather it produces, adding that this figure is independently verified. For years now, it has been presenting this to the market as the lowest carbon-intensity leather in the world. “BioPRO is the next step on that journey,” James Muirhead says.

Appetite for protein

Collagen content makes up 20% of the foam’s composition. SLG says it is “intercepting” the protein from cattle hides near the start of its leather manufacturing process and subjecting it to hydrolysis. It insists its biofoam can replace melamine, bromine, titanium phosphate, graphite and per- and polyfluoroalkyl substances (PFAS), as well as PU, in the foam materials that its customers have been using until now.

In a summary of the benefits, the group says that choosing BioPRO instead will help automotive and aviation customers reduce their use of fossil-derived content, improve circularity and lower environmental impact. It also says it is a recoverable, “truly circular” and sustainable material. Tests suggest that, at the end of a car- or aircraft-seat’s life, the foam can be recovered through an easy-to-carry-out acidolysis process and reused, which means circular thinking has been part of this project from the outset. In addition, the foam can be moulded to an exact specification each time, eliminating, the group states, the material waste associated with conventional cut foams, which often require multiple cut parts. This can also help reduce weight.

Natural comfort

Head of biofoam projects, Andie Burrows, says the research that SLG has done shows that the protein in the foam “possesses remarkable properties”. He explains that traditional, flexible-PU foam is only able to achieve the safety standards that aviation and automotive customers require by adding the fossil-fuel-derived retardants and absorbent mineral fillers mentioned above. Airlines and car companies can tell a greener, cleaner story, he argues, if they choose to use this “wonderful natural product” in their seats instead.

This is a project SLG’s head of innovation and sustainability, Dr Warren Bowden, has led. “Collagen is the first thing produced in the making of leather,” he explains, “and when it is hydrolised it forms gels and foams. Through its natural chemistry, it is also flame-retardant. What we have done is create a new chemistry. We have impregnated collagen into a urea-urethane polymer structure. The protein is an integral part of the chemistry. It has additional layers of bonding and perhaps this explains why the foams we are making in this way have a different feel. They feel more comfortable and lighter in weight.”

Weight loss

Figures that Andie Burrows shares with customers give a weight of 47 kilos per cubic-metre for the biofoam SLG is able to make, compared to 55 kilos for foam from conventional suppliers. Seats account for a substantial proportion of the weight of an aircraft (before passengers sit in them). Even a small weight saving, multiplied across the whole fleet of a major airline, can make an important difference to fuel burn and to carbon emissions. In this case, though, the weight saving is not small; it is a reduction of 14.5%.

This matters in automotive, too, Mr Burrows explains. Original equipment manufacturers are focusing more and more on electric vehicles and are working hard to extend battery range. Any weight saving in the interior can help them in the quest to increase the number of kilometres a vehicle can run on a single charge.

Then there is the advantage of being able to precision-mould BioPRO, which is important because customers use different moulds for different types of seating. With BioPRO, dimensional stability will be the same, from one mould to another. In contrast, because flexible PU foams are made in blocks, which are then cut down into smaller blocks, human input, inefficiency and waste are unavoidable.

Carbon savings

Returning to the question of compliance with the strict safety regulations that apply to seating in aircraft and cars, SLG explains that one important benefit of its new product is that it does not burn in the same way as foams constructed without protein. “Almost anything will burn eventually,” Warren Bowden says, “but BioPRO has the ability to quench the gas phase. It will carbonise on the surface and form a carbon char layer, which doesn’t combust. It resists flaming and, as a result, it is, basically, self-extinguishing.” Other foams use graphite particles to slow the spread of flames and achieve compliance.

SLG’s view is that its biofoam can beat these competitor products on durability. “The graphite that normal foam contains is highly abrasive,” Dr Bowden continues. “It destroys the matrix it is sitting in. This abrasion means those foams will lose their integrity over time, giving them a comparatively low service life. The service life of BioPRO is far longer. The protein delivers the flame-retardancy that other foams need graphite to achieve. Because BioPRO is a gel-like material, it contours, it springs back into shape and does not abrade itself during its service life.” He describes this as “quite a step” in challenging the conventions.

In comparison to graphite moulded foam, BioPRO’s construction means it has only around 50% of the embedded carbon footprint. In addition, the new biofoam offers customers important carbon savings in the use phase. The combination of the saving in weight and additional durability suggest a saving of more than 480 tonnes of emissions for each aircraft over a span of 10 years of use. SLG says this figure comes from an independent estimate.

Years in the making

SLG’s direct work on this began in January 2021 in partnership with a third party with expertise in moulds. It is    part of a longer-running strategy. It announced ten years ago that it would invest and innovate to help its customers in transportation develop “the sustainable seat of the future”.

Explaining BioPRO’s contribution to this, Warren Bowden says: “In this case, the functionality that the collagen has is the key driver. It has allowed us to create something that out-performs the conventional fossil-fuel-derived PU, which has been around for 90 years.” He adds that the foam immediately seemed to be a product with great potential, although it took two or three years “to unravel exactly what we had managed to achieve”. SLG viewed this reverse-engineering as a necessary step before bringing its innovation to market.

The first prototypes emerged in 2023 and the group applied for a patent for what it refers to as the “novel chemistry and novel methodology” involved in the product. This included “several clever bits and pieces at the front end of the process” to make the material solubilise and emulsify before reacting. The patent application met with no objection but it still took until February 2025 for it to be granted.

And now that it has a full understanding of how the product works and its international patent in place, the group has set up a new biofoam division, working out of its site on Dunn Street in the east end of Glasgow. It describes this as a way of diversifying its business and of helping it use to the fullest extent possible the hides it sources for leather manufacturing. 

If you take an average hide of the type SLG works with, from cattle fed on grass in the UK and Ireland, Andie Burrows says that 11.25% of it, by weight, becomes finished leather. More than half, 51.25% goes towards energy production at the on-site thermal energy plant the group installed at its Bridge of Weir site more than 15 years ago. This, too, is an innovation that Warren Bowden pioneered. He explains that one 40-kilo hide can yield two litres of oil “with an enormous calorific value”. The remaining 37.5% is what Mr Burrows refers to as ‘co-products’, some of which, from now on, will be used to make BioPRO. Using collagen from cattle hides to produce in-demand foam material strikes SLG as a natural step.

At every stage

“One of the things that is often overlooked is that we, as leather manufacturers, are one of the biggest processors of collagen,” Dr Bowden continues. “It is right for us to look at new applications for collagen as well as for hides. We can account for the entirety of the hide. We can add value at every stage. There are markets for all of it.”

The foam production facility will share the space at Dunn Street with the group’s cabin engineering team, which works on the design of prototypes for aviation, automotive, rail and bus applications. There are also extensive testing facilities at the site. Taking the discussion back to the initial idea of “the sustainable seat of the future”, SLG says it can now serve its customers as a single, vertically integrated supplier of everything they need.

Foam to fill seats and leather to cover them. SLG is now a vertically integrated supplier of what transport companies need in their seating systems. Credit: Scottish Leather Group

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