Inspired by local microbreweries, London-based start-up Arda Biomaterials has made a plastic-free leather alternative by altering the protein structures in brewer's spent grain.

Arda's New Grain material is made by taking the spent grain or "draff" from beer or whisky production and reconstructing its plant proteins to make them more like animal proteins.

The resulting material is soft, supple and durable like animal leather or synthetic polyurethane, and does not require the plastic binders or coatings common to plant-based alternatives made from mycelium, bacterial cellulose or plant waste fibres.

"We are one of extremely few solutions that have remained completely plastic-free," Arda commercial lead Camelia Hamdi-Cherif told Dezeen.

"The interim class of materials [made to replace leather and synthetics] still ended up having to rely on adding different petrochemical or plastic binders or top coats to perform, and that's kind of become the standard," she added.

"We really don't see that as a long-term solution, and neither do customers in textiles and fashion."

Currently in the demonstration stage with its technology, Arda is based in the London neighbourhood of Bermondsey – appropriately, a historic leather tanning district and current craft brewing hub.

Founders Edward "TJ" Mitchell and Brett Cotten had the idea to use an abundant waste product of the area while experimenting with potential biomaterial formulations in Mitchell's home kitchen.

Brewer's spent grain is the soggy, low-value byproduct left over from mashing malt during beer production and typically ends up being used as animal feed.

However, the material is rich in protein, and Mitchell and Cotten reasoned that by developing a method based on recent research into plant protein modification, they could transform it into a higher-value product.

Arda's spent grain-specific proprietary process is a type of "green chemistry" involving non-toxic and non-hazardous substances. It requires isolating and reconfiguring the plant protein molecules within the grain into stronger chains.

"Plant proteins come in this really coiled up, kind of messy state," said Hamdi-Cherif. "We basically unravel these fibres into longer chains and then link them to each other, so that you get the building blocks for something that looks like collagen."

In the process, liquid protein is extracted from the grain and purified in a similar way to how plant proteins are treated to create meat alternatives. They are then mixed with different bio-based ingredients that help recreate the buttery feel of leather or encourage new connections to form between the protein chains.

Natural pigments are added for colour before the goop is placed in trays with textured paper on the bottom to imbue the leather alternative with surface patterns such as pebble grain. Once dried, the sheets are stuck to a natural textile backing.

Scaled up, this stage would take place using roll-to-roll manufacturing, where the material is fed from one roller onto another while being dried and printed.

The process is conducted with readily available equipment, half of which comes from the brewing industry and half of which is common to polyurethane production.

When you combine this with the low cost of the feedstock, Arda believes New Grain can be made cost-competitive with both animal leather and standard polyurethane at scale.

"On our batch process now we cost more closely to a luxury animal leather," said Hamdi-Cherif. "But our projections for roll-to-roll [are that] we'll be able to get really, really competitive unit costs that we hope should rival synthetics in the next three to four years."

Arda says that according to its calculations, the carbon footprint of New Grain is 96 per cent lower than cow leather and 72 per cent lower than synthetic leather. The material is theoretically biodegradable and is currently being tested against established standards.

The company has recently demonstrated its material's potential in a partnership with accessories brand BEEN London, which has seen it used to make handbags and tennis racquet covers.

Hamdi-Cherif told Dezeen that the company is starting with wallets, bags and similar accessories and will look at moving into items such as footwear, automotive interiors and furniture that require proven high performance as the technology matures.

Arda is planning a limited commercial launch in 2026 and has established partnerships with both the world's largest beer company, AB InBev, and largest whisky company, Diageo, for grain use and product development.

Other biomaterial alternatives to leather include Modern Synthesis's bacterial nanocellulose and Osmose's mycelium material.

Other plant-based "leathers" on the market often displace some but not all of their petroleum-derived ingredients with crop waste such as apple scraps, lowering the carbon impact but still adding to plastic production.