Grown, Not Tanned: A Biofabrication Primer on Lab-Made Leather Alternatives

Leather has a long history and a heavy footprint, which is why materials scientists have spent years trying to grow something similar in a lab. The results are often described as "lab-made" or "bio-based," phrases that sound precise and are not. This primer explains how these materials are made in general terms, without naming any brand, and what the labels do and do not tell you.

Two main routes: cells and fungi

Most biofabricated leather alternatives follow one of two broad approaches. In the first, animal cells, typically skin-related cells, are cultured in a nutrient-rich liquid, encouraged to produce the structural protein collagen and arranged into a sheet. In principle, the result resembles the fibrous structure of hide, without raising and processing an animal.

In the second approach, the starting material is mycelium, the root-like network of a fungus. Mycelium grows as a dense mat when fed on agricultural by-products such as sawdust or plant residue. The mat is harvested, compressed and treated to become flexible. It does not contain animal cells at all, and its properties come from fungal biology rather than collagen.

From culture to a usable sheet

Growing the material is only the start. After harvest, a sheet usually goes through steps that resemble conventional leatherworking: preservation to stop it from degrading, softening to adjust texture, and finishing to improve color and surface. Many products are also backed with or blended with other materials for strength.

This is where much of the real engineering happens. A raw grown sheet can be thin, uneven or fragile. Making it durable enough for shoes or bags, where it must flex thousands of times, is a separate challenge from growing it in the first place.

What "bio-based" really means

The label bio-based means that some portion of a material comes from biological sources, such as plants, fungi or cells, rather than from fossil fuels. It does not say how much, and it does not describe the rest. A product could be partly bio-based and still include a petroleum-derived coating or binder.

Other terms need the same care:

• "Lab-grown" describes a process, not an environmental result.
• "Vegan" means no animal-derived inputs, which is true of fungal materials but not necessarily of cell-cultured ones.
• "Biodegradable" depends on the full composition, including coatings, and on the conditions where the product ends up.
• "Sustainable" has no fixed definition and is best checked against a published life-cycle assessment.

Ask what percentage is bio-based, what the rest is, and whether anyone outside the company tested it. Those three questions cut through most of the marketing. — a materials scientist at a university lab

Honest limits

This field is young, and several important questions are unsettled. Independent, published comparisons of footprint between biofabricated materials and conventional leather are limited, and results depend heavily on the energy used in production and on what the feedstock is. Durability over years of wear is less well documented than durability in short tests. Costs are another unknown: growing cells in controlled vessels is expensive, and scaling to industrial volumes is a hurdle that has slowed many ventures. Regulatory and labeling rules also differ by jurisdiction, so a term allowed in one market may be restricted in another.

It is also worth being careful about comparisons. Conventional leather is itself a by-product of the meat industry, and its footprint depends on how animals were raised and how hides were tanned. A fair comparison needs consistent boundaries, and not every claim you will see in advertising meets that standard.

The bottom line

Biofabrication is a real and interesting set of techniques, and some products will likely prove durable and attractive. As a shopper or reader, treat labels as the start of a question rather than the end of one. Look for the percentage of bio-based content, the identity of any coatings, third-party testing and a published life-cycle assessment. Where those are missing, the sensible reading is that the material is promising but unproven. Growing a material is impressive. Showing that it is better, in measurable ways, is the harder and more interesting part.