Abstract: Traditionally, fashion has been a low-tech industry that hasn't changed much over centuries. The current leather manufacturing process is unsustainable, gruesome, polluting and inefficient. The cell-based approach has the potential to provide a sustainable, efficient and higher-quality leather. While borrowing the technology from the cultivated meat industry, cultivated leather can accelerate synbio due to the relatively less regulatory nature of the leather industry as opposed to the meat industry.
Throughout human history, we have transformed resources around us into something useful. Leather, one of humanity’s most useful discoveries and one of the oldest crafts known to mankind, is one such example. In the Stone Age, our hominid ancestors used the skins of the animals they hunted:
i. to protect themselves from the harsh weather,
ii. as ornaments, totems, amulets, or for musical instruments, and
iii. to carry their belongings whilst they roamed afar.
Source: Liberty Leather Goods
Over the centuries, humans learned to prevent the leather from decomposing by tanning them and leather eventually became part of what is today a $2 trillion fashion industry. There have been so many articles floating around that claim Fashion to be the 2nd most polluting industry after oil. But the sources of information in the articles are weak. The data is still unclear. Our World in Data, one of the most reliable websites, makes no mention anywhere of the fashion industry directly on the impact front. Global Fashion agenda claims in 2018, fashion industry produced 2.1 Billion tonnes of CO2, about 4% of the global carbon emissions.
Fashion, one of the world’s major manufacturing sectors is now poised for disruption. With the advancements in bio-fabrication, leather, in particular, offers a huge opportunity.
Within the fashion industry, a legitimate claim is that leather is the material with the largest net footprint among others.
Source: Conservationhierarchy.org adapted from Kering report
To understand why we need to dive a bit into the whole leather making process.
Almost any animal can be the source of leather such as pigs, sheep, goats, rabbits and even crocodiles. But the most common source is a cow. The art of making leather involves this very important product called 'hide'.
Leather is mostly made of collagen - the main proteins of any skin - which needs to be extracted from the hide. The proteins are made of amino acids, which are in turn built of carbon, oxygen and hydrogen. The protein strands are made of specific amino acids - glycine, proline, hydroxyproline and arginine- in the form of a long string twisted in helix shape and are bundled together to form collagen fibrils. Collagen provides the tough and rigid structure found in skins which are then translated to leather. To make leather, everything else needs to be removed from the skin while strengthening the collagen. The first step is the hide preparation.
Collagen. Source: Journal Leather Science and Engineering
The hide is a by-product of the meat and dairy industry which is then transformed into leather i.e waste being made into useful material. Isn't that a good thing? Yes and no. (Later on this)
To prepare a hide, the animal skin and then the flesh are removed leaving behind a white, clean surface. In order to prevent it from decomposing, the hide is placed in a salt brine and then placed in a lime bath (calcium oxide) to remove any hair on the hide. The two processes increase the moisture in leather which makes the product quite thick that it could be split into two layers.
The upper layer is more durable owing to its tight fibre structure and is used for high-quality leather products such as car seats, fashion clothes etc. The lower layer is used for cheap leather in products such as shoes, gloves, bags etc.
Source: Pearl Academy of Fashion, Slideshare
Once the hide is prepared, the second step involves a process called tanning which converts the hides into leather. The tanning process stabilizes the collagen in skins so that they stop biodegrading. The hide is mixed with a tanning solution in the form of either vegetable tanning agents or chromium salt mix in a tanning drum. Special fats are added to the leather to make it stronger and softer.
The ancient Greeks are credited with developing tanning formulas and making it a well-established trade around 500 BC. To preserve the leather, they created the earliest known vegetable tanned leather using certain tree barks and leaves soaked in water.
The third step in the process is dyeing which adds colour to the leather is a lengthy process that involves adding a dye to the leather in a large drum. The final process, appropriately called finishing, is the stage where leather is worked to ensure it has both the desired flexibility and a glossy finish.
Impact of Leather:
While leather is often considered a byproduct of the meat industry, the material is part of the business model. Critics claim that leathers leave farmers with more profit generated than from meat production. Therefore, arguing that buying leather is equivalent to supporting the meat industry. Nevertheless, unless there are alternate solutions, the leather industry's environmental footprint should be accounted for.
The GHG footprint of the food industry, from which leather is sourced, is already complex, and the allocation of the impact of leather is a bit sketchy. There seem to be highly contradicting data points and unclear measurement tools.
A report on leatherpanel.org claims carbon footprint in the leather making process can be classified into two parts:
- 110 kg CO2e/m2 of leather including cattle farming
- 17 kg CO2e/m2 of leather after slaughterhouse
Carbon footprint largely depends on the source of energy used in various processes. It is important to consider that shifting to renewable sources of energy wherever possible in the entire leather-making process is a viable option. However, carbon footprint isn't the only concern in this industry. For example, to strip the hairs from the hide during the tanning process used for mammal leathers requires strong chemical products that release gasses such as hydrogen sulfide which is a corrosive, flammable and explosive gas.
Water is both consumed at a high rate in the leather industry and contaminated by polluting chemicals. The data here again is unclear.
Leatherpanel.org claims the hide preparation process consumes somewhere between 7 and 25 m3 water per ton of hides, the tanning process between 1 and 3 m3 and post-tanning combined with finishing between 4 and 9 m3.
A report by Credit Suisse claims the total amount of water required to make a pair of leather shoes at 13,725 litres.
However, the biggest impact of leather may be Eutrophication: enrichment of water by nutrient salts that causes structural changes to the ecosystem. These include excess production of algae and aquatic plants, depletion of fish species, general deterioration of water quality, etc.
The number of chemicals and amount of water used in hide preparation, tanning, dyeing and finishing processes are a cause for concern as they are claimed to destroy natural ecosystems.
(Note: synthetic leather in the image below refers to leather made out of polyurethane)
Currently, the majority of alternate/vegan leather is made from polyurethane, a plastic derived from fossil fuels. While this may score better than animal leather for global warming and pollution, disposal of PU poses its own environmental problems.
The need for new and alternate solutions can be alluded to:
- Companies and brands struggling to trace their footprint
- carefully designing processes to reduce footprint and provide better quality
- a vast majority of hides going to waste
There are 5 broadly defined ways to make leather artificially in a sustainable fashion:
- Recycled Leather:
As the name suggests, recycling leather is definitely necessary to reduce waste and minimize the footprint. As demand increases, the original source of recycled leather will still depend on the unethical and non-environmental friendly way of sourcing leather unless other alternatives are discovered.
2. Plant-based leather:
By extracting cellulose fibers from plants to make leather, few startups such as Pinatex and Natural Fiber Welding have already entered the market in making leather alternatives. While some use plastic and some do not in the process, the overall performance of plant-based alternatives are still below that of animal-based leather. While plant-based leather products score high on sustainability, durability is far from desired standards
3. Fish-based leather:
Sourcing leather from fish waste that is farmed is another way that has less environmental impact compared to traditional ways since the least amount of chemicals are being used during the tanning and dyeing process. But it still cannot be considered animal-friendly.
4. Mycelium based leather:
Alternatively, mycelium which is mushroom-based is used in the bio-fabrication process. Mycelium, prevalent across the globe, is a sprawling, infinitely renewable, interlaced web present in the soil, plant bodies, and along river beds. Given the right environmental conditions such as humidity, temperature and sawdust as feed, mycelium can grow into a foamy which when harvested grows into a sheet of layer resembling leather. These sheets are then processed and dyed to be used in traditional leather-based products.
5. Recombinant Protein-based leather:
Biofabricating leather through engineering cells at the DNA level using recombinant microorganisms (through genetic modifications) that produce proteins such as collagen. The process combines select proteins with bio-based polymers that provide durability and resistance properties. Just like brewing beer or making wine, this process turns commercial yeast into collagen-producing cell factories through fermentation.
6. Cultivated cell-based leather:
Cultivated leather is grown in a process very similar to cultivated meat:
a. Cell Sourcing:
The cells are sourced from a one-time biopsy process from an animal such as a cow. Following which the cells are immortalized which offers the cells the ability to reproduce unlimitedly.
b. Cell Production:
The immortalized cells are then grown inside a bioreactor to develop a cell line that can proliferate. This avoids the necessity to source new cells from the animal.
c. Cell Seeding:
Inside the bioreactor, cells are attached to a porous scaffold and made to expand for tissue generation.
d. Cell Nurturing:
Following this, growth factors and the right nutrients are added for the cells to produce different kinds of proteins such as collagen that is essential for providing the mechanical strength associated with traditional leather. The cells are stimulated in the process to produce the sheet(hide).
e. Hide Harvesting:
The hides are then harvested and prepared for tanning.
f. Tanning and Finishing:
The hides are then tanned and finished via the conventional process. But unlike the traditional hides, cell-based hides require 90% fewer chemicals, consume far less energy and water, and generate little waste Since the process is relatively simplified, it has a far less environmental impact since only the required ingredients are grown and there is no removal of materials such as hair that come along with the natural hide.
Modern Meadow was the first leather bio-fabrication company to enter the space. The company was founded by Andras Forgacs and his father pioneered bio-printing of human tissues through Orgnova. With 184 Million $ in funding, the company is expected to manufacture new bio-materials after the successful launch of the world’s first bio-leather materials brand created with collagen, but grown without animal derivative in 2017.
Bolt Threads is the oldest company that entered the biofabrication space but the company started with biofabricating silk by studying spiders and developing the associated proteins through yeast fermentation. The company has also developed leather through a similar process. With 214 M $ in funding, the company is going all out to disrupt the fashion industry.
Mycoworks and Ecovative design are other players leveraging microorganisms to bio-fabricate leather. Provenence Bio is another company developing a synthetic biology platform to produce proteins that can be used in the meat, leather and therapeutics industries. Hide Biotech is a seed stage startup that harnesses waste from fish farming to use them as raw materials to create collagen-based leather.
The most exciting startups are the ones trying to recreate animal leather with a cell-based approach. Qorium is a cultivated leather startup based in the Netherlands. Mark Post, the Chief Scientific Officer at Mosa Meat, the scientist behind the world's first cultured burger, is functioning the same role at Qorium. Faircraft, currently raising seed fund, is a Paris based startup that aims to manufacture leather that is based on rabbit cells.
Leather bio-fabricating process. Source: VitroLabs
VitroLabs is a US based company that leverages 3D tissue engineering using stem cell-based technologies to manufacture real leather. The company develops a fully scalable tissue engineering platform combining stem cell research and biomaterials.
With consumer demand for sustainable products rising, and increasing pressure on the leather industry to offer sustainable solutions, the cultured leather approach positions itself to provide both a sustainable and higher-quality leather alternative.
Global Fashion Agenda organizes summits and produces reports focused on making the fashion industry more sustainable.
Kering Group has open-sourced its sustainability reports and come up with an internal Profit and Loss measurement tool that takes impact into account.