The ethics of leather is hotly contested. On the one hand, raising cattle is known to be a major contributor to climate change. Leather tanning processes – both chrome and vegetable tanning – are known to be harmful to the environment. But leather is steeped in a heritage of being a natural animal product.
In this series, we will explore the different facets of leather production and its associated sustainability claims. Here, in Part 2, we examine the environmental impact of leather and the long-term consequences of industrial animal farming.
“Over the past forty years, more than 18% of the Amazon Rainforest has been lost, about 80% of which has been attributed to cattle ranching.”
Rainforest Deforestation
One of the main environmental impacts of leather comes from raising cattle. As leather production industrialized in the 1950s and production exploded in scale, farmers raced to clear land for more grazing pastures. Today, many of these grazing pastures are encroaching on the most sensitive habitats in the world – including the Amazon rainforest – and the risk of permanent ecosystem collapse is becoming more concerning.
Exploring the Amazon Rainforest as an example: Brazil is the world’s leading exporter of beef, and the areas by the rainforest have now become one of the largest cattle ranching regions in the world. Over the past forty years, more than 18% of the Amazon Rainforest has been lost, about 80% of which has been attributed to cattle ranching. Year after year, large swathes of the forest are being burned and replaced by pastures or slaughterhouses.
The rainforest is an irreplaceable source of biodiversity and also the world’s largest carbon sink. It is estimated that the trees and the soil of the rainforest store roughly 123 billion tons of carbon. However, when deforestation occurs for pastures, carbon is released into the atmosphere through tree cutting, land burning, and cattle grazing. Recent studies have shown that as deforestation has progressed, parts of the Amazon now release more carbon than it absorbs.
And it’s not just greenhouse gasses that are impacted. With rainforests playing a vital role in regulating rainfall by pulling groundwater up through tree roots and releasing water vapor into the atmosphere, deforestation means areas around the Amazon experience longer periods of drought.
In response to the effects of deforestation, commitments have sprouted up to hold corporations accountable for sourcing leather from pastures that are not linked to environmental degradation. However, the leather supply chain is opaque at best, and implementing these policies is inconsistent.
Enteric Methane from Cattle
As cows, sheep, goats, and other ruminants digest grass and feed, microbes within their digestive tract produce methane as a byproduct, then released into the atmosphere, contributing to rising greenhouse gasses. This enteric methane accounts for as much as 30% of global anthropogenic methane emissions. Methane — although representing a smaller proportion of greenhouse gasses in our atmosphere — is more than 25 times more potent than carbon dioxide at trapping heat within the atmosphere. The very existence of cows and their digestive systems largely impacts global greenhouse gas emissions.
Possible ways of minimizing enteric methane emissions from livestock are being explored. These ideas include genetically selecting animals that produce lower methane emissions, modifying diets, or using algal supplements. However, many of these strategies are still in the early stages of development and adoption.
Leather Tanning
Aside from cattle rearing, leather tanning and finishing is another environmentally harmful aspect of leather production. Since hides will naturally decompose, tanning stabilizes the collagen fibers and prevents degradation. Historically, common tanning agents included brain, urine, and tree tannins. Today, the most common tanning process is chrome tanning, which is favored for its quick turnaround and lower prices.
During chrome tanning, the hide is soaked in a chemical bath which includes chromium (III) as the tanning agent. If not managed properly, chromium (III) can oxidize into chromium (VI), an extremely toxic chemical. Many smaller tanneries in rural areas do not have the wastewater treatment capabilities to manage these harmful toxins. The effluent is therefore released into local communities where it pollutes waterways and poisons groundwater. In these communities, workers suffer from skin diseases and other illnesses as a result of being exposed to toxic water.
Chrome-free tanning and vegetable tanning similarly soak hides in a chemical bath to prevent degradation. However, instead of using chromium as the tanning agent, chrome-free tanning often uses aldehydes. Vegetable tanning replaces the tanning agent with bark or plant tannins.
While these alternative tanning methods appear more sustainable by replacing the harmful chromium tanning agent, these other methods still use chemical baths that contain a myriad of other ingredients which can be released into the local water supply. Life cycle analyses of these three different tanning methods do not show a significant difference in the degree to which they negatively impact the environment.
But Wait, Isn’t Leather Biodegradable?
A major selling point of leather is its natural origin. It is often assumed that leather is from nature and, therefore, biodegradable. It’s worth remembering that leather was created with the intent of preserving it so that it would not degrade after long periods of wear. Even though leather comes from animals and is naturally sourced, there are many chemical changes that it undergoes as hides become leather.
Also, different standards agree on different definitions of biodegradability. In the EU, a material is considered to be ‘Readily Biodegradable’ if more than 70% of it is converted into carbon dioxide, water, and minerals within 28 days. Leather can be expected to biodegrade in industrial composting conditions within 10 to 12 months— in controlled temperature and pressure settings. This means that while leather does biodegrade, it does not meet the EU standards for biodegradability – even though leather that is tanned with organic substances will biodegrade significantly quicker than chrome-tanned leather.
Leather is a luxurious material that has natural origins, but with a holistic view of sustainability, we can also be reminded of the many aspects of modern leather production that damage the environment. That is why new alternatives to leather now look to provide solutions to these problems, focusing on creating natural materials without harmful chemicals or deforestation.
Note: Bucha Bio rebranded to Rheom Materials in January 2024 to better reflect their process and offerings. The new name combines the Greek word "rhéō" (meaning "flow") and "form," describing how a melt-extruder works, where the biopolymers flow into place and then solidify, or form, the final product.
