Tanning pays off! The circularity of leather production

In recent years, some stakeholders in the fashion and automotive industries are questioning the circularity paradigm at the heart of the tanning sector, i.e. that tanneries are processors of a by-product of the food industry with consequent environmental benefits. Studies such as “Circumfauna” on the initiative of Collective Fashion Justice, conclude, in fact, that from a sustainability point of view it is more convenient not to process the hides and skins, but to send them to landfill and replace them with alternative materials (e.g. synthetics) [1].
As is well known, from the raw hides and skins resulting from slaughtering, only a part is destined for leather processing; the layers that cannot be ennobled through tanning processes are used in other industrial sectors for the production of, for example, gelatines, products for cosmetics or agriculture (fertilisers). As reported in the “Business case” published by the Markets Institute (World Wildlife Fund – WWF) [3], if raw hides and skins were not recovered for leather production, their disposal in landfills would result in the release of greenhouse gases [3] such as carbon dioxide and methane, with consequent impact on the environment. The non-reuse of raw hides, conversely, would result in the production of alternative upholstery materials. Such materials are often identified as vegan ‘skins’, in many cases produced from plastic, i.e. raw materials derived from fossil fuels [3].
The question to be answered is: is leather production actually a process with a positive environmental balance? Or is it more cost-effective to replace it with alternative materials and dispose of raw hides and skins in landfills after slaughter?
This question has already been answered in the article ‘Would it really be better to let hides rot than turn them into leather? No…” by Leather Trade House published on its website leatheruk.org [2]. In the article, the calculation on carbon dioxide emissions performed by Circumfauna [1] is taken up, correcting some values of CO2 emitted by considering the real weight of raw hides and taking into account the formation of methane in the degradation processes of hides in landfills.
In terms of the balance of CO2 emitted, the lack of tanning of part of the raw hides and skins would entail the substitution of the leather with an alternative material and the disposal of the hides and skins, i.e. we would have to compare the CO2 emitted for tanning production with the sum of the CO2 deriving from the production of the alternative material and that from disposal. Going into the details of the values (excluding for simplicity’s sake emissions from livestock farming, which would always be present) and considering as valid the balance that only takes into account the portion of raw hide used in tanning processes, the values of CO2 [2] emitted for landfill disposal, synthetic leather production [1] and leather production are as follows:

– Emissions from landfill of leather: 4.08 – 8.78 kg CO2e/m2 [2]
– Emissions from synthetic leather production: 15.8 kg CO2e/m2 [1].
– Emissions from leather production: 7.0 – 17.0 kg CO2e/m2

In the data reported for landfill emissions, the maximum value of 8.78 kg CO2e takes into account the impact of methane production in the degradation process of the landfilled leather. Furthermore, the value reported in the Circumfauna study on CO2 emissions is higher than the value calculated by SSIP in some studies carried out on typical tanneries for the production of automotive metal free leather and chrome leather for footwear, for which actual emissions between 7.0 and 11 kg CO2e/m2 were found. A comparison of leather production with the proposed alternative of landfilling and substitution with other coating material is schematically presented in Table 1, including minimum and maximum values for disposal and leather production data.

PROCESS CO2e/m2 (min) CO2e/m2 (max)
Landfilling 4.08 8.78
Alternative synthetic production 15.80 15.80
19.88 24.58
Leather production 7.0 17.0

Once again, it appears that tanning is indeed a process with environmental benefits. Add to this, as stated in the Markets Institute’s Business Case [3], that from the point of view of circularity, leather can be recycled and reused and has superior durability compared to many synthetic alternatives.

by Ing. Rosario Mascolo, Technical-Scientific Coordinator Product Development Department SSIP
Contributors: Dr. Gianluigi Calvanese – Dr. Marco Nogarole

[1] https://circumfauna.org/leather-carbon-footprint
[2] https://leatheruk.org/would-it-really-be-better-to-let-hides-rot-than-turn-them-into-leather-no/
[3] https://files.worldwildlife.org/wwfcmsprod/files/Publication/file/3gs7vgqvmc_DCF_Leather_Business_Case_10_22_v4.pdf