A Technician's Perspective: Understanding Recyclable, Biodegradable & Compostable Materials

Year after year, the search for ecological materials becomes more and more urgent, which begs the question, how do we know what materials truly have a positive impact on our planet? Read on to learn what Daniel Pistorio, a seasoned leather technician thinks.

Consumer demand incentivises most brands to adopt environmentally friendly materials in their supply chains.  For example, brands like Adidas heavily invest in advertising alternative materials, as seen in using vegan leather to make one of their most famous sneakers - the 'Stan Smith'. However, to prove the actual ecological gains of vegan leather, more research is required. As of today, the eco-friendliness of vegan leather remains inconclusive, and brands are further confusing vegan leather for environmental sustainability when it relates more to an ethical choice to not consume animal products.

If you wish to understand the eco-friendliness of vegan leather is and how other materials that imitate real leather are made, I invite you to read the article I wrote some time ago.

This article explains what biodegradability, recyclability, and compostability mean and what compels us to buy such products.

Recyclable materials and reusable materials

The term recycling refers to a very complex production system, which begins with collecting materials (or products containing the materials), continues with their separation and subsequent treatment, and ends with obtaining regenerated raw materials or semi-finished products.

Recycling requires a lot of energy and utilises a unique production system that has individual environmental costs. The raw materials' yields are often low, and their quality is often not par with the original materials. Furthermore, recycled materials have higher fees than non-recycled ones.

All this should reflect that recycling is the real usefulness of introducing materials that are already present in our consumption cycles, without requiring new ones and postponing many environmental problems.

It is not an elimination of the problem but a postponement. We are talking about recovery costs: energy, means of transport, industrial processes, use of reagents, production of waste and slag and much more.

With recycling, we recover our raw materials but always remember that we pay a cost that can be very high and not for nothing in environmental terms.

There is a very open debate on the convenience of recycling.

Therefore, when you buy products manufactured with materials that have the above logo, keep in mind that it is not always true that you are doing the environment a favour.

The real utility of recycling lies not in the recycling itself but the reuse of materials. An example is glass bottles, which companies can reuse indefinitely. Or the canvas bags we use for shopping, or glasses and cutlery that are not plastic.

The materials that are recycled are different, the most common of which are:

  • Metals (ferrous materials) that can be remelted and converted into other ferrous materials;
  • Aluminum;
  • Glass. Usually, new glass mixes contain a percentage of recycled glass.
  • Paper and cardboard, whose recovery of cellulose fibres allows for significant water, wood, and energy savings. The costs of recycling are lower than those of incineration and the production of new products. The substantial reduction in deforestation gives a second benefit.
  • Wood - think chipboard panels or pallets of crushed wood. Wood recycling is also eco-friendly because it reduces deforestation;
  • Plastics (PVC, PS, PE, PET, PP) which companies can recover mechanically or by crushing them to obtain inert powders;
  • Natural fabrics, from which it is possible to recover parts of yarn;
  • Waste oils for food and non-food use; and
  • Organic food waste, which wastes management companies, should send organic waste to composting plants.

Leather companies can also recycle leather. The leather residues that are ground and incorporated into panels of a material resemble chipboard and lower technological properties than real leather. Recycled leather can accept its finishing operations as natural leather. Products that withstand little mechanical stress can use recycled leather as an alternative to genuine leather. For example, footwear or technical clothing should not utilise recycled leather, but fashion and lifestyle designers can use it to create bags or accessories.

Fig.1: Recycled leather

Materials such as PU, PVC and vegan leather imitations produced with vegetable powders are not reusable. Still, they must are recycled as plastic products, i.e. shredded and transformed into inert powders, which are incorporated, in turn, into other inert materials, such as insulating panels in the building sector. The support non-woven fabrics (the so-called bases), being synthetic fibres, can, in turn, be recycled like other plastic materials and not as fabrics. Remember this aspect when you find yourself buying products made with imitations of real leather.

Biodegradability and biodegradable materials

Biodegradable materials are materials that are capable of undergoing the biodegradation process.

Biodegradation is a natural process of degradation of a material (regardless of whether it is of natural or synthetic origin) through enzymatic processes due to the action of bacteria, fungi or other microorganisms. Implying that these microorganisms feed on biodegradable materials through two phases, the first of decomposition (enzymatic step) and the second of assimilation.

Biodegradation under normal circumstances
Fig.2: Example of biodegradation

Microorganisms are present in any environment and feed on organic waste, transforming it into carbon dioxide, water and biomass.

All materials, even non-organic ones, are biodegradable; that is, if placed in any environment, sooner or later, they will wear out and disappear. The determining factor is the speed with which the process takes place. For this reason, the definition of biodegradable material includes a time frame within which a certain amount of material must decompose and define a standard using the UNI EN ISO 14855 and UNI EN 14046 standards. The standards explain that materials that biodegrade by 90% in less than six months are known as biodegradable material.

Biodegradation can occur in many ecosystems and conditions with the presence or absence of oxygen. The rules governing biodegradability are different and consider all these factors (UNI EN ISO 14851, 14852, 14853, 14855, 17556, 15985 and UNI EN 14046).

Decomposition does not mean that it is not dangerous because we have to see what it decomposes into and what substances it can release. Materials decompose into nutrients for the soil, but we know that many materials contain dangerous substances. Decomposition implies that microorganisms breakdown such substance, which may lead to the gaseous release of toxic chemicals.

Biodegradation under dangerous conditions
Fig.3: Example of biodegradation that is dangerous for the environment

The above example shows that we need to be extra cautious when dealing with chrome-tanned leather and post-industrial waste. If thrown into the ground, Chromium (VI) may seep into the surrounding environment and affect biodiversity and settlements around the disposal sites. Chromium isn't necessarily hazardous, but tanneries must be pro-active in having the right waste management procedures in place.

Biodegradability is not an absolute measure of sustainability.  Indeed, very often (and this happens mostly for synthetic materials), the exact opposite occurs.

To have more guarantees in this regard, we must take a step forward and consider the materials' compostability.

Compostability and compostable materials

Compostable materials are materials that, as a result of biodegradation, do not release toxic and dangerous substances into the environment.

Composting transforms organic waste into compost through an industrial process at temperatures of 60-70 ° C and relative humidity values of 50-60%. Under these conditions, microorganisms begin to consume nutrients and degrade organic molecules producing biomass (which make the compost fertile), carbon dioxide, water, and heat:

Composting process
Fig.4: Composting process

The evaluation takes place through the UNI EN ISO 14995 standard (relating to plastics) and UNI EN ISO 13432 (relating to packaging). As it is easy to understand, we are talking about a completely different process from home composting.

Compostable materials are environmentally friendly materials. As we can understand from the definition, biodegradability is necessary to ensure that a material can compostable, but it is not the only one.

Compostable materials must be biodegradable, while not all biodegradable materials are compostable.

Difference between compostability and biodegradability
Fig.5: Difference between compostability and biodegradability

Some of the characteristics of compostability include:

  • Biodegradability of the material;
  • Physical disintegration of the material;
  • Quality of the compost obtained.

Identifying the material's compostability requires at least 50% of volatile solids, and this limit excludes inert materials. The second condition is the concentration of heavy metals that must be less than or equal to the values listed in Table 1. The values follow the ecological criteria for awarding the 'community eco label' and are set at 50% of the maximum concentration of these requirements.

Limits for dangerous substances
Table 1: Limits for dangerous substances

Biodegradability and compostability on leathers, eco-leathers, PU and PVC materials and vegan leather

We need to make some critical distinctions when it comes to the chemical breakdown of leather imitations.

According to the UNI EN ISO 14855 and 14046 standards, tanning and re-tanning operations determine leather's biodegradability. Tanning gives leather stability over time. On the other hand, re-tanning is a series of processes that provide tanned leathers with their characteristics (consistency, softness, colour).

Leather tanned with vegetables and with aldehydes can biodegrade given that tanners used the same chemicals during the re-tanning cycles.  As a result of selected chrome-free and innovative tanning methods, leathers can obtain compostable characteristics, primarily when tanners use vegetable and natural products in tanning and re-tanning.

Materials such as PU and PVC imitations, of course, have no biodegradability characteristics, as well as vegan leather produced using powdered vegetable derivatives. When these materials reach the end of their life cycles, the only conceivable way is recycling as components of inert materials.

Materials such as vegan leather obtained explicitly from the mycelium of mushrooms or Pinatex may biodegrade depending on the stabilisation treatments they receive. However, the manufacturing companies are yet to provide data in this regard.

Thanks for reading!

If the article was useful to you, leave a comment and keep in touch with me!

And if there is something you think is wrong, please report it to me!

Daniele Pistorio

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