Biodegradability and compostability: these two terms have now entered our everyday life. Do we really know what they mean? Are they synonyms or do they indicate different concepts?
We often confuse “biodegradable” with “compostable“, but the meaning is not the same. Knowing the true meaning of these terms is the first step we need to take to turn on our environmental awareness.
If we wanted to give a quick definition of the two terms, we could say that the difference between a biodegradable and a compostable material lies in the degradation time: a compostable material disintegrates in less than 3 months while to be biodegradable, 90% of the material has to decompose within 6 months.
Let’s see these differences in detail and let’s understand what is the process for the certification of biodegradability and compostability of a product …
But first … some definitions!
Biodegradability is the ability of an organic material to be broken down by natural microorganisms into simpler substances. The concept of biodegradability therefore does not refer to time or to biodegradation conditions (in soil, water, composting), but we could say that any material is biodegradable in shorter or longer times (from a few weeks to hundreds of years), depending on the conditions (temperature, oxygen, humidity): the more time an object takes to biodegrade, the more consistent its environmental footprint will be.
A certain object is defined as compostable if, as the word itself suggests, it becomes compost when it enters, for a certain period of time, in contact with elements rich in nutrients or fertilizers (such as fertile soil) and turns into compost. In this case, therefore, a set time has to be respected, which is regulated by the standard UNI EN 13432: 2002. The standard requires that composting (final transformation into biomass, water and CO2) takes place within 6 months (while the disintegration of the material must take place in 3 months).
Compostability therefore exploits biodegradability, that means that a compostable material is always biodegradable, but the opposite is not always true.
And what about Renewability?
We have heard of renewability in relation to the new legislation, in force since January 1, 2018, on the obligation to use organic bags for the purchase of fruit and vegetables: in fact, these bags must be less than 15 microns thick and must be composed of raw materials renewable energy equal to at least 40% of the total, according to EN 16640: 2017. Futhermore, they must be biodegradable and compostable, according to UNI EN 13432, standard that we will analyze later in this article.
So, if we wanted to give a definition to Renewability, we can say that it is concerns the origin of a product and in particular the characteristic of those raw materials, mainly made of plants and that have in general animal origins, to regenerate quickly (plants, trees, their derivatives and waste), in opposition to raw materials from fossil sources (oil).
As previously mentioned, the standard UNI EN 13432 regulates the biodegradability and compostability of a product. It establishes all the requirements, timescales and procedures for obtaining the compostability mark.
What are compostability requirements?
In order for a material to be defined as compostable, it must have these five characteristics:
- The material must degrade by minimum 90% in an environment rich in carbon dioxide after six months;
- At least 90% of the mass of the material must be reduced to fragments smaller than two millimeters after a maximum of three months of direct contact with organic materials;
- The material must not have negative effects on the composting process;
- There must be a low concentration of heavy metals added to the material;
- The pH, saline content, volatile solids concentration, nitrogen, phosphorus, magnesium and potassium concentration must be within the established limits.
Which laboratory tests must be done?
There are a series of steps that must be taken to get to the validation of biodegradability, first, and subsequently compostability. All these tests are based on pass-not-pass values that distinguish compostable objects, and in our case packaging, from non-compostable ones.
1) Chemical characterization of the packaging material:
Potential hazardous substances (such as heavy metals and fluorine) must be determined. Furthermore, all the components of the material from which the packaging is made must be identified and declared. Then the content of organic carbon, total dry residue and volatile solids have to be determined.
Laboratory tests must subsequently be carried out in an aerobic environment and in the presence of mature compost for the purpose of determining biodegradability. The aerobic biodegradability test in compost determines the mineralization of the material with carbon dioxide and water by microorganisms.
After the first two steps, you can arrive at the determination of the disintegration of a packaging in a biological waste treatment process. The disintegration test of the packaging in its final form is conducted in the presence of an organic waste prepared in the laboratory under controlled conditions of temperature and humidity.
4) Quality of the compost obtained from the disintegration test:
Therefore, the determination of chemical-physical parameters and the consequent evaluation of the ecotoxicity of the compost on higher plants takes place.
For each analysis step there is a list of requirements that the material must respect, and in particular:
1) Chemical characteristics
- Minimum 50% of volatile solids (organic material).
- Metals and other toxic and dangerous substances (with the limits set out in the table below).
Element mg/kg dry residue EU+EFTA USA Canada Japan Zn 150 1400 463 180 Cu 50 750 189 60 Ni 25 210 45 30 Cd 0.5 17 5 0.5 Pb 50 150 125 10 Hg 0.5 8.5 1 0.2 Cr 50 – 265 50 Mo 1 – 5 – Se 0.75 50 4 – As 5 20.5 19 5 F 100 – – – Co – – 38 –
- It must be determined for each significant constituent (> 1%).
- The total of components that are NOT biodegradable or whose biodegradability has not been determined must not exceed 5% in total.
- The test can last up to 6 months.
- The percentage of biodegradation must be at least 90%
- At the end of the three-month composting process, the packaging must have disintegrated for at least 90% of its initial weight, i.e. no more than 10% of the initial dry mass of the sample must be recovered from the final compost by means of a sieve with mesh equal to 2 mm.
- The percentage of germination and growth of seeds of standard plants, in the presence of compost obtained after disintegration of the analyzed material, must be at least 90% compared to that obtained using a reference compost.
After the analysis process, the product can obtain the certification of biodegradability or compostability.
We want to remind that this certification is a voluntary act. There are some main certification agencies in Europe, such as DIN CERTCO (Germany) and TUV Austria-Belgium. These organisms work on European and international standards for compostability. In addition to industrial composting, it is also possible to certify materials suitable for home composting as well as biodegradable materials in soil and water.