Buzzword „Biodegradability“

Biodegradability

Biodegradability is the capability of a material to disintegrate biologically – by the help of organisms and enzymes. A material is considered to be biodegradable when it can decompose into energy, bio mass, H₂O and CO₂/CH₄ with the help of microorganisms such as bacteria or fungi. Environmental conditions such as the temperature or humidity, but above all time, are all factors, which impact this process and are correspondingly responsible for a faster or slower decomposition of the material.

In practice the term biodegradability is often used imprecisely. Basically a lot of materials are biodegradable. One big difference is, however, the time factor. Thus the term „biodegradability“ should actually always be used with some indication of the material, the time span and the environmental conditions in which the decomposition process is taking place. It would be better if it was only used for products which are „rapidly biodegradable“ (example given, when a product completely decomposes in sea water after less than 6 months).

Biodegradability vs. compostability:

„Biodegradability“ is often wrongly equated with „compostability“. In the process of compostability biodegradability is just a section of it, meaning that compostable materials, as for example organic waste, disintegrates within a certain amount of time. The resultant „compost“ is harmless for the environment and can be used to improve and fertilise the soil in agriculture or in the garden. Likewise here external environmental influences such as the water, oxygen and temperature play a decisive role for the speed at which the compost evolves.
There are also different measuring methods for compostability. The European standard testing is the EN 13432. In this limit values are determined for potentially dangerous substances and biological tests are made to evaluate the growth of the plants. A material is only considered to be compostable when it fulfils the demands of compostability in relation to biodegradability in a certain period and according to specific criteria for eco toxicity (e.g. if 90% of the material was converted in a maximum of 12 weeks at a raised temperature to CO2). 

A difference is made between

Garden compost
(uncontrolled conditions at approx. 28°C)

Industrial compost
(controlled conditions at a raised temperature ~°60C).

If the composting of a per se bio-degradable material is not possible, the final products can be burned whilst recovering the energy contained in it. Since compostable products are made of natural polymers, these are neutral for the climate if burnt, i.e. only the amount of CO2 is released which was previously stored in the plant.

Source & further informations:

biobagworld.com/de/umwelt/biologisch-abbaubar-und-kompostierbar/
de.wikipedia.org/wiki/Biologische_Abbaubarkeit
www.bioplastics.ch/EN-13432.pdf
www.alpenverein.at/tk-innsbruck_wAssets/docs/Verrottungstabelle-filled.pdf
www.augsburger-allgemeine.de/geld-leben/So-lange-braucht-unser-Abfall-um-in-der-Natur-zu-verrotten-id55066971.html