Biodegradability of products
This means that all the constituents can be broken down into ever-simpler units by the effect of living beings, until natural metabolic waste products (carbon dioxide, water, mineral and trace elements) are obtained. These can be used by plants for renewed production of biomasses.
Biomasses contain a large variety of individual constituents, which can differ greatly with regard to the speed with which they are biodegraded. This is made clear by taking a look at the biowaste produced by households. The particularly fast degrading constituents are degraded during the short time in which the biowaste is stored in the household collection vessel and in the biowaste bin. Only around half of the initial organic constituents present in the biowaste are retained until delivery of the biowaste to the recycling plant.
At the time of delivery the biowaste contains only small residual levels of fast biodegrading constituents: Around 40 % of the organic constituents of the biowaste delivered are not biodegraded, even during long composting periods. These are highly lignified and humified constituents which, as „organic substance“, contribute to the nutrient-contributing properties of the compost and are retained in the soil for hundreds or even thousands of years.
Unlike natural biowaste constituents, according to the specifications of EN 13432, packaging materials are only deemed to be biodegradable if they are completely degraded within a maximum of 180 days. In addition, within 84 days at least 90 % of the product must disintegrate in composting, so that residues are no longer present in the oversize material of the 2 mm screening fraction. Corresponding products must therefore be biodegraded more quickly than the slowly degrading fractions of natural biomass constituents.
These exacting standards are fulfilled, among other things, by biowaste bags tested and certified to EN 13432. However, various influences can have a negative effect on the degrading performance. An unfavourable effect is caused if several layers of the bags are lying on top of each other (for example, due to avoidable knotting of bags). In addition, biological acidification of the bag contents („silage“) can slow down the degrading processes if the bags are composted without being reduced in size or broken up first. Unfavourable temperatures and material moisture contents can also be disadvantageous; however, these can be adjusted in most cases. If inadequate degradation of products conforming to EN 13432 is observed, it is advisable to clarify the cause, as often slight adjustments are enough to achieve degradation which fulfils the target specifications.