Biodegradable or Compostable?

          Biodegradable or compostable?

       Compostable plastics are a subgroup of biodegradable plastics and are biologically

decomposed under composting conditions and within the relatively short period of a

composting cycle.

    Compostable always means biodegradable. Biodegradable does not necessarily mean compostable. The rule is that compostable plastics are biodegradable, while biodegradable plastics are not necessarily compostable (because biodegradation may take longer than required in composting). Therefore, compostable plastics are a subgroup of biodegradable plastic materials. The susceptibility of a polymer or a plastic material to biodegradation depends exclusively on the chemical structure of the polymer. For this reason, whether the polymer is made of renewable resources (biomass) or nonrenewable (fossil) resources is irrelevant to biodegradability. What matters is the final structure. Biodegradable polymers can be there-fore be made of renewable or non-renewable resources.

     A common misunderstanding is that all biodegradable polymers are made from renewable resources.

The manufacturing of biodegradable polymers can include different procedures without affecting material biodegradability. They can be synthetic (chemical) or biotechnological (affected by microorganisms or enzymes). The most common procedures are:

(a) Chemical synthesis of a polymer from a monomer produced by biotechnological conversion of a renewable resource (e.g. use of lactic acid produced from the fermentation of sugars for the production of polylactic acid – PLA). In this case, the polymer is produced chemically based on a renewable resource.

(b) Production of a polymer by a biotechnological procedure based on a renewable resource(e.g. fermentation of sugars where natural microorganisms synthesize thermoplastic aliphatic polyesters, such as polyhydroxybutyrate - PHB).

Today, commercial biodegradable plastics are offered on the market by an increasing number of manufacturers. Those most common materials can be classified into the following groups:

1. Starch-based plastics:

2. Polylactide-based plastics (PLA)

3. Polyhydroxyalkanoate-based plastics (PHB, PHBV, etc.)

4. Aliphatic-aromatic-polyester-based plastics

5. Cellulose-based plastics (cellophane, etc.)

6. Lignin-based plastics

Apart from the polymers, plastics contain other materials or additives and this combination determines their processing options and the product's final properties. These other materials include stabilization additives, lubricants, pigments, different fillers, and others. For biodegradable plastics, it is very important that all additional components are biodegradable as well. The standards for compostable plastics require the testing of all additives (and other substances used in the production of the final product, e.g. inks and colors) to ensure they do not have a negative effect on the compost.

The overall effect of biodegradable plastics:

 There are two primary angles dependent on which the shopper chooses whether or not they will utilize a plastic material: the financial/business angel and the ecological angle. Even though they cannot be entirely separated – using environmentally less harmful materials can have commercial and marketing benefits and can help achieve higher prices – they can be treated separately. The fundamental benefit of biodegradable plastics applies to ecological properties, principally with regards to the treatment of waste plastics and the impacts of their disintegration on the climate.

A blend of biodegradability and the utilization of inexhaustible/ nonrenewable assets to create biodegradable plastics gives an exceptional chance of adjusting the whole life pattern of plastics with the characteristic cycles: plastics are produced from and return to the natural renewable resource.