+ WHAT ARE BIODEGRADABLE PLASTICS?

Biodegradable plastics decompose completely to carbon dioxide (CO²), water (H²O) and biomass during composting by microorganisms. During fermentation, methane is produced in addition to water, CO² and biomass (CH⁴). The following parameters are important for composting:

  • Temperature
  • Humidity
  • pH value
  • Coating thickness
  • the surface of the product.

The origin of the raw material - whether from renewable or fossil sources - is not important for the degradability. Only the chemical structure is decisive. Only if the microorganisms or their enzymes are able to split and completely metabolise the molecules {of which the plastic is made} is it biodegradable.

+ When is a plastic considered compostable?

Biodegradable plastics are considered compostable if they decompose completely to water, CO² and biomass under defined conditions within a defined period of time in a technical composting plant.

DIN14995 defines the compostability of plastics. The relevant DIN EN 13432 specifies the compostability of packaging. However, the underlying criteria are the same for both standards.

To comply with the above standards, the plastic and its packaging must meet the following criteria:

  • Specification of the material contents
  • biodegradation (at least 90 percent must be broken down within 3 months)
  • after composting, a maximum of 10 percent may remain in a 2-millimeter sieve fraction after a maximum of 12 weeks
  • Checking the compost quality using plant growth tests
  • Additives containing less than 1 percent must be harmless for composting
  • residual materials contained in the packaging must be harmless for composting
  • the total sum of organic compounds not intended for biodegradation must not exceed 5
  • organic additives (less than 1 percent) must meet the requirements of biodegradable additives

If all the above requirements are met and tested, the product is considered compostable and may bear the logo "Keimling", "OK Compost" or "OK compost HOME".

The best known certification bodies for this are DIN Certco and Vincotte.

Basically there are 2 different types of composting:

Industrial composting (seedling / OK compost): Composting of these articles is only possible in industrial composting plants. Unfortunately, there are no plants in this country that would accept such articles for recycling at all. So far, the reasons for this are only economic.

Domestic composting (OK compost HOME): For these articles, the conditions regarding the temperatures under which the product can decompose are much lower. They can therefore also be composted in regular household compost if the necessary conditions such as humidity, temperature, pH value, layer thickness and surface are suitable.

+ Are bioplastics actually degradable?

Yes, according to the above-mentioned framework conditions in industrial composting or, if labelled with the "OK compost HOME", even in regular household compost.

+ Does the compostable packaging belong in the organic waste?

As described above, the packaging composts both in the industrial composting process and in household compost. At least 90 percent of the material must be degraded within 90 days.

Since the current processing times of the recyclers (= conditioners after sorting) are sometimes only 6 weeks, the materials cannot decompose sufficiently there. As a result, too many residual components remain. Due to the currently still small amount of bio-plastics (0.5 percent of all resulting packaging), separate sorting and composting is neither ecologically nor economically sensible. This is because the entire composting process in an industrial composting plant requires energy and the entire process consumes valuable resources.

For this reason, trade associations recommend disposal via recycling waste and subsequent thermal recycling.

+ Is packaging made of bio plastic recyclable?

Bioplastics like PLA are fully recyclable. A study by the Fraunhofer Institute proves that they can be separated from petroleum-based plastics in the sorting process. However, the quantities currently produced are too small to make the separation of the different types of plastics economically viable. With increasing use of bioplastics, separation will also become more interesting for recycling companies in the future.

Until then, thermal recycling makes the most sense.

+ Does the use of bioplastics make sense?

Bioplastics are used as an alternative to petroleum-based plastics and have the same properties. They reduce the dependence on crude oil and contribute to the saving of non-renewable resources. PLA, for example, consists of the renewable vegetable raw material corn. More concretely: from special types of corn for industrial use that are not suitable for human consumption.

Of the areas cultivated worldwide, only 0.05 percent are currently used for bioplastics. Cultivation in this respect has no influence on the food supply for humans and animals. As soon as the proportion of bioplastics increases, the areas required for cultivation will also increase. It is therefore already important to obtain raw materials from other sources. For example from agricultural waste or secondary products such as cellulose from corn straw, starch from corn, potatoes, sugar cane, wheat,...

In contrast to petroleum-based plastics (such as PS/PET), about 60 percent less CO² emissions are emitted and 50 percent less energy from non-renewable sources is used. Also in cradle-to-cradle studies, for example, the raw material PLA has decisive positive effects in terms of the greenhouse effect and resource conservation compared to fossil raw materials.

It should be noted that studies may differ due to different calculation factors. The bio-based plastics according to DIN 13432 decompose at least 90 percent within 90 days in the industrial composting process.

Decomposition takes much longer outdoors due to various factors. After decomposition, apart from the organic basic substances, no toxic residues such as chlorine-hydrocarbon compounds or inorganic substances remain.

The decomposition of petroleum-based plastics, on the other hand, can take centuries or millennia. Even after that, tiny residual particles remain, which are absorbed by animals and humans. Even in water, these microparticles absorb toxins from the water. Toxic substances can also be released on land and thus affect the soil. It is therefore important to replace the durable plastic products with more short-lived bioplastics.

In the following you will find investigations based on a study of the Federal Environment Agency in cooperation with the Fraunhofer Institute. The results, based on a search of the relevant technical literature, showed that the speed of biodegradation depends strongly on the environmental conditions.

Under conditions of "industrial compostability" biodegradable at 58° ± 2° Celsius in maximum 6 months

  • TPS, PHA, PCL – in about 4 to 6 weeks
  • PLA, PBAT, PBST – in about 6 to 9 weeks
  • PBS – in about 21 Wochen

Biodegradable in soil at 20° to 28° Celsius in maximum 2 years

  • TPS, PHA, PBSe, PBSeT, PBAT, PCL – in about 7 to 12 months
  • PLA – no dismantling after 1 year

Biodegradable in fresh water at 20° to 25° Celsius in maximum 56 days

  • TPS, PCL, PHA – in less than 56 days
  • PBS, PBSA – in about 3 Monaten
  • PLA, PBAT – in less than 1.5 years

Biodegradable in sea water at 30° Celsius in maximum 6 months

  • PHA, PCL, TPS, PBSe – in less than 6 months
  • PLA, PBAT – in over 1.5 years

Source: TEXTE 57/2018 Project number 93711 UBA-FB 002676. Expert opinion on the treatment of biodegradable plastics. By Maria Burgstaller, Alexander Potrykus, Jakob Weißenbacher BiPRO GmbH - Part of Ramboll, Munich Dr. Stephan Kabasci, Dr. Ute Merrettig-Bruns, Bettina Sayder Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT, Oberhausen On behalf of the Federal Environment Agency*.