Sulapac® key feature: Industrially compostable

Sulapac materials are industrially compostable meaning they have been tested for disintegration, biodegradability, effect on the biological treatment process and effect on the quality of the resulting compost (biomass) and ecotoxicity during a composting process at 40-60^oC (104-140^oF).

Background

Industrial composting is an aerobic (oxygen present) process which takes place in controlled conditions. The composting process is governed by a number of factors including temperature (typically 40–60°C/104-140^oF), moisture, amount of oxygen, particle size, the carbon-to-nitrogen ratio and the degree of turning involved. Generally, effective management of these factors will accelerate the composting process. The outcomes of industrial composting process are CO₂, water and compost. The compost includes nutrients, and can be used, for example, in agriculture to enhance the quality of soil.

It should be highlighted that the conditions in an industrial compost differ from those in a home compost, and thus materials which are industrially compostable are not necessarily home compostable.  F.ex. the temperature in a home compost is typically much lower than 40–60°C (104-140^oF).

The requirements for industrial composting are specified in standards (e.g. ASTM 6400, ASTM 7878, EN 13432, EN14995). They include the test scheme and pass/fail criteria for a material to be claimed to be industrially compostable. A material may be deemed to be compostable only if all the constituents and components of the material are compostable.

The Seedling (EU), OK compost INDUSTRIAL (EU) and BPI (US) certificates are examples of international certificates that can be used as an independent proof of the industrial compostability of a product [1, 2]. After independent review of test results, applicant enters into licensing agreement granting them right to use the Compostable Logo of Seedling or BPI trademark. The technical content of these three certificates is almost identical. The certificates are application specific and have to be periodically renewed and inspected. F.ex. in the case of packaging, the contents of the packaging has to fulfill the compostability criteria too, unless it’s possible to remove the contents without leaving any traces behind.

In the EU legislation (Directive 94/62/EC) industrial composting is considered a specific form of material recycling.

Key feature

Sulapac materials are industrially compostable.

Criteria

A product is suitable for industrial composting if it has been successfully tested for the following properties

Biodegradation during biological treatment

• Aerobic biodegradation has been defined as ‘molecular breakdown of an organic chemical compound by micro-organisms in the presence of oxygen to CO₂, water and mineral salts of any other elements present (mineralization) and new biomass.
• in the testing procedure the material is in powdered form; the measured quantity is CO₂ formation as a function of time
• Pass/fail criteria: in aerobic biodegradation tests the sample’s CO₂ production level has to reach 90% of that of the reference material (cellulose) in 6 months.
• Two ways to organize testing: i) test all raw materials individually or ii) test the composition of the final product

Disintegration during biological treatment

• The physical decomposition of a product into tiny pieces during the industrial composting process
• Pass/fail criteria: after 12 weeks at least 90% of the product should be able to pass through a 2 x 2 mm mesh.
• As the disintegration property depends on the thickness of the material, disintegration testing is always performed for the final product/ item. Passing document is tied to the thickness of the tested sample- disintegration will be guaranteed up to this specific thickness.

Effect on the biological treatment process/ Chemical characterization

• The sample should contain a minimum of 50% of volatile solids, meaning ‘the amount of solids obtained by subtracting the residues of a known amount of test material or compost after incineration at about 550 °C from the total dry solids content of the same sample.’ The volatile solids content is an indication of the amount of organic matter.
• The sample should not contain hazardous substances, e.g. heavy metals. The concentration of the following substances needs to be measured and shall not exceed the maximum values defined: zinc, copper, nickel, cadmium, lead, mercury, chromium, molybdenum, selenium, arsenic, fluorine.
• The sample should not have any negative effect on the biological treatment process.
  Any negative effects of the test material on the composting process can be detected by direct comparison of process parameters in reactors with and without test material.

Effect on the Quality of the resulting compost (biomass) and ecotoxicity

• The quality of the compost should not decline as a result of the sample.
• This is checked via ecotoxicity tests: this involves making an examination to see if the germination and biomass production of plants are not adversely affected by the influence of composted sample. The sample compost and the blank compost are compared on the basis of germination numbers (number of grown plants) and the plant biomass. The growth rate in the test compost must be higher than 90% of that of blank compost.

Validation

Sulapac Universal, Premium and Flow materials have been tested by an independent testing laboratory, like OWS [3], following the test regime explained above. Based on these testing results, the compliance for the materials to EN13432 can be either self-declared or certified by a third party notified body.

To complete the pilot-scale composting simulations, we have ourselves carried out testing in an industrial scale biowaste management plant Kekkilä in Finland. The pilot-scale composting simulations and industrial-scale testing has confirmed that the Sulapac® materials are suitable for industrial composting process. Local differences between industrial biowaste management facilities exist, which is why the acceptance of compostable materials has to be checked locally.