Background

Industrial composting is considered a specific form of material recycling according to EU legislation (Directive 94/62/EC).

Industrial composting is an aerobic (oxygen present) process which takes place in controlled conditions. The composting period is governed by a number of factors including temperature (typically 50–60°C), 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.

The requirements for industrial composting are speciefied in the European standard EN 13432. It includes the test scheme and evaluation criteria for the compostability and anaerobic treatability of packaging and packaging materials in controlled waste treatment plants. The technical content of EN13432 is identical with EN14995, which is applicable to other than packaging applications.

The Seedling certificate is an example of an international certificate that complies with the standard and can be used as an independent proof of the industrial compostability of a product. However, Seedling or similar certificate is not obliged by any legislative authority in Europe.

KEY FEATURE: COMPOSTABLE

The Sulapac Straw is industrially compostable in accordance with the European Standard EN 13432.

Criteria

According to the European Standard EN 13432 a product suitable for industrial composting must fulfill the following criteria:

  • Contains a minimum of 50% of volatile solids.Volatile solids means ‘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.
  • Does 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.
  • Is inherently and ultimately biodegradable as demonstrated in laboratory tests. Aerobic biodegradation has been defined as ‘breakdown of an organic chemical compound by naturally occurring micro-organisms in the presence of oxygen to CO2, water and mineral salts of any other elements present (mineralization) and new biomass. In aerobic biodegradation tests the sample’s CO2 production level has to reach 90% of that of the reference material in 6 months.
  • Disintegrates in a biological waste treatment process.With the term disintegration the standard refers to ‘the physical falling apart into very small fragments of packaging and packaging materials’. After 12 weeks no more that 10% of the original dry weight of test material fails to pass a > 2mm fraction sieve.
  • Has no 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.
  • Has no negative effect on the quality of the resulting compost.The compost quality shall not be negatively affected by the addition of the packaging defined by the following physical-chemical parameters: volumetric weight (density), total dry solids, volatile solids, salt content, pH, the presence of total nitrogen, ammonium nitrogen, phosphorus, magnesium and potassium.Possible environmental risks attached to the end compost must be evaluated for example, by determination of the ecotoxicological effects of the biodegradation products or by performing ecotoxicological tests with compost produced with and without packaging material and comparison of the test results. Following the OECD Guideline for testing of chemicals 208 “Terrestrial Plants, Growth Test” the sample compost and the blank compost are being 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 products have been tested by independent, accredited testing laboratory OWS following the test regime applied in the Seedling certification process, in accordance with the EN 13432.

According to the EN 13432 a controlled pilot-scale test shall be used as the reference test method. A test in a full-scale treatment facility, may, however, be accepted as equivalent. The OWS tests for Sulapac products have been carried out in a pilot-scale setting. Sulapac’s test results are as follows:

  • Volatile solids The volatile solids content of the Sulapac straw is 99.8%. A minimum of 50% of volatile solids is being required by EN 13432.
  • Hazardous substances The heavy metal and fluorine levels of the Sulapac® straw lay well below the maximum levels set in EN 13432.
  • Biodegradability Sulapac® fulfills the biodegradability requirements of EN 13432. EN 13432 requires that in 6 months the sample’s CO2 production level has to reach 90% of that of the reference material.
  • Disintegration Not a single piece of Sulapac material was found after sieving with 2mm sieve after 12 weeks of composting. EN 13432 requires that no more that 10% of the original dry weight of test material fail to pass the sieve.
  • Quality of end compost No negative effect on emerge or growth of the plants grown in the test composts (25% and 50% concentrations) was observed. According to EN 13432 the growth rate in the test compost must be higher than 90% of that of blank compost.

In addition to the pilot-scale compostability simulations by OWS, tests in full-scale treatment facility have been carried out by Kekkilä. The industrial-scale testing confirmed that the Sulapac® straw complies with the EN 13432 and is suitable for industrial composting.

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