COMPOSTABILITY and BIODEGRADABILITY EVALUATION – Fate of man-made materials in soil and composts
(for standardized protocols for compost biodegradation testing please see our ASTM page).
Composting is a loose term that is considered by experts to be an instance or subset of biodegradability, but occurring inside a compost pile. Composting is associated with some measure of heat rise and fall that includes thermophilic (>45C) and mesophilic (<45C) conditions. As a biodegradation process composting is validated by at least 40% reduction in organic matter (ROM test). Protocols that are unable to validate composting by ROM are also unable to accurately measure real biodegradation.
ASTM and ISO methods are frequently used to validate compostability claims, in the narrow context of industrial-scale composts. These methods have been useful in setting a tone for manufacturers to seek common rules, following an era in the 80′s and early 90′s of significant falsification of claims. However, current challenges show that these early rigid test methods are falling out of favor in view of a more natural, holistic awareness that composting must not be divorced from true concept of biodegradability, in which nature does not set strict temperature boundaries. To attain this new realization and objective requires that the materials or chemicals in question be tested against a real-world background of actively decaying organic materials, in which the variables are the microbes and not the incubator.
Compost Test Bins: Small Bins can be used to test compostability but often do not attain sufficient heating to be considered thermophilic.
In Set Theory, Biodegradation is the broad condition, and composting the narrow condition wholly contained and more specific within biodegradation. Biodegradation refers broadly to conversion of organic matter to carbon dioxide, water and biomass within any normal environment. Products are considered biodegradable which for all purposes decay in moist soil under ambient temperature conditions,- they may also be defined as products that decay in water or in marine environments, which are subsets.
Half-life decay kinetics apply to all these groups and are generally determined based on decay curves (loss of mass) corrected to background conditions in the appropriate environment. These data are then fit to an exponential model to derive a constant from which half-life may be calculated.
Conservation of Carbon: Some carbon is always retained during biodegradation within microbial biomass and which is self replicating in soil. Therefore, in nature, technically there is no such thing as “100% biodegradable” as is often implied in product advertising. Either the actual material will be partially retained, or by-product metabolites of it, or both. In only rare instances does biodegradation to CO2 and H2O exceed 60-80% of total original carbon. Several standard tests only require that a material attain “relative” degradation. i.e. in relation to another well-known substance (such as cellulose).
Real-time testing for decay requires a set of parameters be monitored. This includes sourcing ingredients and mixing them in proper ratios to result in a suitable compost; then to manage and conduct the composting process in pilot-scale setups that resemble real composting; and finally to have the laboratory skills to suitably test the content and products to interpret the overall result. These broad skills are clearly possessed by Woods End Laboratories.
* Woods End Lab is BPI-Approved facility and conduct compostability trials.