Biodegradation: DOC, CO2, O2 Measurements & Methods
Liquids and formulations are tested using simulated conditions that represent common water and marine environments. The selection of a liquid biodegradation laboratory test is based on the need to simulate the intended use and waste stream (disposal) of the product.
For liquid biodegradation, there are several measurements for biodegradability that can be used. The most common of which is a measurement of CO2 production (ex. OECD 301B). CO2 being the final byproduct of respiration of the microorganisms as they consume the carbon material provided by the tested product (see image).
Commonly; this type of biodegradation (method OECD 301B) is used to evaluate personal care products such as shampoos, soaps, laundry detergents, and other water soluble consumer products. In addition; many oil and lubrication formulations are tested using liquid biodegradation methods due to their outdoor use. Examples of these materials include fuel additives, equipment lubrications (oils and grease), anti-rust materials and coatings; all have an extended environmental durability requirements but will ultimately come into contact with a water environment as they dissipate or migrate from their application site.
Why are different measurements of liquid biodegradation used; DOC, CO2, and O2?
Different compounds and formulations can be quite complicated; and depending on several factors (related to the chemical composition and physical properties of the material); these differences can make the measurement of biological degradation much more difficult. Depending on the formulation; a measurement of the actual dissolved organic carbon (DOC) by a method such as OECD 301A, my be more appropriate for the material; and provide a better understanding of the biodegradation occurring.
For materials that are not expected to be fully degradable, (Ready Biodegradation requires a very high degree of access or consumption by the microorganisms), this may not be feasible; so a measurement of oxygen (O2) consumption may be more appropriate such as measured by OECD 301D.
Meeting the requirements of a biodegradation test is not a given – even for materials made up of materials commonly considered to be biodegradable in natural settings.