According to ISO 14851, the determination of aerobic biodegradability of plastic materials in an aqueous medium can be performed by measuring oxygen consumption or depletion caused by aerobic respiration of microorganisms using BPC Blue as a fully automated closed respirometer. The plastic materials, which is the sole source of carbon and energy, is mixed with selected domestic wastewater, continuously agitated, and incubated at temperature 22 ±1 ^oC. During biodegradation of plastic materials, the consumed oxygen is measured continuously by BPC Blue and the biodegradability is calculated as the ratio of the consumed oxygen to the theoretical value.

The experimental configuration using BPC Blue includes oxygen supply and the biodegradation process is not inhibited by the limitation of available oxygen in the headspace of test flask. It is therefore convenience to perform the analysis with a higher sample amount. In the current study, the impact of sample concentration on the dynamic profile of biodegradability was demonstrated using microcrystalline cellulose. The validity criteria of ISO 14851 are fulfilled (i.e., all samples have > 60% biodegradability with standard deviations range from ±2.1% to ±9.8%, only ±3.5% for three blanks control which is far below the max limit ±20%) at the plateau phase within 60 days.