This document specifies a laboratory test method to determine the degree and rate of aerobic biodegradation level of plastic materials. This test method can also be applied to other materials. Biodegradation is determined by measuring the CO2 evolved by the plastic material when exposed to marine sediments sampled from a sandy tidal zone and kept wet with salt-water under laboratory conditions. This test method is a simulation under laboratory conditions of the habitat found in sandy tidal zone that, in marine science, is called eulittoral zone. The conditions described in this document might not always correspond to the optimum conditions for the maximum degree of biodegradation to occur. Deviations from the test conditions described in this document are justified in the test report.