The respiratory activity of the microorganisms in samples of soil, determined by measuring the biological oxygen demand, has long been related to soil fertility. BPC Blue could be used to follow soil respiration in real-time and compare the microbial activity of standard soils or soils of natural origin. For instance, activity of soil organisms was examined in the breakdown of soil organic matter, as well as using microcrystalline cellulose as a reference sample to evaluate various commercially available sandy-loam soils for biodegradation at temperature 22 ±1 ^oC. The purpose is to select suitable type of soil for performing biodegedability test according to ISO 17556.

The degradation curves illustrate the different kinetics of cellulose biodegradation in the different soils and show that the fastest initial degradation rate and the highest biodegradability were achieved with Soil B. Using Soil C as an example, it is possible to distinguish a lag phase (day 0 to 6), where adaption of the soil inoculum to the cellulose occurs, a degradation phase, in which the microorganisms metabolize the sample, and a plateau phase, in which the biodegradation has ended.

The test is considered valid for all soils investigated except Soil A, as the degree of biodegradation of microcrystalline cellulose reached more than 60% in less than six months and all the blanks are within ±20% of the mean at the end of the test (i.e., the standard deviations are less than ±4% for all blanks).