Anaerobic and Aerobic Digestion
Anaerobic Digestion is the natural process that happens when a waste feedstock contained in a sealed tank and under the correct conditions, oxygen free, degenerates to produce biogas and bio-fertiliser also known as a digestate.
Supporting the industry, MSSL provides the following analysis:
bio-methane potential test
Biomethane Potential (BMP) is a biological test to evaluate the potential methane/biogas volume generated from a feedstock. In the UK an equivalent test, residual biogas potential (RBP), is described in the WRAP report OFW004-005 and has become a certified method.
The test consists of batch reactors containing the test substrate, an aqueous mineral medium and an innoculum of digested sludge (that contains methanogenic bacteria).The produced biogas is measured and converted to units of ml gas/gram VS (volatile solids) substrate at Standard conditions for temperature and pressure (STP). This test can take up to 50 days depending on the potential of the sample.
DR4 composting test
This is a shorter 4-day aerobic biodegradability test to determine the biodegradability of waste samples. This can be used for correlation with the BMP test. Here the dry sample is mixed with an equal amount of mature compost (seed) and supplemented with nitrogen and phosphorus nutrients. The mix is incubated for four days at 35C˚ under aerobic conditions. The CO2 produced is measured and converted to the equivalent O2 consumption. The DR4 value is reported in units gm O/Kg LOI – mass of Oxygen (g) consumed over four days per Kg of LOI of the test material.