The biogas and methane production potential of sewage sludge and other organic materials are typically measured using the biochemical methane potential (BMP) or residual biogas potential (RBP) tests. The BMP is a measure of the methane potential of the feedstock, whereas the RBP is a measure of the residual biogas of the digested product following anaerobic digestion (AD).

The RBP of digested sewage sludge is being used to benchmark the performance of wastewater sludge digesters in England, and to try and develop a criteria for demonstrating whether a treated digestate is stable. The test is also currently being used as a surrogate for estimating biogas and methane emissions from sewage sludge and non-sewage sludge digestate.

This paper investigates the production of biogas between sampling and analysis, the production of biogas during the RBP test, and then presents two methods for inhibiting biogas production and reducing the residual biogas in the digestate. Data will be presented that quantifies the ‘lost gas’ which evolves from the sludge prior to analysis and provides supporting evidence for a mechanism for reducing the residual biogas by approximately 30%. The paper also demonstrates that using kinetic modelling in conjunction with biogas potential testing can reduce the duration of the RBP test to 18 days.