The residual gas potential (RGP) or residual biogas potential (RBP) test is designed to measure the stability of digestate samples under anaerobic conditions. Stability is assessed by the measurement of the total quantity of biogas produced by the digestate sample during a specified period of time, which is an indicator of its residual biodegradability.

The test involves placing the digestate, along with excess nutrients and microorganisms, in laboratory-scale reactors and measuring biogas production for a pre-defined time period (such as 28 days) at an average mesophilic (37 °C ± 1 °C) or average thermophilic temperature (55 °C ± 1 °C). When investigating the residual gas potential at reduced temperatures (psychrophilic condition), this test procedure can be carried out at room temperature, i.e., 20 °C ± 1 °C. 

Determining the residual gas potential of the digestate of a biogas plant can answer the following questions: How large is the emission potential? What quantity of biogas or methane is lost after leaving the gas-tight part of the biogas plant?

Automatic Methane Potential Test System (AMPTS) III is the research-standard analytical tool preferred by scientists and engineers for conducting various anaerobic batch fermentation tests. AMPTS is the only automated test apparatus referenced in VDI 4630 for biochemical methane potential (BMP), specific methanogenic activity (SMA) and residual gas potential (RGP).

The system consists of 18 parallel reactors (9 reactor configuration available) and the same number of gas flow meters (flow cells) attached to a detection unit for online, automatic data acquisition.  This allows for the real-time investigation of a high number of feedstock samples with high precision and accuracy.