Tools of the Trade: Carbon Dioxide Testing Unit

Early detection of a potential upset in an anaerobic digester can prevent weeks or even months of frustration and recovery headaches. One of the best and earliest indicators of a healthy or unhealthy digester is methane production. A drop in the percentage of methane in digester gas is one of the first signs that your digester may be headed for trouble. To keep your finger on the pulse of your anaerobic process, we suggest testing for methane daily, or at a minimum, weekly.

Methane production, however, is not the easiest parameter for which to test. Unless your facility is equipped with a gas chromatograph calibrated to methane, testing for methane can be an expensive and cumbersome task. It typically involves the collection of a biogas sample from your reactor and overnight shipment to a certified laboratory for analysis. Luckily, there is an easier way to monitor the health of your anaerobic digester. Why not test for carbon dioxide (CO₂) instead?

Carbon dioxide typically comprises 25-35% of the biogas content. The remainder is mostly methane with trace amounts of hydrogen sulfide and other minor gas components. By testing for CO₂ you can readily estimate the methane content of your reactor.