AbstractAn adaptive control algorithm has been implemented on a biomethanation process to maintain propionate concentration, a stable variable, at a given low value, by steering the dilution rate. It was thereby expected to ensure the stability of the process during the startup and during steady‐state running with an acceptable performance. The methane pilot reactor was operated in the completely mixed, once‐through mode and computer‐controlled during 161 days. The results yielded the real‐life validation of the adaptive control algorithm, and documented the stability and acceptable performance expected.