Electrode specific information from voltammetric monitoring of biogas production

A sensor employing pulse voltammetry monitored the liquid phase of a biogas reactor during 32 days of gas production. An electrode array consisting of stainless steel, platinum and rhodium electrodes generated current responses for a sequence of voltage pulses. Plots of individual current responses against time indicated the electrochemical changes occurring in the broth from the perspective of each electrode. The responses from stainless steel had a pronounced diurnal oscillation which followed the daily introduction and consumption of substrate. The current responses for platinum were in a narrow range whereas those for rhodium exhibited several minima. A disturbance in the reactor caused by omission of substrate led to decreases in both gas production and current responses for all the electrodes. Multivariate data evaluation of all the current responses by principal component analysis indicated the daily fluctuations for concentrations of ions and redox active compounds in the broth.