Influence of iron, nickel and cobalt on biogas production during the anaerobic fermentation of fresh residual biomass

We have investigated the dependence of the rate of the production of biogas upon the concentration of nickel, cobalt and iron at sub-toxic concentration and monitored its composition as amount of hydrogen, methane and carbon dioxide. The distribution of the added metals between the liquid and solid phase has also been monitored.

The results of our investigations show that the addition of any of the listed metals to the sludge may cause the production of a higher amount of biogas and influence the methane or carbon dioxide percentage. Conversely, the effect on the hydrogen production depends upon the metal added, the age of the active sludge used, and its adaptation to the susbtrate. As a general feature, during the acidogenesis phase, nickel reduces, while iron increases, the percentage of dihydrogen in the biogas, while cobalt has no influence.