Anaerobic fermentation of maize (Zea mays) contaminated with cadmium

Maize (CE 220 hybrid) was chosen as a phytoremediation plant for Cd decontamination. A solution combining CdCl2 and EDTA was added into the nutrient solution during the growing phase of the maize plants cultivated hydroponically. The contaminated maize plants were harvested and fed into model biogas plant reactors. Inoculum sourced from agricultural biogas plant operations was applied into these 3-litre reactors, with the addition of Cd-contaminated maize plants. Subsequently, there was an analysis of the quantity and quality of the biogas produced in the reactors. The addition of maize plants increased production of both biogas and methane compared with control samples without the addition. Cd-contaminated maize can therefore be biotechnologically processed in biogas plant reactors, in a mesophilic, anaerobic environment. Analyses of Cd concentration in fermentation residues and grown contaminated plants confirmed the presence of Cd while providing the evidence of the fact that at such concentrations Cd presence in maize plants does not form an element inhibiting biogas production. Fermentation residues may however be not suitable, given the content of Cd, for application to agricultural land. Recommended measures involve analysis of the cadmium concentration and then disposal of the fermentation residue in compliance with applicable legislation.