Effect of ethylenediaminetetraacetic acid (EDTA) on the bioavailability of trace elements during anaerobic digestion

The uptake of essential trace elements by methanogenic bacteria can be obstructed by precipitation in the presence of sulfides and carbonates. The objective of this study was to investigate whether the bioavailability of trace elements, and therefore the methane yield, can be improved through the use of complexing agents. Research showed that the use of EDTA as a complexing agent in the biogas process increases the solubility of essential metals and enhances their bioavailability. If the substrate of a biogas digester has a low content of trace elements, solutions of elements essential for the methanogenic bacteria have to be added to the process. If these metals are complexed with EDTA prior to their supply, the necessary amount can be reduced by up to 75% compared to the non-complexed metals. Therefore, it would be advantageous for environmental and economic reasons to complex trace elements prior to their addition to the biogas process.