Anaerobic digestion describes the ability of certain microorganisms to break down organic matter in the absence of oxygen. The term methanization is used to speak of this process when harnessed by humankind to produce methane-enriched biogas, which can be used cogeneratively to produce electricity or, once refined, injected into a gas grid. Digestate describes the organic matter that remains after methanization, which is often repurposed into fertilizer.
Methanization for public health: chlordecone biodegradation
A team of researchers from the Genomics Metabolics mixed research unit (Genoscope/CEA-Jacob) and the University of Lorraine's ENSAIA faculty and AFPA research unit recently showed that anaerobic digestion can also be harnessed to break down chlordecone.
Chlordecone is a now-outlawed organochlorine insecticide that was used massively in the French West Indies between 1972 and 1993 to control banana weevils. Its particular structure makes it very stable and very difficult to break down. Resultantly, the Antilles soils and a part of the islands' food chain still suffer today from persistent chlordecone pollution.
In their study published in Science of The Total Environment, the researchers first verified that chlordecone did not inhibit methane production by the microorganisms. They then developed an assay protocol for chlordecone and its transformation products. Thereafter, the team tested two methanization conditions using digestates from digesters functioning on plant and animal waste. The team's chemical analyses showed a reduction in chlordecone concentrations, particularly in thermophilic conditions at 55°C compared to mesophilic conditions at 37°C. The appearance over time of several transformation products confirmed chlordecone degradation, thus demoting the hypothesis of its fixation on the digestate's organic matter.
The study's results suggest the possibility of using methanization as a chlordecone remediation tactic, while maintaining the process's energy validation interest. Such a strategy would be extremely pertinent for the French West Indies, first for the bioremediation of the chlordecone pollution affecting this island territory particularly, and second as a source of autochthonous energy production. There remains however a number of hurdles to clear before a transfer of technology can see the day.
Contact :
CEA : Pierre-Loïc Saaidi | plsaaidi@genoscope.cns.fr
Université de Lorraine : Yves Le Roux | yves.leroux@univ-lorraine.fr