Decomposition of Hydrocarbon Gases using a Novel Bioelectrochemical-Based Composite Biofilter

Activated carbon filters installed in existing air cleaners only adsorb harmful gases, such as hydrocarbon gases, without fundamentally decomposing them. Therefore, there is a great concern that the harmful gases may be re-released into the atmosphere according to changes in environmental factors; moreover, when the fixation capacity of the carbon filter reaches its limit, harmful gases might no longer be captured by the filter. To overcome the abovementioned problems of activated carbon filters, in this study, we devised a new concept for a composite filter system (bioelectrochemical-based composite biofilter consisting of living microorganisms, a complex graphite felt filter with working and counter electrodes, and an electrochemical reducing power supply system) capable of inducing the complete decomposition of harmful gases. The composite biofilter was made of graphite felt for high conductivity and modified with chitosan and phosphate to increase the moisture content. In addition, it can supply electrochemical reducing power to accelerate the metabolism of microorganisms that comprise a part of the composite filter; these microbes can completely decompose the harmful gases, which act as carbon sources derived from the environment through metabolic processes. Based on the performance of this composite biofilter, the newly developed microbe-carrying bioelectrochemical-based composite biofilter effectively decomposed 50% (2000 ppm) of the harmful gases (lower hydrocarbons), including methane, propane, and butane, within 3 days. Unlike the limited use of conventional biological filters, this strongly suggests that the above microbe-carrying bioelectrochemical-based composite biofilter can be actively utilized as a new alternative air-cleaning filter for full-scale detoxification of harmful toxic gases, even under general indoor atmospheric conditions.