Inhibitions from Syngas Impurities: Impact of Common Tar Components on a Consortium Adapted for Syngas Biomethanation

In a circular economy approach, syngas biomethanation is a promising technology for waste to energy conversion. However, syngas can contain impurities, notably tar, that can limit the processes upgrading syngas downstream gasification. The effect of tar on syngas biomethanation is unknown. Therefore, for the first time, common tar components were tested on a consortium adapted for syngas biomethanation to assess the resistance of the microorganisms. Four light tar components (benzene, toluene, styrene and phenol) commonly found in syngas were selected and tested at different concentrations in batch tests. Adding pollutant up to inhibitory concentrations affected both the lag phase of microbial growth and the rates of the bioreactions. Hydrogenotrophic methanogens were found to be more sensitive than carboxydotrophs. Amongst the four tested pollutants, phenol appears to be the most problematic, due not only to its high inhibitory effect but also to its high solubility, allowing phenol in the syngas to reach high inhibitory concentrations. This study paves the way for further research on the resistance of syngas biomethanation to impurities contained in the syngas.