The part of SYNFERON project within “Biorefinery Conversions” aims at exploiting the potential of converting synthesis gas, a mixture of CO, H2 and CO2, to methane and alcohols through biological processing. Methane is a versatile energy source with a broad spectrum of applications while alcohols can be used as drop-in fuel for the transportation and aviation sector and in the chemical industry.
Gasification allows for a very high conversion (approaching 100%) of most type of biomasses to syngas and it is an already developed and commercially available technology for Combined Heat & Power, CHP, production. By combining the CHP production with the fermentation of syngas, the processing of syngas can always follow the optimum path. That is, the final production will be easily diverted to CHP or biofuels satisfying thus the supply and demand of the biomass and energy markets. For example, when the heating demand is high, the syngas will mainly be exploited through CHP but when the heating demand is low, the syngas will be fermented to storable liquid or gaseous biofuels.
Biofuels production through fermentation of the syngas has significant advantages over the conventional chemical catalytic processes: a) high specificity which leads to high product yield, b) the biocatalyst (microbes) are cheap and easily adaptable or highly tolerant to gas impurities, c) no fixed H2/CO ratio is required and d) the process is odourless, it does not create any health hazard and it generates less environmental pollution.
The part of SYNFERON project within “Biorefinery Conversions” targets the challenging aspect of eliminating the need of maintaining sterile conditions during syngas fermentation by applying open mixed microbial consortia, MMC, fermentations and overcoming rate limitations by designing and testing a novel reactor configuration.
MMC fermentations is a recently emerging field with very high potential, which have the advantage of being carried out by stable mixed microbial consortia, as typically found in nature and therefore not requiring sterile conditions, lowering thus substantially the operating costs.
Within SYNFERON we apply naturally occurring MMC of anaerobic bacteria and methanogenic archaea to convert CO, CO2 and H2 into CH4. We also apply suitable enrichment strategies and operating conditions in order to direct the fermentation of syngas to alcohols. Thermodynamics and their interplay with microbial growth kinetics is vital in order to understand interactions, competitions and final dominance of specific metabolic routes in the mixed microbial consortia and hold a significant role within SYNFERON.
Selection of an appropriate bioreactor configuration that could overcome mass transfer limitations and achieve high cell density is vital for efficient syngas fermentation. Attached growth systems are ideal for achieving high cell densities and working with MMC makes this a feasible option. Within SYNFERON, a novel trickle bed reactor combining high mass transfer rates and cell densities is being tested for bioconversion of syngas to methane and alcohols by MMC.