Hungary produces a vast amount of organic waste and agricultural by-products relative to its size. Unfortunately, this potential has not yet been exploited. Presently there are only two biogas plant equipped with upgrading units, producing biomethane. Despite the less than friendly conditions for the industry, biogas-related research and development at Hungarian universities is remarkably strong and successful.
The growth of the biogas industry in Hungary is hampered primarily by the lack of straightforward and supportive policies. The possibilities, current situation and developments were summarized in a joint paper by EBA and HBA (A. Kovács, K.L. Kovács. Developments in biogas/biomethane industry. Eur. Energy Innovation. Autumn, 68-69. (2015)).
The biotechnological aspects of anaerobic microbiology in which methane formation and utilization has been reviewed recently (Bagi et al., Biomethane: the energy storage, platform chemical and greenhouse gas mitigation target. Anaerobe, 46:13-22. (2017)). Biomethane can serve as a platform chemical in various chemical and biochemical processes. At the same time methane emission mitigation is an important task in the anaerobic microbiology of ruminants.
Ongoing research addresses the intriguing and important role of hydrogen in biomethane formation. Hydrogen, which is being produced by some members of the biogas microbial community, is quickly consumed by the methane forming microbes. This stabilizes the life of the entire community because hydrogen accumulation is apparently toxic for those, who produce it. Nevertheless, addition of a properly selected hydrogen producer bacterium to the biogas reactor augments biogas production while maintaining the balance (Ács et al., Bioaugmentation of biogas production by a hydrogen-producing bacterium. Biores. Technol., 186:286-293. (2015)). This and related findings (e.g., Strang et al., Bioaugmentation of the thermophilic anaerobic biodegradation of cellulose and corn stover. Anaerobe, 46:104-113 (2017) demonstrated that suitable management of the biogas microbes can improve process efficiency. Hydrogen (and carbon dioxide) are the ingredients of the power-to-gas process. The efficient conversion of these gases to biomethane is carried out by the effluent from the biogas plant and employed process technology further improves the methane yield (Szuhaj et al., Conversion of H2 and CO2 to CH4 and acetate in fed-batch biogas reactors by mixed biogas community: a novel route for the power-to-gas concept. Biotechnology for Biofuels, 9:102. (2016)).
A hot topic in biogas related research and development is the replacement of plant biomass, which is cultivated for energetic purposes, with alternative biomass sources. Lignocellulose-rich woody biomass is produced in vast amounts but they are difficult to decompose efficiently. Some energy woods, like the willow cultivated on marginal lands, however, can be harvested when the shoots are still green and are excellent substrates for biogas production. Other lignocellulosic agricultural by-products, e.g. corn stover, can be made suitable for the biogas reactor after biological pretreatment and employing innovative reactor arrangement (Kakuk et al., Adaptation of continuous biogas reactors operating under wet fermentation conditions to dry conditions with corn stover as substrate. Anaerobe, 46:78-85. (2017)). Traditionally, biogas operators refrain from putting significant amounts of poultry manure into their reactors due to the toxic level of nitrogen compounds in this material. Nevertheless, the toxic components can be easily removed by a simple water extraction or they can be efficiently “diluted” by carbon-rich biomass, e.g. corn stover (Böjti et al., Pretreatment of poultry manure for efficient biogas production as monosubstrate or co-fermentation with maize silage and corn stover. Anaerobe, 46:138-145. (2017)). The water, which contains lots of nitrogen- and phosphorus-compounds, then is used as a culture medium for the production of algal biomass. The algae can be returned to the biogas plant, completing a circular bioenergy production cycle (Wirth et al., Exploitation of algal-bacterial associations in a two-stage biohydrogen and biogas-generation process. Biotechnol. Biofuels. 8:59, (2015); Wirth et al., Metagenome changes in the mesophilic biogas-producing community during fermentation of the green alga Scenedesmus obliquus. J. Biotechnol., 215:52-61, (2015)).
All these research efforts have been inspired by the BIOSURF project and the encouragement from the project partners is greatly appreciated.
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