Design of a two-step hydrogen and methane process from lignocellulosic biomass

The production of biogas from lignocellulose biomass is a promising area of research from both an environmental and economic point of view. However, the future of biogas as an industrial relevant product will rely on both minimizing production cost and maximizing productivity. The Metanova system currently under development aims to accomplish this by employing a two-step consolidated bioprocess, consisting of uncoupled production of hydrogen and methane, while reducing the number of process steps and chemical input. The pretreated biomass will be digested through thermophilic dark fermentation using species of Caldicellulosiruptor producing H₂ and acetic acid, followed by anaerobic digestion of the acetic acid to achieve CH₄. The advantage of using the microorganism Caldicellulosiruptor is its high hydrogen and acetate yield as well as its ability to grow on a wide variety of substrates.

Mesophilic biogas production has shown to be more stable and give higher productivity when it is preceded by a hydrogen production step rather than produced in a single step. The project aims to achieve high H₂ productivities using designed co-cultures of osmotolerant strains as well as high CH₄ productivities from the effluent of the H₂ reactor, enabling short hydraulic retention times. Thus, interactive modeling is a part of the project in order to study process kinetics and degradation pathways with the aim to identify process parameters for further optimization.