The aim of this work was to investigate the productivity of continuous lactate fermentations at increased cell densities on simulated lignocellulosic hydrolyzate and wheat straw hydrolyzates using Ca(OH)₂suspensions as base. To this end, a semi-automated membrane bioreactor prototype with external tubular membranes was designed and constructed. Long-term continuous fermentations were run in membrane bioreactor mode and compared to batch and continuous mode. Fouling of the membranes proved to be the major bottleneck in the process. The semi-automated membrane module switch elegantly circumvented this problem, allowing constant operating conditions throughout extended periods of time. Maximal productivities of 30.5 g kg⁻¹.h⁻¹could be reached in the prototype during 30.5 h combined with an average lactate concentration of 85.4 g kg⁻¹and complete consumption of C5 and C6 carbohydrates. In this fermentation zone, the (liquid) residence time was 2.8 h. These numbers demonstrate significant performance improvements in comparison with batch and (regular) continuous conditions.

A study on integration of Power-to-Gas technology with bio-methane production from bio-syngas produced by biomass gasification shows that a significant amount of excess electricity can be accommodated in bio-SNG production. By adding hydrogen produced from intermittent renewable sources to a CO₂ methanation section, production capacity of methane can be doubled. The business case for Power-to-Gas for bio-methane has been evaluated using three future cumulative electricity prices curves. Results show that a positive business case exists only for price curves based on large amounts of intermittent electricity installed. The room for investment for the electrolyser will mainly and highly depend on future commodity prices and price curves, and will benefit significantly from a decrease in the cost price of the electrolyser. The projected room for investment available for a PEM electrolyser is lower than for a Solid Oxide Electrolyzer (SOE), because of its lower efficiency and resulting higher operating costs. In the case of large capacity of intermittent electricity, the projected room for investment of an SOE electrolyser is 650 €/kW and for a PEM electrolyser 350 €/kW, which corresponds to the projections of future electrolyser costs.