Thermal-expansionary pretreatment is a novel environmentally friendly technology that has high potential to be installed in various industrial biofuel technologies where lignocellulosic biomass is processed. It is based on the boiling of biomass in water maintained by pressure in the liquid state, under a process temperature and a residence time with subsequent rapid batch decompression. The performance of the intensified pretreatment technology was shown in an intensified full-scale biogas plant. Wheat straw was used as the model processing substrate. To show the improvement, the results were compared with the regular non-intensified biogas plant. It was found that the intensified plant had a much higher power. The economic analysis and payback period were performed for both types of plant.

A techno‐economic analysis for four different types of biogas plant realizations was performed, including one biogas biorefinery concept. For each concept detail, a process flow diagram was created. Mass and energy balances were estimated. The net present value and payback were calculated for each concept for a better feasibility understanding. The results showed that with the used expensive substrate, namely, wheat straw, the obtained paybacks appeared to be more than 100 years. Sensitivity analysis was done for the price range of a substrate. Critical factors were defined to improve feasibility.

A techno‐economic analysis was performed for a biogas plant with in‐built algae production. Degradation in the fermenter occurs under mesophilic conditions, to produce 605 Nm3t−1TS of biogas and 343 Nm3t−1TS of methane after 50 days. The biogas was combusted in a combined heat‐and‐power unit to produce heat and electricity. Cultivation of Chlorella vulgaris was done in co‐annular photo‐bioreactors, with an annual productivity of 107.5 t. For cultivation, both autotrophic and mixotrophic growth were assumed. Detailed mass and energy balances were done. For both conditions of algae growth, the results are approximately the same after a 30‐year payback period.