Bioflex - biobased energy carriers and their contribution to a flexible energy system

Bioflex aims at increasing the flexibility, redundancy, and robustness of the energy system by integrating biobased energy carriers (biohydrogen/biogas) with electrolytic hydrogen. By combining 2 energy carriers, the project intended to investigate possible synergy effects between the different production pathways. The combination of energy carriers is expected to generate 3 main effects: more efficient resource utilization, increased share of biobased energy and increased flexibility in local energy systems.

The project performed a lab and pilot study of a two-stage bioprocesses, investigated synergy effects and flexibility in the interaction between the bioprocesses and electrolysis, techno-economic analysis of the system and an actor and stakeholder analysis. The goals of the project were to 1) demonstrate the two-stage bioprocess in pilot scale (TRL 5), reduce the hydraulic retention time (HRT) for biogas production by 50% and optimize nutrient supply, and 2) formulate an implementation plan and recommendations to the stakeholders.

The results from the lab and pilot study show that biohydrogen and biogas can be efficiently produced in a two-stage bioprocess and that this leads to higher carbon utilization (from substrate), higher energy recovery and lower emissions (from digestate). Comparisons with existing biogas production with the same process water indicate that the two-stage bioprocess in total delivers equal amounts of biogas compared to the base case, but more energy is produced in total since biohydrogen is also produced. Calculations with linear scaling would give approx. 30% more energy already in the first bioreactor. That scaling up in reality would be linear is however unlikely where a number of other conditions come into play. Therefore, this process needs successively to find key parameters for scaling effects.

Calculations on integration with electrolytic hydrogens show that it is beneficial to use waste heat from electrolysis to heat the bioprocesses, since heat costs are otherwise a large cost item for the two-stage bioprocess.

The techno-economic calculations show that the major cost driver for the entire system is the electrolysis system. The payback period is also highly dependent on the selling price of hydrogen. If the selling price of hydrogen is high, the payback period will be shorter.

The results from the stakeholder mapping and scenario analysis show that: 1. Collaborations are desired for sharing the risk when investing in this type of new technology. In particular, clear collaborations are required when it comes to symbiosis solutions. 2. Clear prerequisites for policy and regulations are requested from many parts of the value chain. 3. Biohydrogen is a niche and its possible position in the market needs further investigation. 4. The two-step bioprocess combined with electrolysis can increase the supply security of renewable energy sources locally and thus increase preparedness. 5. The replicability of the concept with the two-step bioprocess is assessed as high, since there are many different ways it could be done depending on local conditions, but the replicability decreases with increased complexity in the symbiosis solution.