Besides dark fermentation, electrohydrogenesis (electrolysis using microbes) is another possibility. Using microbial fuel cells , wastewater or plants can be used to generate power. Biocatalysed electrolysis should not be confused with biological hydrogen production , as the latter only uses algae and with the latter, the algae itself generates the hydrogen instantly, where with biocatalysed electrolysis, this happens after running through the microbial fuel cell and a variety of aquatic plants  can be used. These include reed sweetgrass , cordgrass, rice, tomatoes, lupines and algae. 
Clearly there is a business opportunity to satisfy the increasing demand for butadiene, which is likely to persist. The main alternative technology is butane dehydrogenation route with the main issue to be addressed being the high capital cost of dehydrogenation and separation of butadiene; butadiene separation is a complex process involving extraction and distillation of the raw product streams. There are clearly opportunities to lower this cost by finding alternative routes. Some of these routes could be based on older, now largely abandoned processes.