Working with representatives of small- and medium-sized companies scientists at the Fraunhofer Institute for Ceramic Technologies and Systems in Dresden have brought a biogas-electricity plant on-line that relies solely on plant waste, such as straw, but in this case corn stover—the leaves and stalks of the plants.
The pilot plant—claimed to be the first ever of its kind—runs biogas produced by anaerobic fermentation of corn stover through a high-temperature fuel cell to generate 1.5 kW of electricity, enough to power a single home.
By optimizing the process, the R&D team has been able to achieve a remarkable 85% energy conversion efficiency ratio. A typical internal combustion engine in a passenger vehicle has an efficiency of around 30%.
All Parts of the Process
Efficiently converting “woody” plant materials that contain a relatively high proportion of cellulose has been the biggest hurdle when it comes to producing biogas from agricultural waste and other non-food plants as the cellulose has to be broken down before it can undergo anaerobic fermentation, which results in the production of “biogas.”
Optimizing each of the constituent steps in the plant waste to biogas to electricity process, the R&D team’s system has been able to generate significantly more biogas than its predecessors, and do so in a lot less time.
“In our pilot plant, we exclusively use agricultural waste such as corn stalks – that is, the corn plants without the cobs. This allows us to generate 30 percent more biogas than in conventional facilities,” said Institute department head Michael Stelter.
Moreover, the time the decomposing waste silage has to be kept in a fermenter been reduced 50-70%, from 80 to 30 days, according to this report from the German Foreign Office.
The biogas is then shunted into a fuel cell that operates at 850 degrees Celsius (1562 degrees Fahrenheit). The heat from the fuel cell can also be used for direct heating or fed into a heating system network.
The next step for the scientists and their industry partners is building larger scale versions of the plant.