Should we continue to compost and incinerate sewage sludge, organic and green waste when it could be used to make low-cost green hydrogen (H2)? This is the question posed by researchers at the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA) in Stuttgart, who have been working on various biological separation techniques.

Germany produces around 15 million tonnes of biogenic waste from compost bins to agriculture, recycled paper and slurry every year. If it’s incinerated or composted, it releases CO2 into the atmosphere. “Organic waste is far too valuable to be used in this way,” says Johannes Full, head of IPA’s Sustainable Development of Biointelligent Technologies group, in a press release. “It would make more sense to use the material to generate hydrogen. The CO2-carbondioxide emitted during the process could then be separated, stored or used in industrial applications.”

In a pilot project, the waste from local fruit farmers and vintners, as well as rubbished cardboard and wood were converted into H2 gas, which was then used directly by a local factory to process metal. In a first step, the waste was fermented naturally in a dark enclosed container with the help of bacteria which produced H2 and CO2-carbondioxide. In a second step, the fermented residues were converted into methane and then into more H2 and CO2-carbondioxide. In a separate process, the wood and paper were split into the component gases using a wood gasifier.

The team are collaborating with other institutes on various sub-projects including H2Wood – BlackForest, which explores how microbes can break down wood waste to form H2 and other useful chemical materials. The IPA’s study Industrial Hydrogen Hubs in Baden-Württemberg shows how decentralised green H2 production can cover the energy of certain industrial processes and heavy goods traffic regionally. The researchers surmise that 30 percent of fossil energy could be replaced within ten years by regionally-produced regenerative H2.