A pilot project in Germany is collecting food waste from wholesale fruit and vegetable markets and cafeterias to ferment and make methane, which will then be used to power vehicles that have been converted to run on natural gas.
The pilot plant has been developed by the Fraunhofer Institute for Interfacial Engineering and Biotechnology and is located next to Stuttgart's wholesale produce market for easy access to food waste. The plant will make methane from the waste by using microorganisms to break down the food in a two-stage digestion process over a few days.
Because the food waste being fermented on any given day can be more or less acidic depending on what was tossed out, the pH levels have to be constantly monitored in order for the microorganisms to best do their thing. The waste is held in several tanks that feature a management system that monitors many parameters, including pH level. The software then calculates how many liters of which waste should be mixed together to feed to the microorganisms.
The plant produces about two-thirds methane and one-third carbon dioxide from the process, but nothing goes unused: the filtrate water which contains nitrogen and phosphorous, and the carbon dioxide produced from the fermentation are both used to cultivate algae for another project, while the sludge left behind from the fermentation is sent to other institutes that are capable of making methane from it.
The pilot project has been funded by the German Federal Ministry of Education and Research and has partnerships with energy company Energie Baden-Württemberg, which is processing the biogas, and with Daimler, which is supplying natural gas-converted vehicles to run on the fuel.