Nurses and carers at the handicapped and old people's homes are proud that every disposable diaper helps save a little fossil fuel.
"When this thing is running, we don't need any gas or oil in the building," said chief technician Marco Nauerz in the furnace room of the foundation's main site at Meckenbeuren near Lake Constance.
The 11-meter-high (36-feet-high) plant can consume 8 million diapers annually. By Nauerz' calculation, that means it can continuously eliminate the waste from 12,000 incontinent patients. There is no risk the supply will dry up.
Liebenau has already signed up 40 rest homes, some of which it owns and others run by other operators, as suppliers, and it expects to double the number by the end of the year.
The diapers are packed in plastic sacks and arrive in airtight garbage trucks.
"You can't smell anything here, can you?" said Nauerz, showing the "fuel" shed, where extractor fans suck out any odors.
Nauerz, 55, and no stranger to diapers as a father of three, has gained new respect for the soiled nappy through his work.
As much stored energy as wet chopped wood
Engineers say they have an average moisture content of 58 percent and can release as much energy as wet chopped wood. At 910 degrees Celsius, they burn in seconds. The foundation uses the energy to heat water in bathrooms and in its laundry to clean towels and sheets.
The total cost of the plant, the "fuel" depot and new pipes came to 3 million euros ($4 million), Nauerz estimates.
Best of all, Liebenau expects to make a profit from diapers, as it charges rest-home operators to get rid of the waste. The fees are lower than those at land-fills or commercial incinerators.
To date, the foundation has had to pay 350,000 euros ($481,880) annually in land-fill fees for its own 2.1 million used diapers per year.
The furnace was jointly developed by Liebenau staff and an engineering company in Bregenz, Austria. An automatic conveyer from the hopper to the furnace was also specially made for the job.
German law does not recognize diapers as fuel
The partners were surprised to run into legal difficulties, seeing as German law makes no provision for diapers as fuel.
The plant had to have flue-gas treatment like regular commercial incinerators, although the engineers say diapers are mainly organic: just cellulose, biodegradable plastic film and the contents.
As a non-profit charity, Liebenau is also concerned about being kind to the environment, so it insists that all the diapers be "local produce" and rejects long-distance transport of the new fuel. Instead, it hopes to sell the furnaces elsewhere in Europe.
Patents have been applied for, and Nauerz said the partners were developing a business model. Baby diapers are not expected to enter the model, as householders can dump these in domestic rubbish at no extra charge.