Green energy with crambo

In the biomass co-generation plant in Herbrechtingen, Germany, a Crambo e-mobile is hard at work shredding fuel. CEO Jürgen Wiedenmann explains why the semi-mobile electric Crambo is the ideal solution for him.


Twenty years ago an ambitious project started in Herbrechtingen – a privately owned biomass cogeneration plant. The main initiator was a sawmill. It supplied waste material to the plant as fuel, and in return got heat for use in drying. A local pellet plant was another customer for heat. The green energy it made was fed into the grid at EEG rates.

Ups and downs

Jürgen Wiedenmann was there almost from the beginning, and is familiar with the shifting fortunes of the power plant. “after a few years there was a difference in interest that led to the sale of the plant to a US investment fund that wanted to get into renewable energy. The market was tougher than they thought and many of their plans turned out not to be feasible,” he recalls. Since 2016 the power plant has sailed in calmer waters. “A medium-sized disposal company took it over. It was already one of the important fuel suppliers, and has a quite different investment strategy,” says Wiedenmann. “That made many things possible.”


The challenge of fuel supply

After the sawmill became unavailable as a source of fuel, the power plant had to get its own, mostly consisting of processed waste wood. “We need over 100,000 tonnes of fuel per year. There were times when we had 20 to 30 suppliers delivering material of highly varying quality at varying prices,” recalls Wiedermann of this challenging time. The power plant had not originally been designed to take delivery of and process unshredded fuel, but it was obvious that it would make economic sense to do so. And with the new ownership, this was now a viable option.

„We selected the hook-lift frame version. It’s ideal for our needs. I just need to pull the plug, and we can move the machine.“

Jürgen Wiedenmann

The right processing is the key

On-site processing started in August 2020, and since then a Crambo e-mobile has fed the power plant its daily ration of fuel. The plan calls for 1500 operating hours per year. Jürgen Wiedenmann is confident that the machine has what it takes to deliver this. After all, the combustion chamber can’t just take anything, he says. “Since we have a fliuidized bed system, we need a fairly fine grain and dependable metals separation. Especially metals with low melting point can clog the nozzles that keep the bed fluidized, if there is an interruption in operation. Then we have to get out the air hammer to get the cooled metal out of the nozzles.”

So the Crambo has a 100 mm screen. This ensures the right grain for feed and combustion, as well as opening up the wood so that downstream ferrous and non-ferrous separation works reliably. “Naturally we are aware that this excacerbates wear, and reduces throughput. We tested all of that beforehand,” explains Wiedenmann. “But I’d rather quickly take the machine to the shop and change the teeth than risk a power station stoppage at three AM because of a contrary.”


Electric mobility

The plant operators made a conscious decision for the “e-mobile” design. Instead of a diesel engine, it has an electric motor and switchgear. Everything else is just like a normal Crambo. In operation, the only visual difference is the power cable. “We approved it as a mobile machine, and mobile it is,” says Wiedenmann, adding, “We selected the hook-lift frame version. It’s ideal for our needs. I just need to pull the plug, and we can move the machine.”


For today and tomorrow

Jürgen Wiedenmann had the future in mind when he made this decision. “It’s clear to us that our EEG subsidies will come to an end. So I have to think about what comes next. With the e-mobile solution I’m much more flexible in resale than with a stationary, permanently installed machine.” It was clear to him from the start that only an electric machine came into question for the processing. “We make almost 16 megawatts of electric power out of a renewable resource. Nothing else would have made economical or ecological sense. The Crambo e-mobile is like it was made for us.”
It also makes the workday easier: No daily refills, no sensitive exhaust scrubbing, simple maintenance overall – advantages the staff can appreciate. And the wheel loader driver is happy when rootstocks need to be shredded, because that goes especially well with the Crambo.

With his many years of experience, Jürgen Wiedenmann is active in his industry association. “We all want disposal and supply to be regional, and that goes for waste wood as well. We work hard to fulfill our responsibility and provide regionally produced heat and electricity. But to stay competitive, a little more political support and acceptance would be helpful.”