Yesterday’s trash, today’s organic

An MBT reinvents itself and becomes a national showcase project for organic waste treatment. In Gescher, Germany, efficient machines and renewable energy all add up.

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In 2000 the Westmünsterland Disposal Company (EGW) started a mechanical-biological waste treatment plant (MBT-plant) in Gescher. Back then, all was still business as usual in the MBT world. Over the years, EGW faithfully made the upgrades needed to stay up with the latest technology. But in recent years, increasing price pressure from incinerators made economical operations more and more difficult. Instead of giving up, company leaders put their heads together and decided to try a reorientation. In 2012, EGW switched from MBT to the biological treatment of organic waste, first halfway and then completely in 2014. Today, the Gescher site accepts biowaste from the district of Borken and Recklinghausen and the city of Dortmund, totalling over 100,000 tonnes per year, and turns it into high-quality compost.

Prize winning

Thinking about tomorrow and the idea of sustainability seem to have deep roots in this part of Germany. Peter Kleyboldt, long-time CEO of EGW, gives an example: “In 2012 the municipality of Borken decided to take part in the ‘European Energy Award.' Last year we reached our target and received the gold award, which goes to municipalities that actively work to protect the climate and take steps to save energy and promote renewable energy. As the municipality’s own disposal company we naturally want to do our bit. So at this site, over the course of a year we make over eight million kilowatt hours of energy but use only around 4.5 million.”

Old and new harmony

Technical Director Martin Idelmann doubtless had something to do with those great numbers. His job was to harmonize the old and new system components and turn it all into an efficient composting process. Finding synergies and efficient ways to use energy were special priorities. The biological part of the processing is almost the same as before, consisting of tunnel composting and a ventilated flat-top windrow with turner for post-rotting. But the mechanical part is pretty much all new. At its heart is a Terminator 5000 S direct, whose mechanical drive is a perfect fit for the overall concept of the system.

A thrifty successor

“Back when we were just an MBT plant we shredded residual waste with Terminators. We had two machines, one of which had over 30,000 operating hours on the clock by the time we replaced it,” says Martin Idelmann. “The reliability we experienced and good customer service were definitely factors in our decision, but what ultimately sealed the deal was the energy efficiency of the mechanical version.” In addition to saving almost 30 percent in energy compared to its hydraulic predecessor, the new organic waste shredding job requires only one machine. Idelmann depends on the Terminator’s flexibility. “Unfortunately, there are plastic bags and packaging pieces in the waste. So that we don’t shred it too much and can keep parts of biowaste as a structure material, we shred more gently. We run at low drum speed and use the greatest possible gap between drum and counter comb.” This makes it possible to concentrate the plastic in the oversize fraction with downstream drum screening, while getting sufficient structural stability in the cleaned undersize fraction for the rotting process. The oversize fraction is wind sifted with the existing machine, and high-caloric material separated off goes to heating use.

The multipurpose Terminator

Idelmann has another job for the Terminator direct. The plant still takes residual waste from the Borken area, but now the only treatment is mechanical separation into a high-caloric fraction for use in RDF power plants and a low-caloric fraction for incineration. According it Idelmann it is “no problem. Once we’ve gone through the amount of biowaste scheduled for that day, we switch over. From the control room we make the cutting gap in the Terminator narrower, go into second gear with the higher speed, and have the perfect waste shredder.”