A new direction
in Switzerland

Declining margins in the used wood business require a rethink of the most efficient processing methods. Low-speed preshredding followed by star screening is high on the list. Holz- und Stockrecycling AG in Otelfingen is testing the advantages of the combination of Crambo and new Multistar One with overlength return.

January 03, 2017

In Otelfingen near Zürich a new machine combination has been in test operation for a few days. It consists of a Crambo direct 5200 and a Multistar One. The goal of the testing is to get data on profitability and to investigate the influence that the material quality has on combustion processes at the nearby cogeneration plant. 

On-site fuel use
In this case “nearby” is an understatement, since the waste wood processing facility and the cogeneration plant are at one and the same site. There is no need for trucks. A conveyor belt suffices to move the fuel from storage to the intermediate bunker. Andreas Suter, Director of Holz- und Stockrecycling AG, is partly responsible for this favourable situation. With a good dose of pioneer spirit and daring, in 2002 the company opened the Otelfingen power plant. The company invested double-digit millions in the generation of renewable energy. But as business conditions shifted it became ever more difficult to operate profitably, and so in 2008 the company took an international energy group on board, which has since become the majority owner. “In 2011 the entire system was overhauled and a district heating network was built for the surrounding industrial zone. Now the plant operates in the black, but for us as private individuals the investment would not have been possible,” notes Suter, who now concentrates entirely on supplying the fuel.

100 tonnes a day
The cogeneration plant uses 100 tonnes of fuel a day to make 18 million kWh of electricity and 8 million kWh of heat. At 35,000 tonnes per year, the plant takes 90 percent of the fuel produced at the site, with the rest going to other regional power producers. The facility processes waste wood grades AI for untreated wood to AIII for coated and painted particle board. It all needs to be transformed into a homogeneous fuel. The job is handled by an electric Crambo 5000 pre-shredder and a diesel high-speed shredder. 

Plus points of the new technology
In future a screen will take over the role of the high-speed shredder. Currently testing is underway on a combination of a Crambo and a star screen with integrated return of overlengths to the shredder, to see if it can replace the energy- and wear-intensive chipping step. Results are promising. Instead of a several hundred kilowatt shredder with its dust and noise, the almost silent screener draws not even 20 kilowatts. And there is another benefit. Andreas Suter estimates that it reduces fines by 30 to 40 percent. Testing over several days is necessary to determine what effect the changed fuel will have on combustion in the cogeneration plant. After two days of operation Suter is optimistic. “Measurements of the exhaust show a clear downward trend, especially the carbon monoxide. Nitrogen oxides have also fallen. We’re still waiting for the lab results for the ash and exhaust filter samples, but we’re optimistic about them too.”

Suter is sure that, while the new combination give a little less throughput, the higher product quality and lower operating costs will more than make up for it. The Multistar One test machine may have a few teething problems, and certainly for his location Suter needs a stationary version instead of the mobile machine he tested, but one thing is clear – this is a configuration with a future.