Spotlight with Gerhard Kosche

Gerhard Kosche has a lot of post-production wood waste on his hands—which works out fine since he considers it a valuable product deserving a better end than incineration or landfill.

Kosche is owner and CEO of the Kosche group of companies, with its primary business producing wood and chipboard products for the building and construction industry. But his passion has been finding a practical, cost-effective, and environmentally sound use for the wood flour resulting from saw mills and woodcutting. Wood-plastics composites (WPC) offered an opportunity.

However, he didn’t want to mimic what was being done across the Atlantic. He says European needs for such products are different. First of all, vinyl-based WPC, he claims, has to fight an uphill ‘emotional’ battle compared to WPC based on a polyolefin matrix. He also wanted to use clean post-production wood scrap rather than wood that could contain formaldehydes or creosote. He also wanted a filling rate of up to 80% wood flour compared to what he says is a maximum of 50% achievable in PVC-processed WPC.

“PVC works well but here in Europe its acceptance is limited. That’s why we turned to high-density polyethylene as the binding polymer, combined with an adhesive and a color stabilizer,” he says. Any wood product turns grey in UV light, so the light stabilizer is a key element to the company’s formulation, he says.

His company, which turns 40 this year, started early this century experimenting with processing of WPC panels. Working with various equipment manufacturers, it “went through a very long and difficult learning phase, often learning the hard way, to reach the level of technology we are at today,” he recalls. The company’s original extruders only lasted up to 7000 hours before needing replacement and weren’t able to deal with more than 50% wood-flour filler. “What we wanted in equipment and support really wasn’t on the market. You can’t rely on the answers from either the plastics people or those in the wood sector since this is a completely different animal,” says Kosche. “They know plastics or they know wood, but not both.” So in 2005 his company struck a cooperation deal with extruder manufacturer Reifenhäuser (Troisdorf, Germany) and wear-protection screw-and-barrel producer Reiloy (a Reifenhäuser division) to refine the product.

“We decided to take development in our own hands since we are closer to the subject, but relied on Reifenhäuser’s input,” he says. That meant Kosche built extrusion tooling in-house to cope with the highly abrasive wood filling levels and developed some of its own downstream equipment, such as special non-immersion cooling and calibrating tanks. Kosche invested in seven Reifenhäuser Bitruder counter-rotating twin-screw extruders for the job. These now last more than twice as long, based on production hours, compared to extruders from the company’s previous supplier.

Today Kosche is Europe’s largest WPC producer with output of 34.4 tonnes every 24 hours, which, in annual square-meter production (660,000m2) terms, is equivalent to 130 soccer fields measuring 5000m2 each. The 2008 figure should be double the output of 2007, he says, adding, “We could have had up to 40% more WPC sales in 2007 if we had had more capacity.”

The wood flour used in Kosche’s products, marketed under the Kovalex brand, needs to be dried to reduce the 12% moisture content to acceptable extrusion levels. Then it is compounded and pelletized by Haller Formholz in Sulzdorf, Germany before Kosche extrudes it at its Valentin subsidiary in Bicken-Mittenahr, Germany.

The biggest European WPC market is decking. Worth about €224 million in 2006, Europe’s market for WPC decking is showing annual 10% growth and is expected to reach €351 million by 2010. Currently WPC makes up only 6% of Europe’s decking while tropical wood accounts for 54%, but as tropical timber presents environmental concerns, the future looks quite bright for WPC.

Robert Colvin • [email protected]