By Matt Griswold, Plastics News staffAkron, Ohio-It's a new twist on the concept of one man's trash being another's treasure.A handful of closely tied composites makers describe their products as having many of the positive qualities of wood, metals and cement-and few of the negatives.The potential is limitless in countless applications, they said.The future, various company officials claim, is in structural applications -everything from railroad ties and bridges to dog houses and even houses for people.Instead of polyethylene, which most composite makers are using in their products, companies like Century-Board USA, and licensees Century Products llc and Stonewood llc, are using polyurethane.PU's chemical properties allow it to perform better than PE in terms of strength and resilience in rapidly changing environments like harsh weather conditions.The catch: PU resin costs a lot more than PE. According to Plastics News' resin pricing chart, PU is between $1.50 and $3 per pound, while even after historically high price increases, PE is still less than $1 per pound.But in the case of the Century and Stonewood products, even the catch has a catch. The higher cost of PU is negated using a low-cost, and in some cases no-cost, mineral filler like fly ash, which makes up more than half the composite. That's the key to the economics. If it wasn't for the low-cost filler, we would have a very difficult time with pricing," said Wade Brown, president of Fort Myers, Florida-based Century-Board.Fly ash is an industrial waste product of coal-burning power plants. Often, the only cost is transporting it.Century Products' LifeTime Lumber contains 65 percent fly ash, said Jim Mahler, vice president of business development for the fledgling Anaheim, California-based manufacturer. LifeTime Lumber is made from a composite developed by Pittsburgh-based Bayer Material-Science llc. To a large extent, the fly ash is to be credited for making the product work. On its own, PU is still susceptible to extreme weather changes, said Zack Taylor, a co-founder of Murrieta, California-based Stonewood. The mineral content makes it instantly stable in hot and cold," he said. The trash actually makes it better and stronger."Commercial production is still in its infancy. Century-Board ran a pilot programme for a few years but has ceased manufacturing. Brown said the company is focusing on licensing, research and development and supporting its licensees.Century Products is the only one of the group in commercial production. Stonewood is shopping for space and equipment and anticipates cranking up manufacturing operations within the next six months.The composite makers said their PU-fly ash mixture outperforms those with a natural-fibre content. Natural fibres will inevitably decompose over time, they said; fly ash won't. Also, the mineral composite won't absorb water, so it's a viable, low-cost alternative to other materials in marine applications like docks, piers and bridges. The material is naturally non-fouling, which means barnacles won't attach to it, yet it remains nontoxic, Taylor said.Composite decking, which is predominantly made of PE and wood fibre, is taking the residential decking market by storm. Homeowners are buying and installing composite decks at a record pace, and analysts expect the pace to increase. But even plastic composite decks still require pressure-treated lumber substructures.PU-mineral composites could tackle that market, too. Mahler said the business of deck substructure construction is, in itself, a $5000 million industry.The manufacturing process of PU-fly ash composites uses low-viscosity thermoset resins. There's a stage in production where the material is in a state similar to wet cement, which allows manufacturers to add strength reinforcements. We can use anything from natural fibres to glass fibres to graphite fibres," Taylor said. We can use steel rebar if we want. It means we can make something as strong as anyone could want."Mike Wolcott, a professor of civil engineering at Washington State University, said in a telephone interview that urethane's properties allow for PU-based products that can handle loads other plastics cannot.Wolcott said he is involved with U.S. Navy projects, including the making of structures that the military can use out in the field. We will eventually start seeing other applications where this will become more prevalent," he said.Century Products is developing railroad ties. The composite will neither rot nor split, the firm said. All these help put us ahead of everyone else," Mahler said. The thing that seals the deal for me is looking at the ageing characteristics. I feel very comfortable giving a lifetime guarantee."Century Products' LifeTime Lumber has found a niche in equestrian applications, Mahler said. Horses will not chew on the PU-fly ash material. That's a huge disadvantage to wood," he said. We're looking at several different products in the equestrian arena: fencing, stall walls, outside barn siding. Those weren't even areas we intended to get into."With continued efforts in research and development, Brown said, the PU-fly ash composite technology has a bright and lucrative future. It's a difficult technology," he said. It's very sensitive to get the right formulations, but once you get it, it works very well. We think this is going to be a very big business."