Sunday, March 28, 2010

Crossties: Color them green

Written by  Tom Judge, former Engineering Editor

They don’t usually show up on the industry’s “green” index, but the millions of crossties in place make a solid contribution to a better environment.

Millions of crossties support track across the continent. No matter what the material—wood, concrete, plastic composite, steel—each tie makes an important contribution toward helping keep the railroad industry “green.” Valid arguments can be made in favor of one material over another, but the bottom line is that they all work to benefit the environment, in one way or another.

Wood

“Railroads have finally begun to be recognized as one of the most, if not the most, efficient transportation modes for freight in North America, says Jim Gauntt, executive director of the Railway Tie Association. “Moving one ton of freight 457 miles on a single gallon of diesel fuel is certainly an astounding and very ‘green’ feat that railroads do all day long, seven days a week, 365 days a year.”

“The ‘green’ infrastructure behind all of this also plays a significant role in just how green railroading is,” Gauntt points out. “Take for example the treated wood crosstie. Grown using an alternative energy source, solar power, sustainably renewable with modern-day forest management and harvesting practices, and lasting, on average, more than 30 years under tremendous stress and difficult operating conditions, the wood tie continues to be one of the most ‘green’ products in use by North American railroads.

“Wood is remarkable in that as it grows in the form of fast, moderately fast, or slow growing trees, it sequesters carbon by breathing in carbon dioxide from the atmosphere. The wood in every single wood crosstie contains 71 pounds of carbon, which equates to the removal of 260 pounds of carbon dioxide during tree growth. And, not one ounce of electricity, gas or other fuel or energy source makes a tree grow—just the sun.”

Before a tie is placed in service, it is treated with creosote, what Gauntt calls “another modern day miracle product.” Creosote is a triple by-product of the coal coking process used in the steel and aluminum industries.

“It is a marvel in that it is a naturally biodegradable wood preservative,” he notes. “In fact, modern wastewater treating plants use specialized bacteria that ‘eat’ creosote and allow that wastewater to be returned to drinking water standards. And as a useful byproduct, rather than become a waste product itself, creosote further adds to the sequestration of carbon by extending a tie’s life in track.”

“Wood that has not been treated will last only four to seven years in track before decay or termites take their toll on the product,” Gauntt says. “By utilizing wood preservative technology, that life is extended eight to 10 times. So, even though it is true that trees are cut to make ties, the use of wood preservatives, in fact, conserves the forest by extending the resource in a sustainable manner.”

At the end of its life, a used tie can be turned into energy. “A superb source of biomass and containing enough residual creosote to increase BTU content to near that of some coal ore (12,500 BTUs per pound), a used tie can be burned in EPA-approved facilities to generate electricity or be gasified to produce another useable fuel,” says Gauntt. “Environmental life-cycle analyses under way in the industry have shown that if all the ties replaced annually in the U.S. and Canada were recycled for energy, the result would be to offset the greenhouse gas and fossil fuel use equivalent to a city of nearly 100,000 people. So, from one alternative energy source to another, wood offers the railroads superb service life over a period averaging 30-plus years, and does so in a remarkably ‘green’ way.”

Concrete

L.B. Foster, through its wholly owned subsidiary, CXT, Inc., manufactures and supplies a wide range of concrete ties for main line, industrial, port, and transit rail applications. In addition to their cost effectiveness, these ties provide superior energy and environmental benefits over other types of ties in their production, assembly and use, the company points out.

According to National Sales Manager Mark Hammons, “Stiffer track corresponds to a higher track modulus. Higher track modulus, in turn, results in a reduction in rolling resistance. By reducing rolling resistance, freight trains can reduce fuel consumption. Several field tests have been conducted that show that tracks using concrete railroad ties provide a stiffer track structure. This results in an up-to 7% reduction in rolling resistance, providing fuel savings in the range of 1.2-4.5% for the railroads. Concrete ties are also viewed as being environmentally friendly because they’re not treated with any chemicals that have the possibility of leaching into the ground water. In addition, when installed in similar track conditions that use other types of ties, concrete ties tend to have a longer life cycle, minimizing the depletion of natural resources.”

Studies done by the University of Melbourne, whose results were published recently by Precast Solutions and Environmental Science & Technology, indicate that concrete ties produce as little as one-sixth of the greenhouse gas emissions associated with wood ties. However, more than just the overall tie manufacturing process needs to be considered when comparing the environmental impact of the two types of ties. A number of other factors, including the mining of raw materials used to make concrete ties vs. timber harvesting, the actual production of ties, the installation and use of ties, and the final disposal of a tie at the end of its useful life all play key roles. Based on a life-cycle analysis, it was concluded that total greenhouse gas emissions (GHG) from concrete ties could be as little as one-half to one-sixth the amount produced from wood ties.

During the production and assembly of a concrete tie, L.B. Foster uses a number of raw materials and other components that are environmentally sensitive. The wire rod used to reinforce each tie is made from steel that relies on predominately recycled scrap steel during its manufacturing process. Steel components, such as casting, clips, and inserts used in the fastening system, also use recycled steel during the melt process. Upwards of 90% of the steel used by the company is derived from recycled metal.

L.B. Foster has also been looking at ways to reduce energy use during the manufacture of concrete ties. For example, the company’s tie plant has reduced its power consumption for lighting by 50% and its heating power consumption in the manufacturing process by 30%. In addition, concrete ties are a recyclable product and the company is actively investigating opportunities in this area.

Plastic composite

“Plastic composite railroad ties have several environmental benefits compared with conventional, preservative-treated wood ties,” says Henry Sullivan of TieTek LLC. “The primary component of the tie, regardless of the specific manufacturer or formula, is recycled thermoplastic. This raw material is recovered from post-consumer or post-industrial waste after the plastic was first produced and manufactured into products like bottles, bags, automobile parts, toys, packaging, etc. This second use of the material to make a railroad tie does not require petroleum as a feedstock or high energy consumption to create the plastic; it has already been made into a product, discarded, and is headed to a waste site.”

“Conventional ties, on the other hand, require harvesting mature trees,” Sullivan said. “As many as four million trees are cut down per year to make railroad ties with an obvious loss of the trees’ ability to reduce greenhouse gases by sequestering carbon dioxide. Millions of pounds of wood preservative chemicals are also avoided by the use of composite ties.”

“Sustainability Benefits of Plastic Composite Railroad Ties,” a paper coauthored by HDR, Inc., and TieTek, was presented at the APTA 2009 Sustainability Workshop. The paper estimated that just one railroad, Chicago Transit Authority, by installing composite ties, has recycled 17 million pounds of plastic, saved 25,000 mature trees, avoided using one million pounds of creosote, and reduced greenhouse gas emissions by 14,000 tons of CO2 equivalent. This environmental benefit offset the impact of driving a passenger car 100 million miles.

Steel

“Environmental issues are becoming an increasing concern in our society today,” says John Fox, vice president-sales at NARSTCO. “From industrial applications to Class I railways, steel ties are the proven environmentally correct substitute for the traditional wood tie. The steel tie, a recyclable tie, lowers life-cycle costs and, unlike creosote treatment, is environmentally friendly. Steel ties eliminate any of the potential health risks associated with the handling of wood ties.”

The company claims that NARSTCO Steel Ties incorporate recycled materials in their manufacturing process, and eliminate the need for handling the heavy tie plates used with wood ties, thus increasing worker safety. NARSTCO Steel Ties and Turnout Sets “are harmless to the environment; eliminate the need for creosote as well as spikes, gauging, anchors, and tie plates; outlast wooden ties; and are 100% recyclable and thus have scrap value,” Fox says. “They’re an environmentally responsible, economically smart choice for the railroads.”