Railroad ties (or “railway sleepers” outside of the U.S.) are the rectangular load-bearing objects that are used as a base for railroad tracks.  Ties can be made of wood or concrete; wood railroad ties are the predominant type in the United States, while concrete railroad ties are used widely outside of the U.S.  alongside older wood varieties.  In the U.S., approximately 3000 ties are used per mile of railroad track.  Given that approximately 3% of total railroad track is replaced annually for maintenance and disposal,  according to the Railroad Tie Association, and many older railroads get removed each year, many waste railroad ties are discarded regularly and require disposal.  In fact,  13 million ties are removed from the tracks each year (Waste Age). While about half are reused in landscaping projects or bike paths, the other half usually makes it way to the landfill.

Railroad ties must function in varied weather conditions and last for a long time without rotting to minimize the cost of replacement.  Wooden railroad ties are, therefore, treated with chemical wood preservatives, usually containing creosote and/or arsenic, to effectively extend their functional life.  However, these preservatives are toxic and require special handling and disposal when the ties are discarded.  These preservatives can lead to serious health problems, if not handled safely, and many states require that they be disposed of in specially designated landfills to reduce environmental hazards, like potential groundwater contamination.  Thus, new treatments and  disposal methods are always in demand for this difficult waste stream.  The ability to receive railroad ties and use the material for generation of renewable fuel will help to alleviate the challenges with railroad tie management, while keeping this preservative-treated wood material out of the landfill.

For more background on the history of railroad ties check out Railroad Tie Association’s video.