The Utility Solid Waste Activities Group estimates that electric utilities purchase nearly 5 million treated wood poles annually for new installations, expanding the utility grid, replacement of damaged poles, and maintenance.  While companies do make an effort to reuse the poles,  nearly 1 million utility poles are disposed of in landfills each year.  As with railroad crossties, chemical wood preservatives are used on utility poles; therefore, environmentally responsible disposal options can be limited. As a result disposal costs can be both economically and environmentally costly.   The commercial deployment of advanced technologies that can use utility poles for beneficial means, like Ze-gen’s Liquid Metal Gasification technology, represents an opportunity to reduce the burden associated with this “under the radar” waste stream, while also producing fuel that has a wide range of beneficial applications.

Photo: David Humber

Recognizing that diverting carpet waste from the landfill has a long way to go,  carpet industry members, along with government officials, and non-governmental organizations signed a Memorandum of Understanding for Carpet Stewardship (MOU), in January, 2002. The agreement set forth a landfill diversion goal of 40% by 2012. They note the MOU is the “the first step in the eventual elimination of land disposal and incineration of post-consumer carpet.” Ze-gen’s Liquid Metal Gasification (LMG) process represents a possible method to increase carpet waste diversion, while using the material in a beneficial manner. The ground-up carpet material may be used as a feedstock, blended with primary feedstock materials, such as a wood waste, to create a high-quality syngas that can be used in a wide range of industrial applications.

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.

Why do you think he encountered so much resistance?

Do you think increasing the visibility of our waste output would change our consumption habits?

The article reminds us that with right investment in technology, we really can effectively and economically harness the energy value of waste.  Whether it’s onion waste, biosolids, cow manure, or you’re home’s rennovation debris, using the inherent energy value in these materials can have significant positive impacts on our environment and energy usage.

“Biosolids,” also called “sludge,” is created when clean, usable water is separated from the wastes it transports.  The process occurs in municipal wastewater treatment plants that are connected to every toilet, sink, and drain.  Screens and filters accomplish the first step by physically separating large solids from liquids.  In sedimentation ponds, buoyant substances like fats, oils and greases float to the top while heavy materials such as rocks and sand settle to the bottom, allowing easy removal.  This is followed by biological processes that use bacteria or “bugs” to digest dissolved wastes.  A final series of steps uses chemicals such as chlorine to disinfect the effluent before it is reintroduced to the ecosystem.

Wastewater treatment process flow diagram (source: www.biosolids.com.au)

Water is infinitely recyclable using these methods, but the biosolids left behind at each treatment plant are decidedly less convenient to manage.  They accumulate by the ton and eventually require disposal to keep the plant from becoming inundated.

There are several options.  As with nearly all waste, properly treated biosolids can simply be buried in a landfill.  Another low-tech solution is incineration, used by some facilities as a way to kill bacteria and to recover some energy value in the form of heat.  Increasingly though, biosolids are being recognized for their nutrient rich properties and are becoming a significant source of fertilizer products.  Spreading biosolids over arable land creates synergistic benefits by giving farmers a low-cost alternative to petroleum-based fertilizers and helping treatment plant operators manage waste (see Milorganite video).

Biosolids disposal options (source: www.biosolids.com.au)

Land application of biosolids has not been uniformly embraced.  Environmental groups and community activists contend that pollutants and pathogens make biosolids too dangerous to use in farming.  While this conclusion is disputed, biosolids are EPA approved for diverse agricultural uses and are regulated accordingly. Yet there is admittedly little data available on the topic and it continues to be studied (see NY Times article for further insight).

To the extent that biosolids can be safely re-purposed as fertilizer, this is likely the best use of this waste stream.  But for urban centers and areas with limited demand for fertilizers, a more efficient method of unlocking biosolids’ energy content could be the next best option.

Gasification technology creates a renewable fuel by using biosolids as a feedstock.  The fuel, known as synthesis gas, is a mixture of carbon monoxide and hydrogen that can substitute for natural gas in many industrial applications, including steam and electricity generation.   By converting the solid matter to energy in a low-oxygen, high temperature environment, gasification is able to avoid many of the pollutants produced by simply burning waste.

Rethinking the management of “under the radar” wastes like biosolids will help us to continue finding and utilizing resources that are often overlooked.

Scrap automobiles are rich in resources.  They are complex assemblies of steel, rubber, electronics, plastic and glass.  This complexity makes it hard for wreckers to sort out the components efficiently.  Tires and windows are comparatively easy to remove and recycle, but some recycling operations are more painstaking than others.  It is not unheard-of for a whole vehicle to be ground-up all at once.

Cannibalizing a vehicle to keep another roadworthy is cheaper than buying new parts and certainly less wasteful than replacing the entire thing.  As searchable databases have hit the web, finding model-specific auto parts has gotten simpler.  Selling salvaged parts is estimated to be a $10 billion per year industry.

Reclaiming metals is also lucrative, but reverse engineering a finished vehicle into raw material is only worth the effort for particular substances.  The quickest way to isolate the steel from everything that’s bolted to it is to rip the car to pieces in the monstrous jaws of an industrial shredder.  The detritus that’s left is carried underneath electro-magnets using conveyors.  The steel leaps away from the fragments of headlamp, stereo and upholstery that the magnets don’t attract.  Froth flotation can lift lighter materials like plastics while allowing heavier, more valuable chunks of copper to sink.

After this step though, further sorting is tricky and the cost of the effort stops making financial sense.  The remaining debris, known as “shredder residue” or “car fluff” has lots of hydro-carbon energy locked up in its pieces of plastic and rubber, but bits of mercury, lead and traces of PCBs make the mix toxic.  That makes finding good uses for shredder residue a bewildering challenge.

How big is the problem?   Around 20% of a shredded automobile becomes fluff.  The 13 million cars that are scrapped each year in the U.S. pile up nearly five million tons of shredder residue.  Nearly all of it ends up in landfills.

Video: Shredder in action