Burning tires is most definitely renewable
— Rich Trzupek is a chemist and principal consultant at Mostardi Platt Environmental. He also writes for bigjournalism.com and frontpagemag.com on science, the environment and politics. The views expressed here are his own. —
Wind and solar energy are the best known forms of renewable power, but they don’t wholly define this particular universe.
Biomass combustion, hydroelectric power and geothermal derived energy all fall under the Department of Energy’s official definition of renewable energy.
Should recovering the energy contained in old tires be blessed with renewable tag as well? If we’re going to continue to follow the DOE’s guidelines and pursue its domestic energy goals, the answer is clearly “yes.”
(Geneva Energy, the tire incineration company that stands to gain from a proposed change to legislation in Illinois that would redefine renewable energy to include tire incineration, generates power by burning scrap tires.)
The energy contained in used tires is primarily tied up in three compounds: natural rubber, synthetic rubber and carbon black.
The first of these, natural rubber, is renewable by anyone’s definition of the word. (Can it be replaced by natural processes at a rate comparable or faster than its rate of consumption by humans?)
It’s derived from a plant, just like ethanol, wood, switchgrass and other biomass fuels. It would be foolish and inconsistent to call wood chips derived from a pine tree “renewable,” while claiming that latex derived from a rubber tree is not.
Synthetic rubber and carbon black are made from petroleum products, with a few exceptions, thus these compounds are not biomass.
However, we should also consider that used tires are a waste.
If we can find ways to recycle this waste, that’s great. There are in fact limited uses for old tires, some of which are shredded and used as playground cover, backfill, speed bumps, etc.
Yet, even with all of these means of recycling available, it’s not nearly enough. Americans discard about 250 million used tires per year and a large percentage end up in landfills or are illegally abandoned.
As much as we might wish otherwise, millions of old tires cannot be recycled and are therefore a waste, likely to end up in a landfill.
Like the other organic wastes buried in a landfill, the rubber in tires will slowly decay. As they decay, they create energy-rich landfill gas, which can then be burnt to generate power.
And here’s the kicker: when you generate energy using landfill gas, it’s considered renewable energy – another form of biomass.
Accordingly, does it really make sense to say that recovering energy from a tire today is not renewable, but waiting a couple of decades for the tire to decompose is renewable?
Renewable energy is supposed to involve fuel sources that are reliable, predictable and domestically available. Used tire combustion fits that definition, in every particular.
Image shows customers looking over the selection of tires and wheels in the parts department at the Burt GM auto dealer in Denver June 1, 2009. REUTERS/Rick Wilking