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plants operational in the United States as of 2007. The building costs are too high, and

“the products of tire pyrolysis have limited marketability due to their low quality

compared to virgin materials” (Environmental Protection Agency, 2007). Another

problem with pyrolysis is in regards to research. Until recently most of the research

done was through corporations and proper scientific methods were not always

followed. For example, before attempting a large scale process, researchers have to

test the technology with smaller reactors and rubber samples. These samples often did

not include all the constituents of the tyre, such as the metal wires and fibers. This

could drastically affect the outcome of the experiment. Additionally, the reactors must

be brought to full steady state operation before sampling of gases and oils, which

sometimes was not done. Proper research could lead to better reactor designs

(Rodriguez et al, 2000).

The pyrolysis process is very sensitive to the initial conditions and the steady

state temperature of the reactor. Research has shown that the temperature of the

reactor determines the chemical composition of the products, as well as the ratio

between solid and gaseous products (Rodriguez et al, 2000). If a two stage process is

used where gas is passed through a catalyst, it has been found that the catalyst

temperature determines the concentrations of the different gases produced (Williams

& A.J., 2002). The gases produced contain valuable natural gases such as propane.

The oils, which can be burned for energy directly, also contain a number of chemicals

with high commercial value. One such chemical produced in high concentrations is

“limonene”, which has a high industrial value (Williams, 1999). The solid product,

char, can be processed into a product similar to low grade activated carbons (Cunliffe

& P.T., 1998), useful for filtering heavy metals and other contaminates from water or


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