According to French company Aliapur, used tires are not wastes but are traditional solid fuels better than coal or petroleum coke. A three-year study by Aliapur’s Research & Development unit has proven what the French cement industry has known since the 1970s – used tires as fuels have high heat output with less environmental impact than fossil fuels.
Used tires when burned emit less fossil carbon dioxide due to their biomass components. Used passenger car tires, according to the study, have biomass fractions between 17% to 20% while used truck tires are 28% to 30% biomass.
The study, considered to be the first of its kind in Europe, aimed to establish reference values and provide details on the chemical properties of used tires. Results have been submitted to France’s State Department for the Environment as reference for calculations of CO2 emissions from cement plants.
Aliapur collaborated with five companies in France and Beta Analytic, Inc., in Florida, USA for the research and also with independent consultancy firm Price Waterhouse Coopers for the documentation. Aliapur completed the research in July 2009.
The biomass fraction of the used tires was quantified through ASTM D6866, which is a standard method based on radiocarbon dating techniques. The used tires were also characterized by measuring their calorific values (amount of heat released during combustion) and carbon, hydrogen, oxygen, nitrogen, sulfur, chlorine, fluorine, and bromine content.
|Parameter||Used Passenger Car Tires||Used Truck Tires||Coal||Petroleum Coke|
|Biomass||17-20.3% (ave. 18.3%)||28.6-29.7% (29.1 %)||0%||0%|
|Carbon||67.5 – 70.1% (ave. 69.0%)||59.7-62.6% (61.1%)||64-68%||84-97%|
|NCV (MJ/kg)||29.5 – 30.6 (ave. 30.2)||26.1 – 26.7 (26.4)||26||32|
Table 1 – Select values from the Aliapur Study. Details of the results can be downloaded from Aliapur’s Web site.
The Aliapur study presents scientific proof that used tires when burned produce comparable heat output as burning coal or petroleum coke. It also showed that used tires have considerable biomass fractions, which impact their combustion carbon dioxide emissions. Unlike coal and petroleum coke, used tires when burned produce carbon-neutral CO2 emissions due to their organic components, e.g. natural rubber, rayon, and stearic acid.
Due to a higher proportion of metal in used truck tires, they have lower calorific values and carbon content but higher biomass content than used passenger car tires, Aliapur says.
Used tires, also called end-of-life tires (ELT), are converted into tire-derived fuel, which are used tires shredded into sizes based on an industry’s technical requirements. Foremost users of ELT are cement plants, pulp and paper mills, and other energy-intensive industries.
Companies use ELT to reduce their fuel expenses and comply with air quality and pollution control regulations. ELT are cheaper than coal and petroleum coke; thus, ELT use generates savings. Many countries around the world now require companies to annually report their CO2 emissions. Using ELT as fossil fuel alternative enables companies to report lesser fossil CO2 emissions. Moreover, companies participating in cap-and-trade schemes like the European Union Emissions Trading Scheme can also obtain carbon credits when they have low fossil CO2 emissions. Carbon credits have monetary value and can be sold or traded.
Cement plants, in particular, also have an additional benefit in using ELT. They use whole tires in kilns because the metal in tires add iron to the clinker they are producing – a benefit that they cannot get from coal or petroleum coke.
Aliapur focuses on used tires recovery in France. The public limited company was created in 2003 with Bridgestone, Continental, Dunlop, Goodyear, Kléber, Michelin, and Pirelli as founding members and principal customers. Aliapur aims to neutralize the environmental hazards posed by used tires in France.