Environmental impact of energy recovery from waste tyres

Abstract

Accumulation of millions of worn automotive tyres poses a considerable environmental problem. As an important part of the solid waste stream in today’s society, worn tyres have traditionally been discarded in landfills or stored in stockpiles. Over the past several decades, however, innovative alternatives to disposal have been developed, partly as a result of high tipping fees charged by landfill operators. Because of their high heat content and their low levels of moisture and nitrogen compared to coal, tyres are ideally suited for energy recovery through combustion. Utilization of waste tyres as supplemental or alternate fuel in various industrial combustion facilities, thus, has become one of the most important alternatives to disposal. Combustion processes, however, generate gaseous pollutants and solid waste materials, which must be disposed of or re-used as secondary raw materials. It is therefore important to characterize these combustion products in order to assess the environmental impacts of energy recovery from scrap tyres. Studies have shown that substantial reductions of some environmental pollutants can be achieved by partially replacing conventional fuels with waste tyres. On the other hand, using tyres as fuel may lead to considerable increases in the levels of other pollutants. Most notable among the effects of tyre combustion are, relative to conventional fuels, a pronounced decrease in the emission of nitrogen oxides into the atmosphere, and a generally significant increase in atmospheric zinc emissions as well as in the zinc contents of the solid combustion products. The geochemical effects on solid and gaseous combustion products are more or less pronounced depending on fuel composition, conditions of combustion, type of facility, and effectiveness of air pollution control devices. Thus, the use of tyre fuel has environmental impacts that must be weighed against the benefits of reducing the large volume of waste tyres in the global waste stream.

Energy Recovery from Scrap Tires: A Sustainable Option for Small Islands like Puerto Rico

“…However, transforming ST into an energy source, is a double palliative for countries, especially small islands, aiming for sustainable development, but with economies based on fossil fuel importation, inconsistencies in the handling and disposal of this material, and where stealthy dumping is rampant [35], as in Puerto Rico [15] and other Latin American countries [34,57]. To mitigate the adverse economic, environmental and public health effects of the mishandling and disposal of ST, it is crucial to apply the most cost effective techniques headed to recover the energy from this resource [18,58,59].…”

“…Therefore, if Puerto Rico has the capacity to produce TDF, it ought to expand the ST market in order to consider this material as an alternate fuel as done by USA and Germany, two countries with very strict air quality standards, but supporters of the cogeneration of energy using TDF [29]. Despite TDF reduces the cost of energy production [60,61], thermoelectric power plants prefer to use whole ST, since producing TDF can be up to five times more expensive than pulverizing coal [58], while its making consumes large amounts of energy [62]. However, TDF can be used to feed thermal processes in many other industries, for instance metallurgical, cement, pharmaceutical and recycling, or to provide electricity to run the operations of those industries, via energy recovery by pyrolysis, the most recommended method [39,40].…”

Kinetics of zinc release from ground tire rubber and rubber ash in a calcareous soil as alternatives to Zn fertilizers

“…Disposal of rubber tires is a considerable environmental problem in many countries (Giere et al 2004). It is estimated that about 1000 million scrap tires are produced annually throughout the world (Dhir et al 2001).…”

“…On the other hand landfilling of scrap tires is an environmental concern and becoming legally prohibited in different countries. Therefore innovative methods of recycling tire rubber are in great demand (Giere et al 2004). There are some safe technologies for recycling waste tires.…”