CCA Incineration Research
CCA Incineration Research
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Technology Wood used in outdoor environments is typically treated in order to protect it from deterioration from fungi and insects such as termites. Wood treatment chemicals can be subdivided into two general categories: waterborne preservatives and oil borne preservatives. Waterborne preservatives utilize water to carry the wood treatment chemical into the wood during the wood treatment process and hence are more desirable aesthetically because the product can be painted and is non-odorous. The most common waterborne preservative utilized during the last few decades was Chromated Copper Arsenate (CCA).
Frequently asked Questions
What is CCA?CCA is a popular wood preservative made of arsenic, chromium and copper oxides. It is applied to wood products such as utility poles and marine and freshwater docks to prevent environmental decay during outdoor use. Prior to 2004, it was also used to treat wood used for decks, walkways, and fences and as a result it has been the predominant wood preservative observed in the disposal sector in recent years. Back to Top
Why is CCA Treated wood an environmental concern?Prior to 2004, CCA treated wood was used in a variety of residential and industrial applications. In 1996, 13 million cubic meters of CCA-treated wood were produced accounting for about 79% of all the treated wood in the United States. Disposal forecasts indicate that approximately 3.7 million cubic foot (mcf) of CCA chemical was disposed in Florida (31.0 mcf in USA) during 1996. By 2005, this figure is projected to reach 11.2 mcf for Florida (141.5 mcf for USA). It is estimated that by 2015, it will reach 30.9 mcf for Florida and 386.4 mcf for USA(Solo-Gabriele et al, 1998). Thus large amounts of CCA treated wood will enter the waste stream in near future. Due to its common use in the building industry, CCA-treated wood gets mixed with Construction and Demolition (C & D) waste wood and in many cases contaminates with chromium, copper and arsenic. Since these heavy metals are considered hazardous to health and environment, care should be taken when the wood product is handled and disposed. Back to Top
What are the major disposal options for CCA treated wood?The major disposal options for CCA treated wood are -
Some historical estimates suggest that more than half of the wood waste in C & D debris is burned in Waste To Energy (WTE) facilities for energy recovery. The incineration ash is disposed in landfills. There are several advantages associated with incineration of CCA wood waste. Firstly, the ash volume is significantly less than the wood waste, hence prolonging the lifetime of a landfill. Secondly, incineration of C&D debris wood containing CCA-treated wood may provide a valuable energy source. Back to Top
What are the problems with incineration of CCA treated wood?Disposal of CCA-treated wood via incineration may be problematic due to
This could pose serious health and environmental problems. Among the metals contained within CCA, arsenic is considered a volatile metal. During high-temperature combustion of fuel containing arsenic, many arsenic compounds vaporize and form very fine particulate matter when combustion air cools. While particulate control devices such as baghouses or electrostatic precipitators (ESPs) can be good options for controlling particulate emission (depending on the characteristics of the arsenic compounds formed), they are not good at controlling arsenic present in submicron range and in vapor phase. Also, the leaching from arsenic containing fly ash and bottom ash can pose a problem for the ash disposal. Townsend et al,2004 have reported the leaching of arsenic and in some cases chromium from CCA wood ash , beyond the federal regulatory limits. Hence CCA wood ash can not be disposed of as regular waste. Recent studies have suggested an increase in leaching of chromium from CCA-treated wood ash drawn from alkaline environments such as C & D debris landfill. Back to Top
What are the environmental and health impacts of CCA metals?
(Katz et al,1993; Weis et al,1999; Maas et al,2003) Back to Top
What is sorbent technology?Sorbent technology is becoming increasingly popular as a method to remove trace heavy metals from flue gases and aqueous systems. Some of the commonly used sorbents are- activated carbon, lime, etc. In flue gas treatment, sorbents are introduced in the air stream where they adsorb (chemically/physically) heavy metals and form metal-sorbent complexes which are not/less toxic. The particle sizes of these complexes are in the super micron range hence they can be easily captured by particulate control devices like baghouses and ESPs and disposed. You can read more about Sorbent Technology by going through the references given in the Reference Link Or follow the link given below. Municipal Waste Combustion Abstracts Back to Top
How can sorbent technology be utilized to control emission and leaching of CCA metals during incineration?In recent years, research studies have shown the potential of injecting mineral sorbents (e.g. lime, limestone or clay) into combustion system for controlling arsenic. Arsenic captured on the sorbent is transformed into non-leachable compounds, such as calcium arsenate (Ca3As2O8), that become suitable for landfill disposal. Some of the sorbent materials identified in those studies have been used in flue gas treatment and in other industries (such as power plants and waste incinerators). These facilities can be a potential option for thermally processing CCA treated wood. In addition, mineral materials including alumina, calcium hydroxide and ferric hydroxide have also been evaluated for removing arsenic in the aqueous systems. Among the various potential materials, evaluation needs to be carried out to determine the most efficient and cost-effective candidate. Back to Top |
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