The process of coal combustion leaves behind many byproducts. The major byproduct is what's known as fly ash. Coal fly ash is the portion of ash produced during combustion that is small enough to get carried up with flue gases. These fine particles are then collected by either a mechanical collector or and electrostatic precipitator. Once these particles are collected, the question of what to do with them arises. Coal fly ash is often used in making cement or mixing concrete. Another possible use is to apply the fly ash to soil systems.
Coal fly ash has characteristics that can make it useful for applying to a given soil. Fly ash composition can vary greatly, depending on the type of coal that it came from. The silty texture can improve the texture of a soil. Coal fly ash can often contain trace elements and nutrients, which can be useful for a soil that is nutrient deficient. Applying fly ash to soil in moderate amounts can improve crop yield, while preventing the need to dispose of the fly ash in landfills.
Despite these benefits of coal fly ash application to soil, there are many potential drawbacks as well that must be considered. One problem is that fly ash may contain radioactive elements. This is dependent upon the composition of the coal that the ash is made from. Coal containing large amounts of uranium and thorium can lead to fly ash with radioactive properties.
Another problem is the metal content of coal fly ash. Coal fly ash can contain arsenic, cadmium, chromium, mercury, and selenium, among other hazardous substances. These elements can leach from the soil. Once they do that, they may pose a considerable risk to any nearby groundwater sources. Coal fly ash can have other negative impacts to soil systems as well. Coal fly is known for having high boron and soluble salt content, as well as having a high pH. All three of these conditions negatively impact plant growth.
Recently, the EPA proposed regulating coal fly ash as a hazardous waste because of all these potential negative impacts. I believe that because of the potentially hazardous nature of fly ash, its application on soil should be strictly regulated. Application rates should be determined on a site by site basis, taking into consideration each of the potential risks of application. As long as the application rate is determined and enforced, then applying coal fly ash can be beneficial to a soil system. At low rates, the most harmful aspects of application can be avoided.
It seems to me that the potential risks of using coal fly ash in soil greatly outweigh the possible benefits that could be recieved. As you suggest the use of coal fly ash on soil should be stictly regulated, I would go even further and suggest that a great deal more testing needs to be done before this technique is ever used.
ReplyDeleteWhile my blog entry mainly focuses on the risks, the benefits are also important to consider. I believe the biggest benefit of land application is that it provides a use for what would otherwise be a waste product. Anytime we can avoid stuffing our waste into landfills, and put it to good use, it is worth examining that possibility. And while toxic metal content of the fly ash is a risk, the content varies depending on the coal that the fly ash came from. Maybe it's best if we apply only those with low enough metal content to be considered safe. I do agree that regulation is very important with any type of land applied substance such as this.
ReplyDeleteI personally don't think that using fly ash in soil should even be considered. Burning coal as a fuel needs to be phased out as soon as possible. It is both dirty and inefficient. I think that encouraging new uses for fly ash is only going to encourage those to burn more coal instead of trying harder to do away with it to begin with.
ReplyDeleteI agree that coal should be phased out of production in favor of cleaner, more efficient energy sources. Despite this, I don't think we can cut off coal use 100% right away, not until better alternatives becomes more widespread. Until then, it is just s reality that coal combustion byproducts will be produced, and something needs to be done with the waste. I think we can use these byproducts responsibly, while also putting money and researching into other energy technologies.
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