COAL IN CROPS: Coal ash is used to boost soil fertility in some cases but is also adding a dose of arsenic and other toxic substances.
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Crops across the country are grown in soil amended with coal fly ash—the same substance that caused a massive environmental emergency in December when it gushed from a holding pond at a Tennessee power plant.
Tons of fly ash are routinely added to soil to nourish vegetables, peanuts and other crops, primarily in the Midwest and Southeast. But now the spill has raised questions about whether this longstanding agricultural practice is environmentally sound.
Fly ash is a fine powder recovered from gases created by the burning of coal. It is the largest component of coal combustion waste, totaling around 70 million tons annually in the United States.
Adding moderate amounts increases crop yields and stabilizes soils while reducing the need to throw huge quantities in landfills or holding ponds, said Yuncong Li, University of Florida professor of soil and water sciences.
However, fly ash contains various amounts of toxic metals. And studies have shown that food crops grown in large amounts can soak up hazardous concentrations of arsenic.
Because it is not classified as hazardous waste under Environmental Protection Agency standards, there is no federal supervision of its use in agriculture. Some states regulate it but their guidelines vary and often require no monitoring of how it is used, said Jeffrey Stant, director of the Coal Combustion Waste Initiative for the Environmental Integrity Project.
“For soil amendment, most cases are left to the industry itself to monitor where they put fly ash and how much they use of it,” said Stant.
For more than a decade, companies have mixed fly ash with other waste to produce soil and compost. About 50,000 tons are used annually for agriculture nationwide.
One example is N-Viro, an international corporation that specializes in turning waste material into products. The company uses 250 tons of fly ash per day to mix with bio-solids, said Raymond Mayo, Florida N-Viro plant manager. The mixture is then heated to kill bacteria and monitored before it is distributed to farms, added Mayo.
The volume of fly ash created by power plants is increasing, due to more coal burning coupled with more stringent air pollution rules. “Currently the U.S. produces 130 million tons of coal combustion waste every year. In another 10 years it will be 150 million,” said Stant.
As a result, researchers are studying whether larger amounts can be used safely in agriculture.
Fly ash mixtures provide phosphorus, calcium and other nutrients that crops need to grow while increasing soils’ capacity to hold water, said Li. “The material is practically free and coal companies will pay people to dispose of it,” he said.
But arsenic, lead and mercury in fly ash raise concerns about cancer or neurological damage.
Crops grown in quantities of fly ash ranging from 5 to 20 percent of soil weight absorbed toxic metals, according to a study by Indiana State University researchers.
When the amount of fly ash increased, the crops absorbed higher concentrations of arsenic and titanium. Basil and zucchini contained potentially toxic amounts of arsenic exceeding 6 parts per million. Concentrations of greater than 2 ppm had severe effects on vegetables, damaging the plants and decreasing production, wrote the scientists in a 2004 paper published in Environmental Geology.
Although the potential human health effects are unknown, fly ash fertilization can lead to possible toxic accumulation in crops if not monitored properly, concluded the scientists.
Plants grown with smaller amounts of fly ash have fared much better. In a three-year study, University of Florida researchers applied 22,000 pounds of fly ash per acre (1.1 percent of soil weight).
Mixed with yard waste compost, the fly ash increased tomato yields by up to 70 percent. The study found no groundwater contamination or soil-fertility decline after three years, while the presence of trace metals remained low.
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7 Comments
Add CommentIs Coal Ash in Soil a Good Idea?
Reply | Report Abuse | Link to thisIn unregulated quantities - no. The HFCS study is focused on reagents as a "the source" of contaminants, but the soil is also a source.
http://www.washingtonpost.com/wp-dyn/content/article/2009/01/26/AR2009012601831.html
Almost half of tested samples of commercial high-fructose corn syrup (HFCS) contained mercury, which was also found in nearly a third of 55 popular brand-name food and beverage products where HFCS is the first- or second-highest labeled ingredient, according to two new U.S. studies.
Listen to a real farm and soil expert. All soil amendments have good and bad effects on long term crop production. Often small amounts of toxic metals are benificial and large amounts of good neutreants toxic. Adding large amounts of material to the soil is a logistical night mare, 2000lbs. per acre is a lot, 22,000 lbs unbelievable. Even if it's free.
Reply | Report Abuse | Link to thisIf you want to eat, we will have to improve poorer soils to make up for class 1 soils covered by homes, highways, schools and shopping center parking lots.
Coal fired power plants and fuel systems are the dirtiest electric power providers on the planet. They put more radiation into the enviroment then a like sized nuclear power plant, but they are cheap to build and use off the shelf equipment. I most definately would not put nuclear waste on my fields. The dosage makes the poison.
“Although the potential human health effects are unknown…” What the heck does this mean? Of course the POTENTIAL effects are unknown. It is not science to postulate something you cannot test. The actual tests that have been and are being done show that when properly used fly ash in a very useful and beneficial amendment to the soil.
Reply | Report Abuse | Link to thisThe commentor above is right. The difference between a deadly poison and a life giving medicine is often in the dosage. Yes, massive amount of most things are harmful. The essence of intelligence is the ability to make reasonable distinctions.
Based on the information in this article, think we can answer yes to the title question “Is coal ash in soil a good idea.” We have an inexpensive way simultaneously to recycle a waste product, improve our soils and grow more food. We know how to do this in a sustainable way and we are constantly monitoring and improving our methods. Kudos all around.
Its far better to add biochar to soils, as charcoal, unlike coal has not accumulated toxins over hunreds of thousands of years.
Reply | Report Abuse | Link to thissee : www.eprida.com
biochar is a wonderful soil amendment and lasts for an extreamlly long time. the problem is you need many tons per acre to make a usefull difference. it carries little in nutreants . it does hold the nutreants in the soil structure for the plants. very valuable in high rain fall areas. and unlike humus it does not rot away in hot wet soils. very valuable in tropical farm lands, (maybe good way to trap carbon in soils )
Reply | Report Abuse | Link to thisLetter to the Editor
Reply | Report Abuse | Link to thisDear Sir/Madam
We read the article Is Coal Ash in Soil a Good Idea with great interest as we have a combined 40 plus years of experience in both agriculture and beneficial recycling of various types of by-products.
What is often confusing to the uninformed is that the terms fly ash, coal combustion products, bottom ash, flue gas desulfurization (FGD) products, FGD gypsum, coal combustion wastes and similar terms are used interchangeably as if they are all similar in chemical and physical properties. That is certainly not the case and a better term to use that incorporates all of these materials is coal combustion products.
It is certainly true that some coal combustion products can be used beneficially in agriculture to create synthetic soils, treat biosolids to reduce bacteria and pathogen levels, to serve as a source of plant nutrients, to improve soil physical properties such as water infiltration and water holding capacity and to treat soils with high concentrations of phosphorus that can lead to pollution of surface waters. In all of these instances, it is important to know the levels of heavy metals of the coal combustion product before they are land applied. The rate of application of coal combustion products is an important variable and I doubt if any reputable agronomist would recommend applications of 5 to 20 percent, as was noted in the example included in the article. Other studies cited in the article did clearly indicate that more moderate application rates of fly ash could enhance crop yields.
One specific type of coal combustion product is FGD gypsum. This material is created when a calcium based sorbent is reacted with sulfur dioxide gases that are created when high sulfur coal is burned. The calcium and sulfur react to form calcium sulfite that is then oxidized to form a very pure form of calcium sulfate (CaSO4
One specific type of coal combustion product is FGD gypsum. This material is created when a calcium based sorbent is reacted with sulfur dioxide gases that are created when high sulfur coal is burned. The calcium and sulfur react to form calcium sulfite that is then oxidized to form a very pure form of calcium sulfate (CaSO4•2H2O) or gypsum. This gypsum has been compared with mined gypsum and is generally much purer and contains equal to or less quantities of heavy metals. Gypsum has a long history of use in agriculture that goes back to the Roman times and, indeed, even Benjamin Franklin extolled the virtues of gypsum as an agricultural amendment. FGD gypsum, when applied to soil has the potential to provide many benefits including (1) the enhancement of no-tillage crop production, which in turn can help reduce greenhouse gases in the atmosphere as no-tillage removes carbon dioxide and put the carbon back into the soil, (2) improvement of efficacy of N fertilizers for crops, (3) remediation of sodic soils, (4) improvement of water and air entry into soils, (5) reducing the negative effects of subsurface soil acidity on crops, (6) mixing with other materials during composting to reduce ammonia losses and to create synthetic soils, and (7) reducing phosphorus concentrations in surface water runoff. Work in China has unequivocally shown that FGD gypsum can remediate sodic soils so that these lands can be brought back into productive agricultural use and studies in the United States have shown similar benefits.
Reply | Report Abuse | Link to thisFGD gypsum can only be used, however, if the concentrations of heavy metals in the material do not lead to accumulation of the metals in soil. In all of our studies, we have not observed such a phenomenon. The one concern that remains in this regard is mercury and studies are ongoing to determine whether the levels in FGD gypsum, while still very low, pose any environmental and ecological threat. At the same time, studies are being conducted to remove the mercury from the FGD gypsum before it is ever used for land application purposes.
We have seen the enthusiasm by farmer producers in using FGD gypsum to enhance the overall quality of their soils and to improve the yield of crops. When used appropriately, FGD gypsum poses no threat to the environment and the products grown on the land treated with the FGD gypsum at rates we recommend are not significantly enhanced in heavy metal content. The benefits of recycling have been duly noted by many and we look forward to continued use of FGD gypsum to provide economic benefit to our agricultural enterprises as well as environmental benefit in terms of reduced land disturbance to obtain gypsum from mining activities and the remediation of degraded lands.