Sludge By Any Name Will Never Be “Organic”

Fall 2003

By Sue Smith-Heavenrich

For those of us who would compost everything but the kitchen sink, the idea of returning the nutrients from human waste back to the soil is appealing. Indeed, for many hundreds of years farmers have done just that, recycling “night soil” back to the earth. Now the EPA and producers of sewage sludge soil amendments would have us believe that we can turn municipal waste into “organic” fertilizer.

At first glance this idea makes sense. Why not recycle human waste? It is a good source of organic nitrogen, and recycling the nutrients would keep it out of the already cluttered waste stream. Unfortunately, human waste isn’t the only thing that gets flushed down the drain. Schools, hospitals, dry cleaners and industries of all sorts send their wastewater to the same sewage treatment plant that treats household waste. And that is where the problem lies.

Industry uses more than 72,000 chemicals, but only a few are regulated. Pesticides, PCBs, dioxins, radioactive wastes, asbestos, heavy metals and petroleum compounds are among the pollutants found in sludge after municipal waste has been treated. (1) Of these pollutants, the EPA has set standards regulating allowable concentrations for a handful of contaminants: the heavy metals arsenic, cadmium, chromium, copper, lead, mercury, zinc, nickel, molybdenum and selenium.

Section 503 of the Federal Code (which refers to the Clean Water Act amendments) regulates the application of sewage sludge to land. Passed in 1992, the regulations actually lower the standards, allowing sludge with higher concentrations of heavy metals to be applied to soils. Concentrations previously treated as hazardous waste became, at the stroke of a pen, “fertilizer.” For example, lead concentrations were increased from the 1989 allowance of 111 lbs./acre to 267 lbs./acre; arsenic from 12.5 lbs./acre to 36 lbs./acre; and chromium from 472 lbs./acre to 2672 lbs./acre.

According to Charlotte Hartman, coordinator of the National Sludge Alliance, in the years since Congress banned ocean dumping, the EPA has been actively promoting the use of sludge on farmlands, public parks, mine reclamation projects and home gardens. “The U.S. standards are now the most permissive in the industrialized world,” she notes. For some pollutants, the EPA limits are more than 20 times higher than those allowed in Europe. EPA standards are so lax that the National Food Processors Association, and several major food processors, such as Del Monte and Heinz, refuse to accept crops that have been grown on soils treated with sludge. (2)

Some of the heavy metals present in sludge are toxic to plants at high concentrations. Certain metals (lead, cadmium, mercury) are toxic to animals. Grazing cows pull up not only the plants, but also the roots, covered with soil particles. They ingest heavy metals along with their forage. Heavy metals can also kill the soil organisms that are vital to decomposition of leaf litter, as well as harm the beneficial nitrogen-fixing bacteria upon which some crops depend. (3) Unlike the organic components of sludge, the heavy metals do not decompose. They remain in the soil, accumulating to concentrations that can eventually make the soil unfit for farming.

In addition to the metals, sludges contain a host of synthetic organic compounds, including PCBs and pesticides. Aldrin, DDT, Dieldrin, Chlordane – these are only a few of the pesticides that have been found in sludges around the United States. (4) Both pesticides and heavy metals accumulate in the food chain. Earthworms from sludge-treated soils may have such high concentrations of cadmium and other metals within their tissues that they become hazardous to natural predators, such as birds and toads. (5) This is dismal news for organic growers who depend upon natural predators to help keep pests in check.

Fighting Over the “O” Word

Hundreds of thousands of dollars have been spent to promote the benefits of land-applied sludge. Even the name has been changed – It’s now referred to as “biosolids.” One of the major thrusts of pro-sludge PR is to portray sludge-based products, such as Ohio-based N-VIRO soil, fertilizer pellets, and sludge compost, as “organic” soil amendments. ( Those in the sludge industry would like to get farmers and gardeners to talk about “biosolids” instead of sludge; they would like to link the use of “biosolids” to recycling and organic farming.

Page 13 of the Agriculture Use Manual published by Earth-Blends, a distributor of N-VIRO SOIL, reads: “exceptional quality sludge products are increasingly being recognized by organic farming groups as organic fertilizers.” Page 15 reads: “… growers following the trend toward organic farming can use N-VIRO soil with confidence.”

A number of years ago the Massachusetts Water Resources Authority (MWRA) began to bag its composted sludge for market under the label of “Baystate Organic.” The compost was made from residential and industrial sewage sludge from 43 Metropolitan Boston municipalities as well as 137 other water treatment facilities throughout the Commonwealth. A coalition of farmers, environmental organizations and concerned citizens came together in an effort to get the MWRA to remove the word “organic” from the label. “We were willing to embarrass the MWRA in the court of public opinion,” says Jack Kittredge of NOFA-Mass. “They were defrauding innocent organic farmers by calling their sludge product organic, when those farmers would lose certification if they applied the sludge to their land.” The folks of NOFA-Mass. published a fact sheet explaining their position and held a press conference at the Statehouse in Boston to generate public support for a piece of legislation they filed. The legislation would require that the word “organic” be applied only to products approved by the organic certification group recognized by the state’s Department of Food and Agriculture.

“Realizing that we (NOFA) had the moral and public relations edge here, and that we were willing to fight about it, the MWRA wisely withdrew their use of the term ‘organic’ for their sludge product,” notes Kittredge.

Still, controversy, fueled by confusion, surrounds just what “organic” means. Eric Sideman, technical director for MOFGA, points out that USDA’s “Organic Rule” applies not only to food but also to any and all agricultural products. The Rule does, in fact, publish guidelines for making the kind of compost that is permitted in organic production. Sludge is excluded.

However, the word “organic” may also be used to describe materials made from inputs that are carbon-based or from a previously living organism, notes Sideman. This distinction is valuable for conventional farmers who are looking for alternatives to chemical fertilizers. For them, a sludge-based soil amendment provides a source of organic nitrogen.

“But, if the intent is to imply their product is ‘Organic’ according to the standards, or to mislead someone to that end, I think there will be trouble,” says Sideman. “Obviously sludge could never be certified Organic, because it is, by regulation in the NOP Rule, a prohibited material. Not only can it not be certified, it cannot be approved for use in organic crop production.”

Judging Compost by the Packaging

According to Charlotte Hartman of the National Sludge Alliance, a number of fertilizer blends and compost mixes contain sludge, often without being clearly identified as sludge products to the consumer. When I queried Scotts (producer of Scotts and Hyponex soils) in 1998, I was told that they use composted sewage sludge in some of their products. They call it “biosolids” and were quick to point out that when they do use sludge, their “ingredient statements will clearly identify its presence as ‘EQ (exceptional quality) biosolids.’”

“EQ” biosolids are EPA “approved” and sound perfectly safe until you learn that EQ standards allow up to 300 parts per million (ppm) of lead in your compost. Leafy vegetables planted in such soil will incorporate heavy metals such as lead. In one study, lettuce grown in soil amended with sewage sludge incorporated 29% more lead than lettuce grown in soils without sludge added (see sidebar).

Just as you shouldn’t judge a book by its cover, you shouldn’t buy a bag of compost based on the packaging. “Milorganite” isn’t the only sludge compost-like product on the market, and many of the newcomers bear earth-friendly names: “Earthlife,” “EKO Compost,” “SoilRich,” “ERTH food.” A sludge-based fertilizer that can’t call itself organic can still wear the label “natural organic nitrogen” and be clothed in earth-toned packaging replete with recycling symbols, photos of mother and child in the garden, and golden seals from the U.S. Composting Council.

“SoilRich” (an Amerigro product) calls itself a “natural organic fertilizer.” The company’s literature is clear about the product, stating that it is a “type A exceptional quality biosolid.” Even so, the labeling is confusing enough to get the product listed under the “organic gardening” section on the Web site,

ERTH products’ literature tells you that the company recovers biosolids from wastewater treatment. “This wastewater residue is combined with other organic waste products, such as peanut hulls, and then converted into a 100% natural organic fertilizer and soil amendment.” The company makes sure you know they were named “composter of the year” by the U.S. Composting Council.

On EKO Compost’s Web site (, you learn that “EKO compost is the original organic compost.” It “helps promote rich organic soil,” claims the company. Not until you scroll down quite a bit do you discover “every batch of EKO compost is rigorously tested to ensure that it meets and exceeds all process and product standards including the United States Environmental Protection Agency’s class A ‘Exceptional Quality’ compost, good for unrestricted use including food crops …”

EKO Systems, the folks who produce EKO compost, is a residuals management company, says Marc Merritte, a recycling consultant in Maui, Hawaii. EKO Systems does indeed compost sewage sludge, incorporating it into a number of products. Unlike other biosolids producers, EKO Systems makes a point of not mentioning “biosolids” or “sewage sludge” anywhere in its PR. With a bit of word magic, the company has turned “biosolids” into EPA-approved Class A “Exceptional Quality” compost – Class A “Exceptional Quality” organic compost.

Then there’s Milorganite. Milwaukee has been bagging digested sludge since 1925 and selling it as a home and garden fertilizer under the name Milorganite. A few years ago the packaging was labeled in large letters, “Organic,” and you had to read the smaller print on the back to learn that it was processed sewage sludge. According to a chart in its technical bulletin, “Milorganite and Heavy Metals,” the fertilizer contains copper concentrations 13 times higher than those found in typical soils around my upstate N.Y. garden. Mercury and zinc concentrations are eight times higher, and lead, at 74 ppm, five times higher than in my native soils.

“We can’t take out the heavy metals,” admits Mike Archer, who works in Market Development at the company. “But we do monitor it.” According to Archer, about 80 people are employed to constantly sample the wastewater coming into the treatment plant from various industries. If an industry exceeds the EPA limits, it will lose its permit to discharge into the waste stream.

And if an accidental spill of heavy metals or some other pollutant occurs? The treatment plant can isolate that wastewater, Archer explains. “We process it in different tanks and send the dried sludge to a landfill as low-level hazardous waste.” (6)

Since the advent of the National Organic Standards, Milorganite’s packaging has changed. Now the bags are labeled “organic nitrogen,” and if you know where to look, you can see that the bag is clearly stamped, “nutrients derived from sewage sludge.”

“We cannot call ourselves ‘organic fertilizer,’ but we are an organic nitrogen fertilizer,” Archer states. While he and others in the industry are clear on this distinction, consumers may be confused by the similar language.

Milorganite also packages “Garden Care.” Like Milorganite, this product is derived from Milwaukee sewage sludge, but you’d never guess by the package. “For better results,” it says. “Naturally.” The package includes a photo of a smiling child, maybe six years old, trowel in hand, and his mother beaming at him as they admire the flowers and vegetables in their garden.

If We Don’t Use It, Why Should We Worry?

“You’re an organic gardener,” a sludge industry representative commented. “You’ll never use this stuff. Why get involved in this issue?” Three reasons. One: Stuff, whether it’s toys or sludge, doesn’t stay where you put it. Two: In this world everything is connected to everything else. And third: “This is land we’ll all be using in the future, whether we’re organic or not,” says MOFGA member and activist Beedy Parker.

Icky gooey stuff that it is, you’d think sludge would pretty much stay where you put it, especially if you till it into the soil. The organic nitrogen should fertilize the crops, and the toxic metals should stay put. Unfortunately, it doesn’t work that way. Toxic stuff tends to move about in the soil. Heavy metals may leach, travel in water, be taken up by plants or find their way into drinking water.

Two years ago, a Kansas organic farmer who did not want me to use her name, watched as municipal waste haulers applied sludge to her neighbor’s field. “They spread the sludge right up to my property line,” she explained, “right where the orchard is. I’ve been farming organically for over eight years and hoped to get certified [that year].” (7)

This farmer grew produce and herbs for local farmers’ markets, and marketed her own herbal tinctures through natural food stores and co-ops. She was expecting to harvest her first peaches last summer, but the trees have acquired a strange bark disease and aren’t yielding well.

Her neighbor’s land is situated at a higher elevation than hers, sloping down toward her property. This farmer fears that runoff or leaching from the sludge may have contaminated her orchard and gardens. She isn’t the only one. Upon hearing that municipal waste was being applied on land so close to her farm, many customers and retailers quit buying her produce and herbal products.

Although she never officially applied for certification, this farmer did fill out paperwork for a preliminary assessment to learn whether her farm would qualify for organic certification. She was notified by two organic certification organizations that, based on the information she gave them, her farm most likely would not qualify for organic certification. The reason: the slope of the land and potential runoff from her neighbor’s property. It’s a lot like pesticide drift, she commented.

Research for this article was supported by a grant from the Fund for Investigative Journalism.


1. Lisk, Donald, 1988. “The Issue of Sludge Deposit on Land.” A report to the Citizen’s Clearinghouse for Hazardous Waste, Jan. 29, 1988.

2. personal communication

3. Chaudri et al., 1993. “Enumeration of indigenous Rhizobium leguminosarium biovar trifolii in soils previously treated with metal-contaminated sewage sludge.” Soil Biol. Biochem. 25:301-309.

4. Babish, Lisk et al., 1981. Organic toxicants and pathogens in sewage sludge and their environmental effects. Special Report #42.

5. Bayer, Chaney and Mulhorn, 1982. “Heavy metal concentrations from soil amended with sewage sludge.” J. Environ. Qual. 11:381-385.

6. Telephone conversation with Mike Archer, Market Development for Milorganite, July 16, 2003.

7. Personal communication

Accumulation of Heavy Metals by Plants from Sludge-Amended Soils

By Sue Smith-Heavenrich

In some heavily sludged soils, the concentration of metals is high enough to render the soil unsuitable for food crop production. (1) In addition to decreasing crop yield, heavy metals can accumulate in the tissues of food crops grown on sludge-treated soils. Increased concentrations of cadmium, zinc and nickel were found in beets and chard grown on sludge-treated soils. Tackett found a 29.2% increase in lead concentrations in lettuce grown in sludge-amended soil vs. control soil; 8.3% increase in broccoli and eggplant; 7.7% in potatoes; 6.3% in tomatoes; 0% in cucumber; and 8% in string beans. (2)

Even years after sludge applications have ceased, heavy metals may continue to be absorbed and incorporated by the plants. Snap beans grown on land four years after cessation of sludge applications accumulated zinc and copper in the edible tissues. (3) Sweet corn fertilized with sewage sludge had higher concentrations of cadmium and zinc in leaves than did sweet corn fertilized with ammonium sulfate. (4)

In general, cadmium (Cd) tends to accumulate in the leaves of plants, such as tobacco, lettuce, spinach and cabbage, although lettuce also accumulates lead (Pb). (5) Copper (Cu) and zinc (Zn) accumulate in the grains of cereal crops while Pb, Cd, Cu and Zn tend to accumulate in root crops. Overall, Cd and Zn show the greatest tendency to move along the soil-to-plant pathway.

In one study, ryegrass was planted in soils amended with sludge and grown at two temperatures. The sludge applications resulted in elevated concentrations of Cd, Cu, Ni, Pb and Zn in the soils. Plants grown in warmer environments (77 degrees F.) accumulated significantly higher concentrations of all metals than those grown in cooler environments (59 degrees F.). The data show a trend of increasing metal accumulation in plants over successive harvests. (6)

In 1998 the FDA detected elevated concentrations of lead in carrots in mixed frozen vegetables from a supermarket “basket survey.” The carrots were grown in a field that had previously been orchard. The soil was contaminated with lead-arsenate from spray programs that ended over 30 years ago. According to the EPA, the carrots contained 190 ppb (parts per billion) lead – enough to make them “adulterated” according to FDA rules. The concentrations of lead in the soil ranged from 18 ppm to 490 ppm – well within the acceptable concentrations for lead in sludge applied to farmland. (7)


1. Alloway, B.J. and A.P. Jackson, 1991. “The behaviour of heavy metals in sewage sludge-amended soils.” The Science of the Total Environment, 100:151-176.

2. Tackett, Stanford L., “Lead in the Environment: Effects on Human Exposure,” American Laboratory, July 1987.

3. Dowdy, R.H. et al. 1978. “Growth and metal uptake of snap beans grown on sewage sludge-amended soil: a four year field study.” J. Environ. Quality, 7 (2):252-257.

4. Kiemnec, G.L. 1990. “Sweet corn yield and tissue metal concentration after seven years of sewage sludge applications.” J. Prod. Agric., 3 (2): 232-237.

5. Sterrett, et al. 1996. “Influence of fertilizer and sewage sludge compost on yield and heavy metal accumulation by lettuce grown in urban soils.” Environmental Geochemistry & Health, 18: 135-142.

6. Hooda, P.S. and B. J. Alloway, 1994. “The plant availability and DTPA extractability of trace metals in sludge-amended soils.” The Science of the Total Environment, 149: 39 – 51.

7. Businesswire, 1/29/99. and personal communication with Helane Shields (2/2/99)

Looking for a Seal of Approval

Certified compost seal

by Sue Smith-Heavenrich

Gardeners looking for organic compost want to know that the products they buy are free from pesticides, herbicides, heavy metals, toxic waste and sewage sludge. As compost producers have become more savvy with their packaging designs, using earthy colors, recycling logos, and language that incorporates “natural” and “organic,” consumers have more difficulty telling which compost is “organic” and which is “Organic.”

Some compost products are beginning to carry the United States Composting Council Seal of Testing Assurance. This means that the compost has been analyzed for pH, soluble salts, nutrients, organic matter, maturity and stability, pathogens and trace metals. But even sewage sludge composts may qualify for that seal.

To help organic gardeners identify quality tested, organic composts, Rodale Organic Gardening has joined with Woods End Laboratories in a partnership to test and label products with the “Rodale Organic Gardening Compost Quality Seal.” To earn this seal, a compost product must undergo tests for maturity, nutrients and trace elements, pH, carbon to nitrogen ratio, heavy metals, pesticide residues, weed seeds, pathogens and more. Compost products that meet the high standards will be awarded the organic compost quality seal. In addition, they will be identified for their best use, whether it is garden compost, potting mix, seed starter, topsoil blend, mulch or fertilizer.

While Woods End Laboratories accepts and evaluates all types of composts, including those made from sewage sludge, no one will be confused regarding which are Organic amendments. The Rodale Organic Gardening Compost Quality Seal guarantees consumers that the compost products “have been tested for herbicides, weed seeds and contaminants.” Rodale will also list these products on its Web site and in its publications.

None of this comes cheap, though. Compost producers will pay $950 for each batch of product that’s tested, plus an additional $170 for a thousand seals to stick on the bags. For more information, see or the Organic Gardening Magazine Web site (

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