A front-end loader combines sawdust, inoculants and biosolids in the receiving area at Casella Organics’ Hawk Ridge Composting facility in Unity on Friday. Shawn Patrick Ouellette/Staff Photographer

UNITY — State environmental regulators have allowed companies to sell compost made with treated municipal sludge to the public this summer, even as they restrict the use of sludge on many farm fields because of concerns about chemical contamination.

Maine has about a dozen operations that use treated sludge, referred to in the industry as a “biosolid,” to make compost, and they continue to distribute products containing PFAS as environmental regulators and a task force formed by Gov. Janet Mills try to figure out how to deal with the pervasive “forever chemicals.”

Direct application of treated sludge on Maine farm fields has slowed dramatically this year amid new concerns at the Maine Department of Environmental Protection over levels of PFAS in the would-be fertilizer. But the DEP has granted a dozen facilities that mix sludge with other materials to make compost an extension, of sorts, to continue selling their nutrient-rich product to landscapers, nurseries, contractors and home gardeners.

DEP officials and composting facility representatives said they are confident that the compost is safe for use because gardens and lawns likely have much lower background levels of PFAS – a common industrial chemical under increasing scrutiny – than larger farms where more sludge was spread repeatedly.

“We have to make sure that this is safe for our customers,” said Andre Brousseau, superintendent of the Sanford Sewerage District, which recently invested $2 million in a composting facility. “I use this at my house. And we are not going to be giving out a product that is going to be detrimental to health or the environment.”

Some environmental groups involved in the debate remain concerned, however, and are urging the DEP to conduct more testing before allowing PFAS-laced sludge or compost to be spread anywhere.

“I would challenge the assumption that gardens and other places where compost will be used have average or below-average PFAS levels,” said Patrick MacRoy, deputy director of the Portland-based Environmental Health Strategy Center. “And the reason I challenge that is it’s only logical that gardeners are going to use compost year after year.”

Maine’s investigation of PFAS in treatment plant sludge and compost puts the state in the vanguard of research in this field, as concern mounts nationally about potential threats to soil, drinking water, food supplies and human health. The U.S. Environmental Protection Agency has begun to investigate PFAS and may establish protective standards, but that work is far from completion.

CONSUMER DEMAND

DEP permission for compost sales extends only until June 30, 2020, as the state gathers more information and conducts more testing.

“Between now and then, we will be back in communication with those facilities because we recognize they need answers beyond that date,” said David Burns, director of the DEP’s Bureau of Waste Management and Remediation. “But we didn’t feel like we had adequate information (to go beyond a year).”

In many ways, Maine’s sewage treatment plants and biosolid composting facilities are grappling with a problem brought on by consumers’ hunger for high-tech but low-maintenance products.

The large class of per- and polyfluoroalkyl substances collectively known as PFAS have been used for decades to create the nonstick surfaces in cookware and to help make jackets, carpets and other fabrics waterproof or stain-repellent. The hundreds of chemical variants of PFAS are commonly used in dental floss, grease-resistant food packaging, compostable paper dinnerware and in the foam that military bases and airports are required to keep on hand to battle jet fuel fires.

“These compounds have been in use for 30 to 40 years,” said Jeff McBurnie, director of permitting and regulatory affairs at Casella Organics, which operates one of New England’s largest biosolids-based composting programs in Unity. While McBurnie understands the concerns over PFAS, he said, “What we do is such a small component of where the potential impact would be.”

Yet the chemicals’ complex structure means they do not biodegrade in the environment and linger in the human body for years before breaking down. That means PFAS now routinely show up in drinking water and in the human waste that treatment plants must process.

With PFAS nearly ubiquitous in the blood of people and animals around the world, there is mounting concern about the health impacts.

A growing body of scientific studies suggest the chemicals — and in particular two phased-out versions in this country, PFOS and PFOA — can affect liver and thyroid function, raise cholesterol levels, disrupt the immune system and potentially lower birth weights at high dosages. Some studies also suggest a link to cancer.

HOT SPOTS IN MAINE

Most of the high-profile and most severe PFAS contamination cases nationwide have occurred near military bases or industrial facilities that produced or used the chemicals. There is growing interest in Congress to allow PFAS contamination sites to qualify for federal Superfund status to facilitate cleanup.

Maine has several known PFAS hot spots, such as on areas of the former Brunswick Naval Air Station where the chemicals were used in firefighting foam. But PFAS in sludge emerged as an issue in Maine after contamination was found on an Arundel dairy farm that utilized and stockpiled biosolids for fertilizer.

Earlier this year, the Maine DEP began requiring testing of PFAS in treated municipal sludge at facilities that turn those materials into fertilizer or compost. The first round of tests showed elevated levels of PFOS and PFOA in the vast majority of samples.

The agency also collected test results from farm fields where sludge had previously been applied. As of last month, 33 of 43 fields tested had background PFAS levels that were too high to allow additional spreading. Unless treatment plants can find alternative sites, they will be required to landfill the sludge at an additional cost to ratepayers.

The review process for facilities that convert the sludge into compost is different, however.

The DEP cannot test PFAS soil levels on every landscaped lawn, building site or home garden where compost would be spread, so the state is relying on background soil levels gathered from studies in Vermont to determine likely levels of contamination. So far, 12 of 15 composting facilities in Maine have been given the green light to continue selling because – if the compost is applied correctly – the additional PFAS would not tip a hypothetical plot of land above the DEP’s contamination threshold.

“For general distribution (of compost), it is not anticipated the product would be applied to soils year after year like they do with (agricultural) biosolids,” said Burns, who heads the DEP division that oversees reuse of biosolids.

DEP staff also sampled soils from a vegetable garden owned by a person who raised concerns with the agency about repeated use of compost, and they are analyzing potential PFAS uptake in vegetables. Although Burns said he was not prepared to release the results before notifying the homeowner, he said, “It shows that we’re OK.”

Plant uptake of PFAS is an area of ongoing research. In Arundel, however, Stoneridge Farm has been effectively shut down because high levels of PFAS showed up in the milk of cows fed silage grown on farm fields that were fertilized for years with municipal sludge and paper mill waste.

Last week, the attorneys for Stoneridge Farm’s owners, Fred and Laura Stone, reported that blood samples showed the couple had PFAS levels up to 20 times higher than the national average.

The PFAS levels in compost made with biosolids in Maine were magnitudes lower than those found in the soils of Stoneridge Farm.

McBurnie, with Casella Organics, said the compost application rate his company recommends to clients has a safety margin built in. The company also lowered its maximum recommended loading rate slightly – from 4.5 to 4.3 tons per acre – in response to the PFAS tests but is not yet explicitly mentioning PFAS in those recommendations.

“We understand and we take all of the precautions, not only by law but because we want to make sure we are giving customers a good product for their gardens and for their lawns,” said McBurnie, who is a member of Maine’s PFAS task force.

‘SCIENCE’ AND ‘ART’

Located on roughly 15 acres a few miles from downtown Unity, Casella’s Hawk Ridge facility is a massive operation that produces roughly 80,000 cubic yards of compost annually. While the company sells to individuals, most customers of Casella’s various compost blends are contractors, landscapers or others buying in bulk.

Tractor-trailers deliver an estimated 4,800 cubic yards of treated sludge monthly to the Unity facility. After unloading the truck, workers combine the piles of waste with wood shavings, sawdust, wood chips and “starter” compost that adds a carbon base and bulk to the nitrogen-rich waste and begins the composting process.

Jeff McBurnie, left, director of permitting and regulatory affairs, and George Belmont, facility manager of Casella Organics’ Hawk Ridge Composting facility, in Unity on Friday. Shawn Patrick Ouellette/Staff Photographer

“There is a science to it but there is also a little bit of an art, too,” said George Belmont, manager at Hawk Ridge, while standing beside small mountains of wood shavings and treated sludge.

After mixing, the piles are loaded into 128-foot-long, enclosed tunnels or “vessels” where – with the help of oxygen pumped in by huge aeration systems – the microbes that help create compost get to work. By law, the internal temperature of the pile must reach at least 131 degrees Fahrenheit to cook off any pathogens.

After roughly a week in the tunnels, the compost is moved outside to “cure” and continue to cook for several more weeks. Eventually, the materials are piled into massive rows or blocks where sensors monitor temperature, moisture, oxygen and carbon dioxide levels in the final aging and curing process.

All told, the biosolids-based compost could be on-site at Hawk Ridge for six months to nearly a year before it is sold as “Class A” compost that is more than 99.9 percent free of the pathogens found in human waste.

McBurnie said Casella lost a sizable chunk of business as well as a few customers in the spring when the DEP imposed a monthlong moratorium on compost sales while PFAS testing was done. Although sales have been brisk since then, the uncertainty over what happens after June 30 of next year is still “in the back of our minds,” he said.

Even though Casella owns or operates several landfills in Maine, the company does not want to landfill the sludge now being accepted at Hawk Ridge because it recognizes the additional value of the finished product. Landfilling sludge also increases municipalities’ costs and consumes limited landfill space.

“I’m all for doing the right thing, but let’s not act rashly,” McBurnie said. “We understand there are clusters of issues, such as where there are large (PFAS) releases near industries. Let’s focus on them.”

SANFORD’S SITUATION

More than 120 miles to the south, the Sanford Sewerage District distributed 122 cubic yards of compost last month that was made from biosolids. While diminutive compared to Casella’s operation, Sanford’s composting facility allows the district to reduce input into its landfill, which is nearing capacity, while avoiding hundreds of thousands of dollars in annual costs to ship the waste to Hawk Ridge or elsewhere.

“We recently spent close to $2 million on this composting system,” said Brousseau, the superintendent of the Sanford Sewerage District. “The ratepayers are paying for that, so what do we do if we can no longer compost? And that’s still a concern because the deadline is July (2020).”

Like other treatment plant operators, Brousseau stressed that they have no control over the PFAS that flows into their facilities from human waste or industrial sources. Although federal scrutiny is increasing, PFAS chemicals are still not on the long list of substances that companies must report discharging.

Even so, Brousseau estimated that a home gardener would have to spread 7 yards of Sanford’s compost year after year for decades in order to exceed the DEP’s cutoff.

The task force created by the governor this spring is expected to make recommendations on future reuse of biosolids by the end of the year. Several groups involved with the task force or monitoring its work are urging the DEP to err on the side of caution by limiting or prohibiting land application of sludge with elevated PFAS levels.

MacRoy, whose organization the Environmental Health Strategy Center also has a representative on the state’s task force, said it is wrong to automatically assume that gardens or lawns are “virgin land” without elevated PFAS levels, especially if they’ve received compost before. MacRoy also expressed concern that some home gardeners may not follow application guidelines and, in their zeal for a well-nourished garden, may overapply compost.

“I question many of the assumptions that DEP is using,” MacRoy said.