Compost study’s findings ‘startling’

11 mins read

MT VERNON –  Recent findings from a comprehensive three-year scientific study of bacteria found in market-ready compost may have big implications for U.S. food safety standards and recycling regulations.

The research, conducted by Woods End Laboratories, Inc., a Maine-based environmental study group that has a 30-year reputation for promoting composting, was able to demonstrate that a significant percentage of “finished” compost made at the large-scale facilities in California, Oregon and Washington contained bacterial levels that violate federal Environmental Protection Agency laws regarding hygienic standards.

The compost sampled for the study was made from lawn clippings, leaves, wood waste, vegetable food scraps and a small amount of manure.

Compost, used as a soil builder to retain nutrients, is commonly applied on fields where agricultural crops are grown. According to the study, of particular concern is that the many certified organic farms using the nonsludge green waste and manure composts aren’t required by the Department of Agriculture to wait for a period of time between the application of the compost and harvest, which is normally seen when raw manure is applied. The assumption is that the pathogens commonly found in raw manure have been “cooked out” in finished compost.

The study, recently published in the Journal of Food Protection, only included the large facilities on the west coast that, on average, are processing 3 million cubic yards of nonsludge green waste each year. One out of three facilities in California did not pass the basic hygiene standards for fecal coliform bacteria.

William F. Brinton, Jr., an environmental scientist and president at the Woods End Lab who led the study titled, Occurrence and Levels of Fecal Indicators and Pathogenic Bacteria in Market-Ready Recycled Organic Matter Composts, gathered samples of compost ready for sale from 94 large-scale facilities on the west coast. 

Brinton’s team found only one compost sample containing Salmonella, but 28 percent had fecal coliform bacteria with 6 percent of the samples found to have E. coli-O157, all exceeding the EPA’a safety standards. Other potentially heath hazardous pathogens were detected as well in the samples.

The high levels of the various bacteria found present in some of the compost ready for application is “offering the opportunity for pathogen contamination of the crops,” Brinton said.

Two of the large composting facilities tested are located in the “heart of vegetable growing regions in California and found to possess elevated levels of E. coli implicated in recent food contamination cases,” Brinton said. He added the study didn’t include investigating where the compost actually went and researchers have no evidence that any of the infected compost was used on crops.

The Woods End study, which began in 2000 as a request by Dow Industries to investigate the possibility of herbicidal residue from grass clippings turning up in market-ready compost, was conducted just prior to the spinach found to have been tainted with E. coli in 2006. As spinach was pulled in a panic from grocery store shelves, USDA’s investigators traced the source of the tainted spinach to fields in California’s growing region, near the facilities Brinton’s group tested.

“To this day, nobody knows how the spinach was contaminated,” Brinton noted. Although the compost, which was made from grass clippings, was “found to have a lot less of Dow’s herbicide that we thought we’d find,” he said, “we starting seeing spikes in bacteria.” Alarmed, Brinton’s team made up of one scientist in each of the three west coast states taking samples while another crew at the lab in Mt. Vernon tested the samples, continued to find significant amounts of pathogen levels in compost promoted as ready to spread.

“Some of the findings were so startling,” Brinton said. “It’s scary, really bad stuff; particularly finding high levels right in the middle of a growing region.”

Meanwhile the food scares continue. As recently as last summer, the federal government issued a warning advising consumers not to eat raw red tomatoes after an outbreak of salmonella was found to have sickened dozens of people. The cause was never identified.

Brinton’s study concluded that factors contributing to the elevated pathogen levels at the super-max compost facilities is attributed to being just too big. The highest pathogen levels were found in large piles that weren’t regularly turned and weren’t given enough time to “cook.” They found that the facilities gave the material only 30 days to heat up enough to sanitize pathogens, but more time, such as 150 days or three times the current period of time, is needed.

“Results indicated that the compost must be regularly turned for the pathogen to be eliminated; otherwise the pathogen can remain viable for months,” according to the study. Also found was that compost made in windrow formations and turned did much better than larger, single piles, which take up less space.

For Brinton and his research group, “with the growth of the composting industry, there should be additional research to more closely examine critical processing factors that influence pathogen levels in finished compost,”  according to the study’s conclusions.

In Maine, the Department of Environmental Agency oversees various composting facilities, none of which is nearly as large at the west coast examples and, therefore, according to DEP officials and Brinton, come without the higher level of bacterial worry. In addition, Maine’s colder seasons limit year-round composting.

“In Maine, we cannot market quickly because of the short seasons,” Brinton said. “We have to let it go for a long time, which is a good thing.” 

Maine’s DEP composting specialist, Mark King agrees.

“The difference in scale makes all the difference,” King said. Maine doesn’t have California’s huge facilities.

Of Maine’s commercial composting facilities, only 3 to 5 percent add manure and food scraps. King’s agency requires licenses for compost piles making more than 5 cubic yards of food waste a year.

Currently, about 80 facilities in Maine are licensed to compost yard waste, which limitations include leaves and grass clippings but no animal waste. Turnover rates are quick, maybe 30 days for up to 30 cubic yards. There are currently 18 so called “1B” food composters in Maine, such as Barber Foods of Portland, which recycles up to 5,000 cubic yards of waste material from its prepared chicken products.

1B composting facilities require routine testing of their composting product because the potential for pathogen levels is greater when the waste material added is animal based. Other 1B composting facilities include using post-consumer shellfish, such as lobster or clam shells.

Sludge in another highly-tested category of composting. Maine leads the nation in composting 75 percent of its sludge, as opposed to directly applying it to land, or landfilling it or shipping it out of state.

“It’s tested like crazy,” King said, adding composting is what the public wants to see happen. Everywhere, public opinion against landfills leads to pressure to recycle huge amounts of green waste. The problem is the demand just can’t keep up with the number of facilities to turn it out in large populated areas, such as California.

In any case, the large piles along the west coast aren’t going to happen here, King said, with only 1.3 million people in Maine, as compared to a population 30 to 40 times that in those western states.

“Will (Brinton) is right on the money when it come to huge heaps having big problems,” King said. “We (Maine) just don’t have an issue.”

That is if we only use Maine-made compost.

Large chain stores sell the bagged product made at facilities all over the country. A recent survey of garden centers showed compost coming from North Carolina, Pennsylvania and midwestern states with no information on the compost’s ingredients or processing method used is provided.

Therein lies the problem, Brinton said. He would like to see not only more regulation and testing of commercial compost, but standardization of the process put into place. Ideally, bags of compost would have labels with content ingredients so consumers can decide what kind of compost they want to buy.

“It’s important to remember that not all composts are the same,” Brinton said.

For more information on Woods End, go to woodsend.org
Mark King is also director of the Maine Composting School. For more, go to composting.org.
To see a list of Maine’s composting facilities, click here

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1 Comment

  1. Thanks so much for your article on composting, another reason to buy local. It’s great when the Bulldog is also the watchdog.
    I try to recycle as much as possible but am frustrated by so many plastic containers which are not accepted at the
    Farming ton recycling facility. A story to inform us as to why containers marked #s 3,4,5 etc are non recyclable and what consumers can do to change this.

    Thanks again,
    Greg Williams

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