Better than Bait

Worms were crawling up the walls. Thousands were inching across the ceiling. Hundreds more were slithering over the floor. Dave Greninger rubbed his eyes at the early morning horror scene that was unfolding in his small office attached to the family dining room.

“I was like, ‘What is going on?’” Greninger says, remembering one of his first worm farming disasters. It happened after Greninger, a custom interior contractor by day and aspiring worm farmer by night, pulverized some horse manure and fed it to his herd of three thousand nightcrawlers, thinking the manure’s mixture of carbon and nitrogen was the optimum food.

Overnight, the bacteria that co-habit the “Vermy Hiltons”—a row of plastic tub sinks covered with plywood that lines one wall of the office and is home to Greninger’s worms—gorged on horse manure. As they ate, the bacteria generated so much heat that the temperature in the sink soared to over 100 degrees, essentially baking the worms and forcing them to push off a 2-inch-thick lid to escape. Many died; the lucky ones were the worms Greninger found climbing the walls.

“It was our first mass worm killing,” says Greninger, who runs the Bucks County Worm Farm in eastern Pennsylvania with his wife Teresa. “We call that vermicide.”

After a few years of experimenting, Greninger now runs a low-casualty worm farm. He has become an advocate for a practice that is spreading through the United States. Worms are farmed for their manure, which some farmers say is better than cow manure and who have used it for decades to improve their crop health and yield. But while anecdotal evidence and garden folklore about the effects of worm manure on plants is plentiful, little is known about the science that is being put to work by farmers. Researchers, encouraged by gardeners and worm farmers like the Greningers, are beginning to investigate the properties of worms and how their manure affects plant growth. They are discovering that worms may have a place outside the garden. From landfills to agricultural farms, worms and their manure may help to reduce waste, control crop pests, and clean-up soil pollution.

Photographs of huge zucchinis, deep green heads of broccoli and a New York State prize-winning 1,000-pound pumpkin are lined up on the Greningers’ dining room table. All are testaments to the worm manure “magic” that caught the Greninger’s attention about six years ago. The couple was looking for a way to grow more and tastier organic vegetables on a 72-acre farm they were renting. Surfing the Internet, Dave Greninger read about one of the four worm farms in Pennsylvania at the time and contacted the farmer who offered up advice, from one ex-biker to another, about how to begin raising worms.

Worms were traditionally raised for fishing bait and ground up as a source of protein and enzymes for animal food and biodegradable cleansers. But a few decades ago, California farmers began to spread worm manure on their plants and almost immediately reaped the benefits of bigger, healthier and more productive crops. Many gardeners and horticulturists then began using worm manure, and it developed a reputation as one of the most nutrient-rich and microbially-active soil enhancers available.

Greninger gently submerges his big calloused hand into a Vermy Hilton. After breaking through the top layer of developing manure where thousands of worms reside, he hits the bedding—a house recipe of peat moss, lime and other high-carbon materials that simulate the dried leaves in the worms’ natural habitat. Different worm farmers have various bedding mixtures and vermiculture techniques for increasing productivity and yield. Instead of tubs, some worms are grown in long, divided beds. As the bedding is changed in one division, the worms migrate to that section, leaving behind pure manure that can easily be harvested. This horizontal migration system is “a fancy way of saying the worm runs sideways,” says Greninger.

Limited to a small office space adjoining their house, the Greninger’s have four Vermy Hilton tub sinks and two large 40-gallon plastic bins that are home to between 3,000 and 4,000 redworms and European night crawlers. This small operation, one of over a thousand registered worm farms in the country today, produces between one-quarter and one-half ton of manure each month, enough to supply a few local garden centers.

Now on the other side of the room, Greninger kneels down on the floor, dives his hand into a plastic bin and pulls out a handful of the shimmering dry worm manure. The coveted product, which looks like coffee grounds, is ready to be bagged and sold.

“We know what goes into the worm and what comes out, but we don’t know what happens in between,” he says, letting the manure run through his fingers.

Thanks to gardeners and worm farmers spreading anecdotal evidence of the manure’s effectiveness, researchers are now being funded by government agencies, including the U.S. Department of Agriculture, to study vermiculture scientifically. They are finding that the worm’s gut is filled with microorganisms that break down organic matter as it passes through the worm’s digestive system.

“It is a sort of synergy. The earthworms and microbes together can break down organic matter,” says Norman Arancon, a soil ecology researcher at Ohio State University.

Researchers found that what begins as worm food ends up a microorganism-rich manure after it passes through the worm gut. Infused with minerals and microbes that produce plant growth hormones that are readily available to plants, Arancon says, worm manure is an ideal plant fertilizer. Various field and greenhouse studies are confirming what farmers and gardeners claim—crops benefit from worm manure.

“Finally we are getting the science to back up the magic,” says Greninger, as he sits at the head of the table eating a late dinner with his family.

Worm “magic” is already being put to work throughout the country. In North Carolina, farmers are feeding the hog manure that is polluting the state’s waterways to worms. Operators of landfills in California are also feeding organic waste to worms to save precious dump space.

Researchers hope to use worm manure to address a host of other environmental concerns, too. They are investigating how microbes in the manure use pollutants as a source of energy so that manure may someday be used to clean up groundwater contaminated by pesticides. The microbes in worm manure also suppress plant disease and insect pests by competing with pathogens for space and resources.

But the industrial-scale farms that would be needed to supply huge quantities of worms and manure for environmental clean-ups would raise new issues. John O’Sullivan, a professor of agricultural economics at North Carolina A&T State University, points out that large farms need a substantial investment initially and usually run into regulation questions about how to standardize production.

“These are big issues for small farmers,” says O’Sullivan. He expects the small niche market for worm manure will continue to grow but at a certain point, the demand will be above the small farmer.

Greninger is already feeling that pain.

“I wish I had a big building. I’d make millions of castings,” says Greninger. “We can’t meet the demand now so we’re holding back.”

Yet he remains optimistic. Greninger predicts that worm farms will become more widespread because worms and their manure are “so good, so real, it’s going to happen.”