One person's trash is another person's treasure
Intervale Compost Products keeps organic materials out of county landfills while generating a revenue stream for the non-profit Intervale Foundation.

By Dan Sullivan
Posted December 9, 2004

A Volvo excavator does the biweekly job of turning the windrows. It ruffles rather than pulverizes the compost and provides better passive aeration.

Once a breadbasket to the Abenaki Indians, the Intervale lands had been robbed of nutrients by conventional mono-crop agriculture from the 1950s to the 1980s. “One of our biggest barriers was soil fertility,” says Adam Sherman, manager of Intervale Compost Products. “So we started out with a quarter acre of land and a 20 hp farm tractor pushing around 10 cubic yards of leaves.”

Back in the day, Intervale Compost Products used to bribe Burlington residents to bring in their leaves by offering them coupons redeemable for compost in the spring.

Now, operating on a 10-acre site within the 700-acre Intervale compound, the composting operation converts tons of trash—including compostables from Burlington and surrounding area residents and businesses, animal manures from local farms, and about 750,000 gallons of spoiled ice cream from Ben & Jerry’s in nearby St. Albans—into 12,000 cubic yards of black gold. (Tanker trucks from the famous ice-cream company spray the milky slurry over the windrows periodically in order to encourage microbial life.)

What started out as a recycling and soil building venture morphed into a commodities business, says Sherman. “Now, recycling is sort of an afterthought—but it’s still a huge benefit.”

Such a big operation does present its challenges. The 10-acre site that accommodates wave upon wave of 400- to 800-foot-long windrows is just 500 feet from the river, so, even with a significant riparian buffer, runoff and leaching are concerns. At an early point in the learning curve it was discovered--a little too late--that asphalt was a poor choice of material for a compost pad.

A commercial compost turner does not necessarily yield the best product. That expensive piece of equipment now sits idle.

“Blacktop can be a cost-effective impervious surface for storage of finished compost,” says Sherman, adding that—even at twice the price—he’d still recommend concrete. For processing feedstock (raw compost), he has learned that concrete's essential. The acids and microbes that go to work in compost make it an effective bioremediation tool for petrochemical cleanups, Sherman says. This same activity, he said “oxidized the carbon in the blacktop and it became a loose-grain aggregate pad…It was a hard lesson.”

There’s also no slope to speak of at the current site. To remedy all this, a major capital improvement project is under way to resurface the entire site in concrete and give it an ideal 3 percent slope. (A less expensive process in which a mixture of lime and Portland Cement is injected into the soil to create an impervious layer is also being explored.)

Another important lesson learned was that a commercial compost turner does not necessarily yield the best product. That expensive piece of equipment now sits idle (it’s on the auction block) while a Volvo excavator does the biweekly job of turning the windrows, one scoop at a time. The excavator, basically a giant backhoe, ruffles rather than pulverizes the compost and provides better passive aeration, Sherman says. “It usually takes three or four scoops to puncture the core.”

Quality controls at Intervale Compost Products include mixing material at a rate of 27-28:1 carbon to nitrogen (for a finished product that’s about 15-16:1), maintaining a moisture content of about 63 percent, and achieving a 132°F center-of-pile temperature for a consecutive 72 hours between turns.

All this fussiness is necessary to produce a consistent, reliable product, Sherman says.

Adam Sherman, manager of Intervale Compost Products “There’s a difference between composting and making salsa. You’re not just blending it and putting it in a jar. Composting is a complete chemical, physical and biological process. You are changing the very structure of the material.”

“There’s a difference between composting and making salsa,” says Sherman. “You’re not just blending it and putting it in a jar. Composting is a complete chemical, physical and biological process. You are changing the very structure of the material.”

Besides providing low-cost, high-quality compost to Intervale farmers, Intervale Compost Products also sells bulk compost (delivered to area farms and residences), bagged and screened compost though retail outlets (including, of course, Gardener’s Supply Co.), and other bagged products such as germinating mix and potting soil. Blended garden soil—“a blend of Intervale Complete Compost and sandy loam”, according to promotional literature—is a relatively new venture. “We started importing sand because we saw there was a really strong market for manufactured topsoil,” Sherman says, adding that this market was largely created by excavators pawning off poor subsoil as topsoil. Intervale’s bulk compost sells for $32 a cubic yard; a 20-quart bag retails for $4.95.

Sherman would like to see more customers buying in the fall, which he says is the best—if not the most widely practiced—time for applying soil amendments. This public education would also help with cash flow, he says. “Seventy percent of our business falls within a 6-week window [in spring],” he comments.

Intervale Compost Products provides a revenue stream for an integrated community whose goal is to have a positive influence on the greater Burlington area. As a parallel to the Intervale’s goal of providing 10 percent of the city’s local fresh food (it’s more than halfway there), Intervale Compost Products aims to recycle at least 10 percent of the community’s waste.

In 2003, the operation took in 5,140 tons of yard and garden waste—leaves, grass, plants, pine needles and yard trimmings—and 4, 707 tons of food scraps from Chittenden County residents and businesses.

“It’s a significant contribution to the amount of materials diverted in our county from landfilling, says Chittenden County Waste Reduction Manager Nancy Plunckett.