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Composting at 30′

The composting operation on the High Line

Five years ago I tagged along with a High Line gardener on what was then a weekly trip to Staten Island, where the fruits of our Cutback labor were dumped on a giant composting pile in the Fresh Kills landfill. Fresh Kills is a stunningly beautiful place, but the long, bumper-to-bumper, carbon-emitting drive in a panel truck packed with 35-cubic-yard compost bags was not exactly a sustainable operation.  The article I published in 2012 was called “The Choreography of the Cutback.”

Wow, have things changed. Today, Friends of the High Line’s horticultural staff remains on Manhattan island and has created an innovative, state-of-the art composting operation in a small but wonderfully efficient area just above the busy traffic of Tenth Avenue. It’s located on a Spur that once served the New York Central Railroad and the National Biscuit Company, also known as Nabisco. Back in the day, boxcars filled with eggs, milk and butter from the American heartland trundled across this Spur and all those raw ingredients made their way into giant ovens that later cranked out Mallomars, Fig Newtons and Animal Crackers. Today, the Spur is home to a fully sustainable composting operation that runs throughout the year, but just under half its output — between 180 – 220 cubic yards — is generated in March, during the annual Spring Cutback. It’s the horticultural circle of life in action, and I had the great pleasure of witnessing the new era of composting on the High Line just five days after participating in the first Cutback shift of 2017.

This is the story of how the High Line’s plants and grasses go from the volunteer’s trug to a beautiful, aromatic compost, ready to return to the garden and nurture the next generation of growth.

The giant compost bags filled with clippings — as many as 20 from each Cutback shift — are delivered to the Southern Spur on dollies. The first step is a trip through the chipper, a surprisingly small machine that churns the dead plant matter into fluffy pile.

There’s nothing the matter with my lens; the fog is plant dust….

Step Two involves one of life’s greatest pleasures: coffee. Andi Pettis, Director of Horticulture for Friends of the High Line, explains that for high-quality compost you have to begin with the right ratio of carbon-rich (dry) material to nitrogen-rich (wet) material. Most of the dry, plant biomass that’s produced during Cutback is very high in carbon, so it has to be balanced with something rich in nitrogen. Coffee grounds are the perfect ingredient, and luckily there’s an almost endless source just across the street from the High Line.

Say you are one of the thousands of people who stopped for an espresso at The High Line Hotel’s Intelligentsia cafe between 20th – 21st Streets, in the western part of the historic General Theological Seminary. The grounds from the beans used to create your cup of Joe have now made it across Tenth Avenue to the Spur, where they are dropped and raked into the fluffy pile. A handful of stray beans also makes its way into the mix, and as he rakes one of the gardeners observes that all this coffee, with its multinational origins, brings its own flavor of diversity to the High Line via the compost. This is because Intelligentsia sources its beans from family-owned farms, smallholder co-ops and estates from all over the world: Rwanda, Ethiopia, Columbia, Brazil, Peru, Bolivia, Burundi, Honduras.

The company has been around for 21 years and was a pioneer of the direct trade model with its emphasis on sustainable social, environmental and economic practices. But all that happens on the producing end, and this past year Intelligentsia decided to focus on the service end of the coffee chain. The composting collaboration, in which coffee grounds are carried across the street and recycled on the High Line, helps advance that goal. Jennifer Custard-Jarosz, an educator with Intelligentsia, told me the arrangement helps them as much as it does the High Line. “There is so much work that goes into the existence of the coffees we serve, and it’s great to see them perpetuate the growth of other things beyond their consumption.” Like the more than 100,000 plants on the High Line…

Jennifer estimates that Intelligentsia donated 97.8 pounds of organic material during the week of my Cutback shift, but the amount will fluctuate over the course of the year, depending on what people are drinking and when. (Interesting fact: cups of cold brew coffee and tea require more material to produce, and consumption of those drinks rises in hotter weather.)

Coffee grounds and stray beans from the High Line Hotel

After the nitrogen-rich coffee grounds are added, the pile is watered. This elicits a cry of joy from one of the gardeners: “Oh, a nice medium roast!” To my surprise and delight, it turns out that the water used to irrigate the mulch is not New York’s famed tap water but rain, captured in a home-made system that’s filtered before it enters a 250 gallon tank. The gardeners are thus returning a natural resource, recycled rainwater, to the garden beds, and in the process have created for themselves a steady source of water for composting during the winter months when the city’s water system has been turned off.

Espresso, cappuccino, double latte, or black, as I take it…

The Spur now smells of freshly-brewed coffee. The pile is turned, watered, turned again; more coffee is added, more plants are tossed in, and the whole process is repeated many times. We are approaching the perfect balance Pettis spoke of. Finally, the fresh green mulch is loaded into a large wooden bin, where it will rest for a week.

Compost Bins

Then it’s transferred to a second bin, where it will spend another week. The natural decomposition process generates heat, and eventually the bins reach as high as 130 degrees. When the temperature drops to 80 degrees it’s time to move to the adjacent bin. One of the gardeners has placed his sandwich in a heavy plastic bag and stashed it under a tarp; at lunchtime, it will be fully warmed. Nature’s microwave.

Meanwhile, an air circulator helps move the decomposition process along, allowing the microbiology to breathe and stay active.

A forced air system airates the bins

The whole process takes 60 days: thirty days of active “cooking” and another 30 days of curing and developing. Then the mulch is transferred to the sifter where it’s tossed, further aerated, and rendered into a smooth, clump-free finished compost.

Finally, it’s shoveled into a wheelbarrow and returned to the garden beds by a smiling gardener. Home again, but this time as an agent of good, bringing nutrients and proteins and helping the soil retain water during the hot, New York City summer.

The morning I was there, a few gardeners were mulching the maple trees in the Tenth Avenue square:

Mulching the root beds in the Tenth Avenue Square

So here the circle of life continues. It’s a sustainable loop that suggests an unappreciated fact about tourists on the High Line: a great many of them are making a small, unwitting contribution to the health of the park as well as to the values of sustainability that animate it, just by drinking a cup of espresso.

It’s a long way from Staten Island.

The High Line @ Fresh Kills


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