I wanted to write about compost for quite a while. Compost is important, it is what keeps a garden growing. Our garden is getting compost from GreenThumb (the NYC community garden umbrella organization) and from the city’s sanitation department. We are also making some compost ourselves in a tumbler composter. We started this only a few years ago, and we are still learning how to do it best. (We also have a worm composter).

Critical eyes on our tumbler

Last year, we experimented with adding lots of coffee grounds from a local coffee shop to our compost bin. This kicked the decomposition into overdrive. The material in the bin got so hot that steam emerged on a pretty warm morning in May. At other times, some material did not seem to decompose at all.

Steaming compost, enhanced with a lot of coffee ground.

This summer, we invited Master Composter Sashti Balasundaram of the NYC Compost Project to teach a workshop about composting. During this workshop, we learned not only what compost actually is and how it is created, but also how New York City is trying to compost more of the organic waste that residents produce every day, and why this is important.

Sashti Balasundaram teaches about compost

So what is compost? Sashti told us: “Compost is decomposed organic matter through human intervention.” Humans collect the organic matter, combine it, pile it up, turn it and sift it. But the main work in composting is done by others: by bacteria and fungi and by invertebrates like insects, mites, millipedes, nematodes earthworms, snails, among others. These organisms work in succession: bacteria and fungi begin the decomposition process. Through their activity, the material can get quite hot: 150ºF is not unusual. This is too hot for the macroorganisms, who will colonize the compost a little later. They turn it over and aerate it. This is important since composting requires oxygen as well.

Decomposers in compost (from the Compost Project’s tip sheet)

After it is finished, the perfect compost should have a fine, crumbly consistency and smell earthy. To get this outcome, the right stuff has to go in. We are advised to put ½ greens and ½ browns into our bin. “Greens” is plant material that has still some life in it, e.g. leaves and flowers and fruit- and vegetable scraps. These are rich in nitrogen. “Greens” do not have to be green. The coffee ground, which we used so abundantly last year, has lots of nitrogen and qualifies as Greens. “Browns” are rich in carbon, for instance dry stems and leaves, straw, wood shavings and paper. Sashti confirmed what we already learned from experience: what goes into the composter should be bigger than a finger and smaller than a hand. Otherwise, the compost becomes either too dense or it takes too long to break down.

Barbara sifts our compost. The result is pretty good, but some sticks did not break down.

Why composting? Clearly, compost is the best fertilizer for a garden. But there is another advantage of composting: all organic material that is recycled this way does not end up in a landfill, where it would turn into the powerful greenhouse gas methane. In the short and long run, composting is cheaper than trucking organic waste to a landfill. The NYC sanitation department has only recently begun to collect organics from households in some parts of the city, but almost all schools recycle organic waste, and they are even using compostable plates and cutlery. Elsewhere, residents can bring food and kitchen scraps (sans meat) to numerous drop-off sites. There are more than twenty in Manhattan alone.

Organics bins in front of a school in Manhattan (left) and at the drop-off site on Union Square (right).

What we drop off will be taken to composting facilities. One of them is on Governor’s Island. It is a surprisingly pleasant place with a flock of happy chickens and mounds of brown material that does not smell of anything bad at all. Here, all organic waste from the restaurants on the island is processed, too. Some of the finished compost is used at an urban farm, some of it is redistributed to residents.

Our little garden will always need to get compost from one of these facilities to fertilize our plants. But we are thinking of getting a second tumbler to increase our own production as well.

Even with a second composter, we will not have the capacity to process kitchen scraps from all of our members and friends. But there are many collection sites in New York City. The two closest are at the Union Square Farmers Market (Mondays, Wednesdays, Fridays and Saturdays) and on Hudson Square (Tuesdays and Thursdays 8am-11am). We encourage everybody in the city to take their kitchen scraps to one of these sites. They will be put to good use and will not end up in a landfill!

The composting facility on Governor’s Island.