Written by Kina Smith

A leaf falls in the forest, drifts to the ground and settles among other leaves.

On the forest floor it is attacked and devoured by fungi, bacteria, and animals in astounding variety. This leaf is reduced to its core components, mixing with the soil, then recombined into new life. This re-cycling has been happening since long before anything evolved legs, or language.

It is a fundamental action that allows life to continually re-use nutrients and grow. This vital process happens everywhere, but can also be harnessed to do work. It is the principle behind composting, a method of decomposing organic matter into a stable, nutrient rich, and biologically active fertilizer. If we create an ideal environment for these decomposers, they will come and render organic material into compost. The connection between compost, soil, and food is strong, but compost is also connected to our waste and how we deal with our trash.

Hidden Treasure, Illustration by Hannah Stephey
Hidden Treasure, Illustration by Hannah Stephey

Some people, both urban and rural, have their own small compost operation: compost tumbler, or a moldering pile of vegetation in the corner of the yard.

Growing up, my family piled up our garden waste and food scraps and just let them sit, a technique called "Cold Composting". Every spring, we would incorporate it back into our garden to fertilize it. This was normal and unremarkable for us, but there are many people who do not compost or even know what it is. Many of us put our organic byproducts into the trash with plastic, paper, and Styrofoam. New York City generates 20,000 tons of this mixed trash every day and more than 30% of that is organics. The vast majority of it goes into landfills as far away as Virginia, where the organics putrify in an anaerobic environment and create methane, a potent greenhouse gas.

Worldwide, the statistics are worse.

AA recent study puts the percentage of wasted food between 30-50% of our total production.

Poor harvesting techniques, unreliable transportation infrastructure, retail and consumer wastage are all major culprits. But when food goes to waste, we're losing more than just the food itself, we're wasting all of the water, soil, and energy resources that went into growing it.

”For the sixth time in 11 years, the world will consume more food than it produces.”--The Guardian, 2012

This trend has not changed. The resources needed to grow food are becoming increasingly scarce and the world population continues to grow. The natural recycling process of growth and decay could be used to help this, as long as we are willing to recognize the value of our food waste.

Photo Credit: Bron Marshall
Photo Credit: Bron Marshall

Composting in our backyards is something that we all should do, but that in itself is not enough.

The practice needs to be adopted on a systemic level. Consumer food waste in urban areas is an expensive issue from a waste disposal perspective, but if we look at compost as a valuable resource to help revitalize our stressed soil resources, the problem becomes even worse.

Thankfully we're wising up to some extent. San Francisco recently passed an ordinance that makes the separation of recycling and organics mandatory, making it the first city in the nation to universally require source separation of all organic material,including food residuals”. Many other large cities have optional curbside organics collection and contract out the composting to huge industrial processing facilities such as Cedar Grove in Washington State, and Jepson Prairie Organics in California.

In New York City, the infrastructure for organics waste collection is still limited. It is nonexistent in Manhattan, and there are small pilot programs in select areas of the other boroughs.

Residents and local sustainability organizations have stepped up to fill the gap, however. At every farmers market around the city there are food scrap collection sites. The food scraps are collected from neighborhood residents and then some of that is delivered to several small composting operations within the city to be processed. Keeping the processing within the city not only keeps transportation costs down, it allows for community outreach and education about our waste in ways that really resonant and create impactful experiences. The Gowanus Canal Conservancy in Brooklyn is one of these organizations that composts local food scraps and helps educate and engage the community.

Compost Monitors Photo Credit: Kina Smith
Compost Monitors Photo Credit: Kina Smith

I worked with the Gowanus Canal Conservancy last year while pursuing my Masters degree at New York University. I was building an open source, DIY-friendly compost monitoring system for small urban composting operations like the GCC.

Building a Compost Monitor from Kina Smith on Vimeo.

Monitoring becomes important as a composting operation becomes larger because the potential for disaster becomes real, especially in an urban setting. If compost goes wrong, it can create some unpleasant odors, noxious gases, or even catch fire. Developing an efficient workflow to process your materials as efficiently as possible is important. One of the difficulties in starting up a composting operation is getting those workflows figured out, safe-guarding against possible mishap, and being able to process food scraps in a timely and efficient manner. My hope was that an inexpensive and easy to build monitoring system would help increase the efficiency of existing small operations and ease the barrier to entry into the business.

Getting around NYC, Photo Credit: Kina Smith
Getting around NYC, Photo Credit: Kina Smith

I got into this project through my research into food systems, systems thinking, and becoming intimately acquainted with NYC trash through my nightly dumpster diving practice.

I began dumpster diving soon after I moved to the city, partly as a way of getting to know it, but primarily as a way of getting free food.

The foraging was so bountiful that it became easier than grocery shopping and faster than eating out.

On my commute home every night on my bicycle I would stop at a few select bakeries and grocery stores, pick up some bread and pastries, sandwiches, and produce. Sometimes the pickings were slim, a single sandwich or a dozen eggs, but often there would be more than I could possibly eat. I picked up cases of orange juice, organic free-range eggs, a wide variety of produce, chocolate bars, and complete pecan pies.

The quantity of edible food that I personally saw go to waste was astounding, but insignificant compared to the amount of compostable food waste that got mixed in with the trash. On the 3 to 4 stops I made every night, I saw hundreds of pounds of food scraps waiting to get loaded in with the trash.

Observing the food waste problem from such a personal vantage point made it difficult to ignore. I began looking for leverage points in this complex system. A leverage point is a place where “a small shift in one thing can produce big changes in everything”. Composting, in conjunction with community outreach and education, is a very powerful and effective way to teach about food waste, and knowledge and understanding is one of those leverage points that can foster great changes.

Not a backyard operation, Photo Credit: Kina Smith
Not a backyard operation, Photo Credit: Kina Smith

While monitoring is important for neighborhood sized composting operations, the stakes just aren't high enough for it to be needed for a family-sized pile. Understanding how the process works is far more important. The Rodale Compost Book is an excellent read.

The process is simple, but there are a lot of variables to take into consideration. Bacteria and other organisms infiltrate the organic material and begin to eat it. They consume oxygen and create heat as a byproduct of their metabolic processes. This heat can be measured over time and observations can be made about different aspects of the process, which is how my sensor system worked.

The heat produced by the compost has a direct relationship to the biological activity, which is closely tied to overall oxygen levels, the rate of decomposition, and general health of the compost. The compost pile has to be at least a cubic yard in size to have enough mass to generate and sustain heat in this way. Ideal temperatures are between 130 and 160 degrees Fahrenheit.

If the compost piles get too hot, heat can strip nutrients from the final product, encourage an overgrowth of undesirable microorganisms, and in rare situations (in HUGE piles) cause spontaneous combustion!!!


If it is too cold, the process takes a lot longer and any pathogens or weed seeds in the mix won't be killed. For family sized piles, there are analog temperature probes which are made to measure temperature from time to time.

For larger operations, such as at the Gowanus Canal Conservancy, certain aspects of this process become really important.

At the GCC, the food scraps collected at the farmers markets were mixed with wood chips at a specific ratio. This created a mixture of nitrogen rich material and carbon rich material called the 'feedstock'. The wood chips also increased the porosity and stability of the mixture, allowing air to flow through it more easily.

If the pile is too dense or wet it can cause oxygen starvation in areas which creates an anaerobic environment. The bacteria that thrive in an oxygen-free environment produce methane gas, which is what happens inside of a landfill. The mixture of carbon to nitrogen controls the temperature of the pile and which bacteria and fungi are able to thrive. Too much nitrogen rich materials can cause the temperatures to increase to a degree which encourage bacteria which are harmful to the final product. There are a lot of factors to consider, and then everything changes when the constituents of the feedstocks are changed. Without a robust system of monitoring there is no real way measure how the composting process is doing or even if the processes and techniques need to change.

Compost Pile, Photo Credit: Kina Smith
Compost Pile, Photo Credit: Kina Smith

During the development of this compost sensor project, I relied heavily upon the online DIY/Maker community for support and for the amassed collection of knowledge.

Ilearned over and over again that the free sharing of knowledge is the most important thing. Publicly sharing real world successes and failures with the larger community, especially with climate and sustainability related projects, is more important than any piece of hardware.

This open sharing and mixing of ideas is synonymous with the actual composting process in many ways. A delightful mess of decomposing, complete, and partially formed stinky ideas creates a fertile medium for growing tall and delicious ones.

My compost sensor was built and tested at Gowanus Canal Conservancy operation in Brooklyn, but it was my master’s thesis project and unfortunately didn't live beyond that. But it survives on in the lexicon because I wrote detailed instructions on how to replicate it and they are publicly available (and easy to find). It's called Compost Sensor and can be found on Instructables and Farmhack.

When isolated, we are no better than individual bacteria trying to eat a banana peel, but together we are an unstoppable force. If we put our ideas out there, expose them to all of the other shared ideas so that they can intermingle, it creates a fertile bed for new inspirations to arise. Without an understanding of the issues at hand, we have no chance of overcoming them and it is every individuals responsibility to search out and share that information. By reading publications like World-Eats and talking to your friends we might be able to inspire our neighbors or find some of these Leverage Points ourselves.

Kina grew up on a homestead in remote Alaska. He's been working on a diverse variety of fabrication, food, music, bicycle, and technology related projects since he was a young man. He possess a Masters Degree from the Interactive Telecommunications Program in New York City and has most recently moved to Fairbanks, Alaska, to eat good food, build some cool stuff, and watch the Aurora Borealis.