Two Questions

Carbon Sponge began with two basic questions.

First, what is the potential of urban soils to help reverse anthropogenic climate change through a process called carbon sequestration?

And, can anybody (i.e. non-scientists) track the increase or decrease of carbon in soil over time?

About Carbon Sponge

Overview

Carbon Sponge is an interdisciplinary collaboration exploring the potential for urban soils to sequester carbon as a means to mitigate anthropogenic greenhouse gases and build healthy soil. We are a group of artists, scientists, agroecologists, community gardeners and educators based in New York City dedicated to participatory science and transparency in research as well as using art to engage broad audiences.

The Science

Soil can either be a sink or a source of carbon, the building block of life, and we want to sink it. We want to create conditions in which our soil is a sponge and holds onto that carbon for a very long time. One reason is that carbon increases soil’s fertility, structure and capacity to retain water. But also if carbon moves into the ground then guess where it is not? It is not in the atmosphere where carbon levels are currently too high and precipitously climbing, increasing the atmosphere’s greenhouse effect (a.k.a. global warming).

While carbon dioxide levels in the atmosphere have changed throughout Earth’s history, there is scientific consensus that human activities are contributing to the current measured level of 400 parts per million (ppm), which is higher than it has ever been since humans have evolved.

So, how can we garden, grow food and generally cultivate our land in a way that increases the amount of carbon scrubbed from the atmosphere and prevents its return to air? We essentially need a system of accounting. We want to increase our carbon inputs to the land and decrease the outputs back to the air. We want net gains in the ground. That is carbon sequestration—a nature-based solution to a current man-made problem.

Our Studies in NYC

The first Carbon Sponge site was at the New York Hall of Science (NYSCI) in Corona Park, Queens, built in the spring of 2018 and closed in 2020. The second site at Pioneer Works in Red Hook, Brooklyn, built in the spring of 2019 and still active.

At the NYSCI test site, there were eight planting variations in this garden study and each variety is replicated three times, making a total of 24 plots. The variations are: no planting (control), sunflowers, edibles (ground cherries and okra), cover crop mixture, sunflowers and edibles, edibles and cover crop mixture, sunflowers and cover crop mixture and edible, cover crop mixture and sunflower.

The soil is the same in each plot. It is two-thirds sediment from a construction site in Jamaica, Queens, provided to us by the Office of Environmental Remediation’s Clean Soil Bank. This sediment was excavated in 2018 and was originally formed over 20,000 years ago when a glacier covered most of New York City. The sediment is mostly sand – not a great growing medium – and contains very little life or organic material since it has been buried deep in the ground. We have combined this sediment with compost made by NYC’s Department of Sanitation, making a human engineered soil or constructed Technosol. We are turning what is often considered a waste (construction debris and food waste) into a resource (garden soil).

At Pioneer Works, in Redhook, Brooklyn, there are four Carbon Sponge plots constructed in Spring 2019. We have added to the mix a sorghum perennial species breed by The Land Institute in Kansas. Sorghum has a special property called phytolith occlusion that means the plant produces silica bodies in its leaves, husks and other plant parts. The silica helps the plant grow tall and sturdy as well as makes it tolerant of droughts and extreme weather conditions. The silica, when it enters the soil and decomposes with plant litter, is a strong binder and studies have shown it boosts the carbon sequestration process. If you visit the CS plots in the Pioneer Works’ garden, you can look through our root viewing portholes in the beds and see for yourself how amazingly deep, and fast-growing, the sorghum roots are.

The Carbon Sponge Kit

The Carbon Sponge kit is designed to allow land stewards to get a quick read on the level of soil organic carbon (specifically microbial biomass), a plant’s photosynthetic rate, the health of the plant-microbe bridge and other essential soil characteristics. These add up to the soil’s readiness to sequester carbon. It is a proxy, meaning these are early indicators of changes in soil organic matter that have proven to pave the way for eventual and long-term sequestration. It is not a simple yes or no answer, but rather an indicator of readiness. If the data is not in the optimal zone then the question becomes why and how to best address the issue. If you want to use an early version of the kit and help us collect data to further refine it, please be in touch!

Partnerships

This is a project initiated in 2018 by Brooke Singer as Designer in Residence at the New York Hall of Science (NYSCI) and in partnership with the Advanced Science Research Center at The Graduate Center, CUNY (ASRC), Department of Earth and Environmental Sciences at Brooklyn College, Pioneer Works, the NYC Mayor’s Office of Environmental Remediation (OER) and La Casita Verde (a GreenThumb garden). Funders include NYSCI, Patagonia, Brooklyn Arts Council and CUNY’s ASRC.

Special thanks to: Elizabeth Slagus (NYSCI), Erin Thelen (NYSCI), Dr. Peter Groffman (ASRC and Brooklyn College), Dr. Joshua Cheng (Brooklyn College), Judith Fitzpatrick (Microbiometer), James Sotillo, Jon Pope, The City of New York Department of Sanitation, New York City Department of Parks & Recreation, the Queens Botanical Garden and Eyebeam Art & Technology.