Carbon Sponge is an interdisciplinary effort to explore how various conditions affect the amount of carbon stored or released in soils with a focus on urban conditions. Soil is an important retainer of carbon, second only to our oceans. How can land stewards of various kinds turn our soil into a better sink and slow down the release of carbon as a means to reduce CO2 and mitigate anthropogenic climate change? The project is initiated by Brooke Singer, 2018-2019 Designer-in-Residence at the New York Hall of Science and co-founder of La Casita Verde.
During photosynthesis, a plant converts carbon dioxide (CO2) and water (H2O) into food using the energy of the sun. Oxygen is a byproduct of this process and so is excess carbon released through a plant’s roots as sugars, proteins and carbohydrates that nourish and feed the microbes in the soil. An abundant and diverse microbial community will help tie up the carbon and aid in the process of sequestration, making carbon inert over many years. When carbon leaves the soil through microbial respiration or decomposition, it mixes with oxygen and turns back into CO2.
Our goal here is to find the best conditions to store the carbon and minimize its release back into the atmosphere as CO2. Factors that impact this cycle, and therefore we are closely evaluating, include soil temperature, soil type, moisture, microbial activity, plant cover and planting combinations.
The Study Design @ NYSCI
At the New York Hall of Science test site, there are 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).
The Study Design @ Pioneer Works
At Pioneer Works, in Redhook, Brooklyn, there are four additional CS 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. We have also installed a photo scanner in one of the beds that captures the underground world every 30 minutes and will construct a time-lapse video with the saved images.
Monitoring in the Lab and By You
In some of the beds we have electronics housed in clear plastic boxes. These boxes contain microcomputers that use sensors to continuously monitor soil moisture and temperature. We are measuring other soil properties in the lab at ASRC like microbial biomass and composition (the number and kind of microbes), nitrogen cycling and respiration. Through observation in the field we are recording factors like rate of plant growth, root lengths, plant weight and soil horizons. We are also developing a kit that correlates with our lab testing so that anyone inexpensively and easily can track soil changes over time and build their own Carbon Sponge.
Carbon Sponge plots are publicly accessible at NYSCI and Pioneer Works during their regular open hours. We will be releasing our data on this site overtime and with an eye towards developing a “how to” field guide. We are conducting Carbon Sponge analysis at three New York City locations as of now (and more to come!). The three locations currently are: the New York Hall of Science (Queens), the Jacob Riis Settlement House at NYCHA Ravenswood (Queens) and Pioneer Works (Brooklyn).
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, the Jacob Riis Settlement House at NYCHA Ravenswood, the NYC Compost Project hosted by Big Reuse, the NYC Mayor's Office of Environmental Remediation (OER) and La Casita Verde (a GreenThumb garden). Funders include NYSCI, Patagonia 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), Dr. Bharath Prithiviraj (Prime Discoveries), Dr. Kate Scow (UC Davis), 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.