Testing the Compost-Heated Greenhouse in an Urban Setting
The goal of this project is to translate and refine the idea of a compost heated greenhouse to an urban setting. By using different combinations of readily available urban materials such as coffee grounds and yard waste, we aim to divert these items from the waste stream and use them to generate direct heat for soil and seedling trays in a small greenhouse. During this project we are observing the efficacy of a small urban compost heated greenhouse in producing winter produce and spring seedlings as well as quality finished compost.
My cooperators in the project this year are as follows: During the early part of the year I continued to be assisted by Elena Batt, who worked with me once or twice a week to help gather compost materials and bring them into the greenhouse. She also assisted in monitoring the amounts of materials and temperature data, and in communicating with the coffee businesses. From late winter through spring I was assisted by KayCee Wimbish, who took on Elena’s duties as well as assisted me in growing at South Pine Street City Farm, and raising the seedlings in the greenhouse. My technical advisor is Teresa Rusinek and she has helped me in locating the greenhouse, troubleshooting with the compost and plant health and guiding me in creating pathogen-free compost.
2013 has brought much change to South Pine Street City Farm. In the early part of 2013, KayCee Wimbish joined SPSCF as the main grower while she herself was starting a farm right also at the YMCA. The development of another urban farm that will use the greenhouse as a space to raise seedlings underlines the importance of accessible urban greenhouses. Throughout the season, the main function, size and crop plan of SPSCF has not changed much from previous years, and we had a fairly good season. While we have been preparing for next season, we have found that the vandalism pressure on the greenhouse is too great and we are exploring different location and protection options for next year.
From mid-winter through spring this year we continued to maintain the greenhouse, emptying bays as they finished producing their winter crops and getting them filled again for the spring seedlings. We also continued to monitor our various physical and chemical attributes: high and low air temperatures in the greenhouse, temperatures of both the compost and any soil in which plants were growing, and periodic testing of compost for levels of CO2 and Ammonia. In reaction to our observations from the early winter, the formulas of the compost were changed to a 2:1 by volume ratio of coffee grounds to chipped yard waste or leaves. Unfortunately, we were only able to procure dried leaves for composting much later in the season than I had originally planned, so these mixtures of compost were tested in succession, rather than all at the same time.
The compost bays that we prepared for seedlings were filled to the top with compost, then trays of seedlings were laid over the pile with a gap in between so that the seedling roots did not grow into the compost. Eventually, we also had two bays that we could share with the community gardeners at the YMCA. At the end of this year, samples were taken from the finished piles of the three different compost formulas (1:1 coffee to chips, 2:1 coffee to chips and 2:1 coffee to leaves) and sent to University of Pennsylvania’s soil lab for analysis.
Also over the course of the winter and early spring, greens from the greenhouse beds were harvested and sold at the winter farmer’s market in Kingston, NY and seedlings produced from the greenhouse were used at the farm. The total value of both produce sold and seedlings grown was recorded.
During the summer, tours of the greenhouse were given to members of the YMCA community garden and to members of the Hudson Valley Garden Association (HVGA). I was also able to write an educational article about the greenhouse project for the HVGA newsletter. In January 2014 I am scheduled to present a workshop on this project at the winter conference for the Northeast Organic Farmers Association of New York. The workshop is featured in the Urban Agriculture Track, which is making its first appearance at the conference.
The final steps to completing this project will be to write up and publish the methods and results of the project on our own website and perhaps complete our outreach through a Cornell Cooperative Extension presentation or workshop.
Our temperature results from the different mixtures remained positive throughout the winter and spring, although in the dead of winter the compost temperatures peaked at 115-120 degrees Fahrenheit instead of the 125-130 measured earlier in the winter. Bays that were filled after mid-February returned to the higher max temperatures. In all, each of the six bays were filled twice, with seedling production beginning in March. Although we did have several nights when the air temperature in the greenhouse dipped below freezing, these were mostly when only frost hardy plants were in the greenhouse. Seedlings in the greenhouse were protected from frosty nights by a layer of floating row cover in the early part of the spring.
Carbon dioxide and ammonia measurements from the other mixtures still showed very low to negligible ammonia production while remaining in the “ideal active” “ideal curing” range. These results as well as the results from the mature compost test will be discussed with Teresa from CCE.
Physical health of the winter crops remained quite good, except for the last two crops sown in November, which were sickly and never reached market size. All seedlings did well in the greenhouse and were able to be used at the farm. While the value of the winter crops sold was not very high at about $150 total, the gross retail value of the seedlings grown as a cost savings is significant at about $1300 (assuming a $0.50 average retail price per seedling). Also, the seedling value does not take into account the seedlings that were grown by community gardeners in the shared two bays. The extra space could have been used to grow seedlings for sale as an added market.
Unfortunately, throughout the season we were battling vandalism at the greenhouse which may have resulted in lower than expected air temperatures due to holes in the greenhouse plastic. As mentioned earlier, we are exploring covering options and new locations to prevent future damage.
It seems that this project has been a good start to creating a functioning urban compost heated greenhouse. We have found that the seedling production part of the greenhouse might be a valuable area to explore further and that extra care should be taken in the placement of the greenhouse to account for not only sun and wind exposure, but also exposure to damage from the human elements. To bolster winter crop production, perhaps the effect of a bigger greenhouse or one where the compost is piled in a trench below ground level (so more surface area can be dedicated to beds) could be explored.
Impacts and Contributions/Outcomes
Cornell Cooperative Extension
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