Testing the Compost-Heated Greenhouse in an Urban Setting

Testing the Compost-Heated Greenhouse in an Urban Setting

Summary

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. At this point in the project we are in the middle of maintaining compost bins and growing winter produce. We have built the compost bays, added our first combination of materials, created planting beds on top of the compost and seeded or transplanted leafy vegetables such as mesclun, chard and spinach. We are currently monitoring the compost, soil and ambient greenhouse temperatures as well as the carbon dioxide and ammonia levels in the compost. In early January we will begin to transition to our second combination of materials. Our other remaining tasks are to grow seedlings for outdoor production, switch over to the third combination, analyze the finished compost, finish monitoring and analyze the data and do outreach.

Accomplishments/Milestones

So far results have been positive. Compost temperatures for a mixture of 1 to 1 by volume, coffee grounds to chipped yard waste, have maxed out at 125-130 degrees Fahrenheit for a period of approximately six weeks. Soil temperatures near the top of the bed have peaked at 80 degrees, and have remained above 40 as the compost cools down. Greenhouse air temperatures have remained above freezing at night, at approximately 10-12 degrees above outside temperatures. As of late December we have yet to fall below 20 degrees outside at night, but we will be experiencing very cold nights, in the single digits, next week. Carbon dioxide levels have been consistent with active compost, but ammonia levels have been negligible, indicating a too high carbon to nitrogen level in this mixture. Plants grown in the beds on top of the compost mixture have been healthy with the exception of arugula, which was sickly and looked somewhat diseased. This may have been due to older seed that we were using, we will try again when new seed arrives. The chard and mesclun have especially thrived. The first harvest was donated, but we are expecting to sell a single harvest from three beds, 48 sq. ft., at a gross income of $52.00 Our greenhouse has suffered ongoing damage from vandalism and is therefore not as insulated as we would like. In addition, one of my monitoring tools, the data logger for air temperatures, was stolen in November causing a gap in the monitoring. Once I have data from another compost mixture, I will have a better sense of how my project is addressing the problem. The vandalism mentioned above may add another dimension to creating a successful compost-heated urban greenhouse. South Pine Street City Farm will be entering its third year of production in 2013. With the addition of the greenhouse, we are hoping to grow more vegetables than ever before for the main season as well as develop a growing plan for the winter months of next year. By the end of next year, the greenhouse may expand and will be shared with another urban farm starting up in the same location as the greenhouse. Over the late summer and fall I was 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. 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.

Collaborators: