Nutrient Recycling in Urban Agriculture

Final Report for LNE02-161

Project Type: Research and Education
Funds awarded in 2002: $92,230.00
Projected End Date: 12/31/2005
Matching Non-Federal Funds: $88,949.00
Region: Northeast
State: Massachusetts
Project Leader:
Judy Lieberman
Brookwood Community Farm
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Project Information


The Re-Vision Urban Agriculture Project used SARE funds to support a project that demonstrates and evaluates two systems that recycle nutrients for enhanced, energy-efficient plant production: 1) compost heating and enrichment of soil for off-season, greenhouse production of mesclun salad mix, seedlings and other crops; 2) aquaponic plant production that links bio-filtration of fish wastes from a recirculating Tilapia system to nutrient-rich, hydroponic basil production. Both of these technologies serve growers who need to maximize production and income in limited space and who want to recycle on-farm waste products for sustainable cropping. Compost heating and enrichment systems as well as integrated aquaponic systems were utilized over 3 winter growing seasons (2003,2004,2005) at Re-Vision Urban Farm.

Our objective with the compost system was to assess the potential for expanding the practice of integrating composting with greenhouse operation, using heat and CO2 recovered from the composting process, and nutrient-rich finished compost to enhance greenhouse productivity, while fostering more environmentally sound composting methods. In addition to the project at Re-Vision Urban Farm, we worked with growers, with livestock operations, and with compost managers to implement and evaluate greenhouse and season extension systems that effectively recycle nutrients and capture composting byproducts that are usually wasted. Most of the work has been in an urban context, or associated with farms having strong links to urban residents, and has been conducted in settings selected to provide maximum educational exposure through ongoing outreach by the host organization. The projects have demonstrated that the heat and CO2 recovery from compost can be adapted to a variety of settings. A simple technology, utilizing blower-assisted air movement from composting, can raise greenhouse soil temperatures more than 10 degrees in midwinter and elevate greenhouse CO2 levels to triple those of the ambient environment. This, in turn, produces a substantial yield increase in off-season greens and early season crops of tomatoes.

Our objective with integrated aquaculture production was first to build and operate an integrated system at Re-Vision House that would produce healthy Tilapia fish and basil for market, then to collect data and evaluate this system, and ultimately, to share this information and provide technical assistance to other groups interested in starting similar projects. In the 3-story, back-porch bio-shelter, which is attached to the Re-Vision House shelter for homeless mothers and children, project staff and resident interns built and operated two types of recirculating systems. These systems processes fish waste using bio-filtration to break down ammonia (NH4) to nitrate (NO2), a form of nitrogen that can be taken up by plants. Thus, the plants provide further filtration of the water before it circulates back into the fish tanks. When this symbiotic system is balanced and running properly, the result is maximum production of plant and fish crops with minimum waste (water or nutrients), decreasing the possible negative environmental impacts of aquaculture. Fish and plant weights were monitored along with water quality and nutrient levels in different parts of the system. Fish production proved to be disappointing, but aquaponic germination and production records for basil suggest shorter germination and growing times to produce healthy plants. Outreach efforts were slowed by the challenges the project faced on-site, but the program proved to be a valuable learning tool for the internship program and the hands-on experience resulted in the production of an aquaponics guide, which will be used to train future interns and assist other start-up projects. Based on this trial period, Re-Vision Urban Farm plans to continue utilizing, evaluating and improving these systems for sustainable fish and plant production.


The Re-Vision Urban Agriculture Project grows fish and vegetable crops on an acre of remediated land and in two greenhouses in Boston. The project demonstrates sustainable, small-scale, intensive production, provides job training to homeless mothers living at the shelter and increases food security in the low-income neighborhood where the project is located. The urban farm produces a wide variety of food crops for local distribution, and specialty crops, such as mesclun salad mix, herbs and value-added products for income generation. The Urban Agriculture Project is dedicated to using and demonstrating environmentally sound agricultural practices and to raising awareness of food system and land use issues within our community.

This SARE project looks at nutrient recycling in greenhouse agriculture with a focus on production techniques that utilize decomposition of waste products to provide essential nutrients, soil heat and CO2 enrichment to plants. Both soil and hydroponic plant cultivation systems are studied during the project.

Compost linked production-
A range of experimental and operational applications linking greenhouse production and season extension with composting have been demonstrated on farms and at research and educational institutions in New England and elsewhere in the US, Canada and other parts of the world. The heat and carbon dioxide from composting manures and other organic materials is used to reduce the costs of production for greenhouse plants and improve plant productivity and health. Enclosing or covering manures as they compost prevents substantial nutrient losses that are the source of non-point and point source pollution, particularly in surface waters in agricultural communities. The compost produced from a well-managed process has been subjected to high temperatures that kill plant pathogens and weed seeds, and yields a concentrated source of balanced essential plant nutrients that requires less time to apply to fields and gardens than manure. Unlike manure, it gradually releases soluble nutrients and minimizes water pollution from leaching of nitrogen and potassium, holds phosphorus more securely, does not have a strong odors, and does not attract flies or vermin.

With SARE support we sought to implement and evaluate different systems utilizing this general technology, and to assess potential for its future application. We chose partners in the research and implementation that had mutual interests in promoting environmentally responsible urban-linked agriculture and had good public exposure and educational outreach capabilities so that results could be most effectively disseminated. Fieldwork has been conducted on sites in Boston, Lincoln and Orange and Massachusetts and in Burlington, and Enosburg Falls, Vermont. Outreach and technical assistance has been provided to interested parties from many parts of the US and Canada. We have also collaborated on research projects and feasibility studies at University of Vermont, and at Yale University’s Sustainable Food Program, and within the composting industry.

Aquaponic production-
The aquaponics system used at ReVision House Urban Farm is a simple system that can be run by educators, home gardeners, or growers alike. We were attracted to this design for two reasons. First, it is easy to understand for the women we educate through our training program at the shelter. Second, it helps with economic sustainability by providing two high-value products: tilapia and basil.

The concept is simple: fish are raised in one area and the plants in another. The waste from the fish flows into a holding area where it is treated with bacterial agents that help break it down. Then the treated waste is pumped to the plant area to be used as fertilizer for growing basil and other greens. The used water, with most of the nutrients removed, flows from the plant area back to the fish tank and the cycle begins again.

Beyond the work of building and operating the aquaculture system at Re-Vision House, the SARE grant supported outreach efforts to share information and provide technical assistance to other groups with interest in this technology. This included farm tours, a Heifer Project aquaculture workshop, participation in urban agriculture and food security conferences, site visits to 2 schools and 2 farms, and providing fish, equipment and advice to 2 start-up projects.

Performance Target:

1) Compost Heating Systems will be operational at Re-Vision Urban Farm and at 5 other sites in New England during the 3-year period.
In addition to the primary, compost linked greenhouse at Re-Vision Urban Farm, we have succeeded in establishing composting projects with season extension benefits at two sites in Massachusetts and one in Vermont. These three sites use three different compost heat/CO2 recovery systems: an aerated/turned open windrow adjacent to the greenhouse at Intervale Community Farm, for commercial production of tomatoes and mesclun; .a hot-bed used for season extension at Mass Audubon’s educational Drumlin Farm; an enclosed, static pile connected to a hoop-house at Re-Vision Urban Farm.

At Re-Vision Urban Farm, the main site, off-season, compost-linked production operational during the 3 winters of the SARE project period. During the first year (winter 2003), the compost pile was outside, next to the production hoop-house. In the second year (03/04) a greenhouse was erected to enclose the compost pile and provide additional, passively heated growing area. The compost greenhouse was then emptied and refilled with fresh, raw materials in the fall of the third year (2004), and again this past fall (2005).

We have not succeeded in meeting our target of having 5 other composting greenhouses operational in Massachusetts that can be tracked directly to this SARE project. Some of the outreach through conferences may have spawned compost greenhouses that we are unaware of, and have clearly influenced others that are in process in Vermont, Massachusetts and Connecticut. Much of the work with prospective sites where composting greenhouses seem applicable has been consumed with obtaining permission and agreement from all parties concerned with a specific agricultural operation and obtaining resources required to implement a successful project. Some are still moving forward but were not operational during the SARE project period. Other agricultural operations that expressed initial interest in the systems have experienced staff turnover and substantial modifications to their farm plans and activities, which used project time but produced no on-the ground result from the work expended. A list of these outreach efforts and the resulting compost project is included in the appendix of this report.

2) An Integrated Aquaponic System will be operational at Re-Vision House to produce fish and plants for sale through nutrient recycling/plant filtration. Aquaponic systems at 2-4 other sites will come on-line by the end of the project period.
Integrated aquaponic production continues at Re-Vision House, although we have faced endless challenges in producing fish for sale. A number of different integrated systems have been utilized during the SARE project period (2002 – 2005) and although the fish were problematic, due to a wide range of variables that are hard to control, the plants thrived in all of the systems we tested. . Basil was grown in two systems that connect the fingerling tanks (2 shallow tanks holding 500, 1-3” fish each) in the second floor greenhouse to aquaponic plant production (500 basil plants growing in organic media sitting in either shallow tubes or floating on rafts) in the third floor greenhouse. This system seemed to function well- in 2004 we grew 2,500 fingerlings to 3” size (gave away half of those) and harvested approximately 100 lbs of basil (most of which was processed into pesto). In the first floor greenhouse, from 2002 through the summer of 2004, three 420 gal. tanks, which hold 250 fish each, from fingerling size to harvest at 1 lb weight, were not connected to hydroponic systems, but did have basil plants (about 100) growing on top of the tanks on floating rafts. Water in these three tanks was circulated through a rotary drum filter and bio-filter before returning to the fish tanks. Unfortunately, we experienced major fish loss in these tanks due mostly to electrical (power going off) and mechanical (drum filter breaking down and working inconsistently) problems. If nothing else, aquaculture and aquaponics has been a huge learning experience for us and a test of our perseverance. It is an evolutionary process that hopefully will lead to a balanced, healthy and reliable aquaponic system. In the fall of 2004, the first floor systems were rebuilt to follow the design used by Growing Power in Milwaukee, Wisconsin. This more low-tech, and less energy dependent system should better reflect the needs and capacity of a grassroots project and women’s shelter such as ours, and many others who might want to duplicate this food production model. With support from Heifer Project International, and with the help of a team of volunteers, two systems were constructed, linking two of the first floor tanks to three-level, aquaponic structures. The wooden structures have biofiltration on the bottom and plants growing on the next two levels. The water from the fish tanks moves via gravity into the bio-filter (a plastic-lined trough filled with bio-balls) and is pumped from there to two levels of shallow trays where plants grow in porous pots that sit in the shallow water. The water moves through the trays and falls back into the tanks, adding oxygen to the fish water as it does. These two systems were not operational in 2005, due to problems with the heater and a lack of resources to fix it, but Re-Vision house does hope to continue with its aquaponics program in 2006.

Because of the immediate demands of so many problems in Re-Vision House’s aquaculture operation, it was not feasible or sensible to install new systems at other sites. The Aquaculture Manager at RHI did provide technical assistance to a number of organizations, who wanted to start similar aquaponic production systems; Overlook Farm, in Rutland MA- the RHF Aquaculture Manager worked with 2 staff members from Overlook to help them establish their own aquaponic operation in 2004. Re-Vision staff made 3 site visits to Overlook to give technical assistance, provided fish for 2 seasons, and gave technical support over the phone: New Bedford Technical High School- worked with existing aquaculture production program, supplying fish and technical assistance; a home schooled HS student who did an independent science project which involved volunteering at Re-Vision and setting up an aquaculture system in his basement at home.

3) Four to six women from Re-Vision House will be trained annually in aquaculture, aquaponics and greenhouse production. They will gain research skills and work experience by collecting and analyzing data from the compost and aquaponic systems and by producing and marketing crops.
Thirty-two women (an average of 9 per year) from Re-Vision House participated in agriculture and aquaculture production through the job-training internship program. These women worked in all areas of the farm, from data collection and record keeping to weeding and harvesting crops to marketing, teaching and planning. As important as the specific skills they acquired, were the general job readiness concepts they learned through the experience of working and taking responsibility for program and personal performance. In reference to the SARE project, these women, attended workshops on the science and function of both aquaculture and compost systems, and then participated in management and data collection in both systems. This meant doing daily air, soil and compost temperature readings every morning in the greenhouses, and doing water quality/nutrient sampling tests in the aquaculture and hydroponic tanks, as well as measuring plant and fish growth. Interns also learned how to enter and analyze this data to evaluate the compost and aquaponic systems. Over the 3.5-year project period, the Re-Vision Internship program gained more structure and grew stronger, so that women were generally staying in the program longer, assuming more responsibility for farm output and benefiting more from participation. RHI data from the period, 02-05 supports this trend. In 2002, out of 10 interns, only 3 were in the program more than 2 months (the program can only enroll a maximum of 4 at a time), while in 2005, there were also 10 interns, but only 1 spent less than 2 months in the program. In 2003, there were 9 women in the program, 4 of whom work less than 2 months, and in 2004, 6 of 8 resident interns stayed more than 2 months. One of the women, who started as an intern in 2002, is now a Program Assistant and Intern Supervisor. In addition to the Re-Vision resident interns, there was also one High School Intern, who worked with the Aquaculture Program and 6 college Interns who worked for a semester on the urban farm.

4) Extension and technical assistance will be provided to other groups and individuals through workshops, site visits, a website and manuals for aquaculture and compost systems.
Project staff and collaborators have undertaken numerous outreach activities. A major accomplishment for Re-Vision Urban Farm was the creation of a website ( in 2004 where we can post information about our project and network with other organizations and individuals. Products of this SARE project are Aquaculture and Compost system manuals, which are available in hard copy and also posted on the Re-Vision Farm website. The farm gave tours and workshops to many groups who visited during the past 4 years. This type of educational programming increased significantly in the last two years, as greater structure, priority and resources were shifted to this area. Since October 2003 (records not kept in this area before that), more than 85 groups (750 individuals) have visited the farm to learn about innovative urban growing and educational programming at our Dorchester site. Many of these tours focused specifically on compost linked winter greenhouse production and integrated aquaponic production. A sampling of the wide range of programs who came to the farm includes: area colleges (Tufts, BU, BC, UMASS) and Americorps groups; the annual Urban Agriculture Conference tour; K-12 students (Shady Hill School, MathWorks, City on the Hill School, Cambridge Latin School, Prospect Hill Academy, City Schools); Summer camps (Blue Hill Boys & Girls Club, Mass Audubon Nature camp, Brownie Troops); and Community Organizations (Bikes Not Bombs, New England Aquarium, Volunteers for Peace, The Food Project, Brigham and Women’s hospital Staff, Volunteer Family). A hands-on workshop, sponsored by the Heifer Project, in October 2004, built 2 new, integrated, 3-level aquaponic systems at Re-Vision House to enable participants understand aquaponic production and design in a practical, hands-on way. Project staff members also gave talks at the Community Food Security Conference, the NOFA conference, and the Nightengale Community Garden, and at other community organizations. We also exchanged ideas with interested individuals through e-mails, list-serves and the web.

Project consultant Bruce Fulford has presented information regarding the SARE supported compost greenhouse work at BioCycle conferences in Portland, Maine, and in Burlington, Vermont, at two NOFA summer conferences in Amherst, MA and two winter conferences in Barre, Massachusetts, at the Food Project Urban Agriculture Symposium in Boston, and at MIT’s Sustainable Development Forum held each fall at the Massachusetts Institute of Technology in Cambridge, MA. He also presented information about this technology and practice in a Manure Management workshop at the 2005 Annual Meeting of the Massachusetts Farm Bureau in Peabody, MA. The Re-Vision Urban Farm and the compost heated/enriched greenhouse were featured on a series of tours of key agricultural destinations in Boston by hundreds of attendees to the 2004 and 2005 Urban Agricultural Symposium hosted by the Food Project. The Symposium is attended by organic growers, policy makers, urban ecology professionals, students and aspiring agriculturists, predominantly from the northeastern US and Canada. A slide presentation and workshop was presented by Bruce Fulford that highlighted the compost greenhouse system at ReVision House, and Mr. Fulford hosted the portion of the tour that focused on the role and technical details of the greenhouses and the compost in ReVisions Urban Farm program. An article is forthcoming in BioCycle, Journal of Composting & Organics Recycling, in early 2006 that will feature the ReVision compost greenhouse and related compost heat and CO2 recovery developments directly resulting from or indirectly influenced by this grant.


Click linked name(s) to expand
  • Bruce Fulford
  • Adam Hoelper
  • Keith Wilda


Materials and methods:

Since the project included two different integrated systems- Compost heat/CO2 linked winter greenhouse production, recirculating fish and hydroponic plant production, we will describe activities in each separately, beginning with the composting project at Re-Vision House and other sites. The project was designed to build and test low-tech systems over the 3.5-year (3 winter growing seasons) period. The Re-Vision compost growing system consists of two, side-by-side plastic hoop houses (as mentioned earlier, during the first winter, the compost pile was not enclosed). In one, a large pile of leaves and animal waste takes up most of the space. In the other, 2 raised, rectangular growing beds occupy most of the floor space and are used to grow salad greens during the winter. In each of the beds, 2 perforated pipes run lengthwise, 1 foot beneath the surface. Another pipe runs from the middle of the compost pile in the first greenhouse, into the second greenhouse, where a blower pushes the hot, CO2 enriched air up through the 2 growing beds via the 4 underground, perforated pipes. To test the impact of this system, the pipes under one of the growing beds were disconnected and daily soil temperatures were monitored in each bed over the winter season. Each year, Re-Vision Interns attend a workshop after the greenhouse is filled with compost materials and the system is functional, to learn about the biological process and gain an understanding of the mechanics of composting and heat/CO2 transfer. They are also trained to collect and record the temperature data. Temperatures were taken every morning in 4 spots in the compost pile and 3 locations along the length of each of the two growing beds (one with compost heat under the soil and one without). Outside and inside air temperatures were also recorded, along with the max and min temperature for the day. The women record the temperature readings on a clipboard and these readings are later entered into the computer and analyzed. In addition, spinach and other cold-weather leaf crops are cultivated directly on the compost pile making it possible to extend the growing season in an unheated greenhouse. Yield data was also collected from both greenhouses. Additional sites with somewhat different designs were added in the second and third years. Some monitoring of system performance and production took place at these other sites.

We had intended to conduct CO2 monitoring program at the ReVision House greenhouse and other sites, using a Horiba APBA200e infrared CO2 analyzer that had been acquired from a previous greenhouse monitoring project. The unit was not working when we received it, and required substantial effort, and repeated contact with the manufacturer to recondition. In May 2005, the CO2 monitor was taken to Vermont to be used in conjunction with a data logger on loan from the Institute for Sustainable Agriculture which was to be used to track temperatures in the compost and the greenhouse air, outside air and soil profile at Intervale Community Farm. Our efforts to connect the unit to a data logger proved unsuccessful. The unit had not been fully functional, reliable and calibrated following installation, but was left in the greenhouse to provide visual metering and manual recording opportunities. Another CO2 analyzer (Intec 310-ERL) was purchased to connect to the data logger, but this also turned out to be unreliable, and the end result was that we were unable to measure CO2 output from any of the systems. Visual meter readings of greenhouse CO2 concentrations were observed by the technician shortly following the installation of the blowers and slotted pipe in the soil, and appeared to indicate unequal distribution of CO2 in the greenhouse. CO2 concentrations measured highest (1700 ppm) in the air above the soil bed closest to the blower, when the blower was on. These disparities in CO2 distribution are likely to be remedied by adding another blower, placed at the opposite end of the high tunnel greenhouse to increase airflow through the soil matrix.

Aquaculture and hydroponic plant production at Re-Vision House was set up to be a demonstration model for teaching and production to generate income for the program. The aquaculture system is located in a 3-story greenhouse built on the back porches of the homeless women’s shelter. On the first floor, 3 round tanks, holding 500 fish each, were connected to a stock tank, used as a solid separator, and then a bio-filtration tank, which was filled with bio-balls (small, plastic, perforated balls with lots of surface area for nitrogen degrading bacteria to live on). The water circulates through these tanks and back into the fish tanks in a closed loop. Basil plants grow on floating, Styrofoam rafts on the surface of the fish tanks. On the second and third floors of the bio-shelter is a connected system for fish and hydroponic plant production. Fingerlings are raised in two shallow tubs until they reach sufficient size to be transferred to the larger tanks downstairs. From these tanks, water flows into a UV filter and is then pumped up to the third floor, where it runs through pvc pipes that contain soil-less plugs in which basil plants are grown. The water then flows back down to the second floor fish tanks and the cycle repeats. The system was monitored through water sampling from the fish tanks and production was tracked by recording weights of fish and plants. Being a small, community based organization, Re-Vision House did not have the capacity to conduct scientific research on the biological process of biofiltration or nutrient cycles of accumulation and decomposition. We were only able to sample the water in the fish tanks, so it gave us an indication of the water quality, reflecting how effective the filtration was, but it didn’t capture the location or effectiveness of microbes in breaking down ammonia, amounts of nitrite or nitrate in the hydroponic system, or plant up-take of these nutrients. We could monitor some of that indirectly through observations and weights of plants and fish, but it would have been interesting to measure levels of NO4, NO3 and NO2 at different points in the system to get a better idea of microbial and plant activity. Through workshops, the women in the internship program learned about the circulation of the water through fish, biofilter and plant tanks and the nutrient cycle that coincided with this movement. As part of their job, they did water sampling and weighed fish and plants at regular intervals. The data they collected was difficult to interpret due to on-going mechanical failures and repeated problems in the system. The project was designed to have staff and interns assist other groups to build and operate similar aquaponic systems, and then to help those groups monitor nutrient levels and production in their systems to compare with Re-Vision House data. Because farm staff needed to focus so much time and attention on trouble shooting at home, we didn’t get as far as envisioned at other sites.

Research results and discussion:

Compost linked greenhouse production- Our work confirmed that there is a niche for compost linked greenhouse production systems. Operations at Re-Vision urban Farm and other sites demonstrated that these systems can have a positive effect in off-season, greenhouse production by extending the growing season and increasing yields of cool weather crops with minimal heating costs. At Re-Vision Urban farm, where a compost heat system was utilized during the 3 winters of the SARE project, we attempted to measure its effectiveness in raising soil temperature in the growing beds where salad greens were cultivated for market. We were unable to measure CO2 output from the compost pile and related growth effects, but speculate that this was occurring and may have played a role in plant growth. Temperature data was collected for the compost heating system at Re-Vision House for two months or more from the date the composting began each winter, 2003 to 2005 (data sheets are attached to the hard copy). The start date varied somewhat from year to year, depending on various factors which impact getting new materials onto the site, ranging from January 1, in 2005, back to mid-February, in 2003 and 2004. Generally, we found that the compost pile maintained a temperature (taken at 3’ below the top surface) above 100 degrees for about two months. However, in 2005, when composting started earlier in the winter and occurred during very cold temperatures, heat production seemed to drop off much more quickly. Data from the winter of 2004, the first year the compost pile was covered by the greenhouse, shows temperatures of 130 degrees inside the compost pile 1 week after materials were loaded. One month later, the hotter part of the pile (front section) was still between 100 and 120 degrees, while back sections (which were exposed to colder, outside air, due to lack of end wall plastic) were about 90 degrees. At 8 weeks, the pile was still heating to above 100 degrees in some sections, but cooler areas were between 70 and 80 degrees. This fluctuation demonstrates the effectiveness of the plastic structure in minimizing heat loss and maintaining active decomposition inside the pile. Last winter (2005), raw materials for composting were loaded before the first of the year and temperatures were tracked from January 9 through March 16. Again, temperatures readings were taken from different areas of the pile, but with the greenhouse better sealed, readings were highest in the middle sections, ranging from 116 -126 degrees. One month later, in early February, readings had dropped below 100 degrees, ranging from 66 to 92 degrees. By March 9, compost temperatures were between 61 and 78 degrees. There are many factors that contribute to the length and intensity of composting to produce and capture heat. Some of these factors, which were observed at Re-Vision House, include: the content and mix of raw materials- in 2005, we used a mix of leaves and manure that was already partially composted, resulting in a shorter period of active decomposition, but a very nice finished product; physical characteristics of the compost pile, such as moisture, compaction, aeration from blower and external sources, and air temperature.

In the growing beds of the hoop-house, the same tends were reflected in soil temperature readings. In all three years that the compost heat system was active, there was a significant effect in soil heat due to air input from composting. Data from the 3 years shows an 8 to 10 degree difference in soil temperature in the root zone (4-6 inches below the surface) of the growing plants, between the two beds (one connected to the compost pile, and one independent of it). During the winter growing period, when the compost system was running, the air in the greenhouse was minimally heated to maintain temperatures above freezing. Warm air from inside the compost pile was moved through pipes to a blower, which pushed it up into the growing beds, under the soil. Soil temperatures averaged 46-50 degrees in the control bed and 58-60 degrees in the bed connected to the compost pile at the start of the compost period in each of the 3 years. This increase, in turn, resulted in faster germination and growth of the salad greens planted in these beds, and faster regrowth after cutting. The increase soil temperature effect does diminish over time and distance. Readings from sections of the bed closer to the blower are higher and temperatures decrease as you move further away (66, 64, 60 degrees in the bed connected to the compost). In the control bed, temperatures are relatively consistent along the length of the bed (54, 55, 54 degrees). The impact on soil temperatures was most pronounced in the first month of composting, correlating to temperatures inside the compost pile. In 2004, when temperatures were maintained above 100 degrees two months, soil temperatures were raised 8 to 12 degrees for almost as long. By the end of April, 2 months later, the difference in temperature was a 2-4 degree increase. In 2005, the heating period was shorter. In the beginning of January, when monitoring began, composting raised soil temperatures from 49 to 61 degrees. At the beginning of February, that difference was about 6 degrees (from 50 to 56 degrees), and by the beginning of March we were recording a 2-4 degree difference in soil temperatures. At about that time (early March) the blower stopped working, so we could not run or monitor the system for the remainder of that growing season. Comparative harvest data was not kept for the two growing beds, so it is not possible to quantify differences in production linked to the compost system. Farm staff did observe faster germination and grow back between cuttings in the compost-heated bed. An average of two hundred pounds of salad mix is harvested annually (3 month winter growing season) from the two growing beds (approximately 500 square feet of growing space). An added benefit of this system is the additional heated growing space provided by the compost greenhouse. Last winter, Re-Vision Urban Farm grew 66.5 pounds of head lettuce and 33 pounds of spinach on top of the compost pile in March and April. The compost pile is also used for seedlings before they can be transplanted outside in the spring.

At Intervale Community Farm, a 30-acre mixed vegetable farm in Burlington, VT, that trialed compost enhancement of early-season tomatoes in unheated greenhouses last May, improved performance was observed. The grower reported significantly higher yields and overall plant growth, bearing further investigation. Because they transplanted the tomatoes in May, when the need for heat is less, it is unclear whether the improved performance was due more to the early season root-zone heating, or to the supplemental CO2. Temperature data did not show an impact on soil heat and CO2 could not be measured. . In any event, the grower feels that the results warrant more attention and he is interested in looking at the potential for low levels of heat through the winter to improve the performance of our winter salad greens.

At Seeds of Solidarity Farm, a 30-acre organic farm that cultivates close to 3 acres of vegetables, cut flowers, and garlic, a similar system was planned, but was not operational during the growing period. Owners, Deb Habib and Rick Baruc have 6,000 square feet of greenhouse dedicated primarily to greens grown under contract with a local restaurant. The farm sought to improve their farm operation with a new composting/greenhouse system that would perform better and make best use of the compost imported to the farm. We decided that the best compost heating system would be a large windrow located within 20 feet of one of the greenhouses. A composting system was established that captures the maximum value of organic byproducts from a nearby dairy farm, which combined manure with bedding and uneaten hay and with clean leaves dumped at the dairy farm by a local landscaper. These ingredients were bucket-blended with a 3 cubic yard articulating loader, and 150 cubic yards of these self-heating materials were then trucked 4 miles to Seeds of Solidarity Farm in eight loads over three days using a 10 wheel dump truck. Another local equipment operator was hired to form the windrow on top of a matrix of 180 lineal feet of slotted HDPE plastic drainage pipe. The delivery of the composting manure and leaves and the formation of the windrow was completed in mid-April 2005. The compost heated well, reaching in excess of 140 degrees F within three days of delivery to the site and maintaining thermophilic temperatures (in excess of 105 degrees F) until late May. We had planned to connect the compost to the greenhouse using an insulated 8” PVC plastic sewer pipe buried in a boxed trench set under a 12’ wide farm road that separates the greenhouses from the composting pad. However the pipe was not installed under the frozen road as had been planned due to the record setting snowfalls, which came early, and frozen ground. We will connect the variable speed 8” Fantech in- line blower to a 8” PVC plastic compost exhaust feeder pipe that runs under the road and mount it in an insulated box inside the greenhouse. The fan will draw air down through the compost, collecting warmed water vapor in the air stream in 4” that is then ducted it into a 6” PVC header pipe that tees into 4” slotted drainage pipe buried 6” under the surface of the growing beds. The distribution pipe in the growing beds has already been installed. All of the components for the system are on site and will be activated this winter or early spring, 2006. The farm has forged a strong relationship with the Hunt family and anticipates working closely with them to obtain the same blend of leaves, manure and bedding that was delivered in April. The finished compost from the April ‘05 compost is expected to total approximately 40 cubic yards and will be used on the fields and in the greenhouses in the 2006 growing season. Fall 2005 leaves have again been collected from a reliable landscaper at the Hunt farm to mix with manure and will be delivered in blended form to the site this winter.

ReVision House cooperatively operates a CSA program with Drumlin Farm that has provided fresh, organic produce to urban households since 2001. Drumlin Farm is an educational farm, run by Mass Audubon, that strives to exhibit sustainable methods of agriculture. The Drumlin Farm Compost Greenhouse project had a four-year evolutionary process, beginning in 2001 (pre-SARE funding). The farm was interested in a composting greenhouse primarily for spring seedling production. Their existing 17 x 20’ gothic arch double poly greenhouse was too small, was heated by propane, and Drumlin Farm had plans and funding to build a new greenhouse. The composting system would address persistent manure management issues associated with the livestock at the highly public educational farm. In April 2005 a 10 cubic yard compost pile was created from stockpiled cow, horse, sheep and goat manure and bedding, mixed with spoiled hay and formed into a loaf-like shape. It was dubbed ‘the Big Loaf’, and became a central part of the educational exhibit in the garden. The ‘Big Loaf’ was used as a hotbed, providing bottom heat for seedlings that had been germinated in the greenhouse. Immediately following construction of the pile, the compost temperatures quickly climbed and peaked around 160 degrees F. A 2” layer of finished compost and soil on top of the fresh compost acted as a filter for ammonia driven off from the manure and bedding as it heated up. Seedlings in flats were placed on pallets that rested on top of the compost. Plastic and spun polyester row covers were used over the seedlings on cold nights to protect from frost After the seedlings were removed and planted in the garden and fields, the ‘Loaf” was planted to cucumbers and pumpkins that trailed over the sides. By June the compost pile had shrunk to about 3’ high and served as raised growing bed, and provided substantially greater total square footage available for fruiting vines because the growing surface included the elevated top plus four sides. The usable surface area in this cropping scenario is roughly double of the square footage using two-dimensional cropping in the ground. The ‘Big Loaf’ has finished composting, with assistance from E. Foetida ‘red wiggler’ worms that have colonized the compost and enhanced the process and compost product. The compost has been spread on the demonstration gardens at the center of the farm. Plans for next year are to reconstruct the compost pile, install more permanent signage, and operate the compost as a season extension technology. We are considering integrating some of the heating and CO2 attributes of the compost with the greenhouse and will be in discussion with Drumlin Farm over the winter 2006.

Aquaculture– Impacts of the aquaculture project are difficult to summarize and outcomes are not easily quantitative because our experience has been so problematic over the past three and a half years. While building and maintaining the system, and caring for fish and plants, has been a valuable educational experience for our interns and the local community, on-going mechanical and personnel problems have led to fish loss, resulting in an operation that incurs huge costs rather than contributing to income generation. Although Re-Vision interns spent a lot of time collecting data on water quality, fish and plant growth, the data is not meaningful in light of overwhelming impacts from factors, which could not be controlled. During the period, from 2002 through 2005, water quality was generally in the acceptable range and fish gained weight well, but periodically, some event would affect the system, causing fish mortality. These events included power failures, over-feeding, heaters malfunctioning, air blowers failing, poor water quality- high levels of ammonia/low oxygen (due to some of the factors already mentioned or problems with filtration), and others. Regardless of these issues, which negatively impact the fish, plant production was successful- Re-Vision House harvested many pounds of beautiful basil plants from the hydroponic pvc tubes on the third floor of the back-porch greenhouse, above the 2nd floor fish tanks. Germination records show that basil seeds sprouted 4-7 days faster in the warm water than in soil and that days to harvest were fewer. The plants were much less sensitive to water quality issues and other problems in the system, and seemed to have a ready, high-value market. Re-Vision House also used the basil in the production of pesto, a popular value-added product. Despite all the setbacks, the aquaculture project is going forward, with a new, low-tech, integrated system. The Aquaculture program at Re-Vision House has generated a lot of interest in the local community and beyond, and the staff is still optimistic that they will be able to grow fish and plants successfully, on-site in the future, while expanding educational programs and outreach connected to aquaculture.

Participation Summary


Educational approach:

The SARE project produced practical manuals on aquaculture and compost linked season extension, based on the systems at Re-Vision Urban Farm, which will be printed and posted on the web. Outreach efforts of Re-Vision Farm staff include on-site tours and workshops to provide educational programming that highlights these systems. Visits to other sites facilitated an exchange where staff and interns could learn from or provide assistance to farmers, schools or other groups.

The ReVision Urban Farm and the compost heated/enriched greenhouse were featured on a series of tours of key agricultural destinations in Boston by hundreds of attendees to the 2004 and 2005 Urban Agricultural Symposium hosted by the Food Project. Organic growers, policy makers, urban ecology professionals, students and aspiring agriculturists, predominantly from the northeastern US and Canada, attend the Symposium. A slide presentation and workshop was presented by Bruce Fulford that highlighted the compost greenhouse system at ReVision House. The compost heated/enriched greenhouse and posted signage developed during the SARE grant are viewed by visitors to the ReVision Urban Farm which are estimated to number more than 500 annually.

Project consultant Bruce Fulford has presented information regarding the SARE supported compost greenhouse work at BioCycle conferences in Portland, Maine, and in Burlington, Vermont, at two NOFA summer conferences in Amherst, MA and two winter conferences in Barre, Massachusetts, at the Food Project Urban Agriculture Symposium in Boston, and at MIT’s Sustainable Development Forum held each fall at the Massachusetts Institute of Technology in Cambridge, MA. He also presented information about this technology and practice in Manure Management workshop at the 2005 Annual Meeting of the Massachusetts Farm Bureau in Peabody, MA. An article is forthcoming in BioCycle, Journal of Composting & Organics Recycling, in early 2006, which will feature the Re-Vision compost greenhouse and related compost heat and CO2 recovery developments directly resulting from or indirectly influenced by this grant.

Additional Project Outcomes

Project outcomes:

Impacts of Results/Outcomes

Our project has increased the body of knowledge and experience in the recovery of biothermal energy and CO2 from compost. We have a greater understanding of the potential applications and limitations of the settings in which this practice is practical. We have demonstrated that these systems can be built with low cost components and operated with minimal input of labor, resources or technology. The employment of modestly sized blowers can largely replace the need for turning windrows in some settings, which decreases the reliance on burned fuels for powering equipment used in turning compost to achieve effective decomposition. The aeration systems used in two farm settings functioned reliably and

We did not directly participate in projects with as many greenhouse growers, farmers and composters as we anticipated. We devoted most of our resources to fewer on-the-ground projects, and encountered challenges in implementing and operating them that required greater attention and commitments of time than originally planned. We were able to establish and test three different systems for composting and heat/CO2 recovery at high profile farm sites in New England, all focused on increasing community food supply, sustainable farming practices, and forging links with urban agriculture. Each of the farm projects presented challenges that were addressed with varying degrees of success.

Course corrections taken during the project were related to lowering target numbers to reflect difficulties in implementing compost and aquaculture linked production projects at other sites during the relatively short time frame. We instead focused on operating, evaluating and improving the two systems, on-site at Re-Vision Urban Farm, and focused outreach on providing assistance through information and education to a wide range of individuals and groups who are considering using similar systems in the future.

Lessons learned- The logistics of materials handling are the greatest factor influencing the practicality of adopting this general approach to greenhouse heating: Where convenient and where supplies of manure and other readily compostable materials are plentiful, and equipment suited to mixing and forming organic materials into compost piles or loading contained systems- this approach may be worth considering. Where these factors are not in place, this approach is unlikely to be sustainable except on a very modest scale. The approach is probably most suited to adoption in situations where existing composting operations are already established, and the costs of adapting some or all of the composting process to integrated heat and/or CO2 recovery is a relatively inexpensive add-on and benefit. In such settings, the greenhouse grower may not be the same entity as the composter, which can further limit, but can also build or reinforce, synergistic relationships between organic waste generators composters and growers. This model was most clearly highlighted in the Intervale Project, where an established composter (Intervale Compost) supplied the raw materials, the heavy equipment and skilled operator to form and turn the compost windrow used to heat and enrich a commercial greenhouse used to grow tomatoes and mesclun, adjacent to the composting operation, but operated by a separate community-based farm.

On the aquaculture side, our experience taught us that fish production which is dependent on high tech inputs, costly components or advanced expertise may not be successful or economically sustainable for small farms or community organizations. Therefore, we are modifying our system so it will be simpler to operate, and less likely to fail. If we are able to produce fish and plants consistently and reliably at Re-Vision House, we will then be in a position to provide technical assistance to other farms or programs interested in aquaponic production. We have produced an educational manual that provides practical information to our interns, students and others interested in aquaculture. Though we suffered many setbacks, we plan to move forward with the work begun through the SARE grant.

Economic Analysis


The goal of both of these systems, compost linked season extension and aquaponic production of plants and fish, is to increase production through nutrient recycling, lowering input costs while maximizing year-round harvest outputs. With rising energy costs and a growing market for locally grown food, both technologies represent potential gains in farm profitability, though it is unclear if that has been demonstrated in these few, limited, small-scale projects. Fossil fuel energy prices are unknown but unlikely to drop significantly in the future. The costs of heating greenhouses are likely to increase sharply during the winter of 2005/2006, especially for those operations reliant on natural gas/propane that is favored by many growers. Increased energy costs are forcing many growers reasons to investigate alternative fuel supplies and heating systems, as well as re-evaluate cropping and marketing strategies. The ReVision Farm greenhouses would rely on natural gas for all non-solar heating if there were no biothermal heat source. The gas heating cost of production of winter and spring 2006 crops would likely push the total cost of production to exceed the market value of food crops that could be grown in the greenhouse and marketed locally. The greenhouse continues to be used through the summer months, and has been supplied with supplemental CO2 from the ongoing decomposition of the adjacent compost even after it has cooled considerably. Re-Vision Urban Farm and other participating farmers felt that the projects were beneficial to farm production and sustainability. At the Intervale Community Farm, grower Andy Jones noted a roughly 20% greater tomato crop yield in the greenhouse enriched with compost CO2 in contrast to the adjacent control greenhouse, which was constructed and cropped almost identically. Grower assistant and grad student Zak Adams, was instrumental during the setup and monitoring program and has taken an active interest in developing a dynamic computer model of the compost greenhouse system. His focused interest in quantification of the benefits of linked greenhouse and composting systems should help advance the use of this system in appropriate settings.

Aquaponic production contributes to greater production and stability by nourishing two different crops, plants and fish, for market. Many growers who operate such systems find that the plants they grow are more profitable than the fish that are harvested, and the symbiotic relationship of this ecosystem, theoretically, would keep inputs and costs down. Some producers feed the fish excess plant materials, minimizing feed purchases, while fish waste eliminates the need for fertilizers. Yet, the experience at Re-Vision was not that positive. Equipment failure and system problems raised costs, while fish mortality lowered yields and income. Re-Vision House is continuing the aquaculture program with the goal of developing a balanced system that is productive and reliable. Even in its dysfunctional state the aquaculture program has served as a valuable education tool for the internship program, for students and for community members. Despite the hard reality, our aquaculture endeavor is very popular with visitors to the farm is well known in our area and beyond. The urban farm was able to provide fish and assistance to another farm, a couple school programs and a community group. Overlook Farm has been successful with its new aquaponic project, and a couple other sites, connected through outreach activities, plan to start up small-scale projects.

Farmer Adoption

Environmental stewardship and community building

The Urban Farm at Re-Vision House has been enormously beneficial to the surrounding community. The process of changing vacant lots into productive gardens has transformed the neighborhood, from a place people sought to avoid to a place people seek out. Residents now know each other and take pride in their street. They visit the garden, enjoy the produce that comes out of it and exchange garden experiences/wisdom. The activity at Re-Vision House has spilled over to local involvement with other open spaces nearby. The farm hopes to demonstrate intensive, urban agriculture that is environmentally sound. Recirculating aquaculture systems minimize water and solids discharged into the environment. At Re-Vision House, water is added to the system to replace what is lost through evaporation and plant up-take. When water changes are done, the discharged water is used to irrigate outside gardens. Solid wastes are composted with the other organic materials from cropping, as are dead fish. The small-scale compost heat project provides an opportunity to recycle some of the leaves, landscape waste and animal manure from nearby Franklin Park and the Zoo through well managed composting and create high-quality compost for the farm and local gardeners. Initially, neighbors on the street were concerned about the composting so close to houses, but there have been no complaints and some use the compost on their own back-yard gardens.

Larger composting sites are increasingly the source of detrimental community impacts- most notably odors, noise from turning equipment, and airborne particulates. The approach demonstrated at the Intervale Community Farm using a small portion of Intervale Compost’s organic waste stream illustrates a method of composting that reduces fossil fuel use per ton of finished compost, captures the most nitrogen-rich and malodorous off-gases released during composting in the soil biofilter, and utilizes heat and CO2 that are normally waste byproducts of the composting process. The large-scale (approximately 30,000 tons per year) operation at Intervale Compost has struggled with operational issues – largely related to excessive moisture that may in part be improved by the adoption of different composting practices and technology. The heat released during the winter from the Intervale compost operation is roughly estimated at 10,000,000,000 BTU. If a portion of this were captured in a system that accelerated moisture removal there would be significant benefits to the composting operation, and the heat and CO2 could be used to increase the viability of the greenhouses at the Intervale, and reduce or eliminate reliance on fossil fuel sources for their heating. We hope that some of the benefits demonstrated in the Intervale Community Farm greenhouse application influence an in-depth investigation by the Intervale Compost Co. into alternative composting scenarios to the present system.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study


Based on our experiences with this project during the grant period we plan to continue to operate and monitor compost linked growing and aquaponic systems at Re-Vision House. We need to collect more data on temperature and CO2 enrichment from the compost system, along with measuring more specific growth and yield effects, so we can evaluate and adjust the system. We are also looking into ways to generate income from the compost at the end of the season to cover the cost of materials handling keep project running sustainably beyond the end of the grant. Aquaculture at Re-Vision is temporarily on hold, while we wait for heater repairs, but we hope to have the new, first floor systems up and running this winter. These will need to be monitored closely to assess performance and to ensure healthy fish and plants. Data similar to the items that were collected from the old system (water quality, growth rates, plant and fish weights) will be collected and analyzed again. It would be interesting to research the breakdown and up-take process of nitrogen in the system by measuring levels of microbes and the various forms of nitrogen throughout the system, but that is beyond the scope of this project or the capacity of our organization.

ReVision Farm’s planned expansion calls for a ¾ acre greenhouse and the program’s aquaculture, greenhouse and field crop activities will annually generate hundreds of tons of crop residue and other organic waste that will need to be composted and reused on site. The greenhouse, field cropping and landscape will need copious supplies of compost to maintain high productivity. Based on the encouraging results of our work with ReVision’s existing compost-greenhouse we plan to invest in a more sophisticated enclosed composting system and employ upgraded versions of air handling, heat and CO2 recovery features similar to those we have successfully used thus far.

The past three years of research under this grant has highlighted the need for a greater degree of quantification of the thermal recovery using different systems, CO2 dynamics and comparative crop responses in more controlled settings than we established during our project. Replicated side-by-side comparisons using more sophisticated monitoring protocols should be performed on integrated compost –greenhouse systems and control greenhouses. Systems optimizing CO2 concentrations and heat recovery need to be installed and fine tuned, since CO2 output from compost relative to crop demand in wintertime greenhouse environments outpaces compost heat production relative to heat demand for most crop scenarios.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.