Nutrient Recycling in Urban Agriculture

Nutrient Recycling in Urban Agriculture

Summary

The Re-Vision Urban Agriculture Project is using SARE funds to demonstrate 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 biofiltration 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 will be evaluated at Re-Vision Urban Farm and at additional sites that will be added during the three-year project period.

Objectives/Performance Targets

• Compost heating systems will be operational at Re-Vision Urban Farm and at five other sites in Massachusetts during the three-year period.

  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 two to four other sites will come on line by the end of the project period.

  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.

  Extension and technical assistance will be provided to other groups and individuals through workshops, site visits and a project web site.

Accomplishments/Milestones

1. Compost heat systems are in the design or operation stage at four sites, with another greenhouse system planned for 2004. Bruce Fulford, of City Soil and Greenhouse, has been working with Re-Vision Urban Farm to manage the compost system on site and to monitor heat and CO2 output in the greenhouse growing beds.

   During the winter of 2003 organic materials (120 cubic yards of leaves blended with bedding and manure from the Franklin Park stables) were brought on site to compost next to the greenhouse. Heat from this pile was transferred to the growing beds through pipes running from the center of the pile into the greenhouse, then moved by a blower through two pipes running 18 inches under the soil surface in the growing beds. To evaluate the system, we disconnected the pipes in one of the beds and monitored soil temperatures and plant production in the two side-by-side beds.

   Compost projects underway at three other sites in 2003 are described below:

   The UMass/Lowell Wormcycler greenhouse is being loaded with a blend of the university’s leaves and food waste from the dining hall for heat production, CO2 enrichment, vermicompost production, and plant propagation. UML acquired a new skid-steer loader suited for use in the 2000 square foot composting site and 700 sq. ft. greenhouse.

   VanGaurden CSA, in Dover, Massachusetts. Activities have been delayed by damage to their low-tunnel greenhouses by 60 mph winds in December. They will likely resume later this spring when early tomatoes are planted. CO2 enrichment and growth response will be the main focus of evaluation of this application.

   Seeds of Solidarity Farm in Orange, Massachusetts. A new 5,000 square foot composting pad has been prepared and is ready to receive first load of raw compostables to integrate with the greenhouse. It will be loaded in January. An infrared CO2 monitor presently on-site at SOSF will be used at the site by February.

   Integrated aquaponic production is underway at Re-Vision House, although we have not produced many fish for sale yet. Last winter our aquaculture manager, Adam Hoelper, rebuilt the system that connects the fingerling tanks (two shallow tanks holding 500, 1-3” fish each) in the second floor greenhouse to aquaponic plant production (500 basil plants growing in two floating systems) in the third floor greenhouse. This system seemed to function well–in 2003, we grew 2,500 fingerlings to 3” size (we gave away half of those) and harvested approximately 100 lbs of basil (most of which was processed into pesto).

   In the first floor greenhouse, the large 2000 gallon grow-out tank was removed and replaced with three smaller (420 gal.) tanks to accommodate 250 fish each, from fingerling size to harvest at 1 lb weight. This change allows the farm to produce smaller batches of fish at closer intervals–a better marketing strategy and a lower-risk operational scheme. Water in all three tanks circulates through a rotary drum filter and bio-filter before returning to the fish tanks. Plants (about 500) are grown on floating rafts on top of each tank.

   The internship program in the Re-Vision Urban Agriculture Project has been ongoing through the project period. In 2003, nine (two to four at a time) women from the shelter participated in the project as interns, working 20 hours per week in the agriculture and aquaculture programs. Most of these women worked from three to six months, and during that time they became proficient in many areas of fish and plant care and they gained a general understanding of the ecological processes affecting growth and system health.

   Each group of interns receives training in the compost heat and aquaponic systems and they then have monitoring duties related to both SARE projects at Re-Vision Farm. These include collecting temperature data for the compost heat system- recording daily temperatures in the compost pile and in the growing beds and doing water quality testing (measuring O2 and nutrient levels along with bioorganisms in the fish tanks, plant beds and biofilters) at various points in the aquaponic system.

   Numerous outreach activities have been undertaken by project staff and collaborators. Bruce Fulford, of City Soil and Greenhouse attended the Third Massachusetts Organic Materials Management summit coordinated by Massachusetts Department of Environmental Protection MA-DEP, BioCycle Magazine, and the Center for Ecological Technology (CET) based in Northampton, MA. At this meeting he met with a number of composters in the state who have expressed interest in using some elements of the composting greenhouse technology. Presentations on compost heating and aquaponic systems (and tours of Re-Vision Urban Farm) were made by Judy Lieberman, Re-Vision Urban Agriculture Project director, Adam Hoelper and Bruce Fulford at 3 area conferences: Growing Possibilities: Agriculture in the City, April 5th 2003 in Boston; The Community Food Security National Conference, November 1-4 in Boston; Heifer Project International’s Animal well-being, October 24-26 in Rutland MA. Adam Hoelper produced and distributed 800 Tilapia fingerlings to New Bedford Regional Vocational Technical High School for distribution to 35 regional schools as part of a classroom aquaculture program. He also provided technical assistance on two trips to the Heifer Project’s demonstration project, Overlook Farm, and provided them with 500 Tilapia fingerlings.

Impacts and Contributions/Outcomes

Only very preliminary evaluation results are available at this point due to delays in getting the systems operational and functioning properly.

Compost Heat System–We were able to collect temperature data on the compost heat system but got a late start since the compost was not brought in until February, after the coldest weather when additional heat is most valuable. The results of the preliminary data indicate significant temperature differences between the two beds (average 10° higher temperature in the bed with the compost heat pipes) and we observed differences in plant growth as well.

This first year of monitoring was incomplete for a number of reasons. The first issue was that the compost materials were not brought in until February because of equipment and weather problems. Once the system was operational, we began taking daily temperature readings from the compost pile (Temperatures ranged from 90° to 160°) and in the growing beds (60°s & 70°s in the bed with compost heat, 40°s to 50° in bed without compost heat) and observing plant responses. A ‘mesclun’ salad mix was grown for market in both beds. This mix included varieties of lettuces, brassicas, arugula, Asian greens, cress, peas and others. Because it was late in the winter growing season, the higher temperatures were not beneficial to many of these greens and we noticed that they were less leafy and quicker to bolt than the plants in the unheated bed.

We were not able to monitor the system consistently once the busier growing season was underway (March-April) so we don’t know how long the compost pile would be able to provide heat or maintain a 10° heat effect in the greenhouse soil. We also did not have a CO2 meter so we could not tell if the growth effects we observed in plants were due to heat or CO2 increases. To use the heat more effectively, we would either need to have the system running earlier in the winter when temperature gains are more beneficial to a salad crop, or modify our growing plans to produce crops that benefit from higher temperatures. In the 2004 winter growing season we are making changes in production and composting systems to more effectively manage and monitor output.

Aquaponic System–Because our aquaculture manager was new last year and had the task of redesigning and rebuilding the systems on all floors, we did not monitor nutrient levels throughout the system and therefore do not have outcome data to report at this time. Adam did develop a monitoring and evaluation plan that will be implemented this year, so we will have more hard data to analyze and report on in 2004. We also did not grow a large crop of fish to market size due to equipment problems, but these have been corrected during the past 12 months, so we should see real improvement in the coming project year.

Collaborators: