Bioenergy and Biofertilizer for Small-Farm Enterprises

2010 Annual Report for GS09-087

Project Type: Graduate Student
Funds awarded in 2009: $10,000.00
Projected End Date: 12/31/2012
Grant Recipient: University of Florida-IFAS
Region: Southern
State: Florida
Graduate Student:
Major Professor:
Dr. Ann C. Wilkie
University of Florida-IFAS

Bioenergy and Biofertilizer for Small-Farm Enterprises


Sustainable agriculture is reliant on both recovering nutrients and capturing renewable energy. Through biodigestion, small farmers can produce both biogas energy and organic fertilizer from on-farm waste products. Investigations have been undertaken to determine the bioenergy potential from biodigestion of organic wastes, with particular attention to food waste, biodiesel production by-products, and other on-farm wastes. We are constructing a low-cost biodigester design that can be easily implemented on small farms. As a pilot farm-scale biodigester, this will be the centerpiece of the project. Public demonstrations have been conducted to spread awareness of biodigestion for small farms. We have created a website for posting project information at:

Objectives/Performance Targets

The purpose of this project is to study the potential application of bioenergy and biofertilizer production on small farms. Specific objectives include:

1. Determine biogas potential of various organic waste produced by small farms.

2. Demonstrate effective methods of biogas clean-up and storage.

3. Demonstrate a functioning biogas reactor and storage system to the small-farming community.


Objective 1

Several experiments have been conducted to determine the methane potential and digestibility of food waste. These experiments indicated that food waste is both a readily-digestible feedstock (>90% degradability) and has a significant methane production potential, as high as 120 L of methane per kg (wet weight) of food waste. Additionally, food waste was analyzed for total nitrogen and total phosphorous content. On a dry weight basis, food waste was approximately 3% nitrogen and 0.5% phosphorous on average. Because nutrients are conserved through anaerobic digestion, the nutrients in food waste and other organic wastes are captured in the digester effluent (biofertilizer) and can be utilized to supplement on-farm fertilizer needs. Additional organic wastes to be studied will be selected based on waste audits conducted at local small farms. Some of these feedstocks include culled crops, processing waste, manure, weeds, and by-products of biodiesel production. We are currently working with a local biodiesel producer to obtain samples of their waste by-products (glycerin and washwater) to analyze for biogas potential. This analysis will determine the potential for additional energy production from waste for small farmers who produce their own biodiesel. It may also facilitate the spread of small-scale biodiesel production as, currently, the generation of these waste by-products is an impediment to small-scale producers. By reusing the waste as a resource, these barriers are removed while generating additional bioenergy.

Objective 2

Biogas clean-up and storage will be integrated into the farm-scale digester. Work on this objective will be conducted once the digester is constructed.

Objective 3

A farm-scale digester has been designed and is currently under construction. Once completed, exhibitions will be held to demonstrate the digester to the small-farming community. An open house will be held in conjunction with the IFAS Small Farms and Alternative Enterprises Program.

Impacts and Contributions/Outcomes

Through various information dissemination activities, we have demonstrated biodigestion of on-farm organic wastes and how biodigestion can be integrated into sustainable agriculture on small farms.

Information Dissemination Activities
  • We gave a laboratory tour as part of Family Day for Alpha Zeta (an honor fraternity for agriculture and life sciences students) on March 27, 2010. There were approximately 20 participants, which included students and their families. As part of the tour, we included a discussion and a demonstration of anaerobic digestion and how it relates to the students’ studies in agricultural and life sciences. We delivered a presentation entitled “Biofertilizer Potential of Food Waste Anaerobic Digestion on Small Farms” at the 2010 Joint Meeting of the Florida State Horticultural Society and the Soil and Crop Science Society of Florida in Crystal River, Florida, on June 6-8, 2010. At this meeting, we discussed the utilization of biofertilizer from food waste digestion as a novel nutrient source in Florida. Creating value for all the products of anaerobic digestion (energy and nutrients) is critical for widespread adoption. By building support for anaerobic digestion among soil and crop scientists, we are promoting the long-term sustainability of organic waste digestion on small farms. We exhibited at a workshop in Gainesville, Florida, on July 19, 2010, which brought local small farmers and restaurant owners together. This was the first meeting of a “Farm to Restaurant” group that is working to increase communication and partnerships between small farmers and restaurant owners. We were asked to participate in order to share the potential of food waste digestion both on farms and at restaurants, and the synergistic relationships that this can promote. We delivered a presentation entitled “Anaerobic Digestion and Algae Farming: Energy and Nutrients for Small Farms” at the Florida Small Farms and Alternative Enterprises Conference in Kissimmee, Florida, on July 31-August 1, 2010. Several small farmers expressed their interest in further discussions with us about establishing anaerobic digesters on their farms. This conference was beneficial for reaching the state’s network of small farmers. We presented a poster entitled “Energy and Nutrient Resources from Organic Wastes for Small Farms” at the 11th Annual Soil and Water Science Research Forum, University of Florida, Gainesville, Florida, on September 10, 2010. This forum provided an opportunity to share our research on anaerobic digestion with a large group of faculty and students. Our presentation was framed to have relevance to their own research. We exhibited at the 2010 Sunbelt Agricultural Exposition in Moultrie, Georgia, on October 19-21, 2010. At this 3-day event, we had the opportunity to share our research with hundreds of individuals. There was much interest in using organic waste as a source of both energy and fertilizer, particularly among the agricultural community.
Future Contributions
  • Presentation and digester demonstration at the Southeast Bioenergy Conference in Tifton, Georgia, August 9-11, 2011. Once the farm-scale digester is constructed, we will host laboratory tours and field days to provide hands-on experience for small farmers. Posters and presentations delivered for this project will be made available online.


Dr. Ann C. Wilkie
University of Florida-IFAS
Soil and Water Science Department
PO Box 110960
Gainesville, FL 32611-0960
Office Phone: 3523928699
Ryan E. Graunke
Graduate Student
University of Florida-IFAS
Soil and Water Science Department
PO Box 110960
Gainesville, FL 32611-0960
Office Phone: 7723495645