Bioenergy and Biofertilizer for Small-Farm Enterprises

2009 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. Preliminary investigations have been conducted to assess biodigestion of farm waste. Various manures, food and crop wastes have been analyzed for biogas and biofertilizer potential. We are currently designing a low-cost biodigester that can be easily implemented on small farms. As a pilot farm-scale biodigester, this will be the centerpiece of the project. Public demonstrations and class tours have been conducted to spread awareness of biodigestion for small farms.

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

Preliminary characterization studies have been conducted to determine total solids (TS), volatile solids (VS) and chemical oxygen demand (COD) of selected organic wastes. These wastes included flushed dairy manure, poultry litter, and vegetable production waste. Both the poultry litter and the vegetable production wastes had high COD and % VS levels, suggesting that these wastes have high methane production potential.

In addition, ammoniacal nitrogen was measured for these feedstocks. As an undigested feedstock, poultry litter had the highest ammoniacal nitrogen concentration. However, after digestion, vegetable production waste also had a high ammoniacal nitrogen content. The digestion process effectively converts organic nitrogen in the feedstock into plant-available ammonia, which increases the value of the biofertilizer from the digester. For example, of the total nitrogen in vegetable production waste, 99% was organic nitrogen when fresh and 95% was ammoniacal nitrogen after digestion. Future work will include characterization of additional organic wastes and conducting biochemical methane potential (BMP) assays to verify the methane potential of various on-farm organic wastes.

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

As a preliminary demonstration activity, a small food-waste digester was showcased to small farmers at the Agricultural Enterprise Workshop for North Florida, held in Live Oak, FL, on November 5, 2009. A demonstration and discussions were conducted to show the potential of anaerobic digestion as part of a sustainable solution for organic waste management.

The farm-scale digester will be constructed with particular attention to on-farm implementation, to facilitate the construction of similar digesters by small farmers. Readily available materials will be used in the construction, and expensive electronics controls will not be required. A visit to a local small farm, which previously had a functional food-waste digester, gave us insight into what small farmers want and how to design the digester to best meet their needs and abilities.

Impacts and Contributions/Outcomes

During this project, we will be working closely with small farmers and utilizing the resources of the University of Florida – Institute of Food and Agricultural Sciences (IFAS) Small Farms and Alternative Enterprises Program. Through various information dissemination activities, we will demonstrate the suitability of biodigestion of on-farm organic wastes and how biodigestion can be integrated into sustainable agriculture on small farms.

Information Dissemination Activities
  • Ryan Graunke (graduate student) gave a presentation entitled “Anaerobic Digestion: Sustainable Energy and Nutrients from Food Waste” at the 2009 Florida Campus and Community Sustainability Conference at the University of South Florida in Tampa, FL, on October 8, 2009. This is an annual conference that discusses various aspects of sustainability throughout Florida. The presentation was part of a food, agriculture, and gardening session. Several individuals working with small farms in the area were interested in implementing biodigestion for on-farm organic waste. Graduate students brought a small-scale food-waste digester to the Agricultural Enterprise Workshop for North Florida hosted by IFAS in Live Oak, FL, on November 5, 2009. Many small farmers in the local area participated in the workshop. The session included discussions and a demonstration of biodigestion for the small-farm community.
Future Contributions
  • Presentation and digester demonstration at the Florida Small Farms and Alternative Enterprises Conference in Kissimmee, Florida, July 31 – August 1, 2010. Once the farm-scale digester is constructed, we will host laboratory tours and field days facilitated through IFAS 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