clean and clear

agriculture

Alternative Manure Management
October 18, 2004

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AGRICULTURE

Introduction Accepted Agricultural Practices Best Management Practices Conservation Reserve Enhancement Program (CREP) Alternative Manure Management Large Farm Operations Medium Farm Operations Vermont Conservation Districts Nutrient Management Incentive Grants Farm Agronomic Practices Vermont Agricultural Buffer Program

Background

Imagine animal manure as a valuable resource rather than a waste or pollutant. Through the use of alternative manure management technology farmers can realize many benefits from animal manure. In the late 1800's Vermont evolved from sheep and grain based agriculture to dairy based agriculture. Today over 80% of Vermont's agricultural income is from the sale of milk or beef. There are limited acres devoted entirely to fruit, vegetables or grain production. Because Vermont's agriculture is dependent on livestock production, developing new methods of manure management is a critical component for farms to achieve compliance with provisions of the Lake Champlain phosphorus total maximum daily load (TMDL).

Lake Champlain has been identified as an impaired water body and a TMDL was created in 2002 to reduce phosphorus levels 27% from the levels reported in 1991 (Vermont Agency of Natural Resources, 2002). The majority of the point sources in the watershed have been corrected to meet the TMDL requirements, which has caused non-point sources to contribute more (93%) of the total P load to Lake Champlain. Currently, inputs from agriculture account for approximately 56% of the non-point source P pollution in Lake Champlain. In a region with a thriving agricultural community and a high water to land ratio, providing more resources to streams adjoining agricultural lands could provide enormous water quality benefits.

Development of nutrient management technology to remove phosphorus from manure so it can be applied only to phosphorus deficient areas or sold to agricultural producers in need of phosphorus is necessary to achieve the phosphorus TMDL. More than 60% of the phosphorus in dairy rations passes through the cow unused, and into manure. Over time excess phosphorus builds up in soils and leaves farms through erosion and during periods of heavy water runoff. Research is underway to fine-tune the amount of phosphorus required in dairy rations and develop methods to increase uptake by animals. Farms are developing buffers along field edges and rotating crops on erodible soils to minimize runoff.

Until the late 1970's most farms spread manure on a daily basis unless deep snow or heavy mud prevented passage of spreading equipment. As federal cost share funding became available some farms built lagoons, (also known as pits), to hold manure during the winter months and busy periods of the cropping season. Lagoons were a major step forward in decreasing animal agriculture's impact on water quality. The ability to store manure allowed farmers to apply the nutrients in a managed fashion. Applications could be timed to maximize nutrient use and minimize runoff. Vermont developed a state cost share program in 1996 to augment the federal program. Today lagoons have become a common feature on Vermont farms. Although management of nutrients through the use of lagoons reduces field runoff, farms are still faced with the dilemma of utilizing on-farm nutrients, particularly phosphorus, in an appropriate manner.

Utilization of lagoons has created other management challenges. Vermont developed Accepted Agricultural Practices in 1994, which included a prohibition on winter spreading of manure. This coupled with increased farm size has led to larger lagoons and manure spreading equipment. A 6000 gallon tank of manure weighs nearly 50,000 pounds and the combined weight of the tank and tractor can exceed 75,000 pounds. Many farms have chosen to focus their efforts on herd and crop management and hire "custom operators" to spread manure in the spring, once during the summer and again in the fall. Typically custom operators arrive at a farm according to a set schedule and empty lagoons regardless of the weather. Occasionally roads are subjected to frequent trips with large equipment hauling heavy loads. Vermont's back roads do not have sufficient base to support equipment traveling with intensity for short time periods.

Manure stored in lagoons has a strong odor when spread. Because farms only apply nutrients at prescribed periods during the year significant acreage is covered in very short amounts of time. This increases the intensity of odors. The interface between farms and their rural neighbors is often unpleasant during manure spreading season.

Benefits

Alternatives are being developed to address nutrient utilization, equipment size, and odor. The benefits of improved manure handling include:

Figure 3. Construction of a manure digester

A. Reduced or eliminated odor from spreading. Experimentation with attached growth digestion shows promise for reducing manure odor.

B. Reduced wear-and-tear on highways. Several methods of solids separation are being researched to decrease the weight of over the road equipment.

C. Organic fertilizer sources available from the process. Utilization of various biological processes are showing promise in the separation of nutrient components of manure to allow development of organic fertilizers.

D. Power produced to reduce dependence on fossil fuels. With new technology farms in Vermont have the flexibility to manage manure for nutrient control and energy production through anaerobic digestion.

E. Producing bio-diesel from agricultural wastes. Livestock manure can be managed to produce methanol, used in the production of bio-diesel.

F. Reduced pathogen load applied to soils. Several of the experimental technologies show promise of reducing pathogen loads in manure.

Vermont as a Center of Excellence

It is envisioned that Vermont will develop into a center of excellence in the design and construction of alternative manure management technologies. A new technology showing promise allows the separation of manure into components of varying nutrient content to maximize nutrient utilization, decrease phosphorus importation, allow phosphorus exportation, generate renewable energy and minimize runoff. Known as “attached bacterial growth,” a bacterial media is used to digest manure in small vessels and capture the resultant methane. Digestion eliminates odor and pathogens from the manure and the methane can be used to offset farm energy needs. Other technologies will be researched as they develop.

Opportunities for Private Funding Support

A combination of federal and state funds are currently used to provide technical support and cost share funding in the development of alternative manure management. Additional capital is needed to develop new technologies and to make these systems cost effective. Specifically, private funds are needed to:

• Figure 4. Continued growth of animal agriculture in Vermont will require development of new approaches to manure management.

  provide capital to companies developing alternative manure management technology,
• assist companies in development of technology for agricultural applications, and
• decrease the financial risk for farmers implementing new technology.