Converting Dairy Waste into More Usable Products through Vermiculture

Final Report for FW99-073

Project Type: Farmer/Rancher
Funds awarded in 1999: $4,300.00
Projected End Date: 12/31/2004
Region: Western
State: California
Principal Investigator:
Expand All

Project Information


The participants want to show dairies that composting dairy manure using vermiculture can help them become more environmentally conscious and at the same time secure financial benefits from waste management. Further, they want to demonstrate how a complete cycle of agricultural waste management and natural soil-amendment production can help dairies:

· Decrease their manure volume
· Convert it into a value-added product, vermicompost

· Use the vermicompost on crops like alfalfa and corn
· Decrease their cost of fertilizer and freight
· Increase their crop yields as a food source for their dairy cows

In Tulare and King counties of California the volume of dairy waste is ballooning. At the same time, the market for raw manure is decreasing simultaneous with rising concern over the impacts of manure on air, water and soil quality.

The counties have 450,000 head of dairy cow, each generating an average of 16.6 pounds of manure a day, or 1.36 million tons a year. With the approval of five mega-dairies, the annual output of dairy manure is nearly 1.5 million tons. A major concern has been the nitrate levels in the manure and in the water of the holding ponds and lagoons, which results in higher nitrate levels in the groundwater.

Charmaine Harris and Carolyn Fox of C&C Vermiculture in Visalia, Calif., set up an experiment that would compare several ways of handling dairy manure: without worms; irrigated with lagoon water; inoculated with worms and irrigated with well water; and inoculated with worms and irrigated with lagoon water.

Despite adequate drainage, wet bins induced the tiger worms to escape to nearby, drier bedding materials. So Harris and Fox re-inoculated the bins with red worms, which soon began dying. They determined that the worms were "starving" because the original two-year-old bedding material had pre-composted, meaning there was too little bacteria from the decomposing manure upon which the worms feed.

This experience with the worms led Harris and Fox to conclude that the ideal age of manure or other agricultural organic matter for vermicomposting is between two and six months. By allowing the manure to precompost before feeding it to the worms, the "hot" phase, or thermophyllic reaction, is avoided.

"Manure or green waste that has been sitting and decomposing on its own more than two years has very little food value for the worms to convert the material to vermicompost," the two report.

Laboratory analysis yielded several other findings. The manure used for the project had a pH level of 8.1 before it was inoculated with worms and 8.0 after inoculation and irrigation with lagoon water. The pH level of manure inoculated with worms and irrigated with well water was 7.9.

Another important value is the carbon-nitrogen ratio. A beneficial level is 10. The initial manure had a C-N ration of 9.9; that inoculated with worms and irrigated with well water was 11; and that irrigated with lagoon water was 12.2.

The researchers also analyzed the organic matter. On a 100% dry matter basis, the initial manure had 36.7% organic matter, the worm-inoculated manure irrigated with well water had 39.6% and the inoculated manure irrigated with lagoon water had 42.9%.

"As a natural and beneficial soil amendment, (vermicomposted manure) will enrich and restore the soil with organic matter," say Harris and Fox. "As a component of on-site agricultural waste conversion, it is beneficial for dairies to apply the end product to crops used for feed."

The study shows that on-site vermicomposting is a viable option for waste management and conversion to a more valuable product that can be used in place of purchased fertilizers.

So far, there have been no reports of other dairies adopting processes that have been confirmed by this study.

To provide a more indicative analysis regarding the conversion of cow manure to vermicompost, the participants in the SARE study are doing a similar study on their own. They have harvested worms left in the research bins, emptied the over-aged manure and refilled the bins with four-month-old manure. The bins will be irrigated as in the initial study: one bin with worms irrigated with well water, another with worms irrigated with lagoon water and a third without worms irrigated with lagoon water. The research will analyze salt levels and other attributes as well as compare the conversion of organic nitrogen.

The project and its results have been featured in newspaper articles and on television. Additionally, the participants have made presentations on how composting worms function and their benefits during several school programs, at horticulture society meetings and during a two-day Children's Drinking Water Festival sponsored by the Orange County Water District.

A nearby dairy that had begun to vermicompost dairy manure experienced many of the same problems as with the SARE-funded research and shared those for this report. His moisture levels were too high for the tiger worms, which migrated to drier windrows. Those that endured the 15-yard trip survived and thrived. The producer has also inoculated his manure piles with the more adaptable red worms, which resulted in a high worm-to-bedding ratio.


Participation Summary

Research Outcomes

No research outcomes
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.