The knowledge base regarding how earthworms process organic residuals into usable soil amendments is expanding, as researchers and entrepreneurs provide needed information.

David Riggle

Reprinted by permission of BioCycle May 1998 pages54-56

In the world of worms, the amount of quality information available to specialists and novices alike is growing rapidly. At the university level, one of the most vigorous programs of research in earthworm ecology, vermiculture, and vermicomposting in the U.S. today can be found at The Ohio State University (OSU) in Columbus, Ohio. Presently, researchers there are focusing on three areas: 1) understanding the biological and engineering principles underlying the vermicomposting process, with particular attention to management of continuous-flow reactor technologies; 2) evaluating the benefits of soil application of different vermicomposts and composts in intensive horticultural field production systems (e.g., raspberry production); and 3) evaluating the performance of different worm casting products (vermicomposts) and composts when used as components of horticultural container media.

Scott Subler of OSU's Soil Ecology Laboratory describes the research projects and associated results: "Professor Clive Edwards and I are the principal investigators on a two-year project funded by the USDA for research and development of an automated, continuous-flow vermicomposting reactor. We are building a pilot-scale reactor at the Ohio Agricultural Research and Development Center (OARDC) in Wooster, Ohio to investigate the biological principles underlying vermicomposting and to test and optimize various vermicomposting process parameters. This reactor will be similar to the elevated bed systems currently being used for the commercial production of worm castings. We are receiving substantial additional support for this research from OSU, and have assembled a team of over a dozen scientists and graduate students to work with us on this project. One of these Qishui Zhang, a Post Doctoral Scientist (microbiologist) in our lab - is investigating human pathogen reduction during vermicomposting."

In addition, 12 experimental-scale continuous-flow minireactors (two feet by two feet by three feet) became operational this spring (worms added) at the new OARDC Composting Research Facility. The effects of differences in feedstock throughput rates on system function and resulting vermicompost quality will be examined in collaboration with Dr. Harold Keener (OSU Department of Food Agricultural and Biological Engineering).

The benefits of incorporating vermicomposts into horticultural container media are being studied by Rola Atiyeh, a Ph.D. student, and others in the Soil Ecology Lab, in collaboration with the Department of Horticulture and Crop Science. Objectives included determining which growth stages of plant development would benefit most from vermicompost use and the effects of vermicompost amendments on the physical properties of a soilless greenhouse medium. "The incorporation of vermicomposts into MetroMix36O (a widely used commercial growth medium) has had the effect of increasing the mass of shoot and root and leaf area of several bedding plant species, including french marigold, tomato, green pepper, and bachelor button," Subler says. "These increases in growth have been achieved without added fertilization, relying only on the nutrient content provided by the vermicomposts."

Last fall (1997), a greenhouse study was conducted in collaboration with the Department of Horticulture and Crop Science and the OSU Piketon Research and Extension Center. It evaluated raspberry plants grown in soil amended (20 percent) with different vermicomposts and composts. Although data from this three-month study is still being analyzed, the raspberry plants grew as well as or better in soil amended with vermicompost than in soil treated with inorganic fertilizer, and much better than in Soils amended with various commercial composts and compost mixes. This year, large-scale field studies using vermicomposts and composts in raspberry production are planned.


Investigators at the University of Idaho in Moscow, Idaho, including Robert Rynk, Gary Forushell, J.C. Foltz, Kristy Grabenstein, Tom Hess and others, have been engaged in a series of trials over the past few years to evaluate composting and vermicomposting as beneficial management practices for fish manure from aquaculture facilities, an estimated 22 million gal-ions/year which are produced in Idaho alone. Trout manure, specifically, is typically dense, wet and nitrogen-rich (although it can also be relatively dry if drying beds are used). The researchers speculated that vermicomposting might be better suited to the wet nature of fish manure, compared to conventional composting, as fewer dry amendments are likely to be needed. Subsequently, a project was established to first determine whether trout manure could sustain a population of worms, which generally require a moist, aerobic environment at cool to moderate temperatures, but do poorly in anoxic conditions and in materials with high concentrations of ammonia and salts.

A series of laboratory experiments were conducted in which manure worms (Eisenia foetida) were placed in containers of dairy cattle manure and fresh and aged trout manure from several different facilities and observed. Initial results were not positive. After only one week, no worms survived in the containers holding fresh trout manure. They died on the surface of the material and attempted to crawl out of the container rather than burrow into the manure. This same occurrence was repeated in later trials, leading to the supposition that the high ammonia content of fresh trout manure was the most likely cause of worm deaths.

In aged trout manure (collected from drying beds approximately one year after it was harvested from settling ponds), the results were somewhat different. Although there was a high percentage of mortalities at first (80 percent), those that survived generally gained weight. Over successive experiments, by starting worms in dairy manure and gradually adding higher percentages of fish manure, a worm population developed that appeared to be acclimated to both aged and fresh trout manure (only approximately 10 percent mortalities) over a period of six months. "Fish manure is a tough substrate for worms, but it seems they can get used to it," says Rynk. "Once the worms are acclimated, trout manure could be a successful feedstock for vermicomposting." Rynk also speculates that some of the experimental conditions and early handling techniques by the investigators contributed to the high mortality rates. More details of this project, which was completed in March, 1998, will appear in a future issue of BioCycle.


"The participation of industry collaborators is essential for successful completion of some of our projects and for the dissemination and application of research results," notes Subler of OSU. "We recently collected samples from earthworm beds at a large-scale vermicomposting facility managed by Vermicycle Organics in North Carolina, and are analyzing changes in soil biochemical, physical, and microbiological properties during the processing of separated hog manure by earthworms. We are planning similar studies of food waste processing in a continuous-flow reactor system operated by Oregon Soil Corp. in Portland, Oregon. This type of research will improve our basic understanding of the vermicomposting process and, combined with proper process monitoring and control systems, will allow us to manage the vermicomposting process more effectively ultimately increasing material throughput while maintaining a high quality output."

Examples of innovation and process improvement also can be found outside of academia. Harry Windle, president of Worm World, Inc. in Gainesville, Florida, has spent the last two years developing a prototype automated large-scale vermicomposting machine that he calls the Worm Gin. The modular system works as a stacked series of conveyor belts for worm beds. A single module is comprised of two stacks of beds with a feeder down the middle. Manure, food residuals, biosolids or other feedstocks are placed in a hopper above the feeder (usually by conveyor). The Gin distributes it equally to each bed, and after about seven days, vermicompost and excess worms are removed, incrementally via the output conveyor. Windle says each' square foot of bed in his system can process one to three pounds of feedstock per day. The stackable design allows beds to be placed both vertically and horizontally to fill a desired space so that a room with a 20-foot ceiling could vertically accommodate as many as 20 beds. Another advantage, according to Windle, is that the system utilizes thinner beds than most (four inches thick) which aids mesophilic bacterial growth due to increased aeration. "We recently installed a small prototype in North Carolina to handle tobacco and brewery wastes," he says, "but we're hoping to have systems handling over a ton of materials per day running in the next few months."


Some interesting educational resources about worms and vermicomposting recently came to our attention. The first is a 31-minute video called Worm Bin Creatures Alive Through a Microscope. Warren A. Hatch, an elementary school teacher with several other microscope films to his credit, was asked by the Metro Regional Government in Portland, Oregon in 1997 to produce a video that could be used for school science classes. Metro was drawing up a curriculum so that science classes in all of the schools with worm bins could study and learn about the worm bin ecosystem while they were maintaining one. Hatch wasn't sure it would be very interesting at first, but then changed his mind. "We put some worm bin 'dirt' under my microscope and observed it magnified on a TV monitor which is connected via a special video camera," he says. "Within a few minutes an amazing creature that looked like a mini-scorpion walked across the TV screen. I was told that this awesome arachnid was a pseudoscorpion and that it is commonly found in worm bins. From then on, I decided that yes, this might be an interesting project."

Over the next six months, Hatch collected material from four different worm bins in the Portland area and videotaped various samples through a microscope from l0 X to 200X magnification using fiber optic illumination. The result, informally narrated by Hatch, includes up-close-and-personal footage of springtails, bacteria, protozoa, fungi, mites, worms, nematodes, millipedes, sow bugs, fly larvae and other creatures. Videotapes are available from Hatch, P.O. Box 9224, Portland, OR 97207-9224. (503) 221-7154.

Other useful sources of information about earthworms can be found on the Internet. "I compiled a list of sites I knew about on the World Wide Web that addressed worms, vermicomposting, and composting in 1997," says Rhonda Sherman, Waste Management Extension Specialist with the North Carolina Cooperative Extension Service in Raleigh. "Although the list was only about half a page long, within a few months I had to reduce the font size and expand the margins to fit the web sites on two pages. By fall of 1997, I realized that so many wormy web sites had popped up that they would fill at least four pages." Her site (http;// features addresses for such web pages as Mr. Ken's World Wide Worm Links (http:I/, "an exhaustive list of web sites and links to everything you need to know about worms and composting;" Composter's Forum: vermicomposting ( "an excellent source of information where you can post questions and receive answers from vermicomposting experts;" Worm Digest ( /wormlworm.html), "a quarterly newsletter for the vermicomposting enthusiast; Worm Woman (, "Mary Appelhof's site;" and many others.

One final link worth mentioning provides an overview of the activity in these fields. The Sixth International Symposium on Earthworm Ecology (http:/ will take place in Vigo, Spain, August 31 through September 4, 1998. Geared primarily to scientists and those in academic environments, topics related to earthworms that will be covered include biodiversity, soil organic matter and nutrient dynamics, ecotoxicology, agroecosystems and land use,and waste management.

MAY 1998 BIOCYCLE pages 54-56