Implementing Research : Georgia Takes Many Routes to Recycle Food Residuals

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Courtesy of BioCycle Magazine


“One unique local characteristic (and treatment difficulty) we encountered in our composting program,” says Stan Konno, PWC environmental department director head, “is the high level of diesel range total petroleum hydrocarbon (TPH) content in the sludge from the WWTF at Fort Kamehameha.” Oil from past leaks in pipelines and tanks — which go back to 1941 — penetrates the wastewater collection piping system and causes the high hydrocarbon content. “We were asked to develop a process to degrade the TPH contaminants as well as convert the biosolids into compost,” explains Dennis Chang, the solid waste branch manager and site operator.

Contamination levels in the biosolids can be as high as 200,000 ppm (about 20 percent contamination of the biosolids). Resultant analyses confirmed that the finished compost exhibited no detectable toxicity, leading the Hawaii Department of Health to allow unrestricted use of the end product on DOD property. To illustrate that the compost produced would have no ill effects on either plants or the environment, PWC — in cooperation with the Navy Facility Engineering Service Center (NFESC) at Port Hueneme, California — conducted a field study (“Assessing the Fate and Impact of Residual Hydrocarbon-Like Components in Composted Biosolids Applied to Garden Soil”). A test plot (20 by 20 by 3 feet) was divided into four sections. Composts of different ages (20 days, six weeks and 11 weeks of curing) were applied to three sections; the fourth section served as the control. Carrots and onions were planted for evaluation. Studies of plant viability and yield showed that there was no significant difference between plants in the test plots versus the control. Hydrocarbons were not detected in any of the pore water samples using two different EPA methods.


Tipping fees for biosolids delivered to the PWC compost site are comparable to charges at the local landfill, notes Konno. “For city and county deliveries, we charge $72/wet ton, with a ‘surcharge’ of $10/ton for the compost since it gets applied on public projects,” he points out. For the military, there’s currently no extra charge beyond the $72.

Looking ahead to expanding organics recovery on Oahu and other Hawaiian islands, the PWC staff points out that “we’re using almost all the biosolids being generated on the Department of Defense side on Oahu. It’s up to the county to send us additional quantities of biosolids.” The Navy and Army are each sending nine wet tons/day (five days/week) of biosolids to the composting site. The city/county of Honolulu is delivering twice a week, providing a total of 40 wet tons a week. On February 1, 2000, PWC Pearl Harbor was issued a five-year operating permit from the Hawaii Department of Health. The permit provides that compost produced from the military’s wastewater biosolids is not restricted in its use and application provided it remains on DOD property. It also notes that capacity may be increased up to 200 wet tons/week of biosolids from the city and county of Honolulu.

The Navy’s biosolids facility was named Project of the Year by the American Public Works Association Hawaii Chapter for the less than $2 million category. “We’re very proud of our facility and the personnel who manage it,” said Konno. “This award serves to recognize their accomplishments and confirm the Navy’s commitment to protect Hawaii’s fragile environment.

Compost Research On Wisconsin Organic Farm

At Harmony Valley Farms in Viroqua, Wisconsin, owners Richard de Wilde and Linda Halley apply composted manure on their entire 70 acres of vegetables and fruits. But that practice has not always been followed during their 16 years at Harmony Valley.

In 1991, they sold their livestock and stopped using composted manure. Soon de Wilde and Halley noticed an increase in foliar diseases. To determine what was causing the problem, they began working with the Center for Integrated Agricultural Systems (CIAS) at the University of Wisconsin-Madison to conduct joint on-farm research in 1997 and 1998. The first objective involved studying disease suppressive properties of soil amended with dairy manure compost and exploring any influence compost amendments had on crop health and productivity at Harmony Valley. The second goal was to collect soil microbial data on the farm where links between microbial indicators and yield could be investigated. Researchers at the CIAS hoped to use soil from the trials as starting material for developing DNA-based methods for assessing soil microbial communities.

Scientists involved in the study included Robert Goodman, Gary Vallad and Beth Kazmar of the University of Wisconsin’s Plant Pathology Department. They monitored crop disease responses to field treatment. The plant pathologists are continuing their investigations with soils collected from the trials. Research by Jeff Dillen at the University’s Institute for Environmental Studies on samples from another farm showed that a DNA-based method could detect microbial community shifts in response to long-term, 30-year differences in crop management. An extensive collection of microbial DNA samples from the trials at Harmony Valley has been archived for future analysis.

Ten Percent Increase In Yields

Four treatments were studied in the field trials: an untreated control, composted goat manure, composted dairy cow manure, and a commercially available feathermeal product mixed with soybean meal which was included as a NPK fertility control. To help isolate compost’s nonnutrient effects, researchers varied compost application rates between ten and 15 tons/ acre to match compost nutrient levels and those of the NPK control.

The same field was used in both seasons, allowing observations on cumulative effects of compost applications in the second year. Each year, two crops were planted in adjacent strips.

To the researchers’ surprise, using dairy manure compost increased crop yields by an average of ten percent even in the presence of microbial disease. According to Research Brief #45, published by the CIAS, some diseases were less severe in plots treated with the compost, but other diseases, particularly those involving the fungus Rhizoctonia solani, were more severe. Both dairy and goat manure composts appeared to limit the disease Cercospora. However, use of compost increased several diseases caused by the fungus Rhizoctonia solani. But the increase in disease on crops with compost amendments was often accompanied by an increase in yield. Another striking finding was how crops responded to compost in dramatically different ways. The beet crop responded strongly to goat manure compost and dairy manure compost. But the carrot crop planted six feet away responded most strongly to the goat manure compost.

The soil microbiology research also found that the ratio of total fungal to total bacterial biomass was a strong predictor of yield. This measure was capable of distinguishing the soils collected from amended and unamended plots, revealing that the dairy compost had indeed changed the soil microbial community. Composts continue to be a useful part of soil management for Harmony Valley, but de Wilde uses compost in conjunction with other techniques such as extended rotations of susceptible crops and rotation to grasses where feasible in order to manage levels of Rhizoctonia.

Compost Sources

Only dairy compost is now used on Harmony Valley Farm, 80 percent of which is made by de Wilde from bedded manure purchased from neighboring farms. Manure is mixed with legumes, corn stalks, soybeans or hay to achieve a C:N ratio of 20 to 1. His five windrows are turned at least once a week for six to eight weeks. The turner is pulled by a hydrostatic drive tractor; each windrow is 500 feet long and contains 60 tons of feedstocks. Compost is spread in fall over Harmony Valley’s 70 acres at three to five tons per acre, supplying all the nitrogen, phosphorous and potash needed. “The material is dry and crumbly, not wet like raw manure,” says de Wilde. “All my labor and fuel costs are cut in half because I’m spreading only half as much compost (as raw manure), and the load is lighter because it is dryer and spreads faster.”

Harmony Valley purchases the remaining 20 percent of the compost it uses from Paul Rosenow — a dairy farmer in Cochrane, Wisconsin — who beds his free stalls with dry sawdust obtained from local mills, kiln drying and planing operations. Approximately ten percent of the mixture is sawdust bedding and the remaining 90 percent is liquid manure. “The stalls are flushed daily into an alleyway and a reception pit,” says Rosenow. “The reception pit agitates the mixture of water, sawdust and manure with pumps. The mixture is then pumped to an inclined screen separator. The liquid portion falls through the screen and by gravity goes to one of the lagoons. The solid portion slides off the screen onto a watertight concrete stacking pad where it is accumulated and taken to the composting site.”

At the composting site, windrows are formed on two acres of asphalt pad and turned. After the active phase is completed, the compost is put into a larger windrow, for about six months to become market ready. At that time, Rosenow sells the compost at a wholesale price of about $12/cubic yard.

Evaluating Finished Compost Impact On Crops

While the compost purchased from Rosenow constitutes only about 20 percent of his compost source, de Wilde really likes Rosenow’s dairy compost mixture. “It’s a wood derived mixture meaning it is fungus dominated versus bacteria dominated like the corn stalk, hay, and soybean mixture. It has a nice woodsy smell. Our straw based compost is bacteria dominated. The fungus based compost may be better for strawberries, raspberries and our other crops.”

The problem of too much water presents de Wilde’s greatest challenge with composting. In July and early August, the upper Midwest suffered from constant rain that ruined crops for many farmers and threatened compost piles as well. He is considering purchasing covers for the windrows.

Keeping the compost located at a high, dry area helps drainage so windrows are situated on a hill with lengthy grass to absorb and filter any runoff. Odor is not a problem, according to de Wilde, as long as the 20 to 1 C:N ratio is maintained. “Anything less than 20 to 1 would create odor problems,” he says.

 As a result of their willingness to experiment, Richard de Wilde and Linda Halley are contributing to advances in modern science in disease suppression and microbial communities. And they are in turn, fully committed to composting. “Participating in the research project definitely reaffirmed our commitment to compost,” says de Wilde. “But, I’m also glad to contribute to the body of scientific knowledge about farming methods.”

Is compost an economical option for Harmony Valley? “Yes,” says deWilde, “after seeing the results of our experiments, we definitely plan to continue making and using compost. We expect to eventually be able to reduce our application rates as the compost accumulates in the soil, improving soil structure and tilth. These are important long-term benefits with our sandy loam.”

DeWilde figures that if he can average a ten percent yield increase for all crops using compost, he will increase average gross profit sales by $800/acre. This would make it well worth the costs of making the compost including equipment depreciation, even at $25/ton or $300 to $400/acre. “Economic benefits are even greater when long-term effects are accounted for,” says deWilde.

Research data on the benefits of composted manure use at Harmony Valley Farms have been compiled by staff at the Center for Integrated Agricultural Systems (CIAS). The Center brings together university faculty, farmers, policy makers and others to study relationships between farming practices, farm profitability, the environment and rural viability. CIAS is based at the University of Wisconsin’s College of Agricultural and Life Sciences in Madison, WI. (608) 262-5200.

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