As The Compost Turns

October 1, 1997

8 Min Read
As The Compost Turns

Karen Glenn

For composter Jim McNelly, the tried-and-true methods of commercial composting just weren't working. As the operator of a private facility in Minnesota in the early 1990s, McNelly wrestled with odor problems that resulted from being unable to keep his compost pile cool enough.

His temperature control system often was erratic and failed to trigger the air blower when the pile became too hot, causing the bacteria-eating microbes to die.

As he pondered how to spread those microbes more evenly, speeding the organic waste's decomposition, he dealt with smelly leachate oozing from sections of oxygen-deficient compost.

Although McNelly knew his problems were shared among other composters, he felt that the equipment and techniques he was using also were to blame. "I needed a composting system that met all of the operating and processing requirements," he says.

So, he asked himself "What would make my job easier?" To design the best system for his purposes, McNelly began researching the obstacles facing compost facility operators and then started engineering a system that could alleviate some, if not all, of those problems.

First, he focused on how to keep a delicate balance of air and water in the compost pile - a circumstance which is critical to proper decomposition and an uncontaminated end product. While housing the compost in an enclosed building and out of the rain was an option, McNelly dismissed that idea due to the collective threats of odor build-up and fire.

The fruits of his labor resulted in an in-vessel system where the feedstock - such as food and yard waste and sewage sludge - is mixed with a bulking agent like wood chips. The compost then is loaded into covered roll-off containers, ranging in size from 40- to 80-cubic yards.

To tame the ubiquitous odor and excess moisture, a blower pushes air through the container's top and bottom when a computerized temperature gauge signals that the mix is getting too hot. The air is processed through a biofilter, cleaned and then recycled back through the blower. After about two weeks, the compost is screened and dumped into another container to cure for 30 days.

"What used to take 90 to 120 days only takes one-half to one-third of the time," McNelly says. Not surprisingly, today, the in-vessel system has become mainstream, and similar systems are springing up at manufacturers all over.

Don't Tear Out Your Hair Not every composter who is frustrated with his equipment has the time and money to strike out on his own and design a unique system like McNelly. And, even McNelly's in-vessel system would not be a universal answer for all composters, especially those operators who are monitoring their costs and cannot afford the overhead.

For example, Scott Schaible, who, along with his wife Becky, runs Freedom Organic Soils, a dairy manure composting facility in Albany, N.Y., says purchasing an in-vessel system isn't financially feasible for their operation.

The Schaibles' livelihood depends solely on the fertilizer they produce for lawn and garden top soils, and therefore they, like all composters, must try to manufacture a high-quality product at the lowest cost.

Former owners of a landscaping business, the Schaibles know firsthand the components of marketable compost. Like McNelly, they had been frustrated with equipment that turned out shoddy compost. Often, the compost they bought was not mixed properly or was mixed with poor ingredients.

Thus, sensing the need for quality compost, the Schaibles gave up landscaping and entered the world of manure compost. "It was absolutely suicidal," says Scott Schaible. "No one in his right mind would choose to do what we did, but we couldn't find a soil that would work in landscaping."

However, they had their work cut out for them when setting up shop. Schaible reports spending months researching and shopping around with his particular enduser market in mind until he found a machine that would do the job for the right price.

"What we really wanted was something that could kill weed seed, which is deadly for landscapers," he says. "We needed a machine that would invert the soil."

Inverting the soil, he explains, moves the weed seed from the steamy center of a windrow to the cooler outside of the pile where it dies.

Eventually, the Schaibles purchased a small windrow turner from ATI Global/SCAT Engineering, Delhi, Iowa, which they claim gives virtually the same results as the in-vessel system.

Odor control was not an issue when selecting the equipment, Schaible reports, due to his company's location near several farms. This turner, which blends the compost with other ingredients in addition to turning and aerating it, "eliminated the need for a second machine and saved us at least $50,000," Schaible says, noting that the turner was able to solve all of his problems, except one - flies. "Well," he concedes, "no machine can do that."

At the time, the Schaibles had sought a machine that was relatively light and could be towed easily through the windrow. But, now more than a year after launching the company and watching their volume increase, they are finding themselves back on the purchasing merry-go-round as they research larger machines.

Machine Abuse And Misuse In discussing what works and what doesn't when it comes to equipping a composting facility, manufacturers and industry analysts agree that the type of machinery selected should depend mainly on how the feedstock will be processed and what the end product will be.

Most all grinders, mixers, screens, windrow turners and aeration systems, whoever the manufacturer may be, operate in much the same way, says Randy Monk, director of operations for The Composting Council, Alexandria, Va.

Factors that should be considered include the ingredients and the amount to be composted, how often it will be turned, the marketing plan and the environment in which the composting will be done, he says.

Of course, manufacturers counter, how well a machine performs and how long it lasts depends largely on the operator and the environment. Michael Hill of Scarab Manufacturing, White Deer, Texas, says manufacturers increasingly are taking it upon themselves to design machines that can withstand harsh weather and terrain as well as tougher feedstock.

Hill stresses that it's important for manufacturers to know what surface the machine will be used on and the type and quantity of feedstock. Potential customers must be prepared to give specifics. Armed with such information, the salesperson can steer customers to a machine that best fits their needs, he notes.

Problems occur, however, when operators try to cut costs and buy a smaller machine, then use it on a large windrow. Operators also have been known to use the machines on material that is too heavy or difficult to be processed. "I've seen people pulling chunks of concrete out [of the windrow]," Hill says. "Nothing will process that."

Don Brandon of Morbark Industries, Winn, Mich., says tub grinders occasionally will regurgitate materials into the air when the tub is half-full and operators erroneously try to feed in material that is too large.

Such manufacturer observations on composters' machinery misuse highlights a growing problem in the industry, reports Christine Colella of Green Mountain Technologies in Whitingham, Vt., who stresses that once composters have been sold a machine, manufacturers still need to educate them on its proper use.

Operators, especially those who are new to the industry, can find themselves in a smelly jam should they make a mistake in mixing and end up with an anaerobic compost pile. For operators using a containerized system where a lid can be put on the mix and the odor can be treated, this may not be such a big problem. But for someone with an open pile near a residential area, it could spell disaster. "Companies need to see that a little bit of handholding can go a long way," Colella says.

Composting Outside The Lines Many manufacturers currently are turning their focus to customer service when it comes to adapting machines to fit specific needs, Monk reports.

For example, Sonya Alexander, town manager of Wilmington, Vt., says she was hard pressed to come up with a way to dispose of her community's sludge. Uncertain as to how well it would work, she rented a containerized system.

"Since we're a resort area, we were most concerned about the odors that result from dewatering," she says.

While the system worked well in terms of odor control, there was no way she could dewater the sludge without going through a lengthy process. In response, the manufacturer created a container that she could use for both dewatering and composting.

Jeff Gage, the recycling services coordinator for Pierce County (Wash.) Land Recovery Facility, concurs that adaptability is an important consideration when selecting equipment and manufacturers. Gage's facility needed to adapt its windrow turner to toss the compost to the side onto a conveyer instead of behind itself so it could be watered while it was being turned.

"This was important to us in the way that the water helps the compost to remain fluffy and porous," he says. "And we couldn't water it inside the turner because we found that tends to gum things up."

To fill this need, he purchased a stack windrow turner, which slices the compost laterally and shifts it to the side. In addition to using win-drows, Gage also has had to use an in-vessel system, which he reports has saved a lot of space and the cost of constructing a new facility.

When it comes to manufacturers and customer service, the wish list is still unfulfilled for many composters. For example, while Gage admits his turner fits its purpose, he laments that manufacturers, in general, are reluctant "to provide enough of a complete package."

"The individual manufacturers don't work as a system and we, the customers, are left to pick and choose which equipment is right for us," Gage concludes. "Often we can't just get it all at one company and have to go to several before our system is complete."

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