Waste's Silver Lining

Food companies are beginning to look at liquid and solid wastes as opportunities and not simply costs.

By Kevin T. Higgins, Managing Editor

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The wastewater and solid waste generated in food production has to be dealt with, but they typically are disposed of as expediently as possible.

Food Processing’s annual manufacturing trends survey bears this out. Asked to prioritize 11 manufacturing issues, readers ranked wastewater and solid-waste management dead last, with one-third of respondents rating them either 10th or 11th in importance and fewer than 1 in 17 indicating they are top priorities.

Astute business people understand the drag on profitability created by waste. Shown reliable numbers on the cost and missed revenue opportunities in the waste stream, they are happy to change course — provided, of course, that it doesn’t detract from the primary mission of filling orders for finished goods.

A case in point is protein recovery from chicken byproducts going to rendering. Poultry processors typically place two screens, one with a 0.08-in. mesh and the second at 0.02 in., to salvage saleable fines from the offal room. Recovery rates would be higher with a finer mesh, but sourcing and installing a screen and maintaining it are distractions.

Engineers at Lyco Manufacturing Inc. in Columbus, Wis., have tried to fabricate a solution “as long as we’ve been building screens,” about 20 years, says Jeff Zittel, vice president-technology applications. Based on a field test of their micro drum screen, they believe they found a solution.

The screen’s 0.008-in. mesh was able to recover about 9 lbs. per minute at a 2,000 gal. a minute flow rate in the trial. Assuming 16 hours a day operation and 5 cents per lb. for protein, the drum should recover $450 a day worth of meat. To prevent clogging, a continuous flow of filtered water is backflushed, providing “a self-contained CIP system,” Zittel maintains.

“We played with multiple types of interwoven and woven mesh and different wedge wire before finding something that works,” he says. A similar system is on the market, but limited flow rates and “manual interventions” have discouraged most poultry processors from deploying it.

Capital also is an issue: Even with protein, ROI takes about 1½ years. But fewer dissolved air flotation chemicals and avoidance of other downstream treatment costs are other advantages, and Zittel says there is strong interest among carrot and potato processors in recovering saleable fines from their processes.

Mining value from liquid and solid waste is a low priority for most food and beverage processors, as Food Processing’s manufacturing survey confirms, but whether it’s a reaction to costly disposal requirements or a proactive decision to attack waste, companies are finding treasure in unexpected places

Energy harvesting

Cost avoidance drives many of the industry’s wastewater treatment projects, though mandated reductions in phosphorous and other minerals can add urgency to upgrades. Surcharges for exceeding limits for total suspended solids, biological oxygen demand, chemical oxygen demand and other metrics are changing the payback calculation for additional treatment steps at many production sites. At the same time, declining technology costs and more “user friendly” systems are providing more options for food companies.

An example is the membrane bioreactor (MBR), once deployed almost exclusively in municipal treatment plants. Once viewed as too maintenance-intensive and costly for industrial applications, MBR increasingly is part of the solution for process wastewater.

In a recent project proposal, ADI Systems Inc. presented a conventional treatment and MBR, “and they were fairly close in cost,” notes Scott Christian, vice president-business development at the Oromocto, New Brunswick, engineering firm. Effluent quality was superior with MBR, and a smaller footprint and greater load capacity also favored MBR.

Anaerobic MBR is ADI’s signature solution, and processors increasingly opt for that technology and harvest the resulting methane to fire boilers or power a genset for electricity. In a recent upgrade at Kellogg Co.’s Pikeville plant in Kimper, Ky., ADI incorporated anaerobic MBR followed by aerobic polishing before discharge to a nearby creek. Christian believes the combination system is the first of its kind in North America.

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