Catch of the day — fish diapers

Srinivasan Damodaran has a whopper of a fish story.

The UW–Madison food scientist has patented a biochemical process that could turn carp into a cash crop and, at the same time, reduce a swelling environmental problem.

Damodaran has developed a technique to turn dried and chemically stabilized fish proteins into a new class of hydrogels, the material that captures and holds moisture in diapers and scores of commercial products. The advance provides the first biodegradable hydrogel for diapers.

“The hydrogels on the market are made from petroleum and stand little chance of degrading over a reasonable time,” Damodaran says. “Our studies have shown that the fish-based hydrogels get eaten up in a landfill within 28 days.”

The fish-based material also holds its own compared to petroleum-based hydrogels, Damodaran says, and can absorb more than 400 times its weight in water. The petroleum industry makes about 800,000 tons of hydrogels annually.

The production process mixes ground fish with a chemical called EDTA, which adds water-binding molecules. The modified protein is then cross-linked with another chemical to create a “water-soluble matrix” that traps water in a gel. The final product is dried into powdered form.

Millions of tons of fish go to waste every year in commercial fishing and lake rehabilitation programs, and fish gels could turn a waste-disposal headache into a useful resource, Damodaran says.

About 50 percent of the catch from commercial ocean fishing gets chucked back into sea, he adds. On one large lake in southern Wisconsin, people harvest and dump 2 million pounds of carp annually from its waters.

The material may also work in hand lotions, filters and fertilizers, Damodaran says. For example, hydrogels could entrap pesticides and herbicides and allow their controlled release in the soil.

Incidentally, Damodaran says the fish gel is odorless, so fish diapers wouldn’t be adding one unpleasant odor to another.