When shrimp are processed at seafood plants, the resulting wastewater contains a lot of protein. Scientists have now devised a method of harvesting that protein, so it can be used to supplement animal feed or food for humans.
First off, it should be noted that organic matter is already removed from shrimp-processing wastewater before it's discharged back into the waterways. This is typically done by adding chemical additives known as flocculants, that cause the matter to clump together. Those clumps then float to the surface, where they can be skimmed off and collected in the form of sludge.
Unfortunately, though, the most commonly used flocculants are based on iron or other non-food-grade compounds, so the harvested protein isn't fit for consumption. Instead, it's either converted into biogas or simply dumped in a landfill.
One alternative is to filter the organic matter out of the water using permeable membranes. These regularly clog up and need to be replaced, though, which can be costly.
Led by Ingrid Undeland and Bita Forghani, scientists at Sweden's Chalmers University have instead looked to edible flocculants made from alginate and carrageenan, both of which are derived from seaweed. Using these, the researchers were able to extract up to 98 percent of the protein present in shrimp-processing wastewater. After the sludge was dried into a powder, it was found to contain up to 61 percent proteins and 23 percent total lipids – examples of lipids include fatty acids and fat-soluble vitamins.
It is believed that the technology could be easily and inexpensively scaled up for commercial use.
The study is described in a paper that was recently published in the journal ACS Sustainable Chemistry & Engineering.
Source: American Chemical Society
