Pollution-Prevention Branch Helps Navy Deal With Waste.
Author | Baker, A. Duffy |
The U.S. Navy is investing in a combination of new and old-age technologies to make ships compliant with international treaties that ban waste dumping at sea.
The agency in charge of fielding and testing these technologies is the Pollution Prevention and Material Safety Branch at the Carderock Division Naval Surface Warfare Center, located in Bethesda, Md.
"[We do] research and development for pollution-control technology that will enable ships and submarines to operate in the 21st century and be environmentally sound. We provide them with the technologies and procedures to comply with current legislation," said Gary Alexander, technical area manager for the solid waste program.
There are three main areas of research: solid waste, liquid waste and hazardous materials.
Currently, there are four pieces of equipment in use aboard ships that were developed by the solid waste program at Carderock, explained Alexander. To dispose of paper, food and cardboard, they have large and small pulpers. In the pulpers, the waste is chopped up and mixed with water to form a slurry that is then dumped into the wake of the ship, as long as it is three nautical miles from any shoreline. It is biodegradable and "basically fish food," said Alexander. The large pulper can handle 1,000 pounds of waste an hour and the small one, 200 pounds.
Plastic waste is shredded and fed into a processor which melts and compresses it into hard, solid "pizzas" that are approximately 20 inches in diameter and one to two inches thick. The discs can then be stored aboard for later transfer to a landfill. The processor has led to a 30-to-1 reduction in onboard waste volume. It presently is aboard 200 ships. Alexander stared that research has been done into recycling the plastic for use as core material in pier pilings, but thus far that has not proved cost efficient.
The fourth piece of equipment is a shredder for metal and glass. Once broken down, the metal and glass will sink instead of bobbing on the surface when discarded.
Solid waste disposal on submarines is a bit different, explained Tim Bond, one of the developers for submarine plastic waste management. Currently, crews use hydraulic compactors to get rid of solid waste. Pre-made cans are assembled, the waste is compacted into them, they are weighted to sink and then discharged through a hull-penetration valve.
However, amendments to the Act to Prevent Pollution from Ships forbid the discharge of plastic waste after 2008. As a result, changes will be needed to allow onboard storage of waste. "We use the same cans that are used for normal trash compaction, but we line it with the odor-barrier bags. We compact the plastic into the odor-barrier bags, then put it in a second bag, and heat seal it. Then, [it is stored] in a locker onboard" for later disposal, said Bond.
Food waste is ground, placed in plastic mesh "wet bags," weighted for negative buoyancy and discharged with the cans. Bond stated that they are replacing the plastic mesh bags with cloth ones to comply with the no-plastic discharge policy. These changes have led to a 20-to-1 reduction in waste volume.
The technology emphasized in solid-waste disposal is the plasma are waste-destruction system. Plasma is created when an electric are is formed in a gas. This technology is more than 100 years old. The systems are large, use heavy refractories and require a skilled workforce. But the system developed by the Navy has done away with that.
John Cofold, a plasma are expert at...
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