At Sea — December 2000
By Capt. Bill Pike
2: Nassef's system does seem pretty clean.
I studied the machine for a moment. It was about the size of a big suitcase, not counting the five-gallon, plastic pickle bucket that served as an experimental holding tank. I listened to Nassef's explanation of how the unit works. The process starts when various sensors installed on the engine indicate adequate exhaust-header temperatures and exhaust flow. Then the microprocessor signals the unit to begin pulling waste from black- and graywater tanks as well as the bilge, if it contains any pollutants. The first stop is a macerator that chops solids into particles approximately the size of a pencil eraser. The next stop is the heart of the system, a "homogenizer" Nassef designed himself. Via a succession of layered, circular knives, it solubilizes all organic matter by agitating and reducing it to particles no larger than the ball in a ballpoint pen, thus converting it to what Nassef calls "waste fuel." Finally, the waste fuel is atomized by a high-pressure, variable-speed injector pump into the intensely hot "flame zone" of the engine exhaust header, where the water flashes to steam and the solids burn to ash.
I had a couple of questions. First, wouldn't the injector nozzle inside the header clog occasionally, thus shutting down the system? Nassef noted that a microprocessor-controlled pulse of clear water follows each burn period--it flashes harmlessly to steam--to keep the injector orifice clear. Second, in a diesel application, wouldn't the logical placement of the injector upstream of the turbocharger cause residue buildup on the turbine blades, affecting both turbocharger and engine performance?
"I won't know for sure until I do some experimentation on a big diesel powerplant," says Nassef, "although my intuition as an engineer leads me to believe there won't be much more residue than you get with the hydrocarbons already present in the exhaust."
Nassef's system does seem pretty clean. According to emissions testing reports he has from Severn Trent Laboratories in Pensacola, the exhaust gases blasting through the prototype-equipped manifold of the test engine on his Chaparral 21 were not only environmentally acceptable, but also actually showed 98 percent removal of CBOD (carbonaceous biochemical oxygen demand), TSS (total suspended solids), fecal coliform, and TPH (total petroleum hydrocarbon) pollutants.
Following my visit to Pensacola, I talked with a few engine and sanitation experts about Nassef's waste-disposal idea. Some were enthusiastic and interested in seeing blueprints and data. Others saw trouble ahead, mostly related to the possibility of poor engine performance should waste fuel cause header temperatures to drop, an eventuality Nassef addresses with a temperature sensor in the header and microprocessor control of the injector. The toughest questions focused on engine warranties, however. What if corrosive chemicals, volatile liquids, and other dicey substances inadvertently wind up in a holding tank and ultimately an engine? What manufacturer in his right mind would warrant such a situation? Nassef's replies that his system will burn just about anything safely.
Good ideas generate good questions. Answers will come only through testing of Nassef's system on powerplants larger and more sophisticated than the one he says he's had success with. Will this system someday enjoy a lucrative and environmentally friendly career on recreational boats? Who knows? Given the general scuzziness of my own dealings with current methods of sanitary waste disposal afloat, you bet I'm hopeful.
This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.