By Matthew D. Ernst
IOWA CITY, Iowa — Engineers at the University of Iowa have devised a highly combustible solution to safely disposing poultry carcasses and waste in the event of an avian influenza outbreak.
More than 50 million birds were destroyed in the United States as a result of the 2014-15 highly pathogenic avian influenza outbreak. “Iowa is the No. 1 egg-producing state, and there was a big impact from that bird flu outbreak here,” said Al Ratner, associate professor of mechanical engineering at UI.
The avian influenza virus can harbor in poultry tissue and manure. Composting can raise decomposing poultry to the temperature needed to deactivate the flu virus, around 60 degrees Celsius, or about 140 Fahrenheit. But composting takes time and winter can make it more difficult to reach necessary temperatures by this method. The composted matter must also be disposed.
A faster way of heating poultry carcasses and manure could create more cleanup efficiency. Toward that end, the U.S. Poultry & Egg Assoc. and the USPOULTRY Foundation funded research at UI. The researchers looked at using a gasifier to eliminate disease pathogens.
The research, led by Ratner, developed a design for a mobile system that heats poultry carcasses and manure to temperatures great enough to inactivate the flu virus. The system uses potentially low-cost energy sources, like wood chips, that are available on or nearby farms to create the needed bioenergy.
The poultry industry turned to UI engineers because of their experience operating an industrial-scale gasifier fueled by such bioenergy sources. A gasifier is a potentially ideal method for reducing biohazards after an animal disease outbreak, according to Ratner. That is because gasification is an extremely efficient, clean-burning process.
“Gasification involves turning some sort of solid material into gas before you burn it,” he explained.
Ratner gives the example of an outdoor bonfire. The wood is burning and, if the fire is at a high enough temperature, the gas given off by the fire mixes with the air and also burns. “When it does that, it’s burning cleanly, like when you see that blue flame that doesn’t have any soot or anything.”
That’s the goal of a gasifier. “The whole idea of gasification is to take fuel that would normally burn more dirty, if you just tried to burn it, and to get that fuel to burn more cleanly,” he said. “If we gasify it – turn it into gas – we can mix more air with it and get it to burn cleanly.”
The system developed at Iowa used wood chips and expired seed corn to fuel the gasifier. “Those are things likely to be available close to any farm,” noted Ratner. Those fuel sources are also economical. “If you’re going to run everything on propane, it’s going to get real pricey.”
Hot enough, clean enough
Even though the avian flu virus is deactivated at 140 degrees F, the gasifier has to heat poultry and waste to a much higher temperature. “You don’t have to heat things very hot to kill the virus, but you have to heat them all the way through – that’s to the inside of the bone,” said Ratner.
The engineers had to pinpoint the proper time and temperature, within the gasifier, to heat dead poultry and manure hot enough to kill the virus. “Once you dry off a lot of the water that you can easily get out, you get to the fat-melting temperature,” he explained. “Then you have to decide, are you going to heat longer, below the fat-melting temperature to get the temperature all the way through, or do you modify some things so that you can go above the fat-melting temperature without causing that fat to catch on fire?”
The Iowa engineers found it more efficient to heat to a higher temperature. “We came up with some ways, using either air separators or exhaust gas recirculation, to go hotter than the fat-melting temperature, to 400 or 500 degrees Fahrenheit, and not have the fat catch on fire by reducing the amount of oxygen.”
The product left after gasification can be field-applied as a fertilizer or soil amendment. “The way we set it up is that you’d have some charcoal coming out from the wood, and you’d have mostly half-charred pieces of chicken coming out. That material can be field-applied as fertilizer. It’s not a threat anymore,” said Ratner.
The charcoal produced from the wood chips has an added benefit: It helps clean up the gas produced during combustion. In engineering terms, it produces “an in-situ charcoal bed that breaks down organic pollutants.”
“It produces very clean emissions,” Ratner summarized.
The gasifier at UI, which his team used to develop the poultry gasifier design, produces emissions that meet U.S. EPA standards “even if you run some pretty nasty chemicals through it,” he said. “It’s really clean emissions, and that happens because of the charcoal produced.”
The engineers applied the temperature specifications to a design of a mobile commercial-scale gasifier. “The parameters we worked out for a commercial-scale unit, which runs four gasifiers to provide the heat, is that per day you’d be able to process right around three tons of chicken and you’d need right around 2.2 tons a day of wood,” said Ratner.
The commercial-scale unit, being developed by Independence Energy in Des Moines, uses a conveyor to move poultry and manure into the gasifiers. The unit is mounted on a trailer that requires no special highway permits.
“We have the concept design finished and we know it will work,” said Adrian Lanser, Independence Energy CEO. The company is awaiting pre-orders before starting to produce the mobile four-gasifier unit, the AMF 100, said Lanser.
Not just for the birds
The mobile unit has potential applications beyond avian influenza. “If there’s a flood, which happens in the Midwest, you have livestock that are killed. You have water that is polluted. The cleanup can be pretty nasty,” Ratner said.
“This sort of unit can go a long way in helping with cleanup. The temperatures in this unit are high enough that you can disinfect from pretty much any of the pathogens you’d have from dead poultry or even livestock after a flood. You can take any sort of disaster materials and feed it in.”
There’s also another benefit in that the portable gasifier uses wood as fuel. “You often have a lot of woody biomass that’s from a disaster. You can take that, run it through a whisper chipper, which can be a wood source for the gasifiers,” he noted. “You can take the soft biomass and run it through the chicken heating side, then use the wood biomass and use it as a feedstock for the wood bioenergy.”
But the goal of the mobile gasifier unit is disaster preparedness from bird flu. “The units that we’ve designed can be used for other things as well, but they’re designed for avian influenza,” said Ratner.