FINDING NEW FUEL
County zoo tests clean-burning wood chips to power train
It’s easy to tell when the Milwaukee County Zoo’s steam locomotives are chugging around the track that encircles the facility.
The white smoke billowing from the stack is the first clue, and the pungent sulfur smell from burning coal is the second.
But someday, zoo visitors could ride steam trains that emit no smoke and hardly any odor thanks to a solid biofuel made from renewable wood that’s being tested at the zoo.
Developed by the Coalition for Sustainable Rail and the Natural Resources Research Institute, the fuel is made from wood chips. Three different blends have been tested on the zoo’s two steam locomotives, with the most recent test earlier this month.
“It’s really cool to have a different fuel source than coal. It’s cleaner and doesn’t stink,” said Becky Danes, the first female Milwaukee County Zoo train operator in two decades. “There’s no sulfur smell, no heavy metals in the biofuel.”
Any type of wood can be used, and the chips are treated in a kiln similar to a coffee roaster before being turned into pill-shaped briquets with a type of glue called guar gum as a binder, said Davidson Ward, president of the Minnesota nonprofit, the Coalition for Sustainable Rail.
Ward is friends with Milwaukee County Zoo train engineer Ken Ristow. He asked Ristow if the zoo’s two 1958 steam locomotives could be used as guinea pigs to test the biomass fuel.
The first test in June 2016 of small rabbit food-like pellets did not go well because the pellets fell through the coalburning boxes on the locomotives. It burned well — hot enough to power the engine — but the size and shape were not ideal.
A second test in October 2016, this time of the biofuel without a binding agent, fired off way too many sparks. The third attempt earlier this month
was of a larger, more dense briquet that looked like barbecue charcoal on a diet.
Temperature sensors inside the locomotives’ fireboxes showed the biofuel performed comparably to coal.
The third iteration proved to be the most promising — burning hot enough to power the engine, smelling like a very faint campfire and no smoke.
It’s not yet ready for production “but it’s shown it can be tested on a full-size locomotive,” said Ward, a 2006 Whitefish Bay High School graduate.
The Coalition for Sustainable Rail and the Natural Resources Research Institute are raising funds to create enough biofuel to test on a large locomotive in Pennsylvania in March.
The idea is to create a cleaner-burning fuel to replace or reduce the amount of coal burned to power historic steam locomotives at museums and other facilities in the U.S., as well as for use in power plants, Ward said.
With the majority of the nation’s commercial trains operating on diesel or electric and the growing popularity of natural gas to fuel power plants, some coal mines are shutting down and the price of coal is increasing.
“If you’re a train museum, you might burn one train car of coal each season while a power plant might burn 110 rail cars of coal each week,” Ward said, “so it’s getting more expensive for a museum to buy a load of coal.”
Growing up in the Milwaukee area, Ward fondly remembers riding the zoo train as a kid. When Ward married his wife, Sarah, also a Whitefish Bay native, photos of each them riding the zoo train as kids were shown to guests in a slideshow.
The Milwaukee County Zoo’s two steam locomotives are about one-quarter the size of a large engine and burn 6 to 8 tons of coal each season.
The zoo’s trains are now being cleaned and refurbished for the winter and will resume operation in early April.
“It’s been fun doing this. The zoo is happy and proud to have the first locomotive to test this biofuel,” Ristow said.