It turns out that the future of the hydrogen economy may begin with a toilet, a magazine and a locked door.
Researchers have found that waste-water treatment facilities such as Toronto's Ashbridges Bay plant could produce significant amounts of hydrogen by fermenting dried-sludge pellets in a mixture of "primary" sludge – an organic cocktail of feces, rotting fruits and vegetables, textiles and paper.
The idea of producing hydrogen from municipal waste water isn't new, but controlling the amount of hydrogen produced has proven tricky. One problem is that sludge contains bacteria that produce hydrogen and bacteria that consume it, so the net yield tends to be much lower than its potential.
"In order to maximize production you need to kill all micro-organisms that consume hydrogen," said Youssouf Kalogo, a researcher at Hamilton-based environmental consulting firm Hydromantis Inc. Doing this, however, means boiling the sludge – an energy-intensive process that proves uneconomic.
Kalogo, along with former University of Toronto professor David Bagley, who now teaches civil engineering at the University of Wyoming, realized that another option was to spike the primary sludge with dried sludge pellets. It turns out that the process of making the sludge pellets kills off the bad microbes and preserves the good ones.
The two scientists conducted an experiment, the results of which will soon be published in the peer-reviewed journal Bioresource Technology, which showed that pellets obtained from Ashbridges Bay were an inexpensive, practical, and renewable source of microbes for generating hydrogen from sludge.
"This is general research that can be applied to any waste-water treatment plant, and it's a totally new approach," Kalogo told the Toronto Star. "We know that the pellets already exist in plants, so why can't we use the pellets directly as a source of micro-organisms?"
The hydrogen that's produced could be used in a fuel cell to produce electricity and heat for the treatment facility, with any surplus power being sold back into the grid.
"These municipalities have to manage the solids they're producing, and this is a very good way of doing it."
The Ashbridges Bay facility once incinerated its sewage, but the city moved to a cleaner anaerobic digestion process and a system that dries the sludge and turns it into compressed pellets. The pelletizer system was hit by a major fire in August 2003 and has since been out of commission. The city expects it will be back in full-scale production by the summer.
Lou Di Gironimo, director of waste-water treatment for the city, said the sludge digester at Ashbridges Bay produces methane gas that is burned to generate heat or flared when there's too much gas.
"Part of the problem with methane is that the gas is really dirty." He said hydrogen would be a better gas to produce because it burns clean, has higher energy value, and is easier to work with.
"It's not a greenhouse gas concern either, whereas methane is a significant concern."
Methane is 20 times more potent than carbon dioxide as a greenhouse gas.
Di Gironimo, who supplied the pellets to Kalogo and Bagley, said he plans to review their research and will decide then whether to proceed with a pilot project to test their approach.
"The ramifications of this are huge if you look out 10, 20, or 30 years, because the energy benefits are significant," he said.
