Converting human waste to energy, here today; dung farms booming tomorrow
America spends $5 billion a year dealing with sludge. Biosolids producers pay hundreds of dollars a ton to remove it, quickly filling landfills or other means of disposal, Sinton said on Sept. 15 at the AlwaysOn Going Green Conference in Sausalito, California. The scope of the globe's sludge problem is mindboggling. Every year, cattle feedlots produce more than 150 million tons of animal waste; the U.S. and Europe together generate 40 million tons of sludge from sewage treatment; and food production waste weighs in at a staggering billion tons per year.Companies working on these types of technologiesBeyond being socially unpalateable, sludge often contains elevated levels of toxic heavy metals such as lead, nickel, and cadmium, which cause serious health problems even at low levels of absorption into groundwater or farm soil. The technology used to extract the metals from sludge lets companies create "organic fertilizer" from biosolids, but environmentalists vehemently oppose such efforts. (When First Lady Michelle Obama planted an organic vegetable garden on the White House lawn, she sparked a political brouhaha when the soil showed detectable levels of lead, attributed to contaminated sludge fertilizer.)
Other, harder-to-destroy substances found in common sludge include the prions believed to cause "mad cow disease," and endocrine-disrupter compounds: complex chemicals that interfere with human hormones. Europe has instituted a ban on putting organic waste in landfills.
That's where Sinton and PMC hope to step in. His $2 million machine is like a giant Port-a-Potty that takes in sludge, mixes it with bacteria, or renders the organic matter into methane gas, an energy source that can offset the high power requirements of many biosolid treatment facilities. Such facilities are among the largest consumers of electricity in many large cities.
Another process, AquaCritox, cooks sludge in a special pressurized vapor chamber at temperatures above 705 degrees Farenheit. The process provides enough heat to produce 2 megawatts of power, using heat-transfer devices and other standard power-generation equipment. The process's byproducts are carbon dioxide, nitrogen and water; heavy metals are collected in a fine ash and can be recycled for industrial use.
While not as sexy as solar-energy power companies like Ausra or electric-vehicle darlings like Tesla Motors, companies looking into waste-energy technologies. But the mandate to deal with sludge in a more ecofriendly and economical fashion may be more potent than the mandate to move to green power. "Thames Water, which produces 25 percent of the biosolids in the U.K., has been instructed to run their operations as energy neutral within 10 years," says John O'Regan, the founder and CEO of SCFI group, the parent company of AquaCritox. "That means they have to look at biosolids as a source of energy."
The ban on biosolids in landfills in Europe adds pressure to figure out what to do with this ugly form of garbage. And in the U.S., as landfills continue to fill up, cities and large corporations are realizing they'll need to figure out alternative means for disposing of their sludge. A key to the adoption process, Sinton and O'Regan believe, will be that the new generation of biosolids treatment technologies can quickly turn into money-saving measures for cash-strapped sewage-plant and feed-lot operators, among others. "Company's have a budget right now," says O'Regan. "It's difficult to get a new technology adopted if you are asking a customer to pay a lot more for it. It's not going to take."
For his part, Sinton's dream is to put a PMC bioreactor in every backyard. "The technology scales down to fit inside a portable toilet," he says. "I'd like to make it so easy and cheap that we can sell them in Home Depot and give everyone a good source of power as well as a better way to get rid of their waste than flushing it down the toilet. That's like washing money right down the pipes."
And just as the technology scales down, it also can scale up. "There is no reason we should not have giant biosolids power plants that can do the same thing as solar power plants and the like," Sinton says. "All the sludge we bury or throw away is wasted energy."