Human, industrial waste goes green
What do you get when you cross industrial waste with human waste?
Valuable soil where plants can grow, according to new research by a land reclamation expert at the University of Alberta.
Prof. Anne Naeth has been studying the process in which treated sewage sludge -- called biosolids -- is combined with lime-kiln dust, a byproduct produced during the manufacture of lime. Testing in Naeth's U of A greenhouse has shown the mix kills pathogens such as E. coli in the human waste, affects dangerous heavy metals so they won't wash into lakes and rivers, and produces an organic soil material where beneficial bacteria and plants can grow.
The results have exciting implications for the environment and for returning damaged land around Alberta to its natural state, Naeth said.
"For example, there are a lot of gravel quarries and limestone quarries around the Calgary area and in Alberta in general, so there's a huge demand for organic material to reclaim these sites. Because they're such large areas, there's just no way of getting enough material (currently) to fill the holes."According to numbers on Alberta Environment's website, there are about 550 sand and gravel pits larger than five hectares on private land in Alberta. The province estimates there are another 1,500 to 2,000 smaller pits on private land and 650 pits on public land.
Naeth said the most promising use for the soil material she is testing is for reclaiming quarries and thousands of old well sites. By the end of 2008, there were 45,248 oil and gas wells that needed to be reclaimed, according to Alberta Environment.Naeth hopes the product might eventually be used as a type of fertilizer on farmland.Another major plus: It puts two waste products to good use.
"My area of work is reclamation, and one of the things I'm really interested in is using waste materials in a positive way, and I think that's a huge benefit for humans as well as the environment," Naeth said.
"Right now, most of the human waste material is going into the landfill, which personally and professionally I think is kind of ridiculous when we're scrounging for material we can use for reclamations, so I think in that regard, it's pretty huge."
Currently, some damaged lands around the province are reclaimed using "clean fill," or soil dug up during construction projects, said Naeth. However, not enough of that material is available for all the reclamation work that needs to be done, especially since the recession has slowed construction, she said.
"But, of course, the human waste production hasn't slowed down," Naeth said.
For other reclamations, soil is dug up from undisturbed areas then hauled to damaged sites. "When you think about it, it's so ridiculous, because then you have a new disturbance."
Naeth's promising research results come after about six years of work by leaders in the municipal district of Bighorn, where officials needed a better way to handle biosolids and reduce waste.
There was already evidence that lime could be used to stabilize sewage sludge, so leaders in the municipality decided to investigate whether lime kiln dust from the nearby Graymont lime plant might prove useful, said Paul Ryan, a councillor in Bighorn who has worked for years on the project.
"We thought, well, these guys (at Graymont) deposit thousands of tonnes a year of waste from the plant into the landfill, so can we treat biosolids with industrial waste? We discovered very quickly that we can use industrial waste to treat human waste, and we can create a product that will grow natural vegetation in it."
Now, the municipality's big worry is that there won't be enough lime dust coming from the plant near Exshaw, said Dene Cooper, who is chairman of the Bow Valley Waste Management Commission and reeve of the MD of Bighorn.
"We're still digging the quarries. It's not like we're going to run out of room for this product ... So we're not filling up a landfill, we are treating human poop, we're not hauling it great distances, we are reclaiming quarries and we're protecting the water table," Cooper said.
"This is a huge step to getting human waste treated in the Bow Valley."
So far, Naeth has grown grasses and legumes in the soil material. Next, she will try to grow trees and will do more tests to make sure plants don't suck up anything out of the soil material that could harm wildlife.
Officials from the Bighorn area have asked the province to approve a pilot project this summer, so they can start filling in quarries. About a dozen gravel, limestone, sandstone and shale quarries in the area need to be reclaimed and re-established as bighorn sheep habitat, Cooper said.
The towns of Canmore and Banff as well as Banff National Park "have generously supplied raw materials for the trials," Cooper said.
Some municipalities, such as Banff, compost human waste. However, composting the sewage doesn't bind up those water-soluble metals the way lime dust does. That means it makes more sense to use waste treated with lime dust than composted waste near water systems, especially in steep, rocky areas such as the Bow Valley, Cooper said.
"There's lots of metal ions in human poop, and it's not good for the water that Calgary has to drink," Cooper said.
Also, the cost of buying a composter is extremely high, "starting at $8 million for a town the size of Canmore," Cooper said.
"One of the other benefits of lime is that the cost to get into this and produce this product is very low, measured in the hundreds of thousands, not many millions."
However, Cooper said the product isn't something homeowners will spread in their backyards, where they're going to plant gardens and let children play.
"You will not buy a bag of this in your local hardware store to put your petunias in."
Partners in the study as well as representatives from the City of Calgary met last month with provincial officials to discuss the findings.
Allan Mumby, Epcor's program manager of residual organics, who works at Edmonton's Gold Bar Wastewater Treatment Plant, could not attend the meeting but said he is monitoring the studies.
Soil treated with kiln dust is best suited for use in areas where the soil is highly acidic, such as mining sites, because it's high pH level neutralizes acidity, Mumby said. There's not much acidic soil around here, "but there could be other areas in the province that would find a good use for that (product)."
Edmonton composts about half its biosolids, a byproduct of the waste water treatment process, and the other half is stabilized in a secondary treatment system and applied to local farmland.
asands@thejournal.canwest.com
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Posted on January 6th