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Scientists reclaim contaminated soil with ancient technique

By Patricia Robertson A 2,000-year-old method of fertilizing soil may prove to be a faster and more effective way of cleaning up northern sites contaminated by oil spills or heavy metals from mining.

By Patricia Robertson

A 2,000-year-old method of fertilizing soil may prove to be a faster and more effective way of cleaning up northern sites contaminated by oil spills or heavy metals from mining.

Biochar is a form of charcoal produced by heating materials such as wood, mammal bones, or fishbones at very high temperatures with low, or no oxygen, a process known as pyrolysis.

Early dwellers in the Amazon basin developed a rich blend of bone, charcoal, and manure that once supported great civilizations and that was later named terra preta, “black earth,” by the Portuguese explorers of South America.

Now, thanks to a major grant from the Natural Sciences and Engineering Research Council of Canada (NSERC), a team of scientists from Yukon College and the University of Saskatchewan are working with northern industry to explore the potential of biochar in restoring contaminated soil in the north.

“We’re really only at the cusp of being able to understand biochar, its characteristics, and all the ways it can be used,” says Katherine Stewart, the Northern Biochar for Northern Remediation project co-ordinator at the Yukon Research Centre.

Soils contaminated with petroleum are usually treated in land treatment facilities by aeration, or turning the soil over, and commercial fertilizers. In the North, however, where the soil is frozen for much of the year, “the window for treating the soil is pretty limited,” explains Stewart. “We think biochar can help encourage the breakdown of petroleum when the soil is frozen. That means we’re potentially cleaning up soil a lot faster.”

The team includes soil toxicologist Steve Siciliano and soil scientist Derek Peak, along with a number of student researchers. They will work with Whitehorse-based Zakus Farms and two companies that plan to offer biochar-based restoration services in the North: Nunatta Environmental Services in Iqaluit and Federated Co-op Limited in Saskatchewan.

“Biochar can have very different physical and chemical properties, depending on the temperature and length of the burn,” says Stewart. “We’re trying to understand the factors that result in a different product so we can create biochars that do what we want them to do in northern soils.”

Why does biochar help to increase the breakdown of petroleum?

One theory is that high-phosphorus biochars, such as those made from bone, may be more effective than other types.

“Phosphorus is an important nutrient in stimulating the growth and activity of micro-organisms that occur naturally in soil, and that are capable of breaking down the hydrocarbons,” Stewart explains. “Bone biochars may be providing a slow-release form of phosphorus that is ‘feeding,’ or supporting, this microbial community.”

Another theory is that, under frozen conditions, the biochar actually changes the texture of the soil by increasing the number of thin films of water frozen soil contains. “That might be a key factor in increasing the breakdown of petrochemicals in frozen soil because the microbes need that water to grow and be active,” says Stewart.

“So biochar’s effectiveness may have to do with the slow release of phosphorus over time, or it may have to do with liquid water being available. It’s also possible that the hydrocarbons themselves may be sticking to the outside of the biochar.”

In Iqaluit, where Nunnata Environmental runs a land farm - a contained treatment area for contaminated soil - the team is working with the company to find local feedstocks to make biochar, and to examine how the biochars work at a much higher latitude under colder conditions.

They’re also working with Warren Zakus of Zakus Farms, in the Ibex Valley just outside Whitehorse, where Zakus has been making his own biochar using spruce, pine, and now bone meal.

“Having a partner like Warren Zakus is a real bonus for us in terms of having more local knowledge,” notes Stewart. “We wanted to do the research in the North and work with northern soils.”

The team is planning to ship some of Zakus’s biochar to Iqaluit for use this summer. “That will give us a really interesting comparison because we’ve set up an experiment at the land treatment facility near the Whitehorse airport, and we’re now going to repeat that same experiment on the land farm in Iqaluit, which has a longer frozen season.”

The team is working on how to increase the capacity to make biochar on a larger scale. Fishmeal is a potential source because it’s both locally available and high in phosphorus. In Iqaluit, getting local feedstocks is proving to be a challenge. “For example, we were looking at using beluga bones, but the bay is all iced in in Iqaluit right now and people were unable to get out and hunt the beluga. There’s a fish processing plant in Pangnirtung, so we’re going to see if it’s feasible for us to get fishmeal from them.”

The team’s research goal is to be able to identify the types of biochar (the feedstocks and processes) that are effective in working with contaminants in the North. They also want to understand how the biochar helps to accelerate the breakdown of petrochemicals, and how it reduces the uptake of heavy metals by plants in soils affected by mining.

If they can show that it’s worth using biochar to restore contaminated soils, ultimately they would like to see biochar being produced on a relatively large scale in both Whitehorse and Iqaluit.

“Not only do we learn how things are working, but we’re also providing real concrete solutions for dealing with contaminants in the North.”

This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived