Is industrial wood ash safe for farm use?

The large scale use of industrial wood ash on Nova Scotia farms is undergoing a precedent setting review.

Nova Scotia reviewing NS Power application

Advocates say wood ash is safe and effective. (CBC)

Nova Scotia is reviewing the large-scale use of industrial wood ash on farms.

The precedent-setting case involves the Nova Scotia Power biomass plant at Point Tupper, which is expected to generate between 12,000 and 15,000 tonnes of wood ash per year if it gets approval.

It wants to be able to pass it on to farmers for use on fields. 

"This application is the first time we've had the opportunity to look at [wood] ash, because this approval process was re-opened," Randy Delorey, the environment minister, told CBC News Monday.

The material will be evaluated under biosolid guidelines adopted in 2010. It's the first time they've been used in this situation. 

"It’s an opportunity to keep in mind the environmental impacts," Delorey said.

Lise Leblanc, a Nova Scotia Power consultant, said wood ash is a cheap source of nutrients and limestone and has been long used safely on Nova Scotia farms.

"It really improves soil health," she said. "Instead of taking a product that’s waste and taking it to the landfill, we can now combine industry with agriculture, where both industries benefit each other."

Farmer says it works on crops

About 100 farmers use wood ash in Nova Scotia. Brooklyn Energy near Liverpool supplies about 500 tonnes a year to Falmouth farmer Bob Wilson, who spreads it on all of his crops.

"It works well on alfalfa and any legumes," Wilson said.

Farmers only pay for trucking and a portion of that cost is subsidized by the department of agriculture.

"When you compare it to buying potash and limestone, it is considerably less expensive. You have to use twice the amount per acre as limestone, but it is still considerably less expensive," Wilson said. 

JD Irving paper mills in New Brunswick also bring wood ash into Nova Scotia.

Leblanc urged the environment department to use federal rules.

"We're a little concerned they are going to follow biosolid guidelines, which is a much tighter limit, but that’s not based on science. We want the numbers to be based on science," she said.

NSP submitted lab analyses of the Point Tupper ash as part of its application.

"There have been a couple of preliminary but inconclusive tests that came back that we're looking closer at," Delorey said

Temporary permit until January

Last week his department issued a temporary permit to allow NSP to supply stockpiled wood ash from Point Tupper until January. He said that would let them get more samples for better testing. 

The Nova Scotia Federation of Agriculture supports the use of wood ash.

"Wood ash provides a very valuable nutrient and pH neutralizer to Nova Scotia farmers at a fraction of the cost of lime and fertilizer,” the organization said.

“There is a temporary approval currently in place to permit farmers to access the product. We understand that further testing is being conducting, but in the interim farmers are pleased to have access to this low-cost soil amendment.”