But according to the province's new cap-and-trade carbon-pricing plan, nothing comes out of the facility's stacks.

The plan classifies biomass as a carbon-neutral way to create electricity or heat.

The province is taking its cue from federal government policy, along with that of the United States and European Union.

All are attempting to meet promises they made at a much-touted 2015 summit in Paris to reduce carbon emissions to a level that would ideally slow global warming.

The problem is that a tremendous amount of greenhouse gases come out of a biomass plant - often more per unit of electricity than if you'd burned coal.

"It's an accounting fiction," John Sterman, director of the Massachusetts Institute of Technology's System Dynamics Group, said of the carbon neutrality of biomass.

"I'd go so far as to call it an accounting fraud."

Last January, Sterman released a model for analyzing the life-cycle carbon emission of biomass.

He joined a chorus of scientists warning that in the rush to be seen to be doing something to reduce carbon emissions by subsidizing biomass, the western world will actually make them worse.

Almost 800 scientists signed a letter to the EU government warning that providing a subsidy to cut down trees and burn them for fuel would worsen climate change.

Meanwhile, the forestry industry has applauded the move in the United States and Europe.

Biomass has become big business, with coal-fired plants in England and Europe being converted to burn wood pellets. The United Kingdom alone generates 65 per cent of its renewable power this way.

Meanwhile, exports of biomass from North America are surging to meet the demand in Europe.

According to Statistics Canada, exports of wood pellets for biomass from this country nearly doubled between 2012 and 2016, when 2.4 million tonnes were shipped primarily to the United Kingdom.

While British Columbia was responsible for 65 per cent of our exports, Great Northern Timber shipped 140,000 tonnes of hardwood chips from Sheet Harbour in 2016.

The company also recently purchased the Scotia Atlantic pellet mill in Upper Musquodoboit.

The argument for biomass is that trees are already in the carbon cycle - they remove carbon from the atmosphere as they grow and return it when they die and rot.

Meanwhile, fossil fuels are carbon that are essentially locked out of the atmosphere until we drag them from the ground and burn them.

And the scientific community isn't in consensus with Sterman on biomass.

"If I were going into the forest and just cutting the whole stem to use only for biomass, then yes, the time to recapture the benefits would be extremely long," said Evelyne Thiffault.

The professor in Laval University's department of wood and forest science has developed models around carbon-dioxide recapturing from silviculture operations in Quebec.

Thiffault said the key to whether biomass is more carbon-intensive than fossil fuels lies not at the plant, but in the forest.

If you're harvesting a mixed stand and sorting it to its highest uses - with the best logs going to sawmills, lower value wood going for pulp and the remaining going for biomass rather than being left to rot - then she said you're looking at seven to 10 years until the regrowing forest sucks as much carbon back out of the air as was emitted when the biomass was burned.

"In general in Canada, and it's probably also true in Nova Scotia, you don't usually go into a stand and cut it just for wood pellets," Thiffault said.

Biomass is small potatoes in this province's power-generating makeup.

Since 2016, Nova Scotia Power's 60-megawatt Port Hawkesbury generating station in Point Tupper has only run part time - when it is the most cost-effective way to generate electricity. In 2017, the plant ran 22 per cent of the time and accounted for two per cent of the electricity generated in Nova Scotia.

But it has played an outsized role in the discussion around forestry practices in northern Nova Scotia.

A media investigation last winter found Port Hawkesbury Paper was cutting old-growth forest in Guysborough County largely to supply Nova Scotia Power's biomass boiler, which had been running heavily due to high natural gas prices at the time.

According to records provided by Port Hawkesbury Paper, 73 per cent of the hardwood cut in the Loon Lake area went for biomass, 11 per cent for firewood, eight per cent for hardwood pulp, six per cent for saw logs and a very small amount to make pallets.

Though Department of Natural Resources staff initially denied old growth was being cut, a review by the department's old-forest specialist resulted in then-minister Margaret Miller issuing a public apology.

"Only wood chips made from low value wood that has no other commercial use can be used for biomass," Nova Scotia Power spokeswoman Tiffany Chase said Friday.

"Most of the biomass product used to generate electricity at the plant is bark. Forest chip usage has dropped substantially since the plant operations moved to economic dispatch, by more than 75 per cent."

Sterman's model relies on forests being cut to supply a boiler.

He found that depending on the species, it takes anywhere from 44 to 104 years for a regrowing forest to suck as much carbon out of the atmosphere as was released when it was cut.

"We modeled a variety of forests but the one similar to yours would be a mixed hardwood-softwood in northern New England," Sterman said.

"That will take a century or more of regrowth to remove the (carbon dioxide) and store it again on the land. So in the best-case scenario, you don't get carbon neutrality for a century or more. Meanwhile, that excess carbon has been contributing to climate change and the ultimate regrowth of that forest isn't certain. Along the way, there could be wildfire, could be disease or erosion caused after the harvest of wood."

While the debate rages between scientists and policy-makers on the pages of academic journals and in the halls of power, Nova Scotia's new cap-and-trade program will be coming into effect.

Because of it, carbon credits won't have to be purchased to offset emissions from the province's two biomass plants supplying electricity to the grid - at Point Tupper and a 30-megawatt plant owned by Emera in Brooklyn, Queens County.

Chase didn't answer a question as to whether that will result in the biomass plants generating more electricity than prior to the cap-and-trade program.

"We are a Canadian leader in cutting carbon," Chase said in her written response.