NOVA SCOTIA (From CBC News) -- A report released this week by a non-profit, environmental law group questions whether forest biomass is actually a renewable source of fuel.

Biomass -- trunk bark and chips from the tree -- technically meets the definition of a renewable energy source because trees grow back.

In Nova Scotia, provincial regulations treat biomass as a renewable resource.

The equivalent of 50 pulp trucks a day, or 700,000 green tonnes of woody biomass a year, is burned to generate electricity for the Nova Scotia Power grid and Port Hawkesbury Paper mill next door to a biomass boiler that recently came online.

But a new 34-page report from the East Coast Environmental Law Association calls on the governments of Nova Scotia and New Brunswick to take a closer look at how trees are being cut and how electricity is being produced from woody biomass.

The report is written by Jamie Simpson, a former forestry coordinator for the Ecology Action Centre who also has a law degree.

Simpson says the absence of enforceable regulation around clearcutting combined with a lack of reporting about the efficiency of the Port Hawkesbury biomass boiler raises doubts about whether burning trees in Nova Scotia reduces carbon emissions.

The report acknowledges most international agencies -- including the International Panel on Climate Change -- continue to regard forestry biomass as a "carbon neutral" fuel.

However, the report says the situation in Nova Scotia and New Brunswick challenges that assumption.

"While the simple 'burn a tree, grow a tree' formula may seem intuitively sound, research is showing that in many cases, cutting and burning trees for electricity actually increases net carbon emissions for at least several decades, and sometimes for over a century," the report says.

To back up its claim, the report relies on the notion of a "carbon debt," as described in a study from Massachusetts.

The authors of the Manomet study describe a carbon debt as something incurred when biomass is burned, but which can be "repaid" over time, as the harvested forest regrows.

The study goes on to say under "best-case scenarios," with less clearcutting and highly-efficient burning of biomass, the carbon debt can be repaid in 10 to 20 years -- after which emissions of carbon dioxide begin to decrease.

Under "worst-case scenarios" -- involving intensive forest harvesting and the inefficient use of biomass -- the carbon debt will not be repaid for over a century.

The report prepared for the East Coast Environmental Law group says Nova Scotia and New Brunswick both fall under that worst-case scenario.

While Nova Scotia has increased the amount of wood being harvested to supply a 60 megawatt boiler in Port Hawkesbury that came online 2.5 years ago, the report says no one is tracking the impact it has on carbon emissions.

Nova Scotia Power says for the past two years, its biomass boiler at Point Tupper has operated at 36 per cent efficiency, the optimal efficiency level it was designed for.

In Massachusetts, 60 per cent is the new efficiency standard for converting woody biomass to electricity.

The report also says the Department of Natural Resources has yet to bring in regulations defining and governing biomass harvesting. It says the existing regulation pertaining to biodiversity conservation "is limited to ensuring that small clumps of trees are left during clearcutting operations (10 trees per hectare cut), and ensuring that forested buffers are left along watercourses."

The East Coast Environmental Law Association says a 50 to 60 per cent minimum efficiency rate would shift the focus on biomass energy away from electricity generation and toward heating buildings.

The report also recommends the Maritime Provinces introduce biomass harvesting regulations to ensure that biomass harvesting does not "cause significant negative impacts on forest biodiversity."