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“Burn a tree, grow a tree. It’s simple, Jamie!”

So said an exasperated Natural Resources minister to me once. On one level, his argument sounded sensible. The carbon released into the atmosphere by burning one tree should be offset by carbon taken up when a new tree grows and takes its place – or so it might seem. Based on this premise, governments around the world – including Nova Scotia – have introduced policies to encourage biomass energy, buoyed by the hope of reducing carbon emissions.

It’s important to note that nowhere in the world is forest biomass electricity development driven by the energy market; the feasibility of these projects so far depends on support from government policy. When representatives for Nova Scotia Power Inc. (NSPI) were asked whether the company would pursue the Point Tupper biomass project if not for the province’s renewable energy requirements, the answer was a definite “no.” Why not? Cost and risk, of course. The government’s regulated targets for increased renewables provided an opportunity for NSPI to shift that extra cost and risk to Nova Scotian rate-payers.

So hold on. Given that Nova Scotias are picking up the tab, and given that forest biomass electricity hinges on government support, what do Nova Scotians get in return for these costs and risks? And what are we trading for the negative impacts to our forest resource and wildlife habitat, and sacrifice of our higher-value hardwood industries? What about the migrating songbirds, retuning to Nova Scotia in the spring, only to find biomass clearcuts where they once nested and raised their young? If the government’s intention is to reduce our carbon emissions, then Nova Scotians have a right to know whether Point Tupper actually delivers carbon reductions, given the damaging side-effects of burning our forests for electricity.

As it turns out, the assumption that forest biomass electricity reduces carbon emissions is rather brittle. The way forests grow and store carbon, and the way that energy is generated from burning trees, is not as simple as the “burn a tree, grow a tree” argument. Burning trees to make electricity can put more carbon into the atmosphere than burning coal, at least for the next few decades. Burning trees to heat buildings, however, may reduce carbon emissions.

A Critical Climate Accounting Error

So what’s going on here? There are three key issues at play. The first thing to consider is the time it takes a forest to soak up carbon from the atmosphere after biomass is harvested and burned, and whether the forest is even able to soak up an equivalent amount of carbon. The lag time between biomass burning and carbon take-up is important, because we need carbon reduction now, not decades down the road. Scientists tell us that if we can’t get a handle on carbon emissions in the near term, future reductions may not provide much benefit.

A Princeton University scientist named Timothy Searchinger, along with 12 of his colleagues, wrote about this way back in 2009, in an article in the journal Science, titled “Fixing a Critical Climate Accounting Error.” They made the point that land used for biomass fuels may, over the long term, store less carbon per hectare than it did before biomass harvesting. The upshot is that burning forest biomass results in immediate carbon emissions which may or may not be taken up by the forest decades in the future.

Burning trees for Electricity is Inefficient

Burning wood to heat buildings can be 80 percent efficient or even a bit higher. Burning wood to generate electricity, on the other hand, is far less efficient, in the neighborhood of 21.5 percent.

Some biomass electricity facilities can put waste heat to use, thereby increasing their efficiency. By supplying some thermal energy to Hawkesbury Paper, its pulp mill neighbor, Point Tupper, when operating under its best case scenario, can achieve 36 percent efficiency. In other words, of the 50 truckloads of wood delivered to that plant daily (yes, 50 truckloads a day!), 32 to 39 truckloads are wasted, quite literally, up the smokestack.  (Of course, the carbon from all 50 truckloads goes into the atmosphere, regardless of how much energy is produced.)

Furthermore, the carbon footprints of fuels are not equal. For example, electricity from natural gas is far cleaner than coal, and coal is cleaner than wood, on the basis of carbon released at time of burning per unit of energy produced.

A team of forest biomass energy researchers in Massachusetts found that under a best-case scenario (low-impact forest harvesting; use of biomass for heating rather than electricity; and replacing the dirtiest of the fossil fuels), forest biomass can become carbon neutral in as little as 10 to 20 years. However, under a worst-case scenario (clearcutting; burning wood for electricity; and replacing the least dirty of fossil fuels), the researchers found that forest biomass would not become carbon neutral within a century.

To put these results in perspective, the researchers offered a snapshot of estimated carbon emission levels in 2050 (assuming that the forest actually does eventually sequester all of the carbon released). Replacing electricity from coal with electricity from biomass would result in a three percent net increase in emissions by 2050, and replacing a natural gas power plant with biomass would result in a 110 percent net increase in emissions. Replacing an oil-fired heating system with a biomass heating system, on the other hand, could result in a 25 percent net reduction in emissions by 2050.

Researchers in Ontario ended up with similar results. Jon McKechnie and his fellow researchers found that replacing coal-fired electricity with forest biomass electricity would increase carbon emissions for some 16 to 35 years. These researchers also investigated converting trees to ethanol to be used as a substitute for gasoline, and they found that this would increase carbon emissions for more than a century.

Repeat Cutting

A researcher in Norway, Bjart Holtsmark, noted that previous studies had failed to account for the impact of repeated biomass harvests. He found that when multiple biomass harvests on the same piece of land are factored in (based on the forest reaching economic maturity), net carbon emissions from forest biomass electricity remain higher than coal-fired electricity for some 250 years.

There is also research pointing to reduced productivity in certain soils following some types of harvesting. Once the productive capacity of soil is compromised, the forest loses some of its capacity to sequester carbon. This appears to be the case in Nova Scotia, according to research commissioned by the provincial Department of Natural Resources. Unfortunately, DNR has yet to release the results of this study.

Signs of Change

So far, most governments have clung to their policies that make biomass electricity projects economically viable. Under Nova Scotia’s Renewable Energy Standard, biomass electricity still qualifies as renewable, regardless of its actual impact on carbon emissions and our forests. But there are signs of a shift. The European Union has recommended that existing biomass energy facilities should emit 35 percent less greenhouse gases than the fossil fuels they replace, and that new facilities release 60 percent less by 2018.

Massachusetts has gone further by actually changing its energy policy based on our new understanding of carbon accounting in relation to biomass. The state introduced a minimum efficiency requirement of 50 percent for biomass energy projects, a minimum of 60 percent efficiency for projects to receive full renewable energy subsidies, and the further requirement that a proposed biomass facility will reduce carbon emissions by 50 percent over its first 20 years of operation relative to a new natural gas facility. If such requirements were in place in Nova Scotia, the Point Tupper plant would not qualify for the special treatment which enabled NSPI to build it and have electricity customers pick up the tab.

Listen to the Science

What should we do? Nova Scotia’s Department of Energy needs to take a hard look at the science of forest biomass energy and carbon emissions, and adjust its Renewable Energy Standard accordingly. If Point Tupper cannot meet a 60 percent minimum efficiency requirement, perhaps it should no longer qualify as a source of renewable energy. Small-scale biomass heating projects, on the other hand, should be further explored for their potential to reduce carbon emissions while reducing our reliance on fuel oil and electric heat.

Furthermore, Nova Scotia’s Department of Natural Resources should introduce forest harvesting regulations to ensure that carbon storage in Nova Scotia’s forests is increasing over time, rather than decreasing. This would also help avoid the detrimental effects on biodiversity which result from clearcutting for biomass fuel.

Given the negative impacts of forest biomass electricity, it’s time for Nova Scotia to reassess the costs and benefits. Let’s look at the scientific evidence and start making the difficult but necessary decisions. Surely our forests and the wildlife they support are worth it.