Switch to wood pellets would mean a major reduction in greenhouse gas emissions

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Pembina Institute Biomass Sustainability Analysis

M. McKinnon

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A study by the Pembina Institute, an independent not-for-profit think tank focused on developing innovative sustainable energy solutions, suggests forest biomass is a workable solution for energy generation that will not have adverse effects on the environment. In fact, the use of biomass will considerably reduce net emissions of greenhouses gases (GHG), and thus offers a significant environmental advantage over natural gas fired generation.

The report, Biomass Sustainability Analysis, was commissioned by Ontario Power Generation and is available at the OPG website. (The full report is 138 pages; also available is a 14-page summary.)

The report concludes that Ontario’s forests could produce two million tonnes worth of wood pellets annually without being threatened; that using forest biomass can reduce greenhouse gas emissions by 80% on average compared with burning natural gas; and that such a program would create over 3,500 full-time jobs, with the vast majority of them in forest-dependent communities.

“Biomass is perhaps the oldest source of energy in the world,” notes Pembina, which estimates it currently provides about 10% of all energy world-wide. And while much of that is wood used in cooking and heating in less developed areas, biomass is also a mainstay in countries like Sweden, where biomass supplies 32% of energy.

Pembina used the United Nations framework convention on climate change as a guide in defining what qualifies biomass as renewable. That framework requires that biomass come from sustainably managed forests, with a particular eye on forest carbon stocks. Although Ontario has created a huge structure around sustainably managing our forests, it does not specifically manage forest carbon stocks. This presented one of the principal challenges in Pembina’s study, and is an area where it believes more research is required.

Its analysis combined several environmental modeling systems to estimate overall GHG emissions for both biomass- and natural gas-fired generation, and for the state of the carbon stocks in the forests, over a 100-year period.

Forest biomass

The biomass would come from residuals: principally slash (i.e., tree tops, branches, etc., much of which is burned at roadside now) and un-merchantable timber (mostly white birch in this area, but also from fire salvage). About three-quarters of the total volume of fibre for wood pellet production would come from logging residues in the Boreal forest, with another 15% from un-merchantable timber. The remaining 12% would come from logging residues in the Great Lakes St. Lawrence forest.

The report notes that most sawmill waste, a prime biomass source, is already being used in energy generation by the forest industry. It also indicates that half of logging residues “were assumed to remain on site to maintain soil nutrient quality and biodiversity”.

On the whole the study concludes this 2.3 million tonnes of forest biomass (about 15% is lost in the manufacture of pellets) could be taken annually without disrupting the health of the forests, their carbon stocks, or the existing forest industry. (It estimates the maximum sustainable yield of forest biomass from residuals would be enough to produce close to three million tonnes of pellets.)

That translates to about 4.5 million cubic metres of wood. Currently, the Ontario forest industry is harvesting about 11 million cubic metres of wood each year. Going forward from the birth of a wood pellet-fired generation industry, Pembina projected that would rise to 15 million cubic metres a year for 20 years, and then to 20 million cubic metres per year for the following 80 years. Those estimates are in line with the projections in Ontario’s forest sustainability plans.

Two million tonnes is the maximum amount of pellets that OPG foresees for its generating operations: 200,000 at Atikokan; 300,000 at Thunder Bay (OPG aims to convert it to natural gas, while leaving open the possibility of adding a mixed biomass-natural gas), 1,125,000 at Nanticoke and 375,000 at Lambton. As part of its study, Pembina also offered three scaled down scenarios, including one for just 100,000 tonnes of pellets per year for Atikokan GS, another for 200,000 tonnes per year for Atikokan GS, and a third for 500,000 tonnes per year for Atikokan and Thunder Bay GSs. The conclusions about carbon levels, GHG production, and forest sustainability were generally the same.

GHG emissions

The study looked at all the GHG impacts of using wood pellets, from the GHG cost of harvesting and chipping, to wood pellet production, to transportation (both to the mill as raw product, and to the GS as finished pellets) as well as the GHG emissions of burning.

Two million tonnes of wood pellets is enough to generate 3.4 billion megawatt hours of electricity (or 3.4 terawatt hours). Over 100 years, the average annual GHG emissions from producing, transporting and burning those wood pellets ranges roughly between 200,000 and 300,000 tonnes per year. (It’s a little higher some years, especially the first ten as the industry is developed, and a little lower others, due to variations in the age-class structure of the forests.)

By comparison, producing 3.4 terawatt hours of electricity with natural gas would produce a little more than 1,300,000 tonnes of GHG annually.

In the overall provincial picture, 3.4 terawatts (enough to power 280,000 homes for a year) is not very much electricity. Ontarians consume over 150 terawatt hours of electricity each year.

Under its current proposal for switching the Atikokan GS to biomass, OPG expects it will burn about 90,000 tonnes of pellets produce about 0.15 terawatt hours of power each year – less than one-fourth of what it typically produced as a coal-fired generator.

Finally, in order to estimate the impact of life cycle emissions of GHG associated with wood pellet-fired generation, Pembina had to look at how an industry producing two millions tones of wood pellets would work. It concluded that a network 17 pellet plants, stretching from Kenora in the northwest to Iroquois Falls in the Northeast, to Naim Centre and North Bay in the Near North, and Bancroft and Inglewood in the eastern end of the province, would be necessary.

These sites (which include Atikokan and Fort Frances) were chosen as having the smallest GHG emissions impact; they offer the best balance of nearness to the forest resource, the existing industry, and transport links to the generating stations.

“The hauling of the biomass from forest to pellet plants was modeled using trucks, and the transportation of pellets to the generating stations was modeled using truck and rail,” notes the report. Remember, under the maximum use scenario of two million tonnes of wood pellets, the OPG stations at Thunder Bay, Lambton and Nanticoke would also be using wood pellets.

The creation of this network of pellet plants is the main source of the 3,500 new jobs the switch to biomass would create.

Still waiting on power agreement

Although the Ontario government has clearly indicated its goal is to see the Atikokan Generating Station switched from coal to wood biomass, and Ontario Power Generation has made a significant investment in planning for that change, there remain a couple of issues to settle before the project finally goes ahead.

Firstly, the Ontario Power Authority and OPG have to come to an agreement on what the company will be paid for the power produced at a biomass-fired AGS. At an open house in late June, officials indicated that agreement was in the works, and that they had hoped to have it in place by early this summer.

Secondly, OPG’s board of directors will have to approve the switch once an agreement with the Ontario Power Authority is finalized.

Current Ontario law bans the production of coal-fired electricity after December 31, 2013. Current OPG plans are to have the AGS switched over by the end of 2012.

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