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A tale of two biomass technologies

Fluidized bed technology is here. Why not use it?

by Miles Howe

Subsidies and governmental tonnage allocations mean that conventional biomass boilers are increasing demand on 'low value' wood. Can the forests take the strain? [Photo: Zach Stern via flickr]
Subsidies and governmental tonnage allocations mean that conventional biomass boilers are increasing demand on 'low value' wood. Can the forests take the strain? [Photo: Zach Stern via flickr]

KJIPUKTUK (Halifax) - From an environmental perspective, when one contemplates the impact of biomass burning in the province of Nova Scotia, one might be excused if one's overarching assessment of the technology and its effect upon the province's forests was negative. Between the provincial Department of Natural Resources' 2014 primary allocation of 50,000 green metric tons of western Crown Lands to Scotia Atlantic Biomass Company, for the explicit purpose of export-bound wood pellet production, and the usage in 2014 of 194,538 green metric tons of primary biomass to fuel Nova Scotia Power's Port Hawkesbury biomass burner, that's a whole lot of trees getting burned to produce electricity.

The provincial appetite for wood-based biomass, as shown by the nearly 250,000 green metric tons harvested for its use, is far exceeding the supply of secondary sources, waste products from sawmills such as sawdust and bark – sources that give biomass burning its 'green' spin.

In feeling this crunch, Nova Scotia is not alone. North American exports of Europe-bound wood-based biomass is growing exponentially, having doubled between 2011 and 2013 to 4.7 million tons. In the southern United States, various wood hungry European firms have set up satellite operations, created for the sole purpose of exporting pellets to feed their boilers. Reports suggest that European demand alone will likely reach 29 million tons per year by 2020, with European production capacity unable to exceed about 9 million tons. Much of this European demand will come from governmental subsidies offered towards “co-firing” existing coal plants with wood pellets.

Thus, we glimpse the cusp of a new problem: While weaning itself off of coal, and yet keeping the coal-burning technology largely intact, increasing demand on existing forests risks exceeding their ability to replenish themselves. This risks being undermined by the 'well, its greener than coal and trees grow back, you know' argument.

Already, even in Nova Scotia, we see the birth of new economics-based vocabulary to justify the biomass business. Where once wood pellets were understood to be a viable use of secondary products only, like sawdust and bark, now primary sources of wood are used, but only those that are “low value”. As though the stands of smaller species of trees that preclude mature forests are simply a fait accompli. Where suspicions are raised that harvesters are feeding the Port Hawkesbury biomass boiler valuable hardwood timber, industry and government's response is that the science of harvesting is of course “imperfect”, and these mistakes are bound to happen.

If the end-game is feeding existing coal-fired plants primary sourced wood pellets and calling it 'green technology', we're likely in for one more downward spiral as forests suffer.

On the other hand, alternative biomass burning technologies exist, and not just at the 'mom-and-pop' level either. Dalhousie University, as a matter of fact, is a leader in the game of alternative biomass technologies.

“Nobody in their right mind would burn good, quality, wood in a boiler,” says Dr. Prabir Basu, of the Dalhousie Department of Mechanical Engineering. Dr. Basu has been involved in the development of 'fluidized bed' boilers since the early 1970s. “That wood has a higher value use, like as timber or as making paper. What people, I would say, can afford to burn, is waste from wood...If you were to say: 'No, I'm just going to cut wood from the forest.' It would not make economic sense.”

Dr. Basu's life's work, fluidized bed biomass boilers, present an interesting alternative to the classic, conventional, biomass burning technology.

Basu explains:

“In conventional [biomass] technology, you dump the wood, just like your fireplace, in one place, and the air is blown up from the bottom. In this new generation technology, you have what is called a 'mass bed', which means you have, let's say, a bed of sand and then biomass is chopped and injected on that. That gets mixed with the so-called 'sand' and it is then burned in that bed of sand. If you look at it, it looks a lot like burning liquid.”

Basu notes that with fluidized bed boilers, the fuel source can come from a variety of “low grade” biomass options. These include readily available sources like yard waste, dead leaves, distillery waste and a variety of “energy crops” – fast growing crops that require little if any fertilizer, marginal water use, and can grow on otherwise abandoned lands. Basu notes that these crops, contrary to the timber and wood pellets used in conventional technology, are fast growing, coming to maturity in a matter of weeks or months, not years.

These “energy crops” can even include bothersome invasive species, such as Fallopia Japonica (Japanese Knotweed). Indeed, one of Basu's colleagues, working out of Halifax-based Greenfield Research Inc, recently supplied their design to a United Kingdom-based company towards creating a biomass plant with a 137 Megawatt capability in Ethiopia. The biomass plant would be able to use the invasive species Prosopis Julifloria, initially introduced into Ethiopia as a soil binder, as fuel towards electricity production.

So what's the catch?

Nothing, really. Fluidized bed technology is here and there's no difference in terms of capacity when compared to conventional technology. The only catch, as with so many alternative technologies, is that they wrestle control – in terms of fuel production – out of the hands of the few and place it in the hands of the many.

If there's top subsidized dollar to be made in Europe by simply doing the most marginal of upgrades to existing coal-burning plants, and then burning monopoly produced and controlled wood pellets, why change?

If levels of government, such as in Nova Scotia, are complicit in the near giveaway of the forest resources, then why bother building a new fluidized base boiler, be it in England or Port Hawkesbury?

“It is unfortunate that so much improvement in technology has taken place, but its not very well publicized and its not very well utilized,” says Basu. “A lot more superior energy options are available, than even five years back. For different reasons, they're not implemented to the extent that they should be implemented.

“You'd be surprised at the lack of knowledge, even at the highest level. I just read a report prepared by the US government for India. And they had no mention of the most advanced technology that is being used in very large capacity plants...Canada is not the only country, everywhere in the world, they're doing the same thing, with the exception of China. If something's good, they'll jump at it. Everywhere else in the world, the inertia is unbelievable.”

The 'Brooklyn Energy' plant, located across from the now defunct Bowater Mersey mill, utilizes fluidized bed technology. When the mill closed in 2012, Emera Energy Inc, sister company of Nova Scotia Power, snapped up the stranded asset for $25 million. The versatile plant, with a production capacity of 25 Megawatts, operates on an as-needed basis.

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