Willow Trees Could Be Carbon-Neutral Energy Source

Bioenergy studies explore woody biomass for fuel use

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Naresh Thevathasan manages agroforestry research and development at U of G.

You’ve heard of wind and solar power as alternative energy sources. How about willow trees?

In a novel research project, U of G biologists are growing and harvesting willow and poplar on campus as a possible renewable energy alternative to fossil fuels. Their work is part of a national bioenergy network run by the Edmonton-based Canadian Wood Fibre Centre (CWFC) in several sites across the country.

Besides exploring woody biomass for fuel use, the Guelph team is also studying the trees’ potential for capturing and storing carbon to reduce greenhouse gas emissions ─ and perhaps for offering Ontario farmers a potential crop suited to huge patches of abandoned or marginal farmland.

“We want to fully explore the potential of this unique crop,” says Naresh Thevathasan, manager of agroforestry research and development and an adjunct professor in the School of Environmental Sciences (SES). “We have the largest woody bioenergy research site in southern Ontario.”

Five years after beginning their bioenergy studies, he and SES professor Andy Gordon are still learning about efficient ways to plant, grow and harvest willow. And it would take a huge leap and a number of other players to go from their studies here on campus to developing a brand-new Ontario energy sector.

But the Guelph researchers hope to help make the case for woody biomass as a new energy source. “We’re looking for a carbon-neutral source of energy. Bioenergy partly fills that,” says Gordon, pointing out that growers still need to use fossil fuels for equipment used to plant and harvest the trees.

Early studies at U of G have shown that willow and poplar can be grown and harvested effectively. That work occurs mostly at the Guelph Turfgrass Institute. Don’t look for hulking weeping willows. The researchers, including students, begin with neat rows of foot-high cuttings provided by the CWFC.

Cutting each planted stem after a year’s growth encourages the plants to throw out about a dozen new stems. Those stems are then allowed to grow for three years until they’re about three metres high. Then they’re cut and bundled into round bales like hay harvested from a farmer’s field.

Currently the bales are shipped to Windsor, where a partner company turns the wood into pellets. Those pellets could then be turned into charcoal to be used for fuel, says Thevathasan. But so far, that industry doesn’t exist.

Derek Sidders, CWFC regional co-ordinator, says woody biomass might provide an estimated one-quarter of Canada’s energy needs by 2025, but “the biggest hurdle is an established industry that demands the biomass. It doesn’t exist in this form. We’re developing the feedstock, but we need to fill the supply chain to the final user.”

Gordon says many questions remain in the farmer’s field, let alone in a still-nascent industry. Can farmers plant large enough plots to remain cost-effective? How efficiently do plantations recycle nutrients to avoid fertilizer use? How do you bring production facilities closer to farms to reduce transportation costs? What subsidies or public-policy changes might be needed to help grow the woody biomass industry?

Answering some of those questions is Thevathasan’s job.

He has collected data about such factors as growth rates, yield and production costs. He’s also estimating carbon capture and storage and potential reductions in greenhouse-gas emissions. About 40 per cent of the carbon held by the trees stays in the main stems and roots left untouched after harvesting.

Poking at a calculator, he says preliminary results suggest willow can effectively provide a carbon-neutral energy source. “The net gain is lower emission of greenhouse gases.”

Besides studying short-rotation woody biomass, the Guelph researchers are investigating the benefits of growing willow for intercropping. This farming method ─ basically planting corn, beans or wheat between lines of trees ─ has been practised in developing countries for thousands of years to keep soils healthy and reduce the need for fertilizers, water and other resources. Guelph researchers have studied agroforestry in Ghana, among other countries, since the 1970s.

The U of G intercropping plantation was established east of the Arboretum in 1987 and is the largest such site in Canada.

The researchers have found higher willow yields in their intercropped plots than in other areas. They’ve also learned that willow thrives in barren and stony soil ─ suggesting that the trees might fill in millions of scattered hectares across southern Ontario that have been abandoned or considered unsuitable for conventional farming.

Despite its economic and environmental benefits, intercropping has yet to catch on widely in southern Ontario. “There’s a lack of pertinent policy drivers,” says Thevathasan, adding that “there is an emerging interest in the technology at all levels of government.”

The Guelph researchers hope that rising fossil fuel prices and unstable supplies in parts of the world will force policy-makers to look more closely at biomass for energy production.

So does the CWFC’s Derek Sidders, a tree-growing expert who manages the national short-rotation woody crop program from Edmonton. He says the Guelph team provides valuable life cycle analysis, including information about carbon inputs and emissions and the benefits of producing energy from woody biomass. “Without the help of universities like the University of Guelph, we would not have anywhere near the credibility and impact,” he says. “This partnership is invaluable.”

The Canadian Wood Fibre Centre is run by the Canadian Forest Service, part of Natural Resources Canada.