In Depth
Science
Maple sap tapped as potential green products source
March 15, 2007
By Paul Jay | CBC News
Clear sap drips from the branches of a maple tree. Canadian researchers are hoping the liquid can be used in creating natural polymers for industrial applications. (National Research Council)
The maple tree already provides Canadians with a beautiful part of the landscape, a national emblem and the sticky sweet syrup created from its sap. Now researchers have tapped into a new use for the sap: a base for a natural, biodegradable polymer, one they say may reduce our dependence on fossil fuel-based plastics.
The discovery could potentially provide a new range of biodegradable products such as more environmentally friendly packaging material, and could be used for medical applications like drug delivery systems and surgical sutures, the National Research Council said.
It could give a boost to a seasonal industry in which Canada is the dominant player.
Canadian producers accounted for 86 per cent - over 34,000 tonnes - of the world's maple syrup production last year, with the United States accounting for the remainder. This production led to sales of $178 million in 2006, according to Agriculture and Agri-Food Canada.
The production numbers represented a drop of eight per cent from the previous year, mostly because the number of taps in Quebec, which produces 90 per cent of Canada's maple syrup, declined from 38 million to approximately 34.5 million. But it also represents the second straight year syrup production has declined after strong years in 2002 and 2003.
But the decline in taps has more to do with slow sales than a dwindling reservoir of trees from which to tap sap. Agriculture and Agri-Food Canada cites the problem in their 2005-06 industry report, saying "production volume has been increasing much more quickly than domestic sales exports, creating an imbalance between supply and demand of maple products.
"The industry therefore accumulated year-over-year inventory surpluses," the report said.
A naturally sweet discovery
The science of sweet
The sap from sugar maples, red maples and silver maples can produce syrup. The process starts during the growing season, when the trees accumulate starch. During the spring thaw, the trees convert this starch to sugar and it mixes with water drawn up from the roots. In early March, the clear sap starts to run, giving the tree energy to grow. Maple producers typically remove less than one-tenth of a tree's sugar during tapping to be used in creating maple syrup, which allows the tree to be used year after year as a renewable resource.
Those surpluses are also behind the welcome accident that led NRC scientist Jalal Hawari to discover the potential use of the tree's clear but still sugary sap. After reading a report in a Quebec newspaper about the 27 million kilograms of surplus maple sap, Hawari decided to see if the substance might help him with a project he was working on to create natural polymers.
Hawari said the secret behind this new technology is bacteria called Alcaligenes latus, known for transforming sucrose into a group of naturally occurring polymers called polyhydroxyalkannoates, or PHAs. Before turning to maple sap, Hawari's group had been feeding the bacteria liquid waste from the apple juice manufacturing process.
But the bacteria, it seems, like a discerning pancake lover, find the syrup an excellent food source. While the bacteria feed on the sap, they process the sugars and store much of what they cannot eat in the form of PHAs, which can then be extracted and used as a biodegradable material. This is done much more efficiently in maple sap than in other sucrose solutions.
While corn and sugar cane can be used in a similar manner to feed the bacteria, Hawari said breaking them down into a sugary solution palatable to the bacteria adds to the cost.
"There's a cost to transform corn or sugar cane into a ready state the bacteria then interact with," said Hawari, group leader of environmental and analytical chemistry at the NRC's Biotechnology Research Institute. "But with maple sap it's already a liquid and already rich in sugar. You can take it straight from the tree. It's a more cost-effective process."
Natural polymers have medical potential
Hawari said that unlike fossil fuel-based polymers, natural polymers biodegrade over time more readily, but are still stable enough to perform their functions. They are also biologically inert, meaning they won't adversely affect humans if used for medical applications.
Already the Biotechnology Research Institute has applied for a patent for at least one of the products using the maple sap-based polymer, and plans to pursue partnerships with researchers working on possible nanotechnology applications.It could also provide an alternative for maple sap producers beyond the niche market of maple syrup, and could lead to a boom down the road for tree-tappers: Hawari said only one-third of the potential reserves of maple trees in Quebec are tapped.
Hawari credits government interest in pursuing green research designed to reduce our reliance on fossil-fuel products with the discovery.
"Maple trees are such a common thing here in Canada but it took a push towards greener products for us to look at it as an option," said Hawari.
"We're lucky to have stumbled onto it," he said.
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