Mr Green's Vancouver-based firm, mgb ARCHITECTURE, is designing a prototype 30-storey building out of wood at Prince Rupert in northern British Columbia (BC).

''We - the Wood Enterprise Coalition, a combination of industry and the BC government - have a grant from the government to build this, '' he told BusinessDay at the conference, where he was a keynote speaker.

''We have the science and engineering work and need to follow it through and execute the scale that's possible.''

Mr Green said the aim of the prototype was to show clients, developers, architects, contractors and building code authorities that high-rise wooden buildings were possible. ''We need to work on explaining the details of how these things work,'' he said. ''I want to show it's viable in the marketplace, and does not require subsidies. It can work on the economics.''

In the interim, Mr Green's firm has designed a 12-storey building from wood that has been funded by the BC provincial government. This will also be built in Prince Rupert.

''The government has a role, but I want to prove this is a private-sector opportunity. A private-sector developer or contractor who jumps on this first will be the one who will reap rewards. In the future, there will be a lot of tall, wood buildings.''

To coincide with the Green Cities conference, Grocon announced it would build Melbourne's first wooden tower - a 10-storey timber apartment block on the old Carlton & United Breweries site in Swanston Street. Like the nine-storey residential Stadthaus at Hackney, East London - the first in Britain - it will be made of engineered softwood panels imported from Europe.

The Grocon building's lift shafts will also be of timber, and it will have its own gas-fired electrical generator powered by waste woodchips.

For the 30-storey building Mr Green said he would use laminated strand lumber (LSL) - thick, large sheets that were more than 20 metres long, and more convenient than the shorter cross-laminated timber (CLT). ''That's the length that allows us to more easily build the larger buildings, but it can be done with any system,'' he said.

Fire protection was a big issue. ''The [building] code is driven more by emotion than by the fire science. We have two different ways to fire-protect the building,'' he said.

The LSL will be hardwood poplar and birch from eastern Canada and the US. ''You can use fast-growing species. Because you're breaking down the wood fibre into small pieces, 50-75 millimetres long, which are reconstituted together … this allows you to use that fibre strength in the wood and the carbon storage capacity and use the glue, and the fact that the directions of the wood change, to get all that strength,'' he said.

''Instead of using trees that are 50-70 years old to maturity, we can use trees after 10 years.'' This could help reverse deforestation and help afforestation in a variety of countries, such as Brazil.

''We need to find an economic model that makes sense. It's hard to ask people to vacate farmland that's producing revenue and replace it with trees,'' he said.

''But if we can replace that with fast-growth trees, we can get the benefit of the forests from a carbon sink point of view. It also gives an opportunity to create a new industry that changes the value of the land.

''It's not realistic, for example, to expect Brazil to plant crops that will be cut down 50 years from now. If you can use fast-growing tree species - eucalyptus is a good example - and find new technologies to laminate the fibre together and introduce cast wood products, which is what LSL is … then you have potential all around the world to build large buildings made of wood.''

Did traditional appearance-grade hardwood products still have a role? ''Absolutely. The issue is, you have this responsibility. Effectively, I am a lumberjack. Every time I choose a tree, I feel a sense of responsibility towards the tree. I want to know where it came from, whether its ecosystem is well protected,'' he said.

''I want to understand, what I've chosen to use, that it will be successful and celebrated. If it's an older tree, I want to make sure it will be turned into a piece of furniture, not a structural material … something you can really enjoy.''

Mr Green said that in Canada, Greenpeace and the Sierra Club (an American green group) understood that was the lesser of evils.

''If we can learn to harvest the forest more responsibly … that ensures the quality of the wood.''

http://www.mgb-architecture.ca