It seems that you can build just about anything out of wood.
While researching the carbon footprint of steel production for a lecture recently, I came across the line "it takes 200 tons of steel to make a wind turbine" – a justification for steel being green. It reminded me of a trope going around a few years ago where Thomas Homer-Dixon was misquoted as saying:
TreeHugger Mike demonstrated this wasn't true, and Homer-Dixon wasn't too happy about it either, but the steel industry is still pushing the idea that they are essential to a green future. To which Swedish company Modvion says, Oh yeah? We can build a wind turbine tower out of wood!
"A two-megawatt windmill contains 260 tonnes of steel requiring 170 tonnes of coking coal and 300 tonnes of iron ore, all mined, transported and produced by hydrocarbons. A windmill could spin until it falls apart and never generate as much energy as was invested in building it."
There are actually many advantages to this. Not only does it avoid the carbon footprint of making all that steel, but because it is transported in sections rather than as complete tubes, it is not limited in diameter for transport like steel tubes are.
As wind towers rise above 100 meters in height, transportation poses considerable problems given that base diameters for 100+ meter towers exceed 4.3 meters, the limit for transport width in most parts of the USA and the EU.
Because wood is lighter than steel, they can lift bigger sections. "Conventional steel tower constructions get dramatically more expensive with height due to the increasing need for thicker walls."
In Wind Power Monthly, Chief Technical Officer Erik Dölerud explains how they used Laminated Veneer Lumber (LVL) to get the strength they needed. "LVL is a loadbearing plywood structure created through laminating many very thin wood-veneer layers, making the Modvion towers 250% stronger than CLT-based equivalents." (Learn more about the different types of mass timber here.)
CEO Otto Lundman explains how it differs from steel towers.
"Our calculations indicate that the 150-metre tower will reduce mass by about 30% and cut manufacturing costs by roughly 40% compared with an equivalent tubular steel tower with a 6-7-metre base diameter. And wood is a natural product that can often be sourced locally, creating local jobs and other added benefits."
And don't forget about that carbon footprint!
The wooden towers also offer additional environmental benefits compared with steel towers thanks to the lower-carbon manufacturing process. Lundman estimates a saving of 2,000-tonnes of CO2-emission per tower up until deployment. Plus, carbon sequestration in the wood offers the potential to make a wind-power plant carbon neutral.
This is all still at the prototype state, and we probably won't see steel being replaced by wood soon. But it does put paid to the steel industry argument that you absolutely need steel if you are going to go renewable.
And it demonstrates that you can build just about anything out of wood these days.