There’s lots of it! At the industrial level, about 10% of the logs processed in its lumber mills end up as sawdust — three million tons every year. We use it to make particleboard, to generate warmth as wood stove pellets and even as an ingredient in cat litter.
But to me, the most intriguing use of sawdust is pykrete. This concrete-like material is made of 15% sawdust and 85% water, and frozen into sheets. It’s much stronger, less brittle and has a slower melting rate than real ice. It also floats on water, and can be molded into any shape.
Pykrete was developed during World War II, when steel for warships was in short supply. Geoffrey Pyke, an engineer in the Royal Navy of the United Kingdom, proposed it to make huge, unsinkable aircraft carriers.
He argued that if the military could make a pykrete hull thick enough, torpedo damage would have no effect. They could build mile-long floating islands, adding refrigeration coils to keep it from melting. And, when damaged, they could repair it with water. Well, this didn’t happen, but they did build one small test ship before the war ended.
Pykrete remains an unexploited curiosity. Occasionally, architects submit Pykrete designs for gigantic offshore construction projects. But, the material has proven unreliable, as it tends to sag under its own weight at temperatures above 5 degrees.
So, although the world has plenty of sawdust, using it in these novel ways continues to elude us.
