The block in the photo may not look like much. It's a building material, after all. But, rest assured, it's not a normal piece of masonry. For one, it's 35% wood from old doors and windows. For another, it contains nasty pollutants that used to go into the air. Most impressively, it's carbon negative. More CO2 is locked inside than was emitted during the brick's production and transport.
Known as the "Carbon Buster," the block is manufactured by a company in the east of England. Lignacite has been making products from wood for 65 years. But it wasn't until recently that it came up with the world's first carbon negative block. That was possible because of a partnership with another company, Carbon 8, which shares its site in Suffolk.
Carbon 8 takes noxious fumes from waste incinerators and sequesters them in drums full of lyme. It then adds CO2 from a local sugar beet factory, plus cement, water, and sand, and creates a hard pellet, or aggregate. To make a block, Lignacite mixes that with wood shavings it collects from the nearby community (using two converted postal trucks).
Each Carbon Buster is made of 50% recycled material and locks in about 31 pounds of carbon dioxide. That includes the CO2 the original trees took in during photosynthesis, and the CO2 captured in the aggregate-making process.
The result isn't elegant. Giles de Lotbiniere, Lignacite's chairman, says builders don't use the blocks for front-facing purposes (they need to be covered with plaster or something else). But they're relatively lightweight, suitable for the biggest projects, and more fire-resistant than blocks made from stone, which crack and crumble at high temperatures. The wood inside the Carbon Buster won't burn in a fire, because it's not exposed to oxygen. Instead, it will calcify and blacken, but remain in place, de Lotbiniere says.
A builder near Lignacite plant has used Carbon Buster bricks in about about 600 homes so far. De Lotbiniere says they sell at a 5% premium compared to conventional bricks. But he's confident there'll be a market.
"Over the years, we've wondered if we want to continue making blocks out of wood," he says. "Each time we've found another reason to do it. Now, with climate change, we've found another one."
[Image: Flickr user Marit Meyer-bell