Across the globe, the four most common metals used within the construction sector are stainless steel, copper, aluminum, and carbon steel. Carbon sequestration is the process involved in carbon capture and the long-term storage of various forms of this chemical in order to mitigate or combat global warming.
This process has been proposed as a way to slow the atmospheric and marine accumulation of greenhouse gases, which are being released through the burning of fossil fuels. There are a few ways carbon sequestration is done around the world, including biological, chemical, artificial, and physical processes. According to global change report, the latest national climate assessment states that hardwood trees play a major role in carbon sequestration and keeping the air clean.
Over a 25-year period, American forests stored the equivalent of 11% of the country’s carbon dioxide emissions. This occurs whenever trees suck up carbon dioxide and release oxygen, subsequently storing the leftover carbon inside their trunks. Hardwood trees, which can take upwards of 20 years to reach maturity, are very complex and can have a lot of carbon stored within.
“What’s going on inside of these trees, is kind of hidden to use, for the most part,” said Bob Marra, a biologist with the Connecticut Agricultural Experiment Station. “Trees that, otherwise, look to be perfectly fine and you would have no reason to think otherwise, can have internal decay taking place. If we’re going to look to forests as a way to sequester carbon, we should develop much more accurate estimates of how much carbon is actually sequestered.”
Whenever Marra goes into the woods, he brings his magic sonic hammer with him in order to determine exactly how much carbon is stored within each tree. Marra hammers nails into the trunk of the tree, girdling the tree with sensors. Then, he circles and tapes on each nail, which is recorded by a computer. The sound waves show how fast audio travels from the nail being struck with the hammer to the all the other nails in the tree — sonic tomography.
“The denser the wood, the faster the sound waves,” he adds.
Using a grant from the National Science Foundation, Marra has tested and scanned around 70 trees around northwest Connecticut.
Simply identifying how much carbon is stored within an individual tree is one thing, but utilizing that material for industrial usage is entirely another. Thankfully, carbon can be blended with steel to produce useful carbon steel alloys.
There are four types of carbon steel based on the amount of carbon present in the alloy. Lower carbon steels are softer and easily formed, and higher carbon content steels are harder, stronger, and are more difficult to machine and weld. Here are the properties of the four types of carbon alloys:
- Low Carbon Steel — Also known as mild steel, this is a low-cost material that is easy to shape. Composition of 0.05% to 0.25% carbon and up to 0.4% manganese.
- Medium Carbon Steel — This is both ductile and strong, with long-wearing properties. Composition of 0.29% to 0.54% carbon, with as much as 1.65% manganese.
- High Carbon Steel — This is very strong and holds shape memory quite well, making it ideal for springs and wire. Composition of 0.55% to 0.95% carbon with as much as 0.90% manganese.
- Very High Carbon Steel — This is an extremely strong material that requires special handling. Composition of 0.96% to 2.1% carbon.
“If we are going to have a chance at combating climate change, forests are one of our best tools for mitigation because they sequester carbon,” added Chris Topik, director of the Nature Conservancy’s Restoring America’s Forests initiative. “So it’s vital that we help them to adapt.”