What is so special about carbon?
Why the element that fuelled our rise now threatens our climate
If you asked a chemist to choose what is the single most important element for humans, they would likely say carbon.
Firstly, because it’s enormously common, with some 43.5 billion tonnes of carbon stored in the earth’s land, air and oceans.
Secondly, because carbon is humans’ oldest and most prominent source of energy. It was the fuel in wood fires that enabled us to cook raw food and gave us the energy we needed for our bigger brains.
But it is also the carbon dioxide (CO2 ) that is produced when burning fuel that has led to the situation we find ourselves in today, where we urgently need put in place rapid ways to decarbonise.
Burning carbon creates CO2
What we call fossil fuels — including coal, natural gas and oil — are made up of what were once organic, living materials. Over millions of years, the carbon atoms they contain have bonded together in long chains along with some hydrogen to make them hydrocarbons. When these are burnt — combusted — CO2 is produced.
But CO2 occurs naturally in the earth’s atmosphere too. It is released every time an animal breathes out and by microbes breaking down organic matter.
It is also naturally absorbed from the atmosphere, by environments from oceans to mangroves to forests — primarily by plants, making glucose through photosynthesis.
Those carbon-containing plants might then in turn be eaten by animals which breathe the carbon out as CO2. Other plants eventually die and decompose, releasing some of their CO2 as they are broken down by microbes. Eventually, what’s left of the plant is buried and eventually its carbon is turned into materials like fossil fuels.
This movement of carbon around earth balances the levels of CO2 in the atmosphere. Along with many other gases, it helps to regulate the earth’s temperature.
Solar energy from the sun travels to Earth where it is absorbed and radiated back out into space as heat. But a group of gases including CO2 prevent this heat leaving the earth’s atmosphere. This ‘Greenhouse Effect’ is one of the reasons that our planet is warm enough to support life.
However, while these gases help make our planet liveable, excessive levels trap too much heat between the earth and its atmosphere. The result is soaring temperatures on the earth’s surface.
Methane, nitrous oxide, ozone and even water vapour are all Greenhouse Gases, but CO2 is particularly damaging. Most of the others are naturally removed from the atmosphere relatively quickly.
But CO2 can last for much longer, lingering for 300 to 1,000 years. This means that over time, CO2 emissions are making up an ever-larger proportion of the atmosphere. This makes the ‘Greenhouse Effect’ worse.
A growing problem — but one we know how to deal with
Human activity is clearly causing CO2 levels to rise at an alarming rate. The current concentration of CO2 in the earth’s atmosphere is around 412 parts per million. This is an increase of as much as 47% from the beginning of the Industrial Age — around the 1760s — and of 11% from 2000 alone.
Removing it is perhaps the greatest challenge facing humanity today. But it is also one we know how to deal with, thanks to negative emissions techniques and technologies such as bioenergy with carbon capture and storage (BECCS).