Mar 30 2008
Unlike carbon dioxide and methane, laughing gas has been largely ignored by world leaders as a worrying greenhouse gas. But nitrous oxide must be taken more seriously, says Professor David Richardson from the University of East Anglia in Norwich, UK, speaking today (Monday 31 March 2008) at the Society for General Microbiology's 162nd meeting being held this week at the Edinburgh International Conference Centre.
“It only makes up 9% of total greenhouse gas emissions, but it's got 300 times more global warming potential than carbon dioxide”, says Prof Richardson. “It can survive in the atmosphere for 150 years, and it's recognised in the Kyoto protocol as one of the key gases we need to limit”.
The potent gas is mainly coming from waste treatment plants and agriculture. Its release is increasing at the rate of 50 parts per billion or 0.25% every year. This means that it can be better controlled with suitable management strategies, but only if the importance of nitrous oxide (N2O) is widely recognised first.
“When faced with a shortage of oxygen, many species of bacteria can switch from using oxygen to using nitrates instead”, says Prof Richardson. “Nitrates can support their respiration, the equivalent of our breathing, and bacteria can get energy through processes called denitrification and ammonification. When they do this nitrous oxide is released into the environment”.
Municipal sewage treatment plants, landfill sites and marshy areas polluted with too much agricultural fertiliser are all places teeming with so many bacteria that there is a shortage of oxygen for all of them to survive using normal respiration alone. This means they need to use other respiratory strategies, which release nitrous oxide.
The researchers are using a combination of laboratory based studies, fieldwork and computer modelling to understand better the key environmental variables that make different micro-organisms release nitrous oxide.
“We are finding new biological routes for nitrous oxide emission that no-one ever suspected before. This could make a big impact on our environment”, says Prof Richardson. “Global warming affects everyone, and understanding the biology of nitrous oxide emissions will be an important step in mitigating their impact. We urgently need to start developing better strategies to improve management of these emissions in the agricultural and waste treatment sectors”.
What are Greenhouse Gases
The Earth’s atmosphere possesses many chemical compounds that acts as greenhouse gases. Greenhouse gases permits sunlight to penetrate the Earth’s atmosphere freely. The Earth’s surface reflects some of the sunlight as infrared radiation or heat back towards space.
However, these reflected infrared radiations gets absorbed by the greenhouse gases and gets trapped in the Earth’s atmosphere. Over time, the amount of energy sent from the sun to the Earth’s surface is roughly equal to the amount of energy radiated back into space. This leaves the surface temperature of Earth roughly constant.
Gases Exhibiting Greenhouse Gas Properties
A number of gases exhibit greenhouse properties. Some gases such as water vapor, carbon dioxide, methane, and nitrous oxide occurs in nature, while others such as aerosols are man-made.
The levels of a number of important greenhouse gases have increased since large-scale industrialization began around 150 years ago to about 25 percent. Around 75 percent of man-made carbon dioxide emissions during the past 20 years were from the burning of fossil fuels.