Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula N2O. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic effects. It is known as "laughing gas" due to the euphoric effects of inhaling it. N2O is also a greenhouse gas with tremendous global warming potential (GWP). When compared to carbon dioxide (CO2), N2O has 310 times the ability per molecule of gas to trap heat in the atmosphere. N2O is produced naturally in the soil during the microbial processes of nitrification and denitrification. What are the potential environmental problems with this N2O? What can be done? Scientists the world over are joining forces to curtail emissions of nitrous oxide. Norwegian researchers are playing an important role in these efforts.
"Biological fuels are produced as an alternative fuel, intended to replace the burning of oil and gas and thereby reduce global warming. However, since the plants used in the production of biological fuels require fertilizer we cannot eliminate the emission of nitrous oxide; it is a by-product of the process," explains Professor Lars Bakken, a group leader with the Nitrogen Group at the University of Life Sciences (UMB) in Ã…s, Norway.
"The end result is more or less zero gain," he adds. â€œNitrous oxide actually tips the balance in the direction of greater warming, undermining the promise of biological fuels as a means to effect cooling.â€ In other words increased use of fertilizer may lead to higher N2O emissions and a higher potential green house gas effect overall.
Chinese authorities are very focused on securing their countryâ€™s food supply, and therefore provide subsidies for nitrogen-based fertilizers. This increases the use of nitrogen in farming and results in acidification of the soil. Cultivated fields are a direct source of nitrous oxide emissions.
"The amount of nitrous oxide emissions from China is going to escalate in coming years," states Lars Bakken.
The Nitrogen Group is about to publish a study of soil-acidification and the release of nitrous oxide from fields in Nepal and China. They have shown that the enzyme used by bacteria to process nitrous oxide into harmless nitrogen gas does not work at a low pH.
"In developing nations such as China, intensive cultivation of the soil can lead pH levels to fall. We are fairly certain that this will bump up emissions of nitrous oxide. Our study adds to the body of evidence attesting to the significance of the Earthâ€™s acidity level on the environment," says Professor FrostegÃ¥rd.
"We have carried out extended tests as part of our research, experimenting with agricultural lime in China to see what the result would be," Professor Bakken eagerly relates. At the same time, he stresses that there are even better alternatives to agricultural lime for decreasing the Earthâ€™s pH value.