• Mikl Brawner

N2O- The Forgotten Greenhouse Gas

By Mikl Brawner:

Nitrogen is one of the most essential nutrients for plants. It is required for building amino acids, DNA and RNA, in stimulating growth, supporting health, and is a critical ingredient in chlorophyll, the chemical needed for photosynthesis. When nitrogen is lacking in our gardens plants are small and yellow, and roots do not perform well. In Colorado, almost all our soils are deficient in nitrogen and organic matter so we gardeners often add fertilizers and composts to our soils.

Our atmosphere is 78% nitrogen, but it is not readily available. Nitrogen-fixing bacteria on the roots of legumes can take nitrogen from the air and convert it to a useable form for plants. Far more nitrogen comes from the bacterial decomposition of dead plant and animal matter. And these days, much more than that comes from the application of synthetic fertilizers. The nitrogen in plants gets passed to the animals that eat those plants, and it passes through them in their manures. These manures are exposed to air and to the actions of soil microorganisms in a process called denitrification, which results in the release of nitrogen gas and nitrous oxide (N2O). Nitrous oxide is also a by-product of burning fossil fuels and the breakdown and run-off of synthetic fertilizers.

What is nitrous oxide? It is a colorless, odorless gas that is used as a propellant in aerosols, in rocket motors, and in dentist offices as a sedative. It’s also called “Laughing Gas”. In the atmosphere it has become the single most important ozone-depleting substance and is a major, though “forgotten”, greenhouse gas. According to the EPA, nitrous oxide is 250-300 times more potent than carbon dioxide and remains in the atmosphere for 100 years. It warms the earth by absorbing energy and slows the rate of energy escaping to space. Nitrous oxide levels have increased 40-50% over pre-industrial levels, and are now higher than any time in the last 800,000 years.

Much of the increase in nitrous oxide is due to the manufacture and use of synthetic nitrogen fertilizers. In 1908, German chemist Fritz Haber discovered the process for taking nitrogen from the air to make fertilizers to “feed the world” as well as explosives for use in wars. Haber received the Nobel Prize, along with Carl Bosch, for making reactive nitrogen on a grand scale. Hydrogen is required in the process and natural gas is used as the source of hydrogen.

The Haber-Bosch Process now produces 450 million tons of nitrogen fertilizer a year, using 3-5% of the world’s natural gas. So besides being responsible for most of the nitrous oxide in the atmosphere, the Haber-Bosch Process also burns natural gas as fuel, and requires fossil fuels for extracting the gas as well as for transporting the fertilizers. All these emissions contribute to climate change.

Synthetic (chemical) fertilizers fueled the so-called Green Revolution which greatly increased the production of largely animal food and helped to increase the human population. However, although chemical fertilizers contain synthesized NPK (nitrogen, potassium and phosphorus) they're lacking important micronutrients found in the soil, in manures, in the ocean, and in rock minerals. Although needed only in small quantities, these nutrients are very important for building immune function and in supporting health. So while synthetic fertilizers have increased the quantity of crops, they have lost quality. It is believed that deficiencies of important nutrients are causing health problems in plants, animals, and humans, requiring overuse of antibiotics and pesticides.

In addition, synthetic nitrogen fertilizers are water soluble; only 20% of what is applied is actually used by plants. The rest is volatized into the air as nitrous oxide or nitrogen gas, or washes into waterways and oceans where it multiplies oxygen-consuming algae, creating dead zones that total 152,200 square miles. Half the food produced in the world is now grown with synthetic (chemical) fertilizers. Consequently, nearly 80% of the nitrogen in human tissues originally came from chemical fertilizers.

These effects from agriculture-related emissions will be increasing. According to Scientific American, no new ammonia plants (to produce synthetic fertilizers) have been built in the US for more than 20 years. Now with cheap natural gas from the fracking boom, 14 new plants are proposed with 12 million tons of new capacity.

Industrial agriculture may be the source of these global warming emissions, but we gardeners can help. We can grow and eat organic food, we can fertilize our lawns and gardens with organic forms of nitrogen (for example: manures, fish and crustacean wastes, slaughter-house wastes and alfalfa) which are recycled rather than newly created. We can reduce the amounts of fertilizers that we use; overuse causes an exponential rise in the creation of nitrous oxide. We can support a vibrant and healthy soil life with oxygen, moisture, and plant and animal wastes, which improves fertilizer efficiency and lets nitrogen return to nitrogen gas rather than to nitrous oxide. And we can stop using toxic pesticides which kill or reduce our soil life.

Nutrition through biology, nutrient cycling, carbon sequestration in our soils, and microbe farming are the true Green Revolution that has the capacity to feed the world without destroying the planet. We are just beginning to escape the habituated ignorance of Petroleum Thinking. We don’t need oil nearly as much as we need Life – biology with intelligence, a force and a symbiotic system that has evolved over a long time. Life-centric solutions are restorative, regenerative, and support more life.


‘Nitrous Oxide the Forgotten Greenhouse Gas’ – conference of the Royal Society 2011

Proceedings of the National Academy of Sciences

Scientific American 2013 and 2014

“A Natural History of Nitrogen,” Organic Gardener’s Companion by Jane Shellenberger


Mikl & Eve Brawner co-own Harlequin’s Gardens in Boulder, which specializes in organic veggie starts and herbs, natives, sustainable roses, xeriscape, unusual perennials, and products to build healthy soils.