Did you know that the IPCC reports that agriculture practices contribute around 60 percent of total global nitrous oxide (N2O) emissions, the most potent greenhouse gas?  N2O is 300 times more potent than carbon dioxide (CO2).

In the United States, synthetic fertilizers are responsible for three-quarters of N2O emissions. (5)  Given these alarming statistics and great potential to rapidly transition away from using synthetic nitrogen fertilizers, the Center for Food Safety has launched Say No to N2O, a campaign dedicated to reducing the use of synthetic nitrogen fertilizer in commercial agriculture practices.

We believe it is essential to step outside of the dominant thinking that the primary way to reduce GHG emissions is via expensive technologies requiring massive infrastructures.  Governments and civil society will continue to fail in international and domestic arenas if we insist on this path.  Instead, we need a new paradigm—A transition to ecological farming methods is a low-cost, achievable way to reduce GHG emissions and is literally grounded in people’s daily lives and livelihoods.

What exactly is nitrous oxide?

Nitrous oxide is a chemical compound with the formula N2O. It is an oxide of nitrogen. It is one of the three main Greenhouse Gases and accounts for around 6 percent of the heating effect of greenhouse gases in the atmosphere. (1)

Nitrogen fertilizers are the main source in increasing crop yields.  The use of nitrogen fertilizer, however, increases the amount of nitrous oxide emissions from soil and water through nitrification and denitrification processes.

Nitrous oxide emissions are first produced when fertilizer is added to the soil to grow animal feed. Animals then concentrate nitrogen inside their feces and urine, and soil microbes interact with the released waste to create N2O. (3) This makes nitrogen fertilizer responsible of 60% of all global nitrous oxide emissions.

The main sources of nitrous oxide in the United States are: (2)

Table 1 U.S. Nitrous Oxide Emissions by Source (TgCO₂ Equivalents)

Source Category	1990	1995	2000	2005	2006	2007	2008
Agricultural Soil Management	203.5	205.9	210.1	215.8	211.2	211.0	215.9
Mobile Combustion	43.9	54.0	53.2	36.9	33.6	30.3	26.1
Nitric Acid Production	18.9	21.0	20.7	17.6	17.2	20.5	19.0
Manure Management	14.4	15.5	16.7	16.6	17.3	17.3	17.1
Stationary Combustion	12.8	13.3	14.5	14.7	14.5	14.6	14.2
Adipic Acid Production	15.8	17.6	5.5	5.0	4.3	3.7	2.0
Wastewater Treatment	3.7	4.0	4.5	4.7	4.8	4.9	4.9
N2O from Product Uses	4.4	4.6	4.9	4.4	4.4	4.4	4.4
Forest Land Remaining Forest Land	2.7	3.7	12.1	8.4	18.0	16.7	10.1
Composting	0.4	0.8	1.4	1.7	1.8	1.8	1.8
Settlements Remaining Settlements	1.0	1.2	1.1	1.5	1.5	1.6	1.6
Field Burning of Agricultural Residues	0.4	0.4	0.5	0.5	0.5	0.5	0.5
Incineration of Waste	0.5	0.5	0.4	0.4	0.4	0.4	0.4
Wetlands Remaining Wetlands	+	+	+	+	+	+	+
International Bunker Fuels	1.1	0.9	0.9	1.0	1.2	1.2	1.2
Total for U.S.	322.3	342.5	345.5	328.3	329.5	327.7	318.2

To view global nitrous oxide emissions by country, click here.

What are the alternatives?

The benefits of nitrogen fertilizer are more grass and hay and less weeds, but they come with extreme environmental consequences.  The alternative of using synthetic fertilizer is using organic materials, such as:

• Cover Crops: Cover crops can be grown to enrich the soil.  Cover crops provide organic matter to the soil, help bring nutrients to the surface of the soil, and make nitrogen in the air available to crops. Alfalfa, buckwheat, clover, fava beans, mustard, ryegrass, and winter vetch are commonly used for this purpose.
• Manure: Both conventional and organic farms use animal manure as part of regular farm soil fertilization programs.  Many farmers use sheep, beef cattle, swine, poultry, dairy cattle, and horse manure.

It is important to remember that organic materials need to be managed properly to provide a significant source of plant nutrients. (4)

Why don’t farmers use these alternatives?

Subsidies and Farm Policies: In 2009, USDA subsidies in the United States totaled $15.4 billion, with the top 10 percent of recipients receiving 61 percent of all USDA subsidies. (6)  The subsidies are linked to certain commodities, such as corn and soybeans, so farmers continue to conventionally produce large quantities of those crops.

It’s Easy: It is easier for big farms to use nitrogen fertilizer to produce crops.  Chemical fertilizers are readily available in large quantities, are fast acting, easy to apply and inexpensive.   Farmers are used to applying these types of fertilizers and making the switch to becoming

Monocluture Approach: The industrial agricultural industry advocates a monoculture approach to farming.  It is easier, faster, and more profitable to plant hundreds of acres of land of the same, often genetically modified, crop year after year.  Profits are coming in from subsidies on certain commodities, and claim to keep food costs down.  This trend is making it so that animals are no longer on farms providing multi-functional agriculture systems.

Sources:

(1) http://news.nationalgeographic.com/news/2009/09/090908-global-warming-greenhouse-gases.html

(2) http://www.epa.gov/nitrousoxide/sources.html)

(3) http://news.nationalgeographic.com/news/2009/09/090908-global-warming-greenhouse-gases.html

(4) http://www.ext.colostate.edu/pubs/crops/00546.html

(5) http://www.eia.doe.gov/oiaf/1605/ggrpt/nitrous.html

(6) http://farm.ewg.org/progdetail.php?fips=00000&yr=2009&progcode=total&page=conc

Additional Reading:

• Sources and Emissions/Nitrous Oxides, EPA
• Nitrous Oxide from Agricultural Sources: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery, CRS
• Manure, HC TVs Among Greenhouse Gas Sources to Watch, National Geographic News
• Organic Materials as Nitrogen Fertilizers, Colorado State University Extension
• Environmental, Energetic, and Economic Comparisons of Organic and Conventional Farming Systems, BioScience
• Cool Farming: Climate impacts of agriculture and mitigation potential, Greenpeace