Septemeber 23rd 2014

Agricultural Impact on Air Quality 

While water pollution from animal feeding operations and soil nutrients has been a primary focus due to the recent rainfall across the Midwest, another concern associated with agriculture is the impact practices have on air quality. While power and transportation industries are largely responsible for the majority of greenhouse gas emission in the United States, the US Environmental Protection Agency (USEPA) reported that agricultural activities accounted for about 12 percent of emission in 20121.  

Major Sources of Greenhouse Gas Emission

According to the USEPA1, there are four main agricultural activities linked to the production of greenhouse gases. These include soil management, enteric fermentation, manure management and fossil fuel consumption.

Main Pollutants from Agricultural Activity

Methane (CH4) and nitrous oxide (N2O) were the two main gases emitted by agricultural activity in 2012, according to the USEPA1. Methane was primarily produced from enteric fermentation and manure management, while soil management, such as fertilization, was the largest source of nitrous oxide.

Additional Air Pollution from Agriculture

In addition to methane and nitrous oxide, agricultural activities have been linked to the emission of other dangerous gases and pollutants. These include carbon dioxide, ammonia, hydrogen sulfide, and airborne particulate matter, which has been linked to health problems.

How to Decrease Pollution Emission

Various methods to decrease air pollution have been identified and continue to be researched. Techniques including better manure storage, precision nutrient application, and air-breaks between farms can all help decrease the effect of agricultural practices on air quality. Below are several specific ways to reduce agriculture-related pollution as described by Iowa State University Extension and Outreach2 and the USEPA3.

Improving Nutrient Management

One way farmers can reduce nitrous oxide emission is to integrate the use of variable-rate fertilizer or manure management. This method encourages more efficient use of fertilizer by applying a unique amount to each field based on needs of that zone. Farmers use variable-rate manure application to apply varying amounts of fertilizer throughout the field depending on different zones found naturally within it. These zones are created based on soil tests and can be generated using MMP360.

In addition to reducing nitrous oxide emission, precision management can reduce production costs and decrease the risk of water contamination.

Manure Management

While strategies to control odor and dust, such as land application, have been widely adopted, methods to control gas emission still needs focus. In fact, the USEPA1 reported that the emissions of greenhouse gases from manure management increased by 54.7 percent between 1990 and 2012.

Methane is the main gas produced by manure as it decomposes. When stored as a liquid in a lagoon or tank, manure decomposes anaerobically, creating methane emissions. However, manure decomposes aerobically when deposited naturally, creating little methane emissions. Because of this, handling manure as a solid versus a liquid can help decrease emissions.

In addition, storing manure in anaerobic containment areas that utilize technology to capture the methane produced as an energy source is a viable option. Not only does this method reduce emissions, but can also offset costs by decreasing the use of fossil fuel energy2.

Livestock Management

Another way that methane enters the atmosphere is through enteric fermentation. Although this is a normal part of the digestive process, ruminant animals like cattle have a unique digestive system that causes them to be a major emitter of methane. Feed intake and quality influence this level of emission, with lower feed quality and higher intake causing higher methane emissions1.

Continued Research and Incentives

In addition to these practices, research continues to help educate farmers on the best ways to invest to help control pollution and emission. For example, Iowa State University is currently working to define “normal” levels to help determine the best ways to reduce and control emission4. In addition, federal and state governments may consider creating incentives for lowering greenhouse gas emission. With these incentives, farmers could look toward implementing new technology and renewable energy sources to reduce greenhouse gas emission2.


1. US Environmental Protection Agency. "Trends in Greenhouse Gas Emissions." Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012 – Trends. Environmental Protection Agency, Mar. 2014. Web. 5 Aug. 2014.

2. Takle, Eugene. "Global Warming – Agriculture's Impact on Greenhouse Gas Emissions." Iowa State Extension, Apr. 2008. Web. 04 Aug. 2014.>.

3. US Environmental Protection Agency. "Sources of Greenhouse Gas Emissions." Environmental Protection Agency. Web. 06 Aug. 2014.>.>.

4. Xin, Hongwei, and Ed Adcock. "Iowa State University in the Forefront of Air Emissions Research at Midwest Swine Facility." Iowa State University, 3 Sept. 2013. Web. 06 Aug. 2014.>.