California is the nation's largest dairy producer, with approximately 1.5 million cows that produce over three billion gallons of milk and over 30 million tons of manure annually. There are over 1600 dairy farms in the Central Valley, which has been suffering from air and water quality issues.

Cow manure is a natural and excellent source as a fertilizer, but researchers have also estimated that one cow can emit between 100 to 200 liters of methane per day. This doesn't include the methane that continues to be generated through bacterial decomposition in waste storage lagoons. Methane gas is 25 times more powerful a greenhouse gas than carbon dioxide.

The release of methane gas and the waste piles can cause major pollution problems. Preventing pollution from dairy waste can be a challenge, which requires extensive background and knowledge in animal nutrition, nutrient sources, soil types, and precipitation among other factors.

The U.S. EPA continues to revise its waste regulations for dairies with over 700 cows, which are designated concentrated animal feeding operations (CAFO). CAFO's are defined as animal feeding operations that have the potential to discharge pollution into surface water. Many different efforts have been conducted for operators to better manage the pollution the CAFO's and other dairies produce.

Water Pollution
Runoffs from corrals can wash manure into streams and rivers, while major storms can cause waste water lagoons to overflow into other nearby waterways. The waste water from the corrals, waste storage lagoons and when too much manure has been applied as fertilizer can also seep into groundwater.

As the nutrients from the manure enter waterways, it can deplete the water body's dissolved oxygen levels as they begin to decompose, killing fish and other aquatic life. In groundwater, nitrate levels can increase to unhealthy levels, which can cause Blue Baby Syndrome, a potentially fatal blood disorder if the water is consumed. In addition, if drinking water supplies are compromised by high levels of microorganisms or nitrate exceeding the standards in the Safe Drinking Water Act, well owners must find new water sources, causing furthuer difficult and expensive problems.

What to do about it? Several solutions to mitigate this problem include applying watertight plastic or clay waste liners, that can prevent contaminants from seeping into the sides of lagoons. Buffer strips made permanent strips of vegetation between fields and water ways can also be used to absorb nutrients that would otherwise enter waterways as polluted runoff.

Air Pollution
The decomposition of animal wastes in the dairy can cause methane and ammonia gases to be released into the atmosphere. Methane contributes to greenhouse gases, which can lead to global warming, while ammonia can cause respiratory problems, as fine particulate matter formulates in the air. Dust generated from animal activity also causes respiratory diseases, such as asthma.

What to do about this? The methane emissions can be captured and used as an energy source through methane digesters, that can reduce the odor and the release of methane, but the systems are expensive and require a large amount of manure. Dust suppressants can be used to reduce airborne dust.

There is no one best way to prevent these pollutions from occurring, but the U.S. EPA continues to find better technology to help mitigate these problems.

For more information:

• EPA Region 9: Animal Waste Management