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0208 ANM: If the air board ran a dairy, what would it be like?

Charles F. Krauter Published on 27 February 2008

Dairy operations are affected by environmental regulations related to both air and water quality. Air and water issues have been identified and regulated since the 1960s, though dairy operations and agriculture in general were not identified as major sources of problems until the past decade.

Initially, air quality problems were related to combustion products. In California that meant exhaust from cars and trucks. Federally mandated reductions and the design of low emissions vehicles has reduced this major source significantly in the past 30 years. It would take the emissions from about 500 new Ultra Low Emissions Vehicle (ULEV) Hondas to equal the pollution from one 1964 Dodge Dart.



The replacement of older vehicles with new, cleaner running cars and trucks has made a considerable improvement in air quality. They will have to get even better over the next decade because the air quality standards are becoming more stringent. By the end of the next decade the air will have to be better than the current standards and that will require more than cleaner vehicles.

Now that the big problem of vehicle emissions is on the way to a solution, the regulatory agencies are looking at the next emission sources on their list. Agriculture is estimated to be second to vehicles for both of the valley’s major air quality problems and dairies are at the top of the list of ag sources. Since ag emissions have not been studied for as long as vehicles, the “list” is a series of estimates and the proposed mitigation practices are just good guesses as to what will really help solve the problems.

Current research at California State University (CSU) – Fresno, University of California – Davis and elsewhere has improved the estimates of emissions from various dairy operations and is beginning to evaluate changes that might be adopted as mitigation practices. It is very premature to do more than speculate on what the “air friendly dairy” might look like ten years from now. However, if we were to speculate, we might consider the result if the state Air Resources Board or the local Air District decided to design and operate an Ultra Low Emissions Dairy (ULED), the Toyota Prius of milk production.

The ULED would have to reduce the emissions of two federally regulated air pollutants plus greenhouse gasses that were recently added to the “list” in California. The San Joaquin Valley does not meet the federal EPA standards for ozone or particulate matter (PM) and must reduce them significantly. Ozone is not emitted by cows or cars. It is formed in a chemical reaction in the atmosphere. Hot summer temperatures, sunlight, NOx from vehicles and a number of reactive organic gasses (ROG) or volatile organic compounds (VOC) combine to create ozone.

Ozone has been linked to respiratory problems and EPA regulations require a significant reduction of the ozone levels found in the summer in the Central Valley. There is no way to control the naturally occurring atmospheric reaction so reductions in ozone can only be accomplished by decreasing the NOx or VOCs that are its precursors. Cleaner vehicles have reduced NOx and are responsible for the reductions of ozone that have already occurred.


New ozone standards will require further reductions in NOx, but the VOCs must also be decreased to meet the new standards. Dairies appear to emit a considerable volume of those gasses and may be one of the keys to mitigating the ozone problem in the summer.

The second air quality problem that must be solved in California is particulate matter. There are two classes of PM that are subject to regulation. The largest, PM10, is primarily mineral dust from exposed soil, paved and unpaved roads and other urban and rural sources. PM10 was the first agricultural air quality problem to be addressed in the Central Valley and some improvements are already apparent.

The second type of PM is the smaller PM2.5 that is more complex. Most PM2.5 is smoke and soot particles from combustion, particularly diesel emissions. A secondary PM2.5 source is the particles formed from ammonia and various NOx and SOx gasses in an atmospheric chemical reaction.

The health hazards of these smaller PM2.5 particles are much greater than the PM10. They are more likely to be trapped in the lungs where they can cause a number of serious respiratory problems. Sources of PM2.5 are still being identified, but it is likely that dairy operations are a contributing factor.

A number of gasses that may be emitted from dairies are not part of the PM or ozone problem but may be regulated due to recent California legislation related to greenhouse gasses. CO2 ,N2O and methane are not regulated pollutants, but they do affect stratospheric ozone and trap heat in the atmosphere as in a greenhouse. Increased levels of those gasses may be accelerating “global warming.”

AB32 was passed by the California legislature in 2006 to require reductions in greenhouse gasses. The California Air Resources Board is expanding to create a greenhouse gas division to study the problem and recommend mitigation practices that will certainly include dairy operations.


If the air board operated a ULED, what would they be doing that is different from current dairy practices? First, they would try to identify the biggest sources of VOCs, PM and greenhouse gases at their dairy. They would try to reduce the largest problems first to maximize the effects of their mitigation efforts. The regulatory agencies understand very well that a dairy must stay in business to reduce its emissions so any changes made to reduce pollution must be cost-effective as well.

The current research is beginning to confirm the fact that good management or more intensive management will often decrease emissions as much as changing to a completely different management practice. In addition, more monitoring of the activities that go on at the dairy and the quality of feed that is grown or purchased would also be likely to occur.

The air quality problem to which dairies are most likely to contribute is ozone. Reactive organic gasses are emitted from nearly every part of a dairy. In early 2006, two separate research projects identified alcohols, particularly ethanol, as the largest component of the VOCs emitted by dairy operations. That initial indication has been confirmed by CSU Fresno field monitoring. Furthermore, it is now apparent that the major source of alcohols is the silage and, perhaps, other components of the feed ration. If that is confirmed by these current studies, the ULED will pay more attention to the quality of silage and evaluate other parts of the ration, not only for nutritional value and cost but also emission potential.

Ethanol emissions appear to be higher in poor quality, low density silage. The ULED will build its silage piles more carefully to be sure they reach a certain minimum density to avoid the yeast fermentation that can produce ethanol from the pile or the ration when it is fed. Keeping air from the silage is important so the ULED may use better covers or containers for silage to keep the quality high. Alcohol emissions are high from the disturbed face of the pile so covering it, and keeping the pile small to reduce the exposed area of silage will be important. Other ration components that emit alcohols will be kept enclosed or covered. Alcohols are not just from the feed and are not the only large source of VOCs, but these may be the most important mitigation practices.

Some research indicates a considerable VOC emission directly from the animals. It may be possible to reduce the direct emissions of several gasses by changing the feed ration to eliminate a component that causes a problem so long as an acceptable replacement is available.

Some alcohols and other VOCs and ammonia are emitted from fresh manure. Many of the gasses are very soluble in water so the ULED flush-lane dairy may be able to capture them by more frequent flushing before they can escape into the air.

Other parts of the dairy operation can be sources of VOCs though apparently not at the levels of the feed and the housing areas. The exercise corrals have a relatively low emission rate compared to the feed, but since they are a large area of the dairy, the total emissions may be significant. Some of the dairies we are monitoring frequently scrape or harrow the manure pack in the exercise corrals. Their VOC emissions are often lower than those from dairies that only remove the manure once or twice each season. The ULED will keep the exercise pens worked up to reduce not only flies and odor problems but, perhaps also ozone precursors.

Emissions of alcohols from flush water and lagoons is low due to their high solubility in water, but other VOCs may be emitted from the lagoon surface or the flush water as it is pumped around on the dairy. The ULED would have short flush lanes with sufficient gradient to minimize the flowing time in the lanes. The lagoons would be deep to minimize surface area and may be allowed to develop a natural crust to slow down volatilization.

The lagoon at the ULED might be purple. Low organic loading and circulation may result in photosynthetic sulfur bacteria, and the different microbe population may reduce the VOC emissions though the ponds will be larger and the volume of water greater.

Dairies are not as large a PM source as some other forms of agriculture, but there are PM emissions from dairy operations. Traffic on unpaved roads and parking areas can generate PM10, so the ULED will use water or other chemicals as well as issuing speeding tickets to hot-rodding feed trucks and four-wheelers to reduce dust.

The PM2.5 problem is more serious and may require more mitigation practices. Medical research is indicating the greatest PM2.5 hazard is from the very small, organic carbon particles such as those in diesel exhaust. Engines at the ULED will be of recent design and use the low emissions fuels that will be available soon. The potential for emitting very fine organic particles from the manure pack in the exercise corrals has not been evaluated yet, but this may be one more reason to manage it carefully or remove it more frequently at the ULED. Piles of manure or separated solids will be covered at the ULED.

Another component of PM2.5 is the secondary particulates formed from ammonia and NOx. Ammonia is emitted from a number of dairy operations and, though the reduction in ammonia may not directly reduce PM2.5, the regulatory agencies may still require mitigation practices for it. Ammonia is another gas that is very soluble in water so flush lanes will capture it effectively. It volatilizes from water when the temperature increases so land applications of lagoon effluent will be done at night to prevent solar heating of the water in the irrigation furrows.

The reduction of greenhouse gasses mandated by AB32 will be a mixed blessing at dairies. Agriculture is one of the best ways to capture CO2 in the photosynthesis of growing crops. Animals however, generate CO2 when they metabolize those same crops. There are other greenhouse gasses such as N20 and methane that may be more affected by dairy operations.

Methane is produced by anaerobic microbial decomposition when there is little or no oxygen available. It is difficult to provide much aeration in a lagoon or manure pack so methane is usually generated in very large quantities. Methane does not form particulates or ozone, but it is a greenhouse gas.

One way of reducing methane emissions is to contain it, concentrate it and use it as engine fuel. The equipment to accomplish that is expensive and, currently, electric power generated at a dairy can only replace the dairy’s energy requirement, though most dairies can produce more power than they consume. The ULED in the next decade might have an efficient methane digester producing natural gas to provide both energy for the dairy itself and revenue from the excess.

Another greenhouse gas emitted by dairy operations is N2O. It is produced during the conversion of nitrates to reduced forms of N. Two possible sources of N2O at a dairy are the manure pack in corrals when wet by rainfall and denitrification that occurs when high N lagoon effluent or manure is applied to heavy soils with too much water. The frequent removal or manipulation of the manure in exercise corrals to reduce VOC emissions at the ULED will also mitigate the N2O problem when the first fall rains occur.

Forage irrigation at the ULED will incorporate a nutrient management program to match the applications to the water and N requirements of forage production. That will not only minimize the N2O emissions from land applications but also reduce the leaching of nitrates, one of the industry’s most serious water quality issues.

CO2, the most common greenhouse gas, is consumed by the photosynthesis process, the basis for plant growth. Enhancement of plant growth (crop production) is the only significant way to remove CO2 from the atmosphere. Therefore, forage production associated with dairy operations may be encouraged for not only the current economic benefits but also for CO2 mitigation.

The ULED could be a showplace for greenhouse gas reductions by capturing the methane to produce fuel or electric power to reduce energy requirements. The fuel/power would be used to collect and treat the manure to reduce N2O emissions and for irrigation to maximize CO2 consuming crop production.

Public speculation has always been an entertaining but risky practice. Remember the “flying cars” of the ‘50s, the “population bomb” of the ‘60s, the nuclear winter and ice-ages of the ‘70s and the “paperless office” of the ‘80s. An ULED may be added to that list, but perhaps not. Many management practices described above would not only reduce emissions but would also increase efficiency and even revenue. Some will require development of technology but, in a decade, some of this speculated technology will be proven and should be common.

Operation of a dairy is difficult, complex and constantly evolving. The dairy industry is known for organization and innovation. It is quite likely that many of these ULED practices will be developed and adopted by the industry long before the air resources board could ever get around to designing and building their own dairy. ANM

—Excerpts from 2007 California Animal Nutrition Conference Proceedings