Ebook Air Emissions of Ammonia and Methane from Livestock Operations
The animal husbandry industry is a major emitter of methane and ammonia in the United States. Methane, a greenhouse gas (GHG) 23 times as potent as carbon dioxide (CO2), constitutes nearly one tenth of all U.S. GHG emissions. Although methane has a shorter residence time than CO2, methane’s radically higher effect makes it an attractive target for policy measures, especially in the near term. Ammonia is a precursor of fine particulate matter (PM 2.5), arguably the number-one environment related public health threat facing the nation.
The main method of controlling methane emissions in animal husbandry involves using methane digesters to generate and collect methane gas from manure. The captured biogas can then be burned and converted into heat or electricity. Electricity generation through methane digesters reduces farmers’ need to purchase electricity and also can create surplus electricity that can be sold back onto the electricity grid. Control of methane is also a potential offset for CO2 emissions, with a prospective value of tens of dollars per ton given forecasted CO2 control costs in the U.S. regional programs under design (RGGI 2005).
The control of ammonia emissions has the potential to be tied to particulate control policies that offer offsets or emissions reduction credits. However, a large fraction of the benefits from the control of methane and ammonia in animal husbandry accrue outside of existing markets and cannot be appropriated by individual dairy operations that choose whether to invest in methane or ammonia control technology. For example, reductions in GHG emissions from livestock operations currently are not economically rewarded. As a onsequence, dairy operations face only limited incentives for controlling methane emissions with digesters. This situation, in turn, can result in less than optimal adoption of technology for controlling emissions by the dairy industry overall.
In this study, we examine the full potential for methane and ammonia control in animal husbandry. Our objectives are to identify (a) the potential of manure process control for reducing methane and ammonia emissions, (b) the cost thresholds that determine the sensible adoption of different technologies for controlling such emissions, (c) the benefits of controlling such emissions that accrue outside the dairy industry, and (d) the policies or institutions that are necessary to achieve these benefits. This information will be essential to future public policymaking that may give rise to new markets for emissions reductions or to direct financial and technical assistance for methane and ammonia control technologies in agriculture.
We select the California dairy industry for our application. California is a particularly well-suited study area because it is the number-one ranked dairy state in the United States and represents about one-fifth of all U.S. milk production and cows. The California dairy industry generates nearly $5.4 billion in cash receipts and almost a billion dollars in exports, which makes it one of the most economically important agricultural sectors in the state. California cows generate more than 70 billion tons of manure each year—more solid organic waste than the state’s 35 million residents generate (U.S. EPA 2006).
Problems associated with dairy manure in California are heightened by the increasing average dairy size and the concentration of dairies in areas with rapidly growing population and a multitude of air quality problemsexisting. California had about 4,000 dairies in 1992, then the total number dropped to 2,100 by 2004. During the same time period, the total number of cows increased from roughly 1.2 million to 1.7 million, meaning that the average number of cows per dairy more than doubled from about 370 in 1992 to more than 800 in 2004.
California dairy farming is especially concentrated in the Central and San Joaquin Valley regions. These adjacent regions are home to, for example, the five U.S. counties with the highest number of cows per county (Tulare, Merced, Stanislaus, San Bernardino, and Kings Counties). Roughly 1.1 million cows, or about 12 percent of all U.S. cows, inhabit these counties. Tulare County alone has approximately 440,000 dairy cows (4.5 percent of all U.S. dairy cows), more than the total number of cows in any state outside California except for Wisconsin, New York, Pennsylvania, and Minnesota.
These dairy-intensive counties—as well as many other California counties with a significant dairy presence—are also nonattainment areas for particulate matter (PM) and ozone, which means that they do not meet the minimum federal air quality standards (U.S. EPA 2005a). Population growth in the top-five dairy counties in California was more than 20 percent between 1990 and 2000, well above the state average of 13.6 percent (U.S. Census Bureau 2006), which means that the human population exposure to pollution is increasing.
California has initiated several programs to encourage manure treatment with methane digesters, including the Dairy Power Production Program, the Self-Generation Incentive Program, and net metering assembly bills. The Dairy Power Production and Self-Generation Incentive Programs provide cost-share funding for capital investments toward the new installation of methane digesters. Assembly Bills 2228 (signed into law in 2002) and 728 (signed into law in 2005) require the state’s three largest investor-owned utilities (Pacific Gas & Electric [PG&E], Southern California Edison [SCE], and San Diego Gas & Electric [SDG&E]) to offer net metering to dairy farms that install methane digesters. These initiatives encourage the dairy industry to adopt methane digesters but do so without considering all the costs and benefits associated with reducing methane and ammonia emissions.
In this paper, we develop an integrated model to examine the control of methane and ammonia emissions in dairy farming. We pay special attention to the comprehensive accounting of private and social benefits and costs of controlling these emissions. The analysis focuses on the interaction of methane and ammonia with climate, energy, and public health polices, including the potential use of offsets for GHG or regional air pollution policies. The model is designed to provide policymakers a tool for understanding the technical and economic relationships in order to realize the benefits of managing air emissions and waste discharges from agriculture.
In the rest of this paper, we first explain the air pollution issues in dairy operations. We then describe the integrated process model of manure management that constitutes the core of our analysis. The model description includes a depiction of baseline emissions; control technologies for ammonia and methane; and the potential electricity generation, GHG reductions, and health benefits that could result from the adoption of control technologies. Then, we use the model to evaluate different policy options in California. A discussion of results and future plans close the paper.
Contents
1. Introduction
2. Air Pollution Issues in Dairy Operations
- 2.a. Methane
2.b. Ammonia
3. Process-Based Farm-Level Model of Animal Waste Management
- 3.a. Model Structure
3.b. Baseline Emissions
3.c. Ammonia Control Options
3.d. Options for Methane Capture and Electricity Production
3.e. Health Effects of Air Emissions
4. Policy Simulations and Results
- 4.a. GHG Policies
4.b. Policies Related to Ammonia and Fine Particulates
4.c. Important Uncertainties
5. Discussion
References
Figures
Tables
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