The goal of EPA (2001a) was to“develop a method for estimating emissions at the individual farm level.” To accomplish this, EPA (2001a) developed a set of 23 model farms (see Appendix D) intended to represent the majority of commercial-scale AFOs. Each model farm included three variable elements: a confinement area, manure management system, and land application method. The manure management system was subdivided into solid separation and manure storage activities.

Given the specific nature of the questions answered, the committee has not yet addressed some of the broader issues related to AFOs. To the extent possible, these will be addressed in its final report, which will build on the findings of this interim report and include a more detailed response to the committee’s full Statement of Task (see Appendix A). The need for further discussion of some issues in the final report is indicated in various places in this report. These issues fall in eight broad categories: (1) industry size and structure, (2) emission measurement methodology, (3) mitigation technology and best management plans, (4) short- and long-term research priorities, (5) alternative approaches for estimating emissions, (6) human health and environmental impacts, (7) economic analyses, and (8) other potential air emissions of concern.

This interim report represents the consensus views of the committee and has been formally reviewed in accordance with National Research Council (NRC) procedures. In answering these questions and addressing its Statement of Task (Appendix A), the committee has come to consensus on eight findings for the interim report. The basis of these findings is discussed more extensively in the body of the report.

Finding 1: Proposed EPA regulations aimed at improving water quality may affect rates and distributions of air emissions from animal feeding operations.

Discussion: Regulations aimed at protecting water quality would probably affect manure management at the farm level, especially since they might affect the use of lagoons and the application of manure on cropland or forests. For example, the proposed water regulations may mandate nitrogen (N) or phosphorus (P) based comprehensive nutrient management plans (CNMPs). AFOs could be limited in the amount of manure nitrogen and phosphorus that could be applied to cropland. If there is a low risk of phosphorus runoff as determined by a site analysis, farmers will be permitted to overapply phosphorous. However, they will still be prohibited from applying more nitrogen than recommended for crop production. Many AFOs (those currently without CNMPs) likely will have more manure than they can use on their own cropland, and manure export may be cost prohibitive. Thus, AFOs will have an incentive to use crops and management practices that employ applied nitrogen inefficiently (i.e., volatilize ammonia) to decrease the nitrogen remaining after storage or increase the nitrogen requirement for crop production. These