Criteria for evaluating mitigation techniques emphasize information needs for policy analysis. These include both “on-farm,” or primary, effects of changes in policy, incentives, and regulations, and “off-farm,” or secondary, effects. The primary effects include changes in the composition and rates of emissions from farms subject to changes in policy. These farms may adopt mitigation techniques, decrease or cease production, begin or expand production, or otherwise modify production practices and management, all of which are likely to affect air emissions. Information needs for policy analysis also include those related to secondary effects, such as increased air emissions from trucks hauling manure greater distances as a result of changes in regulations.
Analysis of policy changes should, at a minimum, capture the following factors:
effects of changes in land application of manure on groundwater and surface water quality;
effects of the risk of occasional events, such as storms, and policy-related changes in emissions due to those events;
changes in material flow and composition that can be used to analyze secondary effects.
For example, if a proposed change in policy requires impermeable covers on anaerobic treatment containments, then changes in the flow and composition of the supernatant and sludge leaving them must be measured, as well as changes in the rate and composition of direct air emissions from them. Changes in the flow and composition of effluents from the containment can then be used to analyze changes in air emissions and other effects occurring beyond the containment. In this example, such effects might include increased undesirable air emissions from open secondary storage containment, livestock buildings that use recycled containment supernatant for flushing, land on which supernatant and sludge are applied, and increased energy generation required to distribute the supernatant and sludge over a greater area.
Estimated changes in the composition and rate of air emissions resulting from a policy change can be evaluated using fate and transport models and their predicted changes in impacts on public health and the environment. This interim report does not address the accuracy or statistical validity of models that transform emissions estimates into predicted impacts on public health and environmental quality.