Measuring Benefits of Odor Control

Odor control projects invariably involve compromise between the goal of satisfying downwind neighbors and the goal of satisfying those holding the purse strings of capital improvement budgets. How best to use limited funds to gain the most good will (or the most reduction in bad will) with neighbors is the driving consideration. Striking the right balance between these competing goals requires accurately assessing:1. The cost of controlling odor sources (i.e. the cost), and2. The off-site benefit of controlling those sources (i.e. the benefit)Neither of the above-listed tasks is simple. The difficulty of estimating costs accurately, especially early in the design process, is a common problem to all engineering projects. The difficulties of assessing the off-site benefit of odor controls are, however, unique to the odor control field.The goal of the listed tasks is to get accurate measures of the cost and benefit of specific projects in order to prioritize them. Ideally, the project that achieves the highest benefit per dollar should be performed first, and the projects with lower benefit per dollar can be deferred or eliminated. Figure 1 illustrates how the cost-benefit information can be used to prioritize projects. Each line segment on the curve represents the incremental cost and odor emission rate (OER) reduction of a project. OER is calculated as the product of odor concentration, usually measured as dilution to threshold, in a discharge air stream and the volume of the air stream (OER = D/T * cfm). Figure 1 presents the percent reduction of total facility OER versus dollars spent to reduce OER. Within the curve, steeper segments achieve more OER reduction per dollar spent than less steep segments. Ideally a sequence of projects will show diminishing returns from additional spending. In other words, the projects that achieve the most benefit (in this case measured by OER reduction) per dollar spent are performed first and each successive project has the highest benefit to cost of the remaining projects.