Measurements of NOx emissions and in-service duty cycle from a towboat operating on the inland river system

This paper describes measurements of NOx emissions from one engine on a com mercial towboat operating on the Upper Ohio River system around the Port of Pittsburgh. Continuous measurements were made over a one-week period to ch aracterize emissions during normal operations. The average NOx emission fac tor is 70 +/- 4.2 kg of NOx pert of fuel, similar to that of larger marine engines. A vessel-specific duty cycle is derived to characterize the towboa t's operations; more than 50% of the time the vessel engines are at idle. A lthough recently promulgated EPA regulations apply only to new marine engin es, these data provide insight into inland-river operations, which can be u sed to evaluate these regulations within the inland river context. This ves sel operates as a courier service, scheduling pickups and deliveries of sin gle- or multiple-barge loads per customers' requests; as many as 30% of the 277 towboats in the Pittsburgh region operate in this fashion. The EPA-pre scribed ISO E3 duty cycle does not accurately describe inland-river operati ons of this towboat: its application overestimates actual NOx emissions by 14%. Only 41% of this vessel's operations fall within the Not-To-Exceed Zon e defined by the EPA regulations, which limits the effectiveness of this co mponent of the regulations to limit emissions from vessels that operate in a similar fashion.