This the second post in a five-part series about diesel emissions reduction in the Kansas City area. Follow along for more information about how local government, railroads and private-sector companies are working to make Kansas City’s air cleaner.
The Clean School Buses USA program sought to focus attention on diesel emissions around one of our most vulnerable populations — children. School bus improvements have continued to be a priority for funding through the National Clean Diesel Campaign over the last four years.
Our region’s school districts have invested heavily in two forms of emissions control devices on buses:
- Diesel Oxidation Catalysts (DOCs) are installed inside the muffler of a bus to capture tailpipe emissions and particulates that would otherwise be released into the air. The captured materials are burned off within the muffler, leaving the exhaust released from the bus cleaner.
- Closed Crankcase Ventilations systems (CCVs) divert blow-by gases containing harmful emissions, vapor and oil mist back into the engine instead of venting freely into the air. A hose attached to the crankcase collects these gases and sends them to a device which filters out the oil mist, and routes the gases back to the engine’s air intake.
In addition, seven school districts have installed fuel-operated heaters (FOHs) on buses. An FOH has a programmable timer connected to a small, auxiliary diesel heater which pre-heats engine fluids and speeds the warm-up of the bus cabin. This eliminates the need for a bus to idle before its morning route, which reduces fuel usage, emissions and start-up labor. State regulations passed in 2010 and 2011 now limit idling time for empty buses to 15 minutes or less in a 60 minute period. In the past, a solitary mechanic might start hundreds of buses one by one to warm the engines in preparation for drivers and students. The first buses would idle for an hour or more, which wasted fuel and contributed emissions to the air.
These retrofits have contributed to significant reductions of both cost and emissions for school districts. Each DOC captures 20–30 percent of tailpipe emissions, and adding a CCV captures another 5–19 percent. Based on the number of cold-weather idling hours reported by the region’s school districts, FOHs reduce annual fuel consumption by about 62 gallons per bus, for an estimated savings of about $217 (at $3.50 per gallon), and also reduce emissions that would have been caused by using that extra fuel.
To accommodate transportation demands, school districts occasionally have to use and maintain buses for a longer life cycle than they would like, despite poor emissions controls on the older models. In a number of cases, districts have secured supplemental funding in order to purchase a new bus ahead of schedule with the condition that an older, “dirtier” bus be retired and destroyed. This does not allow the district to increase the size of its fleet, but does put a newer, cleaner bus into operation earlier than would have otherwise been possible.