Looking out five years from now, Waste Connections Inc. expects about a fifth of the solid waste management company's total collection fleet will be powered by compressed natural gas.

The Woodlands, Texas-based company figures about a fifth of its new truck purchases this year or early next year also will be CNG-powered. Waste Connections is looking to ramp up use of these vehicles in two different types of markets, CEO Ronald J. Mittlestaedt said during a recent conference call with stock analysts. Waste Connections wants to convert truck fleets in franchised markets on the West Coast where...