In a nut shell, it's cleaner and cheaper then our local alternatives.
Propane is clean burning and effectively competes with other fossil and renewable fuels on efficiency and greenhouse gas emissions in many applications. It also offers additional air quality advantages: when properly mixed with air to form a combustible mixture, propane emits virtually no soot, and low carbon monoxide, hydrocarbons, and oxides of nitrogen, which are the basic precursors of ground-level ozone, or smog. Its simple chemical make-up allows it to burn cleaner than coal, light and heavy petroleum fuels, ethanol, and even natural gas in some cases.
Because propane is stored and transported under pressure, the transportation and storage system prevents any evaporative emissions. In the event of a leak, propane readily vapourizes and dissipates into the atmosphere. In an era of environmental concerns, propane stands above most fuels and rivals the cleanest.