I have heard both of them described as clean-burning. This website claims that propane is much cleaner. Of course, they are a propane company, so they might be exaggerating a little bit to sell more product. Which fuel is cleaner?
propane can be liquefied for storage and transport. natural gas (mostly methane) can’t, at least not under feasible pressures. but that site you linked to claims natural gas isn’t “green” because it’s a greenhouse gas. Which it is, but you have to let it escape for it to become such.
as far as using them as fuel, both should burn pretty cleanly. they’re both naturally gaseous, so they should easily mix readily with air.
One mole of propane will produce three moles of carbon dioxide when burned. One mole of methane (what natural gas mostly is) will produce one mole of carbon dioxide. However, propane gives off 2.2-2.6 times as much heat than natural gas per cubic foot when burned. So, you could use less of it, but not quite three times less. I guess that means propane will produce a bit more CO[sub]2[/sub] when used in place of natural gas.
CO[sub]2[/sub] is a greenhouse gas, as previously mentioned, but any properly operation device using natural gas or propane should only be producing it and water.
The cites up thread say it could not happen but for the 18 years I was serving the mobile home industry, the homes, the stoves etc., were very much dirtier than those on natural gas. This was from 57 through 75 or so. I also can walk into a kitchen to this day that is using propane and tell right away.
Never in the industry and never since have I ever heard a propane service man nor appliance man claim that propane/butane is cleaner than natural gas.
Maybe the experts have the straight dope but I bet not one of them will let me rub their face on the walls of two areas where everything is the same except the fuel.
I still have my jetting resize needles/drills for making conversions.
YMMV
But then when we look at the “big picture,” propane must go through a lot more processing steps compared to natural gas. The additional steps require energy to be expended, I am guessing mostly from the electric grid. It would thus be reasonable to assume the extra electrical energy that is required to produce propane requires the electric power plants to produce more greenhouse gasses. In addition, propane must be delivered to homes using big, diesel-powered trucks.
“Natural gas is methane – a greenhouse gas. Propane on the other hand is considered ‘green energy’. It burns cleaner than natural gas, helping to reduce your carbon footprint.”
That excerpt from the link mixes together two things. The first sentence is true as is the implication of the second. Methane, the main component of natural gas is itself a greenhouse gas (GHG), 25 times more potent than CO2, though it doesn’t remain in the atmosphere as long. Propane isn’t, basically. So leaks in production and distribution systems for NG anywhere upstream of combustion are causing extra greenhouse gas effect, though it’s disputed how much, and subject to improvement*. Same if for example a home heating furnace is incompletely burning the natural gas, not burning some of it at all, then a natural gas furnace might produce the same amount of GHG effect as a propane one though theoretically propane produces around 19% more assuming complete combustion. The propane industry anyway claims this is true, that for home heating the end point GHG effect is about the same for either. They admit it’s more for propane in say a propane burning internal combustion engine than NG burning one. The energy used, and emissions created, to produce and transport nat gas and propane is similar.
But then the third sentence ‘burns cleaner’ is generally understood as referring to CO, NOx, or particulates, not GHG effect. That isn’t particularly true, and the propane industry doesn’t actually claim it in their longer research papers.
*the other wrinkle to the upstream methane leakage issue is that some propane is condensed out of ‘wet’ natural gas wells (some is boiled off from crude oil). For the stuff produced from natural gas, the propane wouldn’t be around if the methane wasn’t being used, and piped, and some of it leaking, so you can’t really ‘charge’ that all to methane production.