Keeping this in mind, I have provided some information below in order to help you better understand why propane can be considered as an alternative fuel source together with natural gas.
Source of Propane
Propane is actually a by-product from two processes namely natural gas processing and refining of crude oil. Natural gas processing generally involves the removal of the various hydrocarbons like butane, propane, ethane and fluids like water vapour1.
Some propane is also produced from oil refineries as a by-product from the “cracking” of crude oil to give gasoline or heating oil. However, the fact that propane is a by-product from the above processes means that its supply cannot be adjusted easily to fulfill its increasing demand as a fuel source.
How is Propane supplied?
Propane can be supplied in tanks or steel cylinders in either gaseous form or it can be compressed under moderate pressure with/or low temperatures into a more compact liquid state to give liquefied petroleum gas (LPG). Like natural gas, propane is odorless and so a similar odorant called mercaptan is added to provide a warning signal in the event of a propane leakage.
Propane is supplied commercially, especially in the United States and Canada in a purity of at least 90% with the remaining comprising of mainly up to 5% propylene and the rest comprising of isobutane, methane and etc. This grade of propane grade is called the HD-5 propane2.
Uses of Propane
Currently there is an excess of propane being produced worldwide with some of the main producers like the United States and Canada.
Propane accounts for 1% of the total energy needs and is ranked 7th in terms of importance as an energy source worldwide. In terms of usage, the United States is the largest single user of propane, with 90% of the propane produced domestically, in the world3.
Using the United States as an example, it is obvious that usage of propane is mostly in the chemical and industrial, with residential and commercial coming a close second. Other components include transportation and agriculture. (Refer to Image 1, modified from http://www.need.org/needpdf/infobook_activities/SecInfo/PropaneS.pdf).
In the industrial and chemical sector, propane is used as a ready fuel source for processes like soldering, vulcanising and other processes. For residential/ commercial sectors, propane is used for air conditioning, heating water, lighting and cooking etc.
Similarly for agricultural sector, propane is also used for such above processes and also for powering farming tools like flame throwers and farming equipment like tractors and irrigation pumps. Propane is also used by cab companies, schools and warehouses to power their vehicles and forklifts.
Advantages of using Propane as a Fuel
a) Cheaper than Electricity
It costs lesser to use propane for household processes like heating of water.
b) Ease of storage/ transportation
Propane can be stored in propane tanks in either liquid or gaseous form hence its name as a portable gas unlike natural gas that can only transported for usage via pipelines. Liquid propane is more compact and so more can be filled into the same propane tanks as compared to gaseous propane.
Therefore it is more cost-effective to use liquid propane tanks as it will be able to provide fuel for a much longer time for a household or commercial purposes.
c) Nontoxic to the Environment
Propane is nontoxic to the environment and is listed in the United States 1990 Clean Air Act and the Energy Policy Act of 1992 as an approved and clean fuel for usage. Tests conducted by the United States Environmental Protection Agency (EPA) also show that vehicles fueled by propane produce 30% to 90% less carbon monoxide, 50% lesser toxins in their emissions as compared to gasoline engines.
d) Propane is all fuel
No additive is required to be added to the tanks of propane-fuelled vehicles5. Even without additives, the octane rating of propane is 110 that is equal to or higher than gasoline.
e) Propane is a Clean Fuel
As mentioned before, propane is a clean fuel with lesser harmful emissions as compared to the other fossil fuels with the exception of natural gas. Combustion of propane also does not leave behind residues like lead and carbon deposits that cause premature wearing of vehicular parts like pistons and spark plugs.
f) Environmentally Friendly Derivatives of Propane
Derivative of propane like isopropane (R-290a) can be used as an environmentally friendly replacement to replace R-12, R-22 and other chlorofluorocarbon or hydrofluorocarbon based refrigerants for usage in fridges and air-conditioning systems6. It possess negligible ozone degradation and low global warming potential.
Amidst the Advantages… there are also Disadvantages3
a) Propane is not Conveniently Available
Propane is a by-product from the processing of natural gas and crude oil therefore it is hard to step up its production in the event of a sudden demand for it.
b) Commercially not Feasible
This is more applicable to propane being used as a transportation fuel. It is very expensive to convert the engine from running on gasoline to that of propane.
Future of Propane7
Production of propane will be probably increase in countries like the United States especially with the increasing usage and development of natural gas as a source of energy. However research have shown that domestic demand for propane in the United States have actually decreased, with a corresponding increase in exports.
This drop in domestic demand is probably due to improvements in building efficiency code and appliances standards. However to date in terms of infrastructure, it will be probably be adequate to handle the produced propane at least within the United States. The prices of propane will probably remained tagged with that of crude oil with no probably no changes regardless of the demand in terms of usage .
1) (http://www.naturalgas.org/naturalgas/processing ng.asp) (accessed 22nd April 2012)
2) (http://www.propane101.com/propanegradesandquality.htm) (accessed 22nd April 2012)
3) (http://www.need.org/needpdf/infobook_activities/SecInfo/PropaneS.pdf) (accessed 22nd April 2012)
4) (http://www.propanecouncil.org/council/what-is-propane/) (accessed 22nd April 2012)
5) (http://www.ftc.gov/bcp/edu/pubs/consumer/autos/aut12.shtm) (accessed 22nd April 2012)
6) (http://www.worldlpgas.com/about-lp-gas/applications/other-uses) (accessed 22nd April 2012)
7) (http://autogasforamerica.org/pdf/AFA_whitePaper.pdf) (accessed 22nd April 2012)