Difference Between LPG & Natural Gas
In New Zealand, we mainly rely on two types of gas for our energy needs. LPG and Natural Gas are widely available and used for thousands of applications in homes and business. However, there are variations of these gases based on composition and method of delivery.
There are also two main differences in the way that LPG (Propane-Butane mix) and natural gas (Methane) are burnt. The first difference is in the energy content. LPG has a higher calorific value, or energy content, so less gas is required to produce the same amount of heat.
The second difference is in the oxygen to gas ratio required for proper combustion. LPG requires an oxygen to gas ratio of approximately 25 to 1. Natural gas requires a ratio of around 10 to 1. To achieve this difference, LPG is typically provided in a smaller quantity but at a higher pressure, drawing more oxygen with it into the combustion process.
LPG (Liquefied Petroleum Gas)
The term LPG actually encompasses more than one type of gas. There are a number of hydrocarbon gases that fall into the category of LPG. Their common characteristic is that they can be compressed into liquid at relatively low pressures. The two most common are Propane and Butane.
Autogas (Propane/Butane mix): Autogas that is sold at NZ petrol stations is typically a Propane/Butane mix. Not only is running an LPG car economical, but Autogas is also cleaner burning fuel than petrol, so engine life is actually extended and greenhouse gas emissions reduced.
Natural Gas (Methane)
Piped Gas: Natural gas or “mains gas” is the gas supplied to homes and businesses by gas pipelines or “gas mains” (reticulation systems). This is how most NZ consumers receive their gas.
CNG (Compressed Natural Gas): Methane gas can be stored at high pressure, typically over 200 bars, but it is not very economical for long distance transport. CNG does have some specific applications where the product is used in close proximity to where it is compressed. City buses are a good example of a successful CNG application.
Common LNG uses include industrial applications and long haul trucking. The technology involved with LNG is generally not cost effective for small volume users, such as homes and small businesses.