LPG for cooking

Introduction - What is LPG?

Liquefied Petroleum Gas (LPG) is a by-product of natural gas extraction and crude oil refining. LPG is a mixture of hydrocarbon gases, the most common being butane and propane. At room temperature, LPG is a colorless and odorless non-toxic gas. Under modest pressure or cooler conditions, it transforms into a liquid state. This process leads to the reduction of the volume to 1/250 of the gaseous aggregate state and allows to store and transport LPG easily in cylinders. For safety reasons, a LPG cylinder is only filled with 80% liquid while the remaining 20% contains gaseous LPG. A typical LPG cooking system is made up of a steel cylinder filled with LPG, a pressure controller, a tube connecting the cylinder to the pressure controller and the burner, and finally the burner itself.

1 kg of LPG has an useful energy value of 20.7 MJ/kg. In comparison, air-dried firewood has an energy content of around 16 MJ/kg and charcoal of 27 - 33 MJ/kg. Depending on the type of woodfuel, charcoal production, and cook stove, between 7.3 and 29.7kg of woodfuel would be required to provide the same amount of useful cooking energy found in 1 kg of LPG. LPG is heavier than air, e.g. propane is one and a half times heavier than air, and can therefore accumulate above the ground. This may lead to LPG-’lakes’ that potentially can causes explosions. A foul smelling odorant is added to help detect leaks and thus reduce the risk of explosion.

LPG Market – Production, Supply and Consumption  

LPG is separated from raw oil and raw gas during extraction or refining. In order to stabilize the raw oil or gas, the accompanying products are extracted during a cleaning process. The accompanying gases are then either processed or burnt on the spot. The latter process is also known as flaring and approximately 140 billion m³ of potential LPG are burnt every year. Through further processing of the accompanying gasses, propane and butane are gained, which are used as LPG.

A sophisticated infrastructure is required for the distribution of LPG (see figure below). It is delivered from supply points in a liquefied form to primary storage facilities, where it is stored under refrigeration or pressurization. It can then be sold to distributors in its refrigerated or pressurized form.

LPG as a by-product of the oil and gas industry is directly dependent on the extraction of fossil fuels. While larger production capacities may open up from the development of new fossil fuel sources, it has to be highlighted that most conventional fossil fuel fields are already being exploited. Additional fossil fuel sources may be harnessed from unconventional sources. However, these are mostly linked to significant environmental risks. More LPG may also be made available from accompanying gases that are currently being flared. This resource offers 70 million tons of gas.

In 2010, LPG consumption amounted to around 249 million tons worldwide. Asia Pacific has also experienced the highest growth rates, around 5% since 2000. The consumption of LPG in Africa is highly clustered in North African countries, comprising around 85% of Africa’s total consumption. Although Nigeria is the largest LPG producer in Sub-Saharan Africa, annual per capita consumption is less than 1kg whereas in countries like Algeria, Egypt, Tunisia, Libya and Morocco, users consume 45kg of LPG per year. A total of 47% of global demand for LPG is covered by the domestic sector in which households use LPG for cooking, water and room heating; in Africa the domestic sector accounts for more than 88% of the demand.

In industrial countries, LPG is used for heating and cooking, as auto gas and in the Petrochemical industry. In developing countries LPG is mainly used as a cooking fuel. The users are predominately middle- to high-income households in regions with a supply network (mostly urban and peri-urban areas). LPG availability remains scarce, especially in rural areas of developing countries. This is mainly due to lacking supply networks, which are not able to supply households.

Utilization of LPG for Cooking

A mixture of air and LPG can be ignited if the amount of LPG in the air is between 2%-10%. The ignition temperature is above 380°C. The maximum flame temperature for LPG is around 2,000°C. The affordability of LPG is still a substantial barrier for many households that want to use LPG. Evidence shows that subsidies have benefitted wealthier urban users more than low-income users as the former are in a better position to afford the high initial costs, e.g. to purchase the cylinder and the LPG burner. In most countries, access to LPG is limited to urban areas and LPG supply shortages are a frequent occurrence in rural areas. Additionally, due to the low cost of fuelwood and lack of awareness, increased LPG use is currently not viable for most rural areas in developing countries. Nevertheless, in regions with low biomass availability, LPG could lead to a significant relief of biomass resources.

Convenience is one of the main reasons why the use of LPG has been growing worldwide. LPG heats quickly and provides much greater efficiency than even the most improved biomass stoves. LPG stoves can also be controlled more precisely to match the user’s requirements and can save time for cooking and cleaning the kitchen. Additionally, LPG can be transported, stored and used virtually anywhere.