When choosing a fuel for cooking or heating in our households, many of us go with the cheapest option. That is a prudent decision considering the present economic situation in the country. For others, the choice depends on what is convenient to use and easier to obtain from the market. There are also a few of us who may consider factoring in the sustainability and environmental impact of each fuel regardless of the price and convenience. In this post, I will summarize the environmental rating of the four common fuel sources used in Nigerian households, namely, kerosene, wood (biomass), electricity, and liquefied petroleum gas (LPG). Focus will be given to their environmental impacts; therefore, the best option may not be the cheapest. For simplicity, I chose certain indicators for environmental impact and rate each of the fuels on a scale of 0-5, with a score of 5 being the cleanest.
The fuel sources
Wood and other biomass materials (e.g., charcoal, wood pellets and dung) are mostly used in the rural areas for cooking and home heating. Innovations in the sector resulted in the availability of efficient and cleaner biomass cooking stoves that are used across both rural and urban areas. Another commonly used fuel is kerosene. Also known as paraffin or lamp oil, it is a clear liquid derived from petroleum (crude oil) and has more carbon per molecule than gasoline. It is commonly used in households to power kerosene stoves and oil lamps. LPG is a mixture of propane and/or butane with a small proportion of other gas fractions from the crude oil. It has the least carbon content per molecule among the petroleum fractions used as fuel sources. It is supplied in pressurized cylinders for household use. Electric stoves and cookers powered by the electricity from the national grid are also commonly used in some Nigerian households.
Biomass is burnt in different forms as a cooking fuel
The environmental impact ranking of the fuel sources
Renewability
The LPG and kerosene are both derived from petroleum (or crude oil), which is a fossil fuel that is found underneath the earth’s surface. The nearly non-replenishable nature of petroleum (it takes millions of years to form) earns it a 0 score on renewability. Electricity generation in Nigeria is also largely from fossil fuels. According to the United States Agency for International Development (USAID), the country has an installed capacity to generate 12,522 MW of electric power and 81% of that is thermal (with fossil fuels of coal and natural gas). The remaining 19% is hydro, which is considered to be a renewable source (not really sustainable though). Biomass will be the most favourable in terms of renewability because plants and other organic matter regrow faster. However, for them to be fully renewable (carbon-neutral), trees need to be replanted as fast as they are being burnt, which is nearly impossible based on the current consumption. Good practices that should be promoted on wood consumption in the country are using dead trees, thinning out overcrowded forests and cutting only part of trees that can regrow.
GHG emissions
The estimate of GHGs emissions by the US’s environmental protection agency (EPA) will be used to rank the fuel sources. Burning of wood and wood residues is the biggest GHGs producer with about 94 kg carbon dioxide (CO2), 7.2kg methane (CH4 and 3.6 kg NO2 per unit heat content (mmBtu). Kerosene produces 75 kg CO2, 3.0 kg CH4 and 0.60 kg NO2 per unit heat content. LPG produces 62 kg CO2, 3.0kg CH4 and 0.6 kg NO2 per unit heat content. Despite the current electricity generation being 81% thermal, it still produces the least GHGs as compared to other cooking fuel sources.
Indoor air pollution
Again, burning biomass should be the least favourable choice with regards to air pollution. In addition to particulate matters, smoke from wood may contain hazardous pollutants such as benzene, and formaldehyde. Benzene poisoning can be lethal by inhibiting the production of blood cells and thereby undermining the immune system. Formaldehyde inhalation can cause skin irritation, burning sensations in the eyes, wheezing, and has been linked to different kinds of skin cancer. Even wood stoves that are certified to be environmentally friendly produce pollutants much more than what is produced by natural gas appliances. Based on a recent study, the burning of wood (whether in an open fire or in modified woodstoves) produces a lot more carbon monoxide, polycyclic aromatic hydrocarbon and particulate matter 2.5 microns than kerosene and LPG. On the other hand, electricity by itself does not produce any of such pollutants in the immediate environment (pollutants may nevertheless be generated from over burning of food, oil, etc).
Waste generation
Another important factor to be considered is the waste generated from using the fuel sources, which may become a nuisance if not properly managed. In this regard, only biomass use generates any tangible waste material.
Table 1: Raking of the environmental impact of the household fuel sources
Legend: a golden star (★) represents a score of 1.
Final Verdict
Judging by the environmental impact of the common fuels we use in the immediate environment, electricity is the best option when and where it is available. Liquefied petroleum gas (cooking gas) should be the second option for households without access to electricity or those in need of a backup. The assessment presented is meant to serve as a quick guide as the precise impact of each of the fuel sources can only be obtained through an in-depth life cycle assessment.
