Ethanol and methanol are alcohol fuels which can be distilled from a wide variety of biomass feedstock. Therefore they are a renewable cooking energy alternative, which are highly convenient to use. The use of ethanol and methanol requires the establishment of a production and supply chain, which very much influences the price of the fuel.
Ethanol (Ethyl Alcohol - C2H5OH) is a clear liquid that can be distilled from starch which first has to be converted into sugar, or sugar-containing biomass feedstock. Bio-ethanol feedstock can be categorized into three major groups:
- sugar crops (e.g. sugarcane, sugar beet, sweet sorghum and fruits),
- starch crops (e.g., corn, wheat, rice, potatoes, cassava, sweet potatoes and barley), and
- lingo-cellulosic biomass (e.g. wood, straw and grasses
Sugar cane and molasses are the most common and economical sources of ethanol. By using biocatalysts, (micro-organisms including yeast and bacteria), starch or sugar rich plants are fermented to produce ethanol in a relatively dilute aqueous solution (e.g. beer, wine). Efficient micro-scale distilleries have the capacity to produce from 150 to 5,000 liters ethanol per day.
Cooking with Ethanol
Ethanol burns with a slow, steady and only slightly visible flame. Ethanol should be stored in closed containers and bottles, mainly due to the combustible nature of the ethanol vapour-air mix at certain concentrations, but also due to the possibility of evaporation. Within the household, care must be taken to fully extinguish the flame when filling ethanol stoves, as the flame is very difficult to see.
Ethanol gel is commonly known as gel fuel and is made from ethanol combined with a thickening agent to make it viscous and easier to handle as a fuel. However, the viscous nature of gel fuel causes it to stick to most surfaces, including clothing and skin. Traditional methods of extinguishing these fires such as stop, drop and roll, will not extinguish such fires. Instead, a dry chemical extinguisher or baking soda is needed to extinguish the flames. The quoted gross calorific value of gel fuel by manufacturers is 22.8 MJ/kg. A major advantage of gel fuel is that it can be distributed in a simple pot without the risk of spilling it. However, this characteristic makes it difficult to control the temperature of the stove accurately, therefore small amounts of colouring and denaturing agents are added to enhance the visibility of the flame and to avoid consumption of the gel fuel respectively. The fuel is generally sold in canisters onto which the burner is set, making it easy to use.
Although ethanol and ethanol based gel fuels can offer a clean and efficient fuel source for households, it might be difficult to set-up a reliable supply chain for ethanol and gel fuel and to encourage rural households, which rely upon cheap or free gathered fuelwood for cooking to switch to using ethanol as cooking fuel.
Advantages and Disadvantages Cooking with Ethanol
The following advantages can be considered when using of ethanol fuel for cooking:
- Consists of renewable primary products
- Very clean combustion with negligible emissions and no soot
- Can safely be used indoors; eliminates Household Air Pollution (HAP)
- Heat available instantly after ignition
- Provides a safe alternative to LPG when not pressurised
- Can be produced from a variety of feedstocks, when grown from sustainably harvested feedstocks, and is a renewable fuel.
- Intrinsically cheap
- The development of alternative feedstocks, more applicable to local conditions, has the potential to improve yields, farmer income and food security
Disadvantages using ethanol as a cooking fuel:
- Low heating value when further diluted with water to make gel-fuel
- High flammability, burns at low temperatures
- In health terms, ethanol causes dryness to the skin and should not stay on the skin for long time. If ingested, it causes intoxication and large quantities can cause damage to the nervous system (as with drinking alcohol). Ethanol should always be denatured and dyed before distribution to prevent unintentional eating
- It can be difficult to establish a fuel supply chain in conjunction with developing a market for a new stove
- The large scale ‘mono-agricultural’ production of ethanol can be environmentally and socially damaging in developing countries
Alcohol fuels are increasingly recognized by the international community as a clean liquid fuel solution of the future. Ethanol and ethanol-based gel-fuel are quite common in niche applications, where clean combustion, safety and convenience are required: e.g. marine markets, camping, catering services and restaurants. Because ethanol can be made from a variety of low-cost, simple feedstocks, it is an intrinsically cheap fuel. Ethanol fuel can be produced at a scale which suits the community in demand. For example, in Ethiopia ethanol is sourced from the government-owned Sugar Corporation to meet the cooking demand of several thousand households and ethanol for household energy use is recognised as an official priority of the National Biofuels Policy. In humanitarian interventions where energy for cooking is in large and urgent demand and resources are extremely scarce, ethanol stoves and fuel have proven successful.
Methanol-use for cooking is still in its infancy, partially due to the fear of the potentially damaging health effects should the fuel be accidentally ingested. Methanol is primarily made from natural gas, but also can be produced from wood, bagasse, grass, or agricultural wastes. If methanol is burned with air in an open flame it burns without any by-products.
This article was originally published by GIZ HERA. It is basically based on experiences, lessons learned and information gathered by GIZ cook stove projects. You can find more information about the authors and experts of the original “GIZ HERA Cooking Energy Compendium” in the Imprint - GIZ HERA Cooking Energy Compendium.
- ↑ http://www.hedon.info/EthanolProduction?bl=y
- ↑ https://projectgaia.com/our-approach/the-fuel/
- ↑ 3.0 3.1 3.2 Practical Action (2011): Ethanol as a Household Fuel in Madagascar http://cleancookstoves.org/resources/231.html
- ↑ http://www.mass.gov/eopss/agencies/dfs/dfs2/osfm/pubed/fs-topics/fs-topics-a/gel-fuel-safety.html
- ↑ Lambe, F. et al (2015) Ethanol: towards a viable alternative for domestic cooking in Ethiopia, Discussion Brief by Stockholm Environmental Institute (SEI) http://cleancookstoves.org/resources/386.html
- ↑ http://www.hedon.info/Ethanol?bl=y
- ↑ http://www.climatetechwiki.org/technology/cook_ethanol
- ↑ https://projectgaia.com/wp-content/uploads/2013/10/Policy-brief-Finaldocx.pdf
- ↑ http://www.projectgaia.com/files/ShimelbaCampGAUNHCR.pdf