HOW ARE BIOFUELS MADE?
Bio-Ethanol (click image to enlarge)
* Chemical reaction caused by addition of dilute sulphuric acid on the active ingredients in the feedstock
** Series of chemical reactions that convert sugars through action by yeast or bacteria to ethanol and carbon dioxide
The raw feedstock, such as sugar cane residues, is ground up to a small size and the active ingredients in the feedstock react with dilute sulphuric acid, breaking down into a mixture of simple sugars, cellulose and cellulose enzymes which are grown at this stage (or they can be bought in). The cellulose is further reacted with the cellulose enzymes to form glucose. Both the simple sugars and the glucose are fermented with yeasts or bacteria, forming ethanol, with carbon dioxide as a by-product. The non-reactive parts of the sugar cane remain as a woody waste which can be used as a fuel to drive the process.
Plant Oils for Energy (click to enlarge)
Plant oils can be extracted using hand tools, such as the Approtech oil expeller shown on the left (Approtech), or the motorised Sundhara-type oil presses, such as the one shown on the right above.
These methods are similar to those used for food oil extraction. Practical Action has extensive information on these types of extraction, including a technical brief specifically on oil extraction.
Biodiesel (click image to enlarge)
The raw oil is reacted with an excess of alcohol (often methanol or ethanol) in the presence of a catalyst (often potassium or sodium hydroxide). The products of this reaction are crude biodiesel and crude glycerine, with an excess alcohol, which is recovered and re-used.
Uses of Biofuels
The main use of biofuels globally is within the transport sector, with bio-ethanol replacing petrol (gasoline) and bio-diesel replacing diesel. Governments have been keen to promote the use of such fuel for transport purposes as they can draw increased revenue from taxing its sale as motor fuel. In the longer term, unregulated planting of energy crops for the transport sector is likely to lead to land degradation, social unrest and famine.
For cooking and lighting within the home, biofuels are hugely beneficial, as they can be burnt completely cleanly. With over 4000 people dying each day globally as a result of indoor air pollution from cooking smoke, providing a clean local alternative fuel in those countries most affected can make substantial inroads into alleviating poverty. Clean cooking provides health, safety and quality of life benefits especially for women and children.
Biofuel stoves have been shown to be effective in reducing or eliminating the practice of gathering biomass; this can be especially critical where deforestation and desertification are pressing issues, or in conflict situations where women fuel-gatherers are particularly vulnerable to assault.
Developing countries with ideal climates for the rapid growth of fuel crops, such as sugar cane, are often the same ones suffering the greatest burden of disease and death from indoor air pollution. This document will discuss mainly the positive technologies for which biofuels should be grown.
TECHNOLOGIES FOR LIQUID BIOFUELS
Liquified Petroleum Gas (LPG) is a fossil-fuel derivative of two large energy industries: natural gas processing and crude oil refining. Currently the demand for LPG is growing at around 0.4% per annum and with the growth in demand in Asia growing at 3.5% per annum (LP Gas Association website (data 2004)). Any downturn in the supply of these two fossil fuels will lead to a reduction in the availability of supplies and consequent price increases. Other clean fuels are needed for cooking both to complement LPG in those countries which are not themselves oil rich, and to supply clean energy to those currently using biomass in traditional cooking stoves and three-stone fires.
Ethanol is easily and safely handled, leading to their use, for years, for the recreational market such as yachts and outdoor activities. Recently, robust, low-cost stoves have been designed specifically for households in the developing world.
This new market has lead to the establishment of ethanol fuel distribution systems, creating opportunities for local commerce. A good example is the CleanCook Stove. This stainless steel stove burns cleanly and has safety features designed particularly for the household:
- A fuel tank holds the ethanol in a special absorptive fibre so that it cannot spill out
- Fuel is denatured so that it cannot be ingested
- The tank is not pressurized so there is no risk of explosion
- The burner flame is easily adjusted or extinguished by means of a simple regulator
This stove is finding a market in both Africa and Latin America. Currently, manufacture of the stove for Ethiopia is being transferred to Addis Ababa, bringing skills and employment close to where the stove will be in use and providing clean fuel for refugee communities (Oâ€™Brien).
Other manufacturers for ethanol stoves include the SuperBlu stove manufactured by Bluwave Ltd. The stove has been designed to be reliable, safe and easy to manufacture. The fuel consumption is highly efficient compared to paraffin stoves, and it burns cleanly with no smell. It has no consumable parts, such as wicks. In cold conditions, it converts into a heater by the simple means of a ceramic cylinder which fits on top of the stove. The cylinder heats up and retains and radiates the heat to warm the surrounds, and on top of the cylinder a space is provided for a kettle. A detailed discussion on testing of this stove can be found on the HEDON Household Energy Network website (Bluwave).