A large amount of energy
is required in mechanical
©Kraft foods Germany
Coffee husk is a source
Joe's Sustainable Farm,
India - Team 01639.
Solar drying saves energy
but has high risk of
Joe's Sustainable Farm,
India - Team 01639. The most energy-consuming step in processing coffee is drying. While sun-drying has many benefits such as helping to conserve energy, minimizing the usage of fossil fuels and cost, it has some potentially serious problems. Parchment coffee, has the potential to be contaminated with dust and dirt during the drying process. Rainstorms can appear even in the dry season, sothe risk of re-wetting is high. Re-wet coffee beans are susceptible to bacterial infection and mouldy growth. In addition, sun-drying is time-consuming. As a result, many processors choose the mechanical drying method.
The energy for mechanical drying comes from wood, coal, or diesel. In Latin America, coffee drying significantly contributes to deforestation. It is estimated that in Honduras alone, "1,885 acres of forest are clear cut annually for coffee processing, using 16% of the industrial consumption of wood in the entire country." Obviously, deforestation is responsible for many negative effects on the natural environment.
Modifications of the sun-drying method, including drying with solar driers are seen as one of the possible solutions to this problem. These driers either operate by solar energy (use solar power for drying or operating fans); or they just help concentrate sunlight and organise the beans for faster and more efficient drying.
Another method is to use alternative sources of energy. Some possible sources of energy are:
Biogas: methane generated from processing wastewater can be used as an energy source. 1m3 of concentrated and neutralised wastewater can give up to 1m3 of methane, which produces about 7 kWH. However, this option is only economically-viable for large scale processors after about 5 years of operation..
Parchment husks: coffee parchment husks can be used as a source of energy for burners for heat exchangers of coffee driers. This way, both waste-recycling and energy-saving can be achieved.
“An Introduction to Good Manufacturing Practices for Post Harvest Processing of Arabica Coffee in Vietnam” - Jan. C von Enden.
Intermediate Technology Development Group
The UMass Lowell Solar Engineering Webpage