|Boiling Point No. 37 - June 1996 : Household Energy in Emergency Situations (Intermediate Technology Development Group , 1996)|
|Non - Theme Articles|
by Washington Nyabeze
Beer brewing and bread making are rural domestic activities now increasing in Zimbabwe to supplement declining incomes from agriculture.
Both processes use wood fuel and their energy requirements are considered in this paper. Seven brewing and five baking enterprises were studied by interviews, questions and daily monitoring over six months. Their energy efficiencies, technologies and environmental impacts were examined in detail.
Beer is generally brewed domestically in a 2001 (45gal) oil drum heated on one side by an open fire.
As only about one third of the drum surface is exposed to the fire less than 50% of the heat produced from the fuel and enters the drum for utilization in the brewing process. Much of this is then lost through the un-insulated, 70% of the drum surface. Woodfuel consumption per litre of beer is between 2.0 and 3.5kg (ave 3.0) and each brew makes 200 to 200 litres.
Bread is usually baked in a double (oil) drum oven although one enterprise used a pit oven and another a Dutch oven. The oven is heated by a fire in a chamber under the oven which may have a door to control the burning rate and some have a chimney with a damper. One loaf (570g) requires 1.8 to 2.8kg of woodfuel, mostly used at the warming up stage.
Opportunities for technical improvements
The study indicated the need for technology advice to be provided to the enterprises and their readiness to accept it.
• research into yeast assisted brews is needed to ease the pressure of some inputs such as rapoko, sorghum and woodfuel
• recipes for more nutritious and tasty beers
• increased production per cycle with better quality control
• more fuel efficient stoves and fire management
• better heat transfer from fire to brew
• fuel switching possibilities, especially with coal.
Business skills - maximum benefits from this technology approach can only be realized if, in addition, the entrepreneurs have skills in costing, sourcing of inputs, marketing of products, record keeping and general business practice. Effective means of developing these skills through training and information supply are needed.
The following opportunities were identified:
• provision of training and information for better design and
• construction methods for baking ovens
• instruction on better use and maintenance of ovens
• better understanding of the relationship between fire management and bread quality control
• use of coal and other locally available, alternative fuels
• making the mixing of ingredients less laborious
• provision of information on alternative baking techniques
• choice of most appropriate scale of technology according to required output.
Again, maximum benefits will depend on better business skills.
Environmental considerations Brick making, beer brewing and bread making are the three largest rural industries in Zimbabwe in terms of woodfuel consumption. Estimates show that they consume about 284,000, 163,000 and 218,000 tonnes of woodfuel per year respectively (brick making is not included in this summary as it is not really a domestic activity). There are 50,000 breweries and 1,200 bakeries in Zimbabwe. Although there are more critical causes of deforestation such as land clearing for agriculture and timber extraction, deforestation itself is a problem for rural industries.
The study showed that for each activity training is urgently needed in technologies, in appropriate business skills and in concern for environmental conservation.
Training manuals on improvements to existing technologies have been prepared for each industry covered. These focused on low cost changes of methods and were for use by small scale rural entrepreneurs, artisans and extension workers and field staff from government and non-government organizations.
Sixty entrepreneurs and 30 extension workers have already been trained in the use of the manuals, through three-day training workshops. Subsequent evaluation shows that more training workshops and exchange visits between entrepreneurs are needed to allow a wider choice of technologies and to promote innovation.
Extracted from a paper by Washington Nyabeze (ITDG Energy Project Manager; Zimbabwe) presented at a Zero workshop, June 1995, entitled 'Energy and Technology Issues in Rural Industries in Zimbabwe'