Biomass
Practical Action
Type of combustion technology
Three-stone fire
Improved wood-burning stove
Charcoal stove with ceramic liner
Sophisticated charcoal-burning stove
Kerosene pressure stove
LPG gas stove
Steam engine
Percentage efficiency
10 - 15
20 - 25
30 - 35
up to 40
53
57
10 - 20
Table 1: efficiencies of some biomass energy conversion systems
Source: Adapted from Kristoferson, 1991
Improved stoves
Much of the research and development work carried out on biomass technologies for rural areas
of developing countries has been based on the improvement of traditional stoves. This was
initially in response to the threat of deforestation but has also been focused on the needs of
women to reduce fuel collection times and improve the kitchen environment by smoke removal.
There have been many approaches to stove improvement, some carried out locally and others as
part of a wider programmes run by international organisations. Figure 2 below shows a variety of
successful improved stove types, some small, portable stoves and others designed for permanent
fixture in a household.
Some of the features of these
improved stoves include:
a chimney to remove smoke
from the kitchen
an enclosed fire to retain the
heat
careful design of pot holder to
maximise the heat transfer
from fire to pot
baffles to create turbulence
and hence improve heat
transfer
dampers to control and
optimise the air flow
a ceramic insert to minimise
the rate of heat loss
a grate to allow for a variety of
fuel to be used and ash to be
removed
metal casing to give strength
and durability
multi pot systems to maximise
heat use and allow several
pots to be heated
simultaneously
Figure 2: Examples of improved stoves.
Improving a stove design is a complex procedure which needs a broad understanding of many
issues. Involvement of users in the design process is essential to gain a thorough understanding
of the user’s needs and requirements for the stove. The stove is not merely an appliance for
heating food (as it has become in WesterFnigsoucreie2ty:),Abvuatriiestyofotef nImapctrsovaesdaCsooockisatlofvoecsus, a means
of
lighting and space heating. Tar from the fire can help to protect a thatched roof, and the smoke
can keep out insects and other pests. Cooking habits need to be considered, as well as the
lifestyle of the users. Light charcoal stoves used for cooking meat and vegetables are of little
use to people who have staple diets such as Ugali (Cornmeal commonly made from maize flour),
3