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continued cleanup, moved more info to improved solid biofuel stoves
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{{Main|Manure}}
 
{{Main|Manure}}
 
Many [[poor]] families in rural and urban areas collect dung as their source of income. There is a group of women in Bangladesh, who traditionally collect dung, make cakes and sell them to commercial markets. The traditional collectors of dung are teenage girls from poor families. They bring back dung to their homes and convert it into round cakes and cone-like sticks for drying in the open air.
 
Many [[poor]] families in rural and urban areas collect dung as their source of income. There is a group of women in Bangladesh, who traditionally collect dung, make cakes and sell them to commercial markets. The traditional collectors of dung are teenage girls from poor families. They bring back dung to their homes and convert it into round cakes and cone-like sticks for drying in the open air.
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{|border="1"
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|-
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|bgcolor="silver"|Dung is considered to be one of the best fuels for the traditional mud stove for the following reasons:
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*it burns slowly
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*cooks fast
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*generates powerful heat compared to other sources of fuel found locally 
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*easy to store
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*Less toxidity
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Problems related to dung as a fuel are:
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*there is a scarcity of dung
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*cattle owners do not permit collection form their fields
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*as dung is being dried there is a risk that it could be stolen 
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*It burns faster than wood when it is not properly compressed   
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|}Source: Mohammed Aslam, Practical Action Bangladesh
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== Combustion theory ==
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For solid biomass to be converted into useful heat energy it has to undergo combustion. Although there are many different combustion technologies available, the principle of biomass combustion is essentially the same for each.  There are three main stages to the combustion process:
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''Drying'' - all biomass contains moisture, and this moisture has to be driven off before combustion proper can take place.  The heat for drying is supplied by radiation from flames and from the
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stored heat in the body of the stove or furnace.
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''Pyrolysis'' - the dry biomass is heated and when the temperature reaches between 200°C and 350°C the volatile gases are released.  These gases mix with oxygen and burn producing a yellow flame.  This process is self-sustaining as the heat from the burning gases is used to dry the fresh fuel and release further volatile gases.  Oxygen has to be provided to sustain this part of the combustion process.  When all the volatiles have been burnt off, charcoal remains.
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''Oxidation'' - at about 800°C the charcoal oxidises or burns. Again oxygen is required, both at the fire bed for the oxidation of the carbon and, secondly, above the fire bed where it mixes with
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carbon monoxide to form carbon dioxide which is given off to the atmosphere.
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It is worth bearing in mind that all the above stages can be occurring within a fire at the same time, although at low temperatures the first stage only will be underway and later, when all the
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volatiles have been burned off and no fresh fuel added, only the final stage will be taking place. Combustion efficiency varies depending on many factors; fuel, moisture content and calorific value of fuel, etc.  The design of the stove or combustion system also affects overall thermal efficiency and table 2 below gives an indication of the efficiencies of some typical systems (including non-biomass systems for comparison).
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{| border="1" cellpadding="3"
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!width="250"|Type of combution technology
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!width="250"|Percentage efficiency
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|-
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|
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Three-stone fire
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<br clear="all" />
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Improved wood-burning stove 
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<br clear="all" />
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Charcoal stove with ceramic liner
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<br clear="all" />
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Sophisticated charcoal-burning stove
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<br clear="all" />
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Kerosene pressure stove
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<br clear="all" />
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LPG gas stove
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<br clear="all" />
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Steam engine
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|
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10 - 15
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<br clear="all" />
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20 - 25
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<br clear="all" />
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30 - 35
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<br clear="all" />
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up to 40
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<br clear="all" />
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53
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<br clear="all" />
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57
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<br clear="all" />
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10 - 20 
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|-
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|}
      
== Densifying biomass ==
 
== Densifying biomass ==
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For using the biomass to fulfill in our own energy needs, there are several options. The most basic (and energy-inefficient option) is the open fire. The open fire fulfills in several needs: it provides [[light]], [[heat]], the option to [[cook]] something, scare wild animals, repel insects, [[Food preservation|smoke food]]. Although open fires and other [[outdoor cooking|outdoor cooking techniques]] still axist, more energy-efficient [[cooker|cooking technologies]] now exist.
 
For using the biomass to fulfill in our own energy needs, there are several options. The most basic (and energy-inefficient option) is the open fire. The open fire fulfills in several needs: it provides [[light]], [[heat]], the option to [[cook]] something, scare wild animals, repel insects, [[Food preservation|smoke food]]. Although open fires and other [[outdoor cooking|outdoor cooking techniques]] still axist, more energy-efficient [[cooker|cooking technologies]] now exist.
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===Biomass use in the developing world===  
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===Local biomass use in the developing world===
More than two million people in the developing world use biomass for the majority of their household energy needs. It is used mainly for cooking, heating water and domestic space heating. Table 1 below shows household energy consumption as a percentage of total biomass consumption in a number of selected countries in Africa. Biomass is also used widely for non-domestic applications.  
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{{Main|Improved solid biofuel stoves}}
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More than two million people in the developing world use biomass for the majority of their household energy needs. It is used mainly for cooking, heating water and domestic space heating. Table 1 below shows household energy consumption as a percentage of total biomass consumption in a number of selected countries in Africa. Biomass is also used widely for non-domestic applications.  
    
{| border="1" cellpadding="1"
 
{| border="1" cellpadding="1"
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|}
 
|}
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===Local utilisation using improved stoves===  
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===Commercial utilisation of biomass===
{{Main|Improved solid biofuel stoves}}
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Biomass can be used for a variety of commercial activities. There are several technologies which employ direct combustion of unprocessed or semi-processed biomass to produce process heat for a variety of end-uses. The most common is the simple furnace and boiler system which raises steam for such applications such as tobacco curing, electricity generation and beer brewing. Biomass is  also used for providing direct heat for brick burning, for lime burning and cement kilns. The advantage of using biomass is that it can be locally sourced, thereby avoiding shortages associated with poor fuel supply networks and fluctuating costs.
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 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.   
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== Combustion theory ==
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For solid biomass to be converted into useful heat energy it has to undergo combustion. Although there are many different combustion technologies available, the principle of biomass combustion is essentially the same for eachThere are three main stages to the combustion process:
 
   
 
   
Some of the features of these improved stoves include:
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''Drying'' - all biomass contains moisture, and this moisture has to be driven off before combustion proper can take place.  The heat for drying is supplied by radiation from flames and from the  
*a chimney to remove smoke from the kitchen
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stored heat in the body of the stove or furnace.
*an enclosed fire to retain the heat
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*careful design of pot holder to maximise the heat transfer from fire to pot
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''Pyrolysis'' - the dry biomass is heated and when the temperature reaches between 200°C and 350°C the volatile gases are released.  These gases mix with oxygen and burn producing a yellow flame.  This process is self-sustaining as the heat from the burning gases is used to dry the fresh fuel and release further volatile gases.  Oxygen has to be provided to sustain this part of the combustion process.  When all the volatiles have been burnt off, charcoal remains.
*baffles to create turbulence and hence improve heat transfer
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*dampers to control and optimise the air flow
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''Oxidation'' - at about 800°C the charcoal oxidises or burns. Again oxygen is required, both at the fire bed for the oxidation of the carbon and, secondly, above the fire bed where it mixes with
*a ceramic insert to minimise the rate of heat loss  
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carbon monoxide to form carbon dioxide which is given off to the atmosphere.
*a grate to allow for a variety of fuel to be used and ash to be removed
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*metal casing to give strength and durability
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It is worth bearing in mind that all the above stages can be occurring within a fire at the same time, although at low temperatures the first stage only will be underway and later, when all the
*multi pot systems to maximise heat use and allow several pots to be heated simultaneously
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volatiles have been burned off and no fresh fuel added, only the final stage will be taking place. Combustion efficiency varies depending on many factors; fuel, moisture content and calorific value of fuel, etc.  The design of the stove or combustion system also affects overall thermal efficiency and table 2 below gives an indication of the efficiencies of some typical systems (including non-biomass systems for comparison).
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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 Western society), but is often acts as a social focus, 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, which require large pots and vigorous stirring.  Fuel type can differ greatly; in some countries cow dung is used as a common fuel source, particularly where wood is scarce.  Cost is also a major factor among low-income groups.  Failing to identify these key socio-economic issues will ensure that a stove programme will fail.  The function of an improved stove is not merely to save fuel.
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{| border="1" cellpadding="3"
 
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!width="250"|Type of combution technology
===Commercial utilisation of biomass===
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!width="250"|Percentage efficiency
Biomass can be used for a variety of commercial activities. There are several technologies which employ direct combustion of unprocessed or semi-processed biomass to produce process heat for a variety of end-uses. The most common is the simple furnace and boiler system which raises steam for such applications such as tobacco curing, electricity generation and beer brewing. Biomass is  also used for providing direct heat for brick burning, for lime burning and cement kilns. The advantage of using biomass is that it can be locally sourced, thereby avoiding shortages associated with poor fuel supply networks and fluctuating costs.
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|-
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|
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Three-stone fire
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<br clear="all" />
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Improved wood-burning stove   
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<br clear="all" />
 +
Charcoal stove with ceramic liner
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<br clear="all" />
 +
Sophisticated charcoal-burning stove
 +
<br clear="all" />
 +
Kerosene pressure stove  
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<br clear="all" />
 +
LPG gas stove
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<br clear="all" />
 +
|
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10 - 15
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<br clear="all" />
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20 - 25
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<br clear="all" />
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30 - 35
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<br clear="all" />
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up to 40
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<br clear="all" />
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53
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<br clear="all" />
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57
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<br clear="all" /> 
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|-
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|}
    
== Other issues ==
 
== Other issues ==
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greater consideration.  These micro environmental needs are often as complex as the broader environmental concerns and this is reflected in the fact that no one improved stove design can meet the needs of a wide and diverse range of peoples.  
 
greater consideration.  These micro environmental needs are often as complex as the broader environmental concerns and this is reflected in the fact that no one improved stove design can meet the needs of a wide and diverse range of peoples.  
 
   
 
   
Large-scale combustion of biomass is only environmentally feasible if carried out on a sustainable basis.  For obvious reasons continual large-scale exploitation of biomass resources without care for its replacement and regeneration will cause environmental damage and also jeopodize the fuel source itself.
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Large-scale combustion of biomass is only environmentally feasible if carried out on a sustainable basis.  For obvious reasons continual large-scale exploitation of biomass resources without care for its replacement and regeneration will cause environmental damage and also jeopodize the fuel source itself.
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===Local manufacture of stoves===
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===Woodfuel and welfare===
{|border="1"
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The effects of inhaling biomass smoke during cooking are receiving attention from researchers; chronic bronchitis, heart disease, acute respiratory diseases and eye infections have been linked with smoky interiors, but the impacts of fuel shortage on cooking and nutrition are scarcely noticed.  
|-
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|bgcolor="silver"|Since 1982, the Kenya Ceramic Jiko (KCJ), an improved charcoal-burning stove aimed at the urban market has been developed and manufactured by large numbers of small producers. The KCJ has two main components; metal and fired clay. Both these parts are made by entrepreneurs; the metal part (cladding) being made by small-scale enterprises or individual artisans, while the clay part (liner) is manufactured by slightly larger and more organised enterprises or women’s groups. The KCJ is sold by the artisans directly to their customers or through commercial outlets such as retail shops and supermarkets. The stove was initially promoted heavily to develop the market, by the NGO KENGO and by the Kenyan Ministry of Energy, through the mass media, market demonstrations and trade fairs. As a result of this substantial promotion, there are now more than 200 artisans and micro-enterprises manufacturing some 13,600 improved stoves every month. To date, it is estimated that there are some 700,000 such stoves in use in Kenyan households. This represents a penetration of 16.8% of all households in Kenya, and 56% of all urban households in the country. 
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|}Source: Dominic Walubengo, Stove Images, 1995
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===Women, woodfuel, work and welfare===
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For resource-poor women the working day stretched from dawn to long after dark.  The pressures on women’s time are heavy, cooking and fuel collection are among the most arduous of their tasks.  The effects of inhaling biomass smoke during cooking are receiving attention from researchers; chronic bronchitis, heart disease, acute respiratory diseases and eye infections have been linked with smoky interiors, but the impacts of fuel shortage on cooking and nutrition are scarcely noticed.  
      
[[Image:Biomass6.jpg|thumb|Figure 6: Women can design and Manufacture improved cook stoves. ©Simon Ekless/Practical Action|right|300px]]  
 
[[Image:Biomass6.jpg|thumb|Figure 6: Women can design and Manufacture improved cook stoves. ©Simon Ekless/Practical Action|right|300px]]  
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*Caroline Ashley and Peter Young, Stoves for Sale: Practical Hints for Commercial Dissemination of improved stoves, IT, FAO, IDEA, GTZ, FWD, 1994  
 
*Caroline Ashley and Peter Young, Stoves for Sale: Practical Hints for Commercial Dissemination of improved stoves, IT, FAO, IDEA, GTZ, FWD, 1994  
 
*Daniel Theuri et al, Smoke Health and Household Energy Volume 1: Participatory Methods for Design, Installation, Monitoring and Assessment of Smoke Alleviation Technologies, ITDG, 2005
 
*Daniel Theuri et al, Smoke Health and Household Energy Volume 1: Participatory Methods for Design, Installation, Monitoring and Assessment of Smoke Alleviation Technologies, ITDG, 2005
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==See also==
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* [[Emancipation of women]]
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* [[Women's health]]
    
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{{attrib PATB}}
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