The direct combustion of solid biomass is probably the oldest household technology and will continue to be the main energy source for cooking, water heating and domestic heating in many developing countries for years to come. A wide range of stove types that use solid biomass as fuel can be found around the world. However, very low quality combustion is an almost universal characteristic of the most traditional and widespread stoves. Two prominent disadvantages derive from the use of these inefficient stoves:
Several alternative (improved) stove models already exist, offering the option to use solid biomass energy sources for cooking, but in a more efficient and cleaner way. However, the large-scale global diffusion of improved stoves is still a goal that should be pursued.
Around 2.7 billion people worldwide rely on solid biomass as fuel for cooking. Accelerating the dissemination of improved solid biomass stoves is one of the main means of achieving universal access to clean cooking facilities.1 Improvements in energy efficiency through the introduction of improved stoves can significantly reduce the pressure on valuable biomass resources that currently provide energy for cooking. The global alliance for clean cookstoves aims to promote the diffusion of improved biomass stoves, with a target of 100 million such stoves to be in use by 2020.2
Similar to the previous analysis, the global impact on greenhouse gas emissions of improving the cooking practices of billions of people would be significant. However, to estimate the precise emission reduction potential is difficult as the exact number of users, the type of equipment used and the energy consumption are complex issues. As a result, the estimates for carbon emission reduction potentials range from 125Mt to 459Mt.3
Up-scaling the adoption of improved biomass stoves is a crucial factor in achieving the MDGs. The use of energy efficient and cleaner solid biomass stoves impact positively on factors driving the vicious cycles of poverty, such as improving health conditions at home and freeing up time and/or reducing the cost associated with the provision of energy for cooking.
If energy efficient biomass stoves were widely adopted, this would significantly contribute to severing the link between cooking activities and deforestation, climate change and indoor air pollution.
The unregulated harvesting of fuel wood and the production of charcoal has become an important driver of deforestation and soil erosion in some regions. Increasing population pressure and a decline in the availability of wood resources will further worsen the situation. If improved biomass stoves were widely adopted, it would appear to be possible to reduce the need for biomass for cooking by at least 50%. This would significantly reduce the pressure on biomass resources.
The potential to reduce greenhouse gas emissions depends on several parameters involved in the combustion process, such as the current cooking practices (baseline), the type of fuel to be used, the type and design of the stove and the operating conditions. Therefore, it is almost impossible to make a definitive prediction about the reduction levels. However, two projects that are registered under the Clean Development Mechanism (CDM) can illustrate the range of potentials. Estimations of the mitigation potential per stove vary between 1.4 to 2.7 tonnes CO2 equivalent per year in Nepal and Nigeria respectively.4, 5
The incomplete combustion of biomass in traditional stoves leads to the emission of multiple health-damaging pollutants. Generally speaking, there are two approaches to reducing the exposure of people to dangerous pollutants from cooking activities with solid biomass: the use of chimneys to channel flue gases out of the kitchen and the improvement of the combustion process in the stove.
Early efforts to improve biomass stoves focused mainly on enhancing the combustion performance of the devices, which led to some reduction in the levels of pollutants in the flue gases. The issue of indoor pollution has since become a central one for most initiatives working on solid biomass stoves. Reduction potentials vary from design to design.
Recent field studies have delivered first evidence on the ability of some efficient stove designs to reduce the emission of pollutants:
Inefficient solid biomass stoves have negative effects on the health and socio-economic conditions of the users. However, using cheap and traditional biomass stoves for cooking is already part of the normal way of life for billions of people. It can be difficult to change behavioural patterns and encourage people to adopt new practices, with the result that the promotion of the technology requires concerted efforts on both individual and community level.
There are many challenges to overcome in increasing the adoption and dissemination of improved solid biomass stoves. Some important issues are:
In order to ensure the success of improved stoves, it is important to fully understand the user's needs and requirements. Therefore, it is necessary to involve the users in the design process and to learn about their cooking habits and lifestyle.8 Meat and vegetables, for example, require a different stove to staple foods.9 Furthermore, the fuel sources and locally available building materials differ widely.
The perceived benefit to the user is commonly an important driver for adopting changes and/or investing "effort“ (e.g. time and money) in a new technology. Awareness campaigns aimed at potentially interested parties should try to trigger their interest in improved stoves, by highlighting the problems related to the use of inefficient stoves and describing possible solutions.
The kind of information and the way of communicating it depend on the audience that has to be reached. Consequently, developing appropriate communications strategies should be part of any measure aimed at supporting the diffusion of improved stoves.
Different kinds of actors may play a role in the diffusion of the technology. There are the users, who are expected to be the main beneficiaries. Added to this group are private investors and/or entrepreneurs who should play an important role in building manufacturing capacities and distribution networks. Government organisations need to establish supporting programmes, as well as to formulate and enforce appropriate regulations. Other kinds of organisations and/or institutions should assume other important functions such as financing, further research and development, testing commercial products etc.10, 11
As is the case with the introduction of other types of innovations, ensuring that potential users have access to improved solid biomass stoves requires the establishment of functioning supply structures, i.e. networks of persons, firms and other organisations that provide materials, equipment, appropriate fuels, know-how and other services (e.g. technical assistance and financing) related to the technology. The lack of such structures, or their breakdown, may reduce the likelihood of the sustainable adoption and diffusion of the technology.
There are several designs and variations of improved solid biomass stoves. They range from simple "do-it-yourself“ concepts, to designs that can be manufactured by local artisans and industrial products comprising fans and controls for air supply. However, the level of commercialisation varies widely from region to region.
Some issues that may contribute to the further development and dissemination of the technologies are:
As previously stated, the performance of any stove depends not only on its technical design, but also on other factors such as the characteristics of the available fuel and, in particular, the traditional cooking habits of the user (as this impacts on how they will use the stove). Assessing the actual benefits to the user requires testing the stoves under real conditions. Greater effort is still needed to compile a solid base of data comprising a broad range of regions and technologies. This information source is a crucial factor in shaping the plans for up-scaling the adoption of improved biomass stoves.
Comparing the widely diverse stove designs is almost impossible. Evaluating and comparing technical options is crucial when making decisions at different levels (e.g. for the design of government programmes, for industry strategies, marketing, or even for individuals). Some methods have commonly been used for testing biomass stoves, such as "water boiling tests“, "controlled cooking tests“ and "kitchen performance tests“.12 However, efforts to further develop appropriate methods and to gain broader acceptance and application of the standards are still required.
The suitability of a stove design varies from region to region. It depends on several cultural, economic, social and technical factors. It is very unlikely that only one concept could respond appropriately to the needs of all users even within one country or region. Consequently, the future scenario may involve the emerging of national and/or regional markets where a set of stove designs are commercialised. The designs should not only be price-competitive but also fulfil specific technical standards of efficiency and emissions. Establishing regional or national systems to formulate and ensure quality standards will be a crucial step towards the mass diffusion of improved stoves
There are prospects for developing the dissemination of improved solid biomass cookstoves on a wide scale, especially in rural areas. To support this development a programme called the UN Global Alliance for Clean Cookstoves has been initiated. The aim is to help to overcome existing market barriers that currently impede the production, deployment and use of clean cookstoves in the developing world. The target is to increase the number of improved cooking stoves to around 100 million by 2020.
Applying the principle of gasification for cooking is a relatively recent development. Several concepts have been already tested and further development of the technology promises to respond to some important issues related to cooking with biomass.13 The technology offers three notable advantages: