Wood-burning stoves worldwide: technology, innovation and policy

Ricardo Luis Teles de Carvalho

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandling

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More than any time in our history, the wood-burning stove continues to be the most popular technology used for cooking and heating worldwide. According to the World Health Organization and recent scientific studies, the inefficient use of solid-fuels in traditional stoves constitutes the major global environmental health risk, since these sources are important contributors to fine particulate matter (PM2.5) in the ambient air that increase climate and health risks.

This thesis explores the social-technical dimensions of both the use of wood-burning stoves (WBSs) and transition to the use of low-emission WBSs worldwide. In chapter 1, an historical view on the development of WBSs is presented taking into account the anthropological aspects associated with the control of the fire. In chapter 2, a scientific review on 9 types of stove technologies was conducted to describe traditional systems, improved efficient retrofits and advanced stove innovations. In chapter 3, four popular wood-burning practices found in five countries were singled-out to be examined closely in four case studies: “cooking in Brazil”, “cooking and heating in Peru”, “heating in Portugal” and “recreational heat in Denmark and Norway”. In each case, investigations were conducted to evaluate potential gains in the performance of WBSs by the adoption of three interventions: 1. Improved cookstoves (ICSs); 2. Efficient chimney retrofits; 3. Digital applications for a smart stove operation. In South-America, the work focused on understanding the effects of cookstove use on the indoor air quality of 20 rural houses. In Europe, qualitative interviews were conducted to study the operation of WBSs in 24 dwellings. The energy and environmental performance of a fireplace, an ordinary wood stove and an automatic stove, were determined through laboratory studies conducted at the University of Aveiro. Finally, energy simulation and indoor climate studies were carried out to analyse the influence of the operation of these types of WBSs on the heating grid of Iberian and Nordic houses. In chapter 4, international energy policies were suggested to facilitate the transition to cleaner wood-burning regimes.

Considering that 40% of the world population continues relying on traditional forms of wood-burning, the design and dissemination of cleaner technologies of WBSs constitute relevant strategies to mitigate global climate and health risks. Indeed, these measures can be especially important in places where many residential stoves are used in the same location during atmospheric inversions. Despite the considerable amount of scientific studies conducted in several developed countries to evaluate the impacts of the inefficient use of WBSs for heating on the environment and health, little attention has been paid to these issues in other parts of the world. In general, it was identified that the usage of heating stoves might cause a larger amount of PM2.5 emissions per year (per household) than the use of cookstoves. Globally, the advanced gasifiers and automatic stoves (Digital and Forced air) were identified to be among the best performing technologies. In spite of the fact that the thermal efficiency of the most advanced type of heating stoves (Gasifier) is around twice larger than that achieved for the most advanced type of cookstoves (Forced air), the PM2.5 emission factors reached during the use of both kinds of stoves are within the same range of values, achieving smaller levels than the targets established for the best performing stoves established through an International Organization for Standardization consensus process. On this background, the adoption of advanced WBSs is able to reduce the PM2.5 emission factors in, at least, 80% in relation to improved WBSs (Rocket, Cast-iron and Heavy). That means that even improved interventions applied in different parts of the world do not prevent air pollution due to the improper use of improved stoves.

In the Brazilian case study, it was observed that the kitchen concentrations of PM2.5 monitored during wood cooking events increased by more than 10 times in relation to the background levels due to the improper use and maintenance of the studied ICSs (rocket stoves).

In Southern Europe, the measured PM2.5 emission factors from cast-iron stoves without a pre-heated secondary air-inlet were higher than the official Ecodesign requirement. The laboratory experiments showed that over 20% energy savings can be addressed by either installing heat recovery systems in the chimney or by coupling digital devices to modern cast-iron stoves in order to support users in the proper regulation of fuel loads and combustion air-inlets. The energy simulations conducted for Iberian and Nordic houses revealed that automatic WBSs can operate in an efficient way as primary heating systems in homes with low-heating demands, avoiding overheating risks. The energy and indoor climate studies conducted in Nordic houses confirmed the trends observed in the energy simulations. Here, the variations observed for the measured indoor concentrations of PM2.5 were considered to be insignificant in relation to the background levels. However, the concentration of ultra-fine particles in some well-insulated houses increased by more than 10 times the background levels, due the improper operation of modern cast-iron stoves and old installations.

On this background, it becomes clear that energy policies can be adopted to facilitate the transition to more intelligent modes of using WBSs by: 1st training solid-fuel users to better operate and maintain existing installations, 2nd harmonizing wood-burning regulations to address the use of seasoned fuels, certified stoves and functioning chimneys; 3rd designing applications to optimize the interaction between user, stove and dwelling; 4th implementing systems of subsidies to promote the accessibility to the most advanced stoves.

As an overall conclusion, the design of future stove interventions might be based on the changes in modern society, considering each community socio-economic context. Here, the understanding of user behaviours and the empowerment of local communities might play a crucial role in the process of accelerating the transition to advanced wood-burning practices. This will be a win-win situation that will contribute to both the mitigation of climate change and protection of the human health.
ForlagAalborg Universitetsforlag
Antal sider120
ISBN (Elektronisk)978-87-7112-735-5
StatusUdgivet - 28 jun. 2016
NavnPh.d.-serien for Det Teknisk-Naturvidenskabelige Fakultet, Aalborg Universitet

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