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In Europe, inappropriate user behaviours in the operation of wood-burning stoves (WBSs) results in substantial energy losses where fireplaces and conventional stoves are major contributors to undue emissions of health damaging fine particulate matter (PM2.5). The design and adoption of cleaner WBSs are relevant issues to save energy and avoid greenhouse gas (CO2e) emissions. This work compares the operating performance of 3 types of biomass stoves used in Europe in their interaction with dwellings. Field studies were conducted in 24 houses in Portugal and Denmark to analyse wood-burning behaviours and their contribution to residential heating. Laboratory and energy simulations were performed to study their thermal efficiency, PM2.5 emissions and the influence of their usage on the indoor climate. This work shows that the operation of enclosed stoves in uninsulated Iberian homes emit more PM2.5 than the Ecodesign thresholds and cannot provide a stable comfort temperature. Despite reducing the CO2e emissions by more than 3 times in relation to the use of open fireplaces, the operation of cast-iron stoves in insulated Nordic dwellings might cause overheating events. Independently of the European latitude, the adoption of more advanced stove retrofits and digital devices is a relevant measure to accomplish the Ecodesign goals through a better regulation of fuel loads and combustion air-inlets. Thus, the knowledge dissemination on cleaner wood-burning practices and the implementation of financial incentives towards a proper operation of biofuels in efficient installations according to each socio-economic context might support the transition to a carbon neutral use of WBSs.

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.

This presentation will focus on the aspects regarding the usage of residential wood-burning stoves in Europe, including the growing adoption of pellet stove technologies in Mediterranean regions. Some results from research work carried out in Denmark, Norway, Portugal and Spain will be presented and analyzed in this session. Experimental results regarding the performance of biomass combustion stoves and the effects of real-life practices in terms of thermal efficiency, particulate and gaseous emissions will be addressed. This research is based on the development of a new testing approach that combines laboratory and field measurements established in the context of the implications of the upcoming eco-design directive. The communication will cover technical aspects concerning the operating performance of different types of biomass stoves and building envelopes, in order to map the ongoing opportunities for the development of proper interplays between advanced technologies and future buildings in the region.

Residential wood combustion (RWC) in fireplaces and conventional appliances is the main contributor to fine particulate matter (PM2.5) emissions in Denmark and Portugal representing more than 30% of the total emissions [1;2]. Such estimations are uncertain concerning the wood consumption and official emission factors, not taking into account actual burning conditions in dwellings [3]. There is limited knowledge on the real-life performance and spatial distribution of existing appliance types. Few studies have been targeting to understand the influence of fuel operation habits on PM2.5 emissions within a specific “wood burning living area”, but one Danish study exists [4]. In previous inventories distinct combustion air operation modes and the growing penetration of automate wood-burning stoves have not been considered. The present work aims to discuss opportunities for improving the available estimations for Denmark and Portugal, suggesting a methodology to increase the accuracy of activity data and emission factors. This work is based on new studies carried out to quantify the PM2.5 emissions in daily life through field experiments in Danish dwellings and by considering typical Portuguese combustion practices in laboratory tests. This study highlights that the previous PM2.5 emission inventories in Denmark and Portugal did not consider the possible variations on fuel moisture, dimensions of wood-logs and air-inlet operation patterns, although they are very important, especially in places where there is a large amount of “non-trained users”. In Denmark, inventories rely on information on emission factors for 4 different categories of wood-log stoves while in Portugal there is available information only for 2 types of wood-log combustion systems. Field measurements in a Danish village indicated that for the community in question the measured average emission factor was approximately half of the official country value. Laboratory experiments in Portugal demonstrate that differences in fuel operating techniques can result in particulate emission factors twice as high when operating low fuel loads as when operating high loads [5]. In both cases, there is a need to improve the quality of activity data to reflect real-life situations.

The indoor emission of (ultra)fine particles and overheating from wood-burning stoves are crucial problems in modern houses when wood is used for heating. The main cause for indoor particle emission is the interaction between user and stove when lighting and refilling the stove. The main causes for overheating are a high thermal insulation level of the house and high (peak) wattage of the stove.This research aims to understand how low wattage stoves with a computer added device and water jacket will perform on the indoor air quality as proper heating appliances for low energy houses.Two field studies were designed to compare the influence of the auto-pilot device and water jacket on the indoor climate. The first experiments were conducted in 8 renovated detached houses using certified stoves while the following experiments were conducted in 4 low energy houses using modern and advanced stoves.The results reveal that the users interaction impacts on the indoor air quality, although, the integration of the appliances in the dwellings, the air-inlets and the design of the chimney are the most relevant aspects to ensure a high indoor air quality.

More than 3 billion people in the world rely on local solid-fuels for domestic cooking and heating through inefficient combustion, causing indoor air pollution and overheating worldwide. Technological regimes were categorized in 18 popular stove models to describe how residential wood combustion is performed across the world. The stoves performance was traced through literature review, laboratory and field studies, according to the population´s income in 7 regions.This technological map revealed that 92% of the wood consumption occurs in the south (cooking) while the largest share of wood heating happens in the north. The adoption of new stoves can save 15-50% of fuel and reduce 2-25 times the daily indoor concentrations of fine particles when moving from traditional to improved/advanced stoves (nanoparticles). Ergonometric combustion chambers and proper exhausts are key-elements to delay biomass consumption, adjust heat/demand through air-staging and ensure the indoor climate performance of advanced stoves in future housing.

Large amounts of forest wood is still being used in rural housing in low and mid-income countries in South America - 36% in Peru and 6% in Brazil - generating hazardous wood smoke. Interviews were conducted to the users of improved stoves in 20 rural households. In Peru, the field study was carried out during the heating season. Real time concentrations of carbon monoxide were measured using HOBO data loggers while fine particles concentrations were measured in Brazil using a TSI Dust-track monitor before and during the stove operation. The adoption of improved stoves is limited by women cooking habits, safety aspects and the transition to LPG. CO concentrations never exceeded 60 mg/m3 (30 minutes) while increased PM2.5 concentrations exceeded 160 µg/m3 (1-hour) in 4 dwellings.Indoor emissions from heating stoves were reported in closed rooms while outdoor-indoor transport was the main source of fine particle in open kitchen balconies.