A Global Review Of End User Needs: Establishing The Need For

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A Global Review of End User Needs: Establishing the Need for Adaptable Cookstoves Kendall S. Thacker McCall Barger Christopher A. Mattson Research Assistant Mechanical Engineering Brigham Young University Provo, Utah 84604 Email: [email protected] Research Assistant Mechanical Engineering Brigham Young University Provo, Utah 84604 Email: [email protected] Associate Professor Mechanical Engineering Brigham Young University Provo, Utah 84604 Email: [email protected] Abstract—Over 100 improved cookstove projects have been initiated since the late 1990s. However, despite the improvements in burn efficiency, such projects have been met with low adoption rates. A leading reason for this is that improved cookstoves often do not meet the needs of the user. This research answers the question: What are the end user needs for a successful cookstove and how do these needs vary across different regions and with differing household preferences? A review of published literature was performed to ascertain the requirements necessary for a successful improved cookstove. The results reveal there exists a set of primary end user needs and a set of secondary end user needs that must be met for users to be satisfied. Additionally, the use and expectations of a cookstove are influenced by a variety of regional, community, and household factors. The successful design of a cookstove requires an understanding of these factors and how they vary with time and circumstance. Given the large variability in cookstove use around the world, it is unlikely that a single rigid stove design will satisfy all the requirements for a successful cookstove. It is recommended that adaptable cookstoves be developed, thus increasing accompanying adoption rates. emergence of 95 new improved cookstove programs and the development of various types of improved cookstoves [8]. Perhaps due to the assumption that more efficient improved stoves would be readily adopted, many early improved cookstove programs failed to report high adoption rates [5]. In his 1994 World Bank technical paper, Barnes [5] asks, “Why, in the face of all of the benefits, have so many potential beneficiaries of improved stoves decided not to purchase or use the stoves when given the opportunity?” One of the central explanations for Barnes’ query is that these early programs did not consider the customs, climate and economics of the dissemination regions when designing the stoves. It therefore becomes evident that the presumption that an improved stove will be adopted simply due to its superior efficiency compared to traditional stoves is false. II. C AUSES OF P OOR A DOPTION The need for improved cookstoves and their widespread adoption remains high since nearly three billion people in the world depend upon coal or biomass as their main source of energy [1]. Within this population, approximately 1.6 million people die each year due to indoor air pollution [2]. Improved cookstoves provide a possible solution due to their ability to greatly reduce harmful emissions and greenhouse gases [3]. Improved cookstoves can reduce air emissions up to 90% [4] and can save a large quantity of time and costs associated with the collection and consumption of biomass fuels. A recent survey from Nepal estimated that women spend 2.5 to 3.6 hours a day collecting fuelwood and other biomass materials [5]. Unfortunately, past improved cookstove programs have often reported poor adoption rates. The lack of adoption following initial stove dissemination could have been a result of numerous factors, such as prevailing biases in the community against improved cookstoves, poor implementation strategy, high costs, low levels of formal education, lack of proper training, incompatibility with local cooking methods, and many other factors [9]–[14]. In the more recent past, numerous authors have started to recognize and emphasize one particular reason for low adoption rates of past improved cookstoves; the end user needs were not sufficiently considered in the design of the improved cookstoves [15]–[20]. Literature, in the past ten years, contains many case studies and examples of how particular improved cookstoves have failed or succeeded in this way. Additionally, Ruiz-Mercado [13] argues that in order to be effective and used long-term, the new cookstove must outperform the traditional stove in individual cooking tasks. Improved cookstoves have evolved as a whole since the first improved cookstove programs were initiated. Since the 1940s, there have been numerous attempts to establish successful improved cookstove programs in developing countries [6]. One of the most successful and largest cookstove programs was the Chinese National Improved Stove Program (CNISP). Between 1982 and 1992, the CNISP installed improved cookstoves in 129 million rural households [7]. Following the great progress of the CNISP, the late 1990s marked the beginning of the One such example of how an improved cookstove has been unsuccessful in outperforming the traditional stove in certain cooking tasks occurred in the Purepecha region in Mexico. The traditional stove of this region is the Lorena cookstove, which is capable of providing home heating, cooking nixtamal (traditional preparation of corn for tortillas), cooking large amounts of food, and heating water for bathing [15], [21]. When the Patsari improved cookstove was disseminated in this region, many households in the Purepecha region resorted to I. I NTRODUCTION 978-1-4799-7193-0/14/$31.00 ©2014 IEEE 649 IEEE 2014 Global Humanitarian Technology Conference fuel stacking (using multiple stoves) to compensate for the Patsari cookstove not being able to perform all the necessary functions [16], [22]. Had the Patsari cookstove been able to account for the diverse functions and capabilities that users expected it to perform, the users may not have had to supplement the Patsari stove with their traditional stoves. is desired by all users and a list of secondary needs that is applicable under certain circumstances. We believe this list is not only useful in establishing the need for adaptable cookstoves, but also in aiding researchers and designers in developing cookstoves that are adopted at higher rates. Another example of how end user needs were not sufficiently considered when designing an improved cookstove is found in rural Ghana. Burwen highlights how the improved cookstoves could not accommodate the large amounts of tisert (boiled maize flour) that the Dagaare women cooked and then consumed throughout the entire week [23]. Furthermore, Burwen found that the improved cookstove designed with a chimney intended to vent outside through the kitchen walls, was unacceptable due to the fact that the homes in rural Ghana are built with interior kitchens. These are just two examples of how recent authors have emphasized that improved cookstoves have repeatedly failed to the meet the collective needs of the end user. A. Primary End User Needs III. R ESEARCH M ETHODS It is our belief, along with other recent authors, that the end user needs were not sufficiently considered in the design of many past improved cookstoves. Therefore, it is important that current cookstove designers and researchers become aware of these user needs and incorporate them in future cookstove designs. Some recent authors have begun publishing examples and results from cookstove projects around the world, concerning the necessity of assessing user needs. The goal in this paper is to combine these findings and provide a clear and succinct list of user needs that should be considered. In order to create such a list, we reviewed over 150 published articles from over 25 different countries. From these articles we extracted the user needs that are required for a successful cookstove. In section IV we present these needs, and categorize them into two types; those that are primary and applicable to everyone, and those that are secondary and apply only to certain places or circumstances. We also identify a variety of regional, community, and household factors that generate diversity in cookstove use and explore how this increases the difficulty of meeting the needs of the end user. These factors are explored and presented in section V of this article. After identifying the requisite user needs and determining what factors create variability in cookstove use, we have come to the conclusion that adaptable cookstoves are necessary in order to accommodate the wide range of functions and circumstances in which cookstoves are expected to perform. Section VI of this article explores potential benefits and drawbacks from such a course of action. IV. I DENTIFYING E ND U SER N EEDS In order for users to adopt improved cookstoves, the cookstove must satisfy their cooking needs. According to the diffusion of innovation theory, innovations that are recognized as having minimal complexity and high compatibility with their cultural needs and traditions are more likely to be adopted [16]. We have determined from an extensive literature survey, a list of end user needs that are required for adoption. This list is split into two types; a primary list of needs that 1) Saves fuel: Fuel savings are desirable in all regions of the world regardless of environment or cooking practices. Cookstove authors state that the reduction of fuel is perhaps the most compelling reason for consumers to adopt an improved cookstove [24]. A study in Bangladesh revealed that 47% of households rate the reduction of fuel costs as the most valuable trait in an improved cookstove [9]. In a paper for the International Conference for Renewable Energies, Karezeki [25] illustrates how in Kenya, improved stoves can save a family 613 USD in yearly charcoal consumption. Economic benefit is not the only motive for saving fuel; women also desire relief from the burden of fuel gathering, which can often last up to three or four hours each day [26]. If improved cookstoves were able to reduce the amount of fuel gathering necessary, many women would continue to use the stove long-term [23]. 2) Flexible with fuel type: Besides reducing the amount of fuel consumed, users have also expressed the desire to be able to burn a variety of types and sizes of fuel [9], [27]. A common complaint of many improved cookstoves is that the entrance of the stove is too small to insert fuel [18], [28] and the amount of preparation time required to chop the wood into smaller pieces is burdensome [29]. In a recent survey, over 45% of women in a Kenyan village stated that they would not adopt an improved cookstove because it required them to chop the wood into small pieces and it could not burn wet wood [30]. 3) Reduces emissions: Lessening emissions from cookstoves is imperative for improvements in overall health of people in developing countries and in the effort to decrease global warming. In Guatemala, women spend approximately 5 hours every day near a lit fire [31]. This high exposure contributes to the high number of respiratory diseases contracted from breathing in carcinogens, especially in young children, who are carried on their mother’s back for a large portion of the day [32]. Furthermore, in the Biomass Cookstoves Technical Meeting Summary report, the attainment of international emission standards demands 90% emission reductions [4], [14], [33]. 4) Cooks quickly: The inability of an improved stove to cook traditional foods as quickly as the users are accustomed to often impedes the transition from a traditional stove to an improved stove. Such results have been found in rural Africa and Guatemala, where long cooking time was the focus of many user complaints [34], [35]. Contrastingly, in Argentina, improved portable wood cookstoves were reported to cut cooking time in half, which led to very high satisfaction among users [36]. Another complication is that although people want their stove to cook fast, they also want to control the amount of heat in order to cook things at lower temperatures. This control is referred to as the turndown ratio. 5) Cooks local food: Regions and communities have various customary foods and meals, which the improved stove is expected to cook in a manner equal to or more efficient than the traditional stove [13], [15], [16], [21]. A common misconception is that users will willingly adapt their cooking habits to fit the new stove when, in reality, improved cookstoves should be designed to be compatible with the user’s customary cooking practices. Improved cookstoves have frequently failed to meet this need by not being big enough to support and cook large meals [35], [37], [38]. In section V, more insight will be shared concerning how specific meal types influence expected stove performance. 6) Accommodates local cooking equipment: Regions where cookstoves are disseminated all employ a specific set of utensils and cooking instruments that the improved cookstove must be compatible with in order to meet their food preparation needs. One such example is the Royal Thai Forestry Department’s improved charcoal stove, which is designed with slanted pot rests that can accommodate the local pots that range from 16-32 cm in diameter [39]. This feature permits the user to cook a larger variety of dishes and also accommodates the needs of different sized families in the community. In his 1996 article, Ayoub asserts that, “a fuel-efficient cookstove design requires appropriate information on the shape and size of cooking pots used as well as the cooking practices of the specific region for which the cookstoves are intended” [36]. 7) Easily maintained: One of the common complaints from improved cookstove users is their dislike for the heavy maintenance required to keep their stoves operational [29], [40]. Recipients of these improved coosktoves often choose not to perform the regular maintenance and the stove’s efficiency and performance suffers, which contributes to the users abandonment of the improved cookstove. In one Himalayan state of India for instance, stove owners neglected to clean the flu pipe which led to the choking of smoke and back fire [18]. A study of the Patsari Stove Project found that when follow-up stove inspections were provided to assess problems with stove maintenance and other difficulties, longterm adoption rates increased 50% - 85% [41]. Furthermore, a follow up survey performed by the National Council of Applied Economic Research found that in rural India, 71.8% of the improved chulhas installed between 1990-1993 were still fully safe and functional [42]. This was a result of regular reparations performed on the improved stoves by the users during important festivals or family functions. 8) Left unattended: In a recent review of cookstove efforts over the past forty years, it was found that one of the main drawbacks to existing improved cookstoves is that they cannot be left unattended for long periods of time [33]. In developing countries, regular meals can take upward to three hours to cook at a time. The long duration of cooking time needed for traditional meals necessitates the ability to leave the cookstove unattended during the cooking process. A survey performed in rural Africa found that participants preferred the Stovetec stove over the Ugastove because it required less tending along with other factors [34]. Similarly, in Kenya, a survey reported that over 65% of the women would not adopt a stove which required constant tending [30]. 9) Aesthetically pleasing: The aesthetic appeal of an improved cookstove is an important motivation for many households to purchase improved cookstoves [43]. A study of the Patsari Stove Project found that while only half of stove adopters cited fuel savings as an important factor in keeping the improved stove, most of the users considered the aesthetics of the stove to also be important [41]. In a Kenya study, over 40% of the participants listed a modern appearance of the stove as one of the incentives for adopting an improved stove [30]. 10)Affordable: Though average incomes and monetary systems vary across regions, the price of the improved cookstove, if not affordable for the average user, will impede users from purchasing the stove. In Tanzania, three improved stoves, the StoveTec, the Advent, and the Envirofit stoves were tested. The retail price for the StoveTec and Advent stoves was between 17-24 USD and the Envirofit cost 35 USD. However, most users were willing to pay only 10 USD for most of the improved stoves despite the fuelwood savings, shortened cooking time and pot size compatibility [34]. Literature on improved cookstoves report that most improved cookstove programs provide the cookstoves at little to no cost. However, some authors believe that large discounts by themselves are unlikely to promote substantial adoption and should be avoided [9]. 11) Safe: Safety is a desirable and necessary trait of improved cookstoves [27]. Several areas of safety to be concerned about are tipping, containment of flaming embers if tipped over, surface temperature, heat transmission to surroundings, and cookstove handle temperature [44]. Burns, scalds and cuts are the most common safety concerns that result from stoves with improper safety precautions [44]. B. Secondary End User Needs Despite the homogenous nature of many of the user needs as established in the previous section, we found there exists a set of end user needs that are unique to certain regions or certain circumstances. In the next portion of this paper we will outline what these needs are and when they might be applicable. 1) Provides space heating: One of the most common additional uses of traditional cookstoves is using it as a heat source in colder climates [27], [28], [33]. In central India, for example, where temperatures reach as low as 2 degrees Celsius during the winter, cookstoves serve as the primary heat source in the home [45]. Several improved cookstove programs have suffered low adoption rates because the improved stove could not perform this additional task [28]. However, intentionally providing space heating is often at competing terms with other cookstoves objectives, such as stove efficiency, since it removes heat from the combustion process. 2) Heats water: The ability to quickly and conveniently heat water is another end user need that differs in extent between regions [33]. For instance, in a small African village, it was found that 27.4% of the wood energy was used for heating water [46], while in a Himalayan region, only 8% of the wood energy was used for heating water [18]. Heated water is predominately used for both meal preparation and for bath water [15], [16]. In some regions, the cookstove’s ability to heat water is so indispensable, that a pot used for heating water is permanently attached to the stove. [47]. The Aprovecho Research Center has proposed benchmarks of improved stove performance for heating of water with woodburning improved cookstoves, which have been adopted by numerous international organizations [48]. 3) Repels insects: In some regions, the smoke from cookstoves is desired for the purpose of repelling insects or fumigating thatched roofs [26], [36]. This desired characteristic poses potential conflict to the goal of reducing indoor air pollution. Most families in developing countries cannot afford refrigerators, so smoking food is necessary for food preservation, and keeping insects and rodents away [49]. Furthermore, many regions are plagued by disease-carrying mosquitoes and poisonous insects, which are most effectively dispelled from the user’s homes using smoke from the cookstove [50]. Additionally, cookstove designers find that although cleaner improved cookstoves may result in a decrease in asthma rates by reducing indoor air pollution, they may trade this benefit for an increase in malaria rates since the mosquitoes are no longer being smoked out of the house [49]. 4) Portable: The ability of a cookstove to be portable is also a regional preference and highly dependent on traditional methods of cooking. The portability of a cookstove has been reported in places such as Mali, Kenya, Chad, and many other locations [36], [46], [51]. In regions where there are large variations in seasonal temperatures, the ability to cook indoors and outdoors is more prevalent [52]. 5) Provides light: Stoves frequently serve an additional non-cooking purpose of producing light to the interior of a home [35]. Kshirsagar and Kalamkar reported that one of the largest obstacles to the acceptance of clean stoves is they do not live give off light like traditional cookstoves [33]. The perceived value of this additional feature is often dependent on the availability of other fuel sources in the community. Kerosene lights or battery powered LED lights are a couple of the alternative light sources that provide light and may lessen users dependence on an open fire or cookstove for lighting. Using a thermo-electric generator in conjunction with a cookstove is another method proposed by Champier to produce light [53]. V. E NVIRONMENTAL AND S OCIAL FACTORS THAT P RODUCE A D IVERSIFIED U SE OF C OOKSTOVES In the previous section we reviewed how there exists two types of end user needs, those that are primary and globally applicable and those that are secondary and unique to certain regions or apply under certain circumstances. It is our belief that for a cookstove to be successful, it must meet all the primary needs and the applicable secondary needs. However, there also exists an array of regional, community, and household factors that makes it increasingly difficult for improved cookstoves to meet the specific user needs. Figure 1 contains a visual summary of these factors. In this section, it is our intent to list the regional, community and household factors and practices that determine how a cookstove is used and how its use changes with time. This list is not only valuable in establishing the need for adaptable cookstoves, but also a valuable tool in helping cookstove researchers in the design process. Literature has stated repeatedly that prior to cookstove design, a study of the user’s needs and culinary practices must be accomplished [33]. However, very few authors have gone to the extent to list what practices and factors specifically need to be considered. Our objective is to fill this gap in this section. Factors that cause variable cookstove use Regional Factors Community Factors Household Factors Local food Household size Meal type and size Fuel Economic status Food type Climate Season Kitchen configuration Fuel type Cooking equipment Fig. 1. Visual depiction of the different factors that affect cookstove use A. Regional Factors that Affect Cookstove Use Simon [19] reports that the delivery of suitable household cooking technologies must account for the diverse regional needs. We add to this finding by emphasizing that if a particular cookstove is meant to serve users across multiple regions, then the cookstove’s design must be capable of accommodating a variety of unique cooking practices and other regional factors. In this section we will list what type of factors differ and give examples of how they might vary from region to region. 1) Food type: Possibly the most significant factor that varies between different regions is the type of local food that is prepared using a cookstove. Each region will have its own unique dishes and methods for cooking meals [13], [23], [24]. In Section IV we established how the ability to cook local foods is a primary user need, in this section we attempt to show how different types of food might affect cookstove use. Cookstove variables that are influenced by they type of food being cooked include cooking time, heat, number of required burners, and required cooking surface type. Table I lists the most common food dishes for three different regions and illustrates how these dishes affect the expected function of the improved cookstove. 2) Fuel type: The type of biomass fuel that is used differs between regions and depends on the resources that are available. For instance, agricultural based regions often use crop residues, such as rice husks [54], corncobs [55], or jatropha plants [56] as fuels. Many African cookstove users prefer to use charcoal when funds are available [17]. Whereas, regions with higher elevation often rely heavily on animal dung to TABLE I. E XAMPLES OF HOW DIFFERENT REGIONAL FOODS AFFECT THE USE OF COOKSTOVES Place Local Food Dish Mexico Tortillas Bangladesh Cury Kenya Ugali Functional Considerations High heat for a short amount of time and a large flat cooking surface required Low simmering heat that can be sustained for long periods of time and the ability to hold large pots Boil large pots of water and support stirring of thick dough like substance supplement their fuel sources. Thus, the type of fuel that is most frequently used in a region can vary substantially from region to region. 3) Climate: The difference of climates between regions will result in varying cooking methods and non-uniform cookstove performance. For instance, the climate often determines what additional functions the cookstove must perform, such as in snow bound regions, where cookstoves are frequently used for space heating [18]. Climate also influences the location of where cooking takes place. In regions where the weather may be favorable, cooking often occurs outside [37], which eliminates the need for chimneys. Climate can also affect the durability of stoves and what type of construction materials are acceptable. In one coastal region, rapid corrosion of metallic cookstove parts occurred causing premature failure [19]. Precipitation in the region is another factor that must be considered, as this affects the moisture content in the wood [57]. Furthermore, prevailing wind patterns can influence the type and placement of chimneys [19]. As demonstrated by these examples, the climate can cause a great variance in the use and function of a cookstove. 4) Kitchen configuration: Another factor that leads to differing cookstove use between regions is the location and size of the kitchen. Numerous authors have reported that kitchens can be located either inside the main house, outside, in a separate shelter designated for cooking [28] or any combination of these. For those homes in which the kitchen is located indoors, L’Orange discovered a dramatic difference in the kitchen size and the air exchange rate across 13 different countries [58]. These different kitchen configurations should be considered when determining the acceptable size of the stove, the need for a chimney, safety implications, and the preferred position of the stove in relation to the cook. Summary of regional factors: In this section, we presented four regional factors that should be considered when designing a cookstove. These four factors are likely to fluctuate between regions and cause inconsistent use and performance of cookstoves. Table II summarizes these regional factors by giving examples from four different regions and how each region requires its own unique design considerations. From this table, it is clear that a cookstove that is to function in different regions, should be able to accommodate a wide variety of uses. B. Community Factors that Affect Cookstove Use Just as the use and performance of a cookstove will vary between different regions, it will also differ between households in the same community. In the literature, many authors report an adoption percentage, ranging anywhere from 5% [18] to 90% [59]. This adoption percentage generally indicates that a portion of the community is satisfied with the improved cookstove, whereas the remaining portion of the community finds the stove’s performance insufficient. The question then arises of why certain households find the improved cookstoves satisfactory and others do not. In this section we partially explore the answer to this question by listing the most significant factors and differences in a community that lead to varying use of improved cookstoves. 1) Household size: The number of people living in a household has a significant impact on the type of cookstove and how it is used. Several studies have documented how household size ranges within a community, such as in one Kenya community, household size ranged from one to eighteen people [60]. In another study, household size of a Bangladesh community ranged from two to eleven people [61]. Varying household sizes require different types and amounts of food, different stove sizes, different cooking utensils, and the different fuel types. 2) Economic status: The economic status of a family can have a drastic effect on what type of stove they purchase, what type of fuel they use, and the type of food they cook. In a study of Mexican households, it was found that the poorer class of people relied on shrubs more often for fuel than the wealthier class who relied exclusively on pine and oak wood [57]. Additionally, several researchers have found that those of a higher economic standing are more likely to adopt improved cookstoves [10]. In order to increase widespread adoption rates, cookstove designers should examine the differing needs of all economic levels. Summary of community factors: Achieving 100% adoption in a community is difficult due to the varied circumstances that exist between households. No two households will be exactly alike in their cooking habits and preferences. Two of the most significant factors that vary in a community are household size and the economic status of each household. Cookstoves that are targeted to serve an entire community should account for these factors and how they differ between households. C. Household Factors that Affect Cookstove Use The third, and possibly the most overlooked category of factors that influence the fluctuating use of cookstoves, are the continually changing circumstances and cooking practices within a single home. Currently, it is common for a household to employ the use of several cookstoves, each cookstove having their preferred function or role, to meet these changing circumstances. Additionally, Muneer found that a single set of preferences within a household cannot be assumed [17]. In this section we explore the factors that lead to such diverse cookstove use within a single household. 1) Meal type and size: The size of meal being cooked is inconsistent and heavily influenced by two factors, household size and what type of meal is being cooked. For instance, breakfast is a much smaller meal than lunch in many cultures and subsequently requires less firepower and fewer cooking surfaces. Johnson [52], found that meal size could range anywhere from 1.2 to 24.7 kg in an African village and similar results could be expected elsewhere in the world. Successful cookstoves must be able to accommodate these varying meal types and sizes. 2) Food type: In previous sections, we established the primary need that cookstoves must be able to cook local foods and that food type will vary from region to region. We also want to establish that food type will vary within a household from meal to meal, day by day, and from season to season. One study in Kenya found there exists six different staple food types that people commonly cook [30]. This means a wide range of cooking times, firepowers and other cooking parameters are employed within a single home. TABLE II. TABLE SHOWING HOW DIFFERENT REGIONAL FACTORS AFFECT THE USE OF IMPROVED COOKSTOVES AND THAT NO TWO REGIONS ARE ALIKE Region Climate Fuel Type Food Type Cooking Location Cookstove considerations Andes Region, Peru Cold winters and mild summers, windy, high elevations Moderate temperatures with cooler winters, heavy rains in June Generally warm with occasional cool, heavy rains from March to June Warm with heavy rains during summer Agricultural waste, dung, and wood Corn, potatoes, and guniea pigs Indoors Pine, oak, brush Tortillas, nixtimal, tamales, beans, and rice Ugali, githeri, sukuma wiki Mostly indoors Rice, fish, pulse, vagetables and chicken Inside during rainy season Stove should provide space heating, vent the smoke, use diverse fuel types, and securely hold a large pot. Stove needs a small amount of space heating, large stove opening, large flat cooking surface, and the ability to heat water in pot. Need to provide high intensity heat for boiling and low heat for simmering. Aluminum sauce pan is most common and portability is desired. Portability is desired along with a large opening for leafy fuel to be inserted. Most fuel is boiled for long durations of time in a round bottom pot. Michoacan, Mexico Embu, Kenya Sylhet district, Gangladesh Wood and Charcoal Wood, twigs, leaves, and cow dung 3) Season: The changing of seasons contributes to fluctuating use of cookstoves. For instance, during the winter cookstoves are often used for space heating, but this feature becomes undesirable during the summer months. The changing of seasons also motivates the use of seasonal fuels. In Bangladesh and Peru, for example, leafy matter and other agricultural residues are burned during the dry season, whereas during the wet season, wood becomes the primary fuel type [62], [63]. Cooking location also fluctuates with the changing of seasons. Outdoor cooking is more common during the dry months and throughout the planting and harvesting seasons so that meals can be served closer to the fields [46]. Season also affects the type of food that is prepared and consumed. From these examples, it becomes clear that if a single cookstove is to provide for the household cooking needs, it must be able to adapt with the changing of seasons. 4) Fuel type: The type of fuel used in a household fluctuates with the changing of season, the meal being cooked, and how quickly the meal needs to be prepared. It also depends on the availability of local fuel supplies and the user’s finances [17]. This is evident in Kenya, where women prefer to cook with charcoal when they can afford it or when the weather is bad, otherwise, they use less expensive biomass fuels [64]. 5) Cooking equipment: As explained in section IV, improved cookstoves need to accommodate local cooking equipment (pots, pans, skillets, etc.). In this section we want to emphasize that the type and size of equipment will vary depending on the size of the meal and the type of food being prepared [21], [31], [36], [47], [65]. For instance, in one study in Uganda, participants overwhelmingly preferred the StoveTec stove compared to other models because its removable pot skirt could accommodate the variety of pot sizes they cooked with [34]. Summary of household factors: In this section we explained a variety of factors and practices that cause cookstove use to fluctuate on a daily, seasonal, and meal-to-meal basis all within the same household. These factors help explain why so many improved cookstove owners employ multiple cookstoves to meet their cooking tasks. To further help show how a single household has fluctuating needs and expectations of their cookstove, we have included table III that exhibits our findings. Mostly outdoors D. Summary of Factors that Cause Variable Use In this section, section V, we outlined the environmental and social factors that contribute to the diverse and varying uses of cookstoves. We organized these factors into three types: regional, community, and household factors. We also found that the expected use of a cookstove will vary dramatically depending on what time of day, and depending on what season. Understanding these factors will help designers be aware and conscientious of how cookstoves need to be adaptable to the variety of circumstances they will be used in. VI. N EED FOR A DAPTABLE C OOKSTOVES It is our belief that adaptable cookstoves are necessary in order to sufficiently meet the wide range of needs and requirements that exist between regions, across a community, or even within a single household. The majority of improved cookstoves disseminated in the past decade have been rigid in their capabilities, been of the mono-function type [33], or developed with a one size fits all notion [19]. Due to these limitations, these cookstoves were restricted in scale and were only able to serve a small portion of the large cookstove market. Adaptable cookstoves possess the potential to overcome these problems by appealing to a large population base and thus reaping the economic benefits that come from large scale production. An adaptable cookstove could be defined as a cooking device whose configuration can be altered in order to satisfy a variety of cooking tasks or respond to a change in operating conditions [66]. Additionally, adaptable cookstoves provide the user with the ability to customize their stove to suit their own design preferences. For instance, at purchase the user could choose from a variety of features, which would best suit their needs, in order to modify their improved stove. Options to select from could include the size and height of the cookstove, the number of cooking surfaces, or appropriately sized pot skirts. The purchase of additional features for the stove also permits the user to account for changes in their household needs, which can fluctuate between meals and seasons. Without adaptability, a very diverse product line would be needed to meet the wide range of preferences and needs of the users [19]. A. Adaptability in literature There is a lack of published literature on adaptable, modular, or adjustable cookstoves. However, there are a number of TABLE III. E XAMPLES OF DIFFERENT SCENARIOS IN A SINGLE HOUSEHOLD THAT AFFECT THE USE OF IMPROVED COOKSTOVES . Scenario Food Dish Season Fuel Type Cooking Equipment Cookstove Considerations A Beans Summer/wet Damp pine Large pot B Tortillas Winter Pine or oak wood Comal C Nixtimal Summer Mixture of pine, leaves, and agricultural waste Large pot Large pot used to cook several day supply of beans which requires long cook times at low simmering heat. Damp wood is difficult to light and a large opening in stove needed to insert wood. Large flat comal needed to cook tortillas at high heat with a large opening needed to insert fuel. The stove also acts as a heat source. Cooking of nixtimal requires a large pot and long cook time. The fire requires constant tending since leafy fuel is consumed quickly. cookstoves on the market that contain a few adjustable features, which can aid in satisfying a small portion of the variability in cookstove use. Several cookstoves have utilized a series of concentric rings around the burner to help accommodate a variety of different pot sizes [31], [47]. Whereas, some stoves have been developed with adjustable air dampers to optimize the air flow into the combustion chamber [18], [56]. Apart from these isolated examples of adjustable features, there are scarce amounts of research that explore the concept of meeting various user needs through adjustable stove design. The proposed notion of adaptable cookstoves coincides very closely with the well researched topics of product family design and reconfigurability. Simpson defined product family design as a set of similar products that are derived from a common platform and yet posses specific features/functionality to meet particular end user requirements [67]. The principles of product family design have been used extensively in automobile construction, consumer electronics, and many other industries. The benefits of product family design are well documented in literature and the applicable benefits will be outlined in the following section. B. Potential Benefits of Adaptable Cookstoves There are many potential benefits that can arise from the development of adaptable cookstoves. The foremost being that diverse user needs are more likely to be met and subsequently better adoption rates will be attained. Another benefit is that larger quantities of cookstoves can be manufactured since they have the potential to provide a sufficient variety for the users while still maintaining their ability to be manufactured [68], [69]. A third potential benefit is that adaptable cookstove design can make improved cookstoves more affordable by lessening the initial cost of purchase. Potential users often have a difficult time saving money long term and generally cannot afford an improved cookstove with an upfront cost that is greater than one or two months worth of savings [44]. The concept of adaptable cookstoves helps remove this upfront cost by only requiring users to initially purchase the most basic stove platform. Additional features or modules could be purchased when more funds become available. C. Challenges of Adaptable Cookstoves The development of adaptable cookstoves does not come without its difficulties and challenges. Adaptable cookstoves are a more complex system than traditional improved cookstoves, thus potentially decreasing the stove’s reliability. Additionally, the creation of adaptable cookstoves risks exceeding the operation capability of the users, who are accustomed to the basic functions and performance of their traditional stoves. Without proper training and education, users may be deterred by the complexity of the stove and abandon its use. Lastly, with greater variability in the functionality of the stove, the stove may not perform at its optimal combustion efficiency. However, despite the risk of decreased efficiency, adaptable cookstoves may still be advantageous to the user’s health and well-being since users would only have to rely on one stove to meet their needs, instead of three. D. Design Methodology for Adaptable Cookstoves In their journal article, Kshirsagar and Kalamkar [33] advocate the value of a systematic design methodology and provide a nine-step approach for modern cookstove design. We rely on their framework for our proposed methodology but suggest a few modifications of our own to aid researchers designing adaptable cookstoves. 1) Problem identification and definition- We modify this step by encouraging researchers to first identify the scope of the target population. Researchers must answer the question, “Is the cookstove we are designing intended to serve a few communities that are similar in social and culinary practices, or will the cookstove be serving end users across multiple regions?” Then researchers must identify both the applicable secondary user needs that exist and how cookstove use will change with time and circumstance. Factors such as the changing of seasons and the differences between meal types must be considered. 2) Problem analysis- In this step appropriate design parameters are established, such as expected power output or target cooking time. We emphasize the fact that in most scenarios a single design parameter will not satisfy the end user needs by itself; a range of design parameters must be chosen. For instance, identifying the range of acceptable pot sizes, the acceptable price points for various features, and desired firepower for all the types of fuels that will be used. 3) Conceptual design- Different design alternatives are developed that meet the design parameters as established in step two of Kshirsagar and Kalamkar’s method. 4) Engineering design- Modern engineering tools are used to simulate the use of the stove and to optimize its design. It is worth noting that there may be many competing design requirements involved in the creation of adaptable cookstoves. For instance, providing space heating may decrease combustion efficiency, or allowing users to control the number of cooking surfaces may decrease the speed of cooking. 5) Construction, testing and evaluation of the prototype- In this step it is important to validate the expected performance and usability of the stove using a physical prototype. We emphasize that the whole range of expected use scenarios should be tested, and not just the most ideal ones. [6] 6) Detailed design and its communication- The complete design of the stove, including the overall geometry, material, and assembly instructions, are communicated in a clear written method. If the stove has adaptable features, then detailed design must be given of all its possible configurations. [7] 7) Production, quality testing and dissemination- The quality and capabilities of the manufacturing process are validated and the distribution channels are verified to be robust. 8) Field-testing and validation- Testing of the cookstove in the actual setting it will be used in, as emphasized by Mattson and Wood [70], is an essential step to the design process. Standard protocols, such as the KPT, BT, and UCT are all specific tests that should be performed. 9) Performance monitoring- The performance of the stove and satisfaction of the end users are monitored. As necessary, additional modules or features are introduced into the market to continue to meet the diverse set of needs and operating conditions. [8] [9] [10] [11] [12] [13] [14] [15] VII. C ONCLUSION Despite their high potential to improve the health of users and reduce the costs associated with fuel gathering and consumption, improved cookstoves have been met with low adoption rates. We believe that one of the major reasons for poor adoption of past improved cookstoves is that these cookstoves did not meet the needs and requirements of the end user. To help cookstove designers identify what those needs are, we provided a list of primary end user needs that are applicable to all regions and a set of secondary needs that are unique to certain regions or circumstances. 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