Pellet-Fed Gasifier Stoves Approach Gas-Stove Like Performance during in-Home Use in Rwanda

Opportunities and Challenges Associated with the Uptake of Residential Clean Fuel Usage

PURPOSE OF REVIEW

Almost 3 billion people worldwide use solid fuel for cooking and heating. This review examines (i) household energy practices and infrastructures and their influence on fuel usage in different contexts; (ii) barriers in adoption of household clean energy technologies and uses in diverse settings and population groups and (iii) potential air pollution exposure reduction in homes through using processed fuel.

RECENT FINDINGS

Population health burden from solid fuel combustion-derived particulate air pollution has been estimated in several low- and middle-income countries. However, such studies have not been carried out in high income countries (e.g., UK). Irrespective of the region, fuel prices are the most dominant factor influencing the choice of fuel. Laboratory studies suggest processed fuel - pellets and briquettes - reduce particulate matter emissions by 70-80% and can be a promising alternative. Adoption of clean fuels for domestic energy needs facilitates progress towards five of the UN Sustainable Development Goals (SDGs). There is evidence that a variety of factors, including cost savings, encourage and hinder such uptake. These factors include price fluctuations, expenses, and the usage of clean fuels. Due to their distinct development scenarios, more expansive policy frameworks, and political economies of energy, these determinants are localized in character and differ significantly amongst economies. Therefore, in order to create innovative plans for the adoption of clean fuel use, strategies centred on local settings must be developed while keeping broad socio-technical and socio-economic issues in mind. Solid fuel processing - pelletization and briquetting - have the potential to reach Liquefied Petroleum Gas (LPG)-like emissions, and could be a potential strategy to mitigate exposure to household air pollution.

Quantifying functional group compositions of household fuel-burning emissions

Globally, billions of people burn fuels indoors for cooking and heating, which contributes to millions of chronic illnesses and premature deaths annually. Additionally, residential burning contributes significantly to black carbon emissions, which have the highest global warming impacts after carbon dioxide and methane. In this study, we use Fourier transform infrared spectroscopy (FTIR) to analyze fine-particulate emissions collected on Teflon membrane filters from 15 cookstove types and 5 fuel types. Emissions from three fuel types (charcoal, kerosene, and red oak wood) were found to have enough FTIR spectral response for functional group (FG) analysis. We present distinct spectral profiles for particulate emissions of these three fuel types. We highlight the influential FGs constituting organic carbon (OC) using a multivariate statistical method and show that OC estimates by collocated FTIR and thermal-optical transmittance (TOT) are highly correlated, with a coefficient determination of 82.5 %. As FTIR analysis is fast and non-destructive and provides complementary FG information, the analysis method demonstrated herein can substantially reduce the need for thermal-optical measurements for source emissions.

A comprehensive review of the production, adoption and sustained use of biomass pellets in Ghana

Ghana's Renewable Energy Master Plan of 2019 includes the production and use of biomass pellets. However, pellets have neither been developed commercially nor included in Ghana's energy mix. This paper reviewed the prospect of production, adoption and sustained use of pellets in Ghana. Besides having abundant biomass resources, Ghana has high market demand and relevant policies for pellet development. The production of pellets can significantly replace traditional household biomass demand and improve environmental and health quality. However, the production and use of pellets are limited due to technical, financial, social and policy issues. Our estimates show that 3% of the annual national average household income will be spent on pellet demand for cooking, with the highest burden on rural households in Ghana. Practical measures are required since the cost of pellets and gasifier stoves may limit pellet adoption and use in Ghana. Based on study findings, it is recommended that the government of Ghana establishes a robust supply chain and provides infrastructure for pellet production and use. Existing renewable energy policies should be reviewed to remove ambiguities, attract investment, and build capacity in the renewable energy sector. Apart from raising public awareness of the benefits of pellets use, the government of Ghana should ensure that continuous and thorough impact assessments are undertaken to assess the implications of pellet production and use. This review will inform policymaking on achieving sustainable production, adoption and use of pellets and assess Ghana's contribution to achieving the United Nations' sustainable development goals.

Community kitchen tandoors (CKT)-a potential candidate for air pollution mitigation strategies?

Community kitchen tandoor (CKT) is a clay-based hollow cylindrical device commonly used in South Asian and Middle Eastern countries for baking flatbreads and cooking meat. These CKTs, generally fuelled by charcoal or wood, contribute significantly to the pollution loads in ambient air along with occupational exposure hazards. CKTs, being a part of the informal sector, lack emissions and safety guidelines. This study surveys 139 restaurants in CKT hotspots of New Delhi, India, to understand tandoor design and operational parameters and to assess PM_2.5 and CO exposure concentrations at representative field restaurants. PM_2.5 and CO exposure concentrations from traditional CKT was found to be several-folds higher than safe indoor air quality levels. Further, the traditional CKT was evaluated for different improved fuels (like briquettes and pellets) in the laboratory for PM_2.5 and CO microenvironment concentrations. It was found that the fuel improvements in traditional CKT could not improve microenvironment concentrations to the desired levels; hence, an automated pellet-fed forced-draft improved tandoor with an improved combustion chamber design is demonstrated. The results of the laboratory trial of improved tandoor were compared with traditional tandoor (using pellets) and have shown 84% and 94% reductions in PM_2.5 and CO concentrations, respectively, indicating significant benefits to the environment and health. We recommend implementing such improved CKT, on a large scale, combined with other identified control options, as a potential candidate under air pollution mitigation strategies in cities' action plans under National Clean Air Programme (NCAP).

Emission Characteristics and Formation Mechanism of Carbonyl Compounds from Residential Solid Fuel Combustion Based on Real-World Measurements and Tube-Furnace Experiments

This study updated carbonyl compound (CC) emission factors (EFs) and composition for residential solid fuel combustion based on real-world measurements of 124 fuel/stove combinations in China and explored the CC formation mechanism using tube-furnace experiments with 19 fuels and low/high temperatures to explain the impact of fuel and stove on CC emission characteristics. The average EF_CC values for straw, wood, and coal were 1.94 ± 1.57, 1.50 ± 0.88, and 0.40 ± 0.54 g/kg, respectively. Formaldehyde and acetaldehyde were the most abundant species, accounting for 40-60% of CCs, followed by acetone (∼20%), aromatic aldehydes (∼10%), and unsaturated aldehydes (∼5%). Different from formaldehyde and acetaldehyde, other species showed significant variation among fuel types. All these characteristics could be explained by the difference in the volatile content and chemical structure of fuel, such as aromatic in coal versus lignin in biomass. The improvement in stove technology reduced CC emissions by 30.4-69.7% (mainly formaldehyde and acetaldehyde) among fuels but increased the proportion of aromatic aldehydes by 24.3-89.4%. Various CC species showed different formation mechanisms related to fuel property and burning temperature. The volatile matter derived from thermal pyrolysis of fuel polymers determined CC composition, while higher temperature preferentially degraded formaldehyde and acetaldehyde but promoted the formation of acetone and aromatic aldehydes. This study not only revealed emission characteristic of CCs from RSFC but also contributed to the improvement of clean combustion technology.

Morphological and heat transfer characteristics of biomass briquette during steam gasification process

The morphological evolution and heat transfer characteristics of biomass briquette greatly affect the directional regulation of target products during steam gasification process. In this work, a visual gasifier with an on-line temperature monitoring system was developed to investigate the coupling relationship between the morphological change and temperature distribution of biomass briquette. The gasification behaviors of biomass briquette at different temperatures and steam concentrations were comprehensively examined and compared. The shrinkage rate and heating rate of biomass briquette both reached the maximum at 1-2 min. The morphological evolution of biomass briquette in the heating process was shrinking particle mode, then changed to the shrinking core mode when the biomass temperature kept relatively stable. The high-quality syngas with a high H₂/CO ratio of 3.07 at 50 vol% steam concentration and 700 °C was obtained, which were idealized to synthesize other fuels/chemicals.

Parametric Analysis of a Gasification-Based Cookstove as a Function of Biomass Density, Gasification Behavior, Airflow Ratio, and Design

The energy performance and emissions (carbon monoxide and total suspended particulate matter) of a biomass gasification-based cookstove under a modified water boiling test (WBT 4.2.3 protocol) were characterized here. The controllable process parameters analyzed were the biomass bulk density (pellets-WP and chips-WCH) and the combustion-air/gasification-air ratio (2.8, 3.0, and 3.2). Moreover, a design parameter of the cookstove was analyzed through two combustion chamber designs (combustion chambers 1 and 2). The cookstove was characterized in detail considering the complete cookstove (control volume 1), the combustion chamber (control volume 2), and the gasification process (control volume 3). The cookstove reached an average efficiency of 25.2% for pellets and 24.1% for chips. The best behavior for the cookstove was achieved when pellets were used, which is attributed to their higher bulk density and to the fact that during their gasification process, the biochar yield was 12% higher, while the biomass consumption decreased by 16% compared to the chips. The carbon monoxide specific emissions were 2.78 g/MJ_d for pellets and 2.75 g/MJ_d for chips. On average, the cookstove released total suspended particulate matter between 74.11 and 122.70 mg/MJ_d. The cookstove low emissions are ascribed to the proper combustion air flow and the combustion chamber design, which favored the mixing between producer gas and combustion air.

A critical review of pollutant emission factors from fuel combustion in home stoves

A large population does not have access to modern household energy and relies on solid fuels such as coal and biomass fuels. Burning of these solid fuels in low-efficiency home stoves produces high amounts of multiple air pollutants, causing severe air pollution and adverse health outcomes. In evaluating impacts on human health and climate, it is critical to understand the formation and emission processes of air pollutants from these combustion sources. Air pollutant emission factors (EFs) from indoor solid fuel combustion usually highly vary among different testing protocols, fuel-stove systems, sampling and analysis instruments, and environmental conditions. In this critical review, we focus on the latest developments in pollutant emission factor studies, with emphases on the difference between lab and field studies, fugitive emission quantification, and factors that contribute to variabilities in EFs. Field studies are expected to provide more realistic EFs for emission inventories since lab studies typically do not simulate real-world burning conditions well. However, the latter has considerable advantages in evaluating formation mechanisms and variational influencing factors in observed pollutant EFs. One main challenge in field emission measurement is the suitable emission sampling system. Reasons for the field and lab differences have yet to be fully elucidated, and operator behavior can have a significant impact on such differences. Fuel properties and stove designs affect emissions, and the variations are complexly affected by several factors. Stove classification is a challenge in the comparison of EF results from different studies. Lab- and field-based methods for quantifying fugitive emissions, as an important contributor to indoor air pollution, have been developed, and priority work is to develop a database covering different fuel-stove combinations. Studies on the dynamics of the combustion process and evolution of air pollutant formation and emissions are scarce, and these factors should be an important aspect of future work.

Cookstove Emissions and Performance Evaluation Using a New ISO Protocol and Comparison of Results with Previous Test Protocols

In 2018, the International Organization for Standardization (ISO) 19867-1 "Harmonized laboratory test protocols" were released for establishing improved quality and comparability for data on cookstove air pollutant emissions, efficiency, safety, and durability. This is the first study that compares emissions [carbon dioxide, carbon monoxide, total hydrocarbons, methane, nitrogen oxides, fine particulate matter (PM_2.5), organic carbon, elemental carbon, and ultrafine particles] and efficiency data between the ISO protocol and the Water Boiling Test (WBT). The study examines six stove/fuel combinations [liquefied petroleum gas (LPG), pellet, wood fan, wood rocket, three stone fire, and charcoal] tested in the same US EPA laboratory. Evaluation of the ISO protocol shows improvements over previous test protocols and that results are relatively consistent with former WBT data in terms of tier ratings for emissions and efficiency, as defined by the ISO 19867-3 "Voluntary Performance Targets." Most stove types remain similarly ranked using ISO and WBT protocols, except charcoal and LPG are in higher PM_2.5 tiers with the ISO protocol. Additionally, emissions data including polycyclic aromatic hydrocarbons are utilized to compare between the ISO and Firepower Sweep Test (FST) protocols. Compared to the FST, the ISO protocol results in generally higher PM_2.5 tier ratings.

Toward Clean Residential Energy: Challenges and Priorities in Research

Solid fuels used for cooking, heating, and lighting are major emission sources of many air pollutants, specifically PM_2.5 and black carbon, resulting in adverse environmental and health impacts. At the same time, the transition from using residential solid fuels toward using cleaner energy sources can result in significant health benefits. Here, we briefly review recent research progress on the emissions of air pollutants from the residential sector and the impacts of emissions on ambient and indoor air quality, population exposure, and health consequences. The major challenges and future research priorities are identified and discussed.

Modeling approaches and performance for estimating personal exposure to household air pollution: A case study in Kenya

This study assessed the performance of modeling approaches to estimate personal exposure in Kenyan homes where cooking fuel combustion contributes substantially to household air pollution (HAP). We measured emissions (PM_2.5 , black carbon, CO); household air pollution (PM_2.5 , CO); personal exposure (PM_2.5 , CO); stove use; and behavioral, socioeconomic, and household environmental characteristics (eg, ventilation and kitchen volume). We then applied various modeling approaches: a single-zone model; indirect exposure models, which combine person-location and area-level measurements; and predictive statistical models, including standard linear regression and ensemble machine learning approaches based on a set of predictors such as fuel type, room volume, and others. The single-zone model was reasonably well-correlated with measured kitchen concentrations of PM_2.5 (R²  = 0.45) and CO (R²  = 0.45), but lacked precision. The best performing regression model used a combination of survey-based data and physical measurements (R²  = 0.76) and a root mean-squared error of 85 µg/m³ , and the survey-only-based regression model was able to predict PM2.5 exposures with an R² of 0.51. Of the machine learning algorithms evaluated, extreme gradient boosting performed best, with an R² of 0.57 and RMSE of 98 µg/m³ .

In-use emissions and usage trend of pellet heating stoves in rural Yangxin, Shandong Province

The use of coal in Chinese households for winter heating emits harmful pollutants that severely affect indoor air quality and climate. Therefore, China has made efforts to transition into clean heating using improved heating stoves and biomass pellets. Although the economic and policy implications of such demonstration projects have been extensively investigated, little has been done to understand the real-world performance and adoption trends of such stoves. This study measured in-use emissions from nine different pellet stoves used for heating among 52 rural households in Yangxin, Shandong Province. The temperature of the stove chimney of 21 households was monitored and 56 households were surveyed to explore the stove use trend. The particulate and gaseous emission concentrations for most of the stoves exceeded the limits specified in the Chinese national standard. The measured fuel energy-based emission factors (mean ± standard deviation) for CO₂, CO, NOx, and PM_2.5 were 103 ± 3, 1.41 ± 1.19, 0.336 ± 0.237, and 0.146 ± 0.108 g/MJ, respectively. Between January to February, the average daily heating duration was 8.71 h, and the sustained use of heating stoves was seen among over 85% of the households. On average, the households used their heating stoves for 3.28 months and the estimated annual pellets consumption for a household was 2.7 tons. Besides inherent variabilities associated with user habits, the stove's design-related shortcomings and low-grade pellets hindered the performance and effectiveness of pellet stoves. This study provides insights into opportunities and challenges for the promotion of cleaner fuels and heating technologies. Furthermore, it will provide information on emissions from rural residential sources to build the emission inventory and inform policymaking for successful stove promotion programs.

Investigating Cooking Activity Patterns and Perceptions of Air Quality Interventions among Women in Urban Rwanda

Household air pollution (HAP) from biomass cooking with traditional stoves is a major cause of morbidity and mortality in low-and-middle-income countries (LMICs) worldwide. Air quality interventions such as improved cookstoves (ICS) may mitigate HAP-related impacts; however, poor understanding of contextual socio-cultural factors such as local cooking practices have limited their widespread adoption. Policymakers and stakeholders require an understanding of local cooking practices to inform effective HAP interventions which meet end-user needs. A semi-structured questionnaire was administered to 36 women residing in biomass-cooking fuel households in Kigali, Rwanda to identify cooking activity patterns, awareness of HAP-related health risks and ICS intervention preferences. Overall, 94% of respondents exclusively used charcoal cooking fuel and 53% cooked one meal each day (range = 1-3 meals). Women were significantly more likely to cook outdoors compared to indoors (64% vs. 36%; p < 0.05). Over half of respondents (53%) were unaware of HAP-related health risks and 64% had no prior awareness of ICS. Participants expressed preferences for stove mobility (89%) and facility for multiple pans (53%) within an ICS intervention. Our findings highlight the need for HAP interventions to be flexible to suit a range of cooking patterns and preferred features for end-users in this context.

In-use emissions from biomass and LPG stoves measured during a large, multi-year cookstove intervention study in rural India

We conducted an emission measurement campaign as a part of a multiyear cookstove intervention trial in two rural locations in northern and southern India. 253 uncontrolled cooking tests measured emissions in control and intervention households during three ~3-month-long measurement periods in each location. We measured pollutants including fine particulate matter (PM_2.5), organic and elemental carbon (OC, EC), black carbon (BC) and carbon monoxide (CO) from stoves ranging from traditional solid fuel (TSF) to improved biomass stoves (rocket, gasifier) to liquefied petroleum gas (LPG) models. TSF stoves showed substantial variability in pollutant emission factors (EFs; g kg^-1 wood) and optical properties across measurement periods. Multilinear regression modeling found that measurement period, fuel properties, relative humidity, and cooking duration are significant predictors of TSF EFs. A rocket stove showed moderate reductions relative to TSF. LPG stoves had the lowest pollutant EFs, with mean PM_2.5 and CO EFs (g MJ_delivered^-1) >90% lower than biomass stoves. However, in-home EFs of LPG were substantially higher than lab EFs, likely influenced by non-ideal combustion performance, emissions from food and possible influence from other combustion sources. In-home emission measurements may depict the actual exposure benefits associated with dissemination of LPG stoves in real world interventions.

Impacts of Global Solid Biofuel Stove Emissions on Ambient Air Quality and Human Health

Global solid biofuel stove emissions strongly impact air quality, climate change, and human health. However, investigations of the impacts of global solid biofuel stove emissions on human health associated with PM2.5 (particulate matter with aerodynamic diameter ≤2.5 μm) and ozone (O3) are limited. Here, we quantify the impacts of global solid biofuel stove emissions on ambient PM2.5 and O3 air quality and the associated human health effects for the year 2010, using the Community Atmosphere Model coupled with Chemistry version 5.3. Annual mean surface PM2.5 concentrations from global solid biofuel stove emissions averaged over 2006-2010 are up to 23.1 μg m-3, with large impacts found over China, India, sub-Saharan Africa, and eastern and central Europe. For surface O3 impacts, we find that global solid biofuel stove emissions lead to increases in surface O3 concentrations by up to 5.7 ppbv for China, India, and sub-Saharan Africa, and negligible impacts or reductions of up to 0.5 ppbv for the US, Europe, and parts of South America. Global solid biofuel stove emissions for the year 2010 contribute to 382,000 [95% confidence interval (95CI): 349,000-409,000] annual premature deaths associated with PM2.5 and O3 exposure, with the corresponding years of life lost as 8.10 million years (95CI: 7.38-8.70 million years). Our study highlights air quality and human health benefits of mitigating emissions from the global solid biofuel stove sector, especially over populous regions of low-income and middle-income countries, through promoting clean household energy programs for the residential energy supply.

Mutagenicity- and pollutant-emission factors of pellet-fueled gasifier cookstoves: Comparison with other combustion sources

Emissions from solid-fuel burning cookstoves are associated with 3 to 4 million premature deaths annually and contribute significantly to impacts on climate. Pellet-fueled gasifier stoves have some emission factors (EFs) approaching those of gas-fuel (liquid petroleum gas) stoves; however, their emissions have not been evaluated for biological effects. Here we used a new International Organization for Standardization (ISO) testing protocol to determine pollutant- and mutagenicity-EFs for a stove designed for pellet fuel, the Mimi Moto, and for two other forced-draft stoves, Xunda and Philips HD4012, burning pellets of hardwood or peanut hulls. The Salmonella assay-based mutagenicity-EFs (revertants/megajouledelivered) spanned three orders of magnitude and correlated highly (r = 0.99; n = 5) with EFs of the sum of 32 particle-phase polycyclic aromatic hydrocarbons (PAHs). The Mimi Moto/hardwood pellet combination had total-PAH- and mutagenicity-EFs 99.2 and 96.6% lower, respectively, compared to data published previously for the Philips stove burning non-pelletized hardwood, and 100 and 99.8% lower, respectively, compared to those of a wood-fueled three-stone fire. The Xunda burning peanut hull pellets had the highest fuel energy-based mutagenicity-EF (revertants/megajoulethermal) of the pellet stove/fuel combinations tested, which was between that of diesel exhaust, a known human carcinogen, and a natural-draft wood stove. Although the Mimi Moto burning hardwood pellets had the lowest fuel energy-based mutagenicity-EF, this value was between that of utility coal and utility wood boilers. This advanced stove/fuel combination has the potential to greatly reduce emissions in contrast to a traditional stove, but adequate ventilation is required to approach acceptable levels of indoor air quality.

Systems Science Approaches for Global Environmental Health Research: Enhancing Intervention Design and Implementation for Household Air Pollution (HAP) and Water, Sanitation, and Hygiene (WASH) Programs

BACKGROUND

Two of the most important causes of global disease fall in the realm of environmental health: household air pollution (HAP) and poor water, sanitation, and hygiene (WASH) conditions. Interventions, such as clean cookstoves, household water treatment, and improved sanitation facilities, have great potential to yield reductions in disease burden. However, in recent trials and implementation efforts, interventions to improve HAP and WASH conditions have shown few of the desired health gains, raising fundamental questions about current approaches.

OBJECTIVES

We describe how the failure to consider the complex systems that characterize diverse real-world conditions may doom promising new approaches prematurely. We provide examples of the application of systems approaches, including system dynamics, network analysis, and agent-based modeling, to the global environmental health priorities of HAP and WASH research and programs. Finally, we offer suggestions on how to approach systems science.

METHODS

Systems science applied to environmental health can address major challenges by a) enhancing understanding of existing system structures and behaviors that accelerate or impede aims; b) developing understanding and agreement on a problem among stakeholders; and c) guiding intervention and policy formulation. When employed in participatory processes that engage study populations, policy makers, and implementers, systems science helps ensure that research is responsive to local priorities and reflect real-world conditions. Systems approaches also help interpret unexpected outcomes by revealing emergent properties of the system due to interactions among variables, yielding complex behaviors and sometimes counterintuitive results.

DISCUSSION

Systems science offers powerful and underused tools to accelerate our ability to identify barriers and facilitators to success in environmental health interventions. This approach is especially useful in the context of implementation research because it explicitly accounts for the interaction of processes occurring at multiple scales, across social and environmental dimensions, with a particular emphasis on linkages and feedback among these processes. https://doi.org/10.1289/EHP7010.

Everybody Stacks: Lessons from household energy case studies to inform design principles for clean energy transitions

Stove stacking (concurrent use of multiple stoves and/or fuels) is a poorly quantified practice in regions where efforts to transition household energy to cleaner stoves/or fuels are on-going. Using biomass-burning stoves alongside clean stoves undermines health and environmental goals. This review synthesizes stove stacking data gathered from eleven case studies of clean cooking programs in low/middle-income country settings. Analyzed data are from ministry and program records, research studies, and informant interviews. Thematic analysis identify key drivers of stove stacking behavior in each setting. Significant (28%-100%) stacking with traditional cooking methods was observed in all cases. Reason for traditional fuel use includes: costs of clean fuel; mismatches between cooking technologies and household needs; and unreliable fuel supply. National household surveys often focus on 'primary' cookstoves and miss stove stacking data. Thus more attention should be paid to discontinuation of traditional stove use, not solely adoption of cleaner stoves/fuels. Future energy policies and programs should acknowledge the realities of stacking and incorporate strategies at the design stage to transition away from polluting stoves/fuels. Seven principles for clean cooking system program design and policy are presented, focused on a shift toward "cleaner stacking" that could yield household air pollution reductions approaching WHO targets.

Adapting and Operationalizing the RE-AIM Framework for Implementation Science in Environmental Health: Clean Fuel Cooking Programs in Low Resource Countries

Introduction: The use of models and frameworks to design and evaluate strategies to improve delivery of evidence-based interventions is a foundational element of implementation science. To date, however, evaluative implementation science frameworks such as Reach, Effectiveness, Adoption, Implementation, Maintenance (RE-AIM) have not been widely employed to examine environmental health interventions. We take advantage of a unique opportunity to utilize and iteratively adapt the RE-AIM framework to guide NIH-funded case studies of the implementation of clean cooking fuel programs in eleven low- and middle-income countries. Methods: We used existing literature and expert consultation to translate and iteratively adapt the RE-AIM framework across several stages of the NIH Clean Cooking Implementation Science case study project. Checklists and templates to guide investigators were developed at each stage. Results: The RE-AIM framework facilitated identification of important emerging issues across this set of case studies, in particular highlighting the fact that data associated with certain important outcomes related to health and welfare are chronically lacking in clean fuel programs. Monitoring of these outcomes should be prioritized in future implementation efforts. As RE-AIM was not originally designed to evaluate household energy interventions, employing the framework required adaptation. Specific adaptations include the broadening of Effectiveness to encompass indicators of success toward any stated programmatic goal, and expansion of Adoption to include household-level uptake of technology. Conclusions: The RE-AIM implementation science framework proved to be a useful organizing schema for 11 case studies of clean fuel cooking programs, in particular highlighting areas requiring emphasis in future research and evaluation efforts. The iterative approach used here to adapt an implementation science framework to a specific programmatic goal may be of value to other multi-country program efforts, such as those led by international development agencies. The checklists and templates developed for this project are publicly available for others to use and/or further modify.

Supply Considerations for Scaling Up Clean Cooking Fuels for Household Energy in Low- and Middle-Income Countries

Promoting access to clean household cooking energy is an important subject for policy making in low- and middle-income countries, in light of urgent and global efforts to achieve universal energy access by 2030 (Sustainable Development Goal 7). In 2014, the World Health Organization issued "Guidelines for Indoor Air Quality: Household Fuel Combustion", which recommended a shift to cleaner fuels rather than promotion of technologies that more efficiently combust solid fuels. This study fills an important gap in the literature on transitions to household use of clean cooking energy by reviewing supply chain considerations for clean fuel options in low- and middle-income countries. For the purpose of this study, we consider electricity, liquefied petroleum gas (LPG), alcohol fuels, biogas, and compressed biomass pellets burned in high performing gasifier stoves to be clean fuel options. Each of the clean fuels reviewed in this study, as well as the supply of electricity, presents both constraints and opportunities for enhanced production, supply, delivery, and long-term sustainability and scalability in resource-poor settings. These options are reviewed and discussed together with policy and regulatory considerations to help in making these fuel and energy choices available and affordable. Our hope is that researchers, government officials and policy makers, and development agencies and investors will be aided by our comparative analysis of these clean household energy choices.

Effectiveness of a Household Energy Package in Improving Indoor Air Quality and Reducing Personal Exposures in Rural China

We evaluated whether an energy package comprising a low-polluting semigasifier cookstove with chimney, water heater, and pelletized biomass fuel would improve air pollution in China. We measured the stove use, 48-h air pollution exposures (PM_2.5, black carbon), and kitchen concentrations (PM_2.5, black carbon, carbon monoxide, nitrogen oxides) for 205 women, along with ambient PM_2.5. Over half (n = 125) were offered the energy package after baseline assessment, forming "treated" and "untreated" groups, and we repeated the measurements up to 3 occasions over 18-months. Kitchen carbon monoxide did not change, and nitrogen oxides increased in summer but decreased in winter for both groups. Summer geometric mean exposures and kitchen concentrations of PM_2.5 and black carbon decreased by 24-67% in women who received the energy package, but greater reductions (48-70%) were observed in untreated homes, likely due to increased use of gas stoves. After adjusting for differences in outdoor PM_2.5, receiving the energy package was associated with decreased winter exposures to PM_2.5 (-46%; 95% CI: -70, -2) and black carbon (-55%; -74, -25) and the summer increases were smaller (PM_2.5: 8%; -22, 51 and black carbon: 37%; -12, 113). However, PM_2.5 exposures remained 1.5-3 times higher than those of health-based international air pollution targets.

In-Home Emissions Performance of Cookstoves in Asia and Africa

This paper presents results from eight field studies in Asia and Africa on the emissions performance of 16 stove/fuel combinations measured during normal cooking events in homes. Characterizing real-world emissions performance is important for understanding the climate and health implications of technologies being promoted as alternatives to displace baseline cooking stoves and fuels. Almost all of the stove interventions were measured to have substantial reductions in PM2.5 and CO emissions compared to their respective baseline technologies (reductions of 24–87% and 25–80%, for PM2.5 and CO emission rates, respectively), though comparison with performance guidance from the World Health Organization (WHO) and the International Organization for Standardization (ISO) suggests that further improvement for biomass stoves would help realize more health benefits. The emissions of LPG stoves were generally below the WHO interim PM2.5 emissions target (1.75 mg/min) though it was not clear how close they were to the most aspirational ISO (0.2 mg/min) or WHO (0.23 mg/min) targets as our limit of detection was 1.1 mg/min. Elemental and organic carbon emission factors and elemental-to-total carbon ratios (medians ranging from 0.11 to 0.42) were in line with previously reported field-based estimates for similar stove/fuel combinations. Two of the better performing forced draft stoves used with pellets—the Oorja (median ET/TC = 0.12) and Eco-Chula (median ET/TC = 0.42)—were at opposite ends of the range, indicating that important differences in combustion conditions can arise even between similar stove/fuel combinations. Field-based tests of stove performance also provide important feedback for laboratory test protocols. Comparison of these results to previously published water boiling test data from the laboratory reinforce the trend that stove performance is generally better during controlled laboratory conditions, with modified combustion efficiency (MCE) being consistently lower in the field for respective stove/fuel categories. New testing approaches, which operate stoves through a broader range of conditions, indicate potential for better MCE agreement than previous versions of water boiling tests. This improved agreement suggests that stove performance estimates from a new ISO laboratory testing protocol, including testing stoves across low, medium, and high firepower, may provide more representative estimates of real-world performance than previously used tests. More representative results from standardized laboratory testing should help push stove designs toward better real-world performance as well as provide a better indication of how the tested technologies will perform for the user.