Nearly 3 billion people rely on solid fuels for their cooking and heating needs, classifying them as "energy poor". This poverty can be attributed to several factors, including a lack of resources (fuel), inefficient infrastructure (production and distribution), limited purchasing power (poverty), and ill-devised policies. Solid fuels, such as biomass, coal, and dung cakes, are burned in inefficient cookstoves. They generate products of incomplete combustion (PIC), such as CO, particulate matter (PM), and CH4, causing household air pollution (HAP) whose adverse impacts on both health and the environment have been well established. HAP causes diseases such as chronic obstructive pulmonary disorders (COPD), acute respiratory infections (ARI), tuberculosis, bladder and lung cancers, cataracts, and pneumonia. The World Health Organization has declared HAP to be the single largest environmental health hazard, accounting for 3.8 million deaths annually. Moreover, residential solid fuel combustion is a leading source of primary aerosols, which play important roles in atmospheric physics and chemistry, and affects regional and global climate with a net warming effect. To curb the adverse impacts of HAP, the United Nations has set a Sustainable Development Goal of eradicating energy poverty by 2030. Research on multiple fronts seeks to provide cleaner cooking energy by engineering either the cooking systems or the fuel. Developing more efficient solid fuel stoves, called improved cookstoves (ICS), has received the highest attention but the low adoption and still high emissions of ICS mean they alone will not eradicate energy poverty. This dissertation focuses on both options, i.e., ICS, and cleaner cooking fuel alternatives. Part 1 discusses the efficacy of current cookstove technology and the research needed to further advance the technology. Research on ICS is hampered by multiple concerns including a lack of fundamental research, real-time measurements to capture temporal variations, and high reliance on rules of thumb and experience. Extensive real-time physical and chemical characterization of pollutants from different ICS cookstoves was performed, and the effects of different operating conditions and fuel types were quantified. A 1-D steady-state model for a co-current moving bed reactor was integrated with a particle growth dynamic model to simulate combustion and pollutant formation in a top-lit updraft ICS. Field studies in India were conducted to explore how the cookstove and its surroundings interact and its subsequent effects on human health. Findings from the work done in Part 1 highlighted the need to look beyond the current metrics for assessing cookstove performance and regulating air quality. Moreover, cookstove combustion and emission characteristics change drastically with inevitable variations in operating parameters, which leads to inconsistent performance and personal exposure. Current ICSs are usually cleaner than traditional cookstoves, but still not close to the desired performance level. Therefore, cleaner fuel alternatives such as liquefied petroleum gas (LPG), natural gas, and electricity must be considered, though they require overcoming challenges such as resource constraints, affordability, accessibility, and policy. Part 2 focuses on understanding the intricate factors governing household fuel preferences via regional scale modelling and analysis from both the user's and provider's perspectives. This newly developed understanding will enable policymakers to target and manipulate the key factors governing household fuel preferences, and thus to promote adoption of cleaner fuel alternatives.