A methodological proposal is presented for the evaluation of the sustainability of solid biofuels. The proposal is comprehensive and can be applied to any type of solid biofuel. It is a comparative methodology that considers the delimitation of biomass with potential application in solid biofuels, defining a functional unit, the physical space, and the temporal analysis of these alternative fuels. The proposal considers the formulation of measurable indicators grouped into parameters associated with the dimensions of sustainability, for example, social, energy-functional, environmental, and economic, and allows its application and weighting, considering the case studies that are desired to be analyzed. The weighting of indicators and parameters allows that multicriteria analyses can be carried out to comparatively evaluate solid biofuels and generate final recommendations. This chapter addresses the application of the methodology to four case studies as a pilot way to explain its operation and promote its replicability. The methodology aims to serve as a reference framework for promoting solid biofuels, especially in developing countries, and to encourage the use of these alternative energy sources which, when used correctly, can be sustainable energy sources.