This book presents research on biomass pretreatments, which are a fundamental part of bioethanol fuel production to make biomass more accessible. This book also includes an introductory section on the bioethanol fuels. Bioethanol Fuel Production Processes. I: Biomass Pretreatments is the first volume in the Handbook of Bioethanol Fuels (Six-Volume Set). The primary pretreatments at the macro level are the biological chemical, hydrothermal, and mechanical pretreatments of the biomass. It also has an introductory section on the biomass pretreatments at large for bioethanol fuel production. The major pretreatments at the micro level are the enzymatic and fungal pretreatments of the biomass as the biological pretreatments, acid, alkaline, ionic liquid, and organic solvent pretreatment pretreatments of the biomass as the chemical pretreatments, steam explosion and liquid hot water pretreatments of the biomass as the hydrothermal pretreatments, and milling, ultrasonic, and microwave pretreatments of the biomass as the mechanical pretreatments. The first volume also indicates that a wide range of pretreatments stand alone or in combination with each other fractionate the biomass to its constituents of cellulose, lignin, and hemicellulose and improve both sugar and bioethanol fuel yield, making this bioethanol fuel more competitive in relation to crude oil- and natural gas-based fossil fuels. This first volume is a valuable resource for the stakeholders primarily in the research fields of energy and fuels, chemical engineering, environmental science and engineering, biotechnology, microbiology, chemistry, physics, mechanical engineering, agricultural sciences, food science and engineering, materials science, biochemistry, genetics, molecular biology, plant sciences, water resources, economics, business, management, transportation science and technology, ecology, public, environmental and occupational health, social sciences, toxicology, multidisciplinary sciences, and humanities among others.