Material and energy balances are fundamental to many engineering disciplines and have a major role in decisions related to sustainable development. This text, which covers the substance of corresponding undergraduate courses, presents the balance concepts and calculations in a format accessible to students, engineering professionals and others who are concerned with the material and energy future of our society. Following a review of the basic science and economics, the text focuses on material and energy accounting in batch and continuous operations, with emphasis on generic process units, flow sheets, stream tables and spreadsheet calculations. There is a unified approach to reactive and non-reactive energy balance calculations, plus chapters dedicated to the general balance equation and simultaneous material and energy balances. Seventy worked examples show the elements of process balances and connect them with the material and energy concerns of the 21st century.