Sustainable engineering brings about multidisciplinary solutions to environmental, sociocultural, and economic needs. Sustainable methods and technologies ensure the effectiveness of products, designs, and infrastructure, and minimize waste. Managing waste is critical in the successful practice of sustainable engineering. Success in the implementation of a waste management program must consider a very important strategy, namely, waste reduction which is highly dependent on social stewardship, education, and waste conversion. A sustainable program mix must include public policy, health management, and engineering. This paper presents a number of proven sources and techniques for wastes minimization and conversion and a discussion about the development of effective decision-making tools to implement the most feasible and cost-effective applications. Specifically, the conversion of waste as a resource is presented including the use of wastewater (greywater) for condenser cooling in a power plant; conversion of restaurant grease into biodiesel; the use of phosphate mine tailings as a road surface material; recycling and reuse of glass, metal, and plastics; reuse of rare metals from discarded computers; and the use of cattle waste as building materials. In all of these, the conservation of energy is realized practically. More emphasis has been focused on the use of greywater because it has direct impact on the energy–water nexus.