One of the greatest challenges facing society in the 21st
century is providing better living standards to all people
while reducing and minimizing the impact of human activities
on Earth’s global environment and climate. During the past
decade, sustainability has emerged as a unifying framework for
addressing the global environmental, economic, and societal
challenges facing the world. The Brundtland Commission of
the United Nations defined “sustainable development” as “that
which meets the needs of the present without compromising
the ability of future generations to meet their own needs”
(available online at http://www.un-documents.net/ocf-02.htm). Materials are the building blocks and pillars of a
sustainable society and global economy. There is a growing
realization that the implementation of clean-energy technologies
of the 21st century will require large amounts of critical
metals including rare-earth elements (REEs), platinum group
metals, copper, lithium, gallium, and precious metals (e.g., silver
and gold). Significant amounts of phosphorus (P) will also be
needed as the world faces the daunting challenge of doubling
the amount of food it currently produces in order to feed
around 9 billion people by 2050. As a society, we utilize and
consume large amounts of minerals, metals, P, and other
materials produced by mining with little or no recycling. Thus,
our current management and stewardship of Earth’s mineral
and metal resources are not sustainable. Increasingly, impaired
water (e.g., seawater, brines, and municipal/industrial wastewater)
and solid wastes (e.g., discarded consumer products and
sludge) are being viewed as alternative sources of critical metals
and valuable elements to address global materials availability
and supply challenges. Thus, in the next decades, environmental
scientists/engineers, business leaders, and policy/
decision makers will be confronted with a new set of exciting
opportunities and challenges to advance the viability of critical
materials recovery from impaired water and solid wastes. In this
special issue of Environmental Science & Technology (ES&T), we
highlight recent advances on the recovery of critical/valuable
metals and P from “wastes”. Two key goals of this special issue
are to (1) provide a retrospective and outlook of the state-of-the-field; and (2) bring into focus crosscutting scientific,
technological, and environmental challenges along with
corresponding societal and regulatory issues.