Charles A S Hall
Hall was born near Boston, and received a B.A. in biology from Colgate University, and a M.A. from Penn State University. He trained as systems ecologist by Howard Odum at the University of North Carolina, where he received a PhD.
Since then he has had a diverse career at Brookhaven Laboratory, The Ecosystems Center at the Marine Biological Laboratory, Woods Hole, Cornell University, University of Montana and, for the last 20 years, at the State University of New York College of Environmental Science and Forestry (SUNY ESF).
Hall, professor of systems ecology at SUNY-ESF teaches a freshman course called The Global Environment and the Evolution of Human Culture and graduate level courses in Systems Ecology, Ecosystems, Energy systems, Tropical Development and Biophysical Economics.
Hall's research interests are in the field of Systems ecology with strong interests in biophysical economics, and the relation of energy to society. His work has involved streams, estuaries and tropical forests but focused increasingly on human-dominated ecosystems in the US and Latin America. His research reflects his interest in understanding and developing analyses and computer simulation models of the complex systems of nature and humans and their interactions. Halls focus has been on energy as it relates to economics and environment. His focus is studying material and energy flows referred to as Industrial ecology, and applying this perspective, to attempting to understand human economies from a biophysical rather than just social perspective.
Systems ecology 
Hall, and other biophysical economic thinkers are trained in ecology and evolutionary biology, fields that break down the natural world as done also by physicists. These views hold the global economy in a different perspective that mainstream economists do not share. Central to Halls argument is an understanding that the survival of all living creatures is limited by the concept of energy return on investment (EROEI): that any living thing or living societies can survive only so long as they are capable of getting more net energy from any activity than they expend during the performance of that activity.
Biophysical economics 
"Energy used by the economy is a proxy of the amount of real work done in our economy," according to Charles A. Hall. In the 1980s, Hall and others hypothesised, "Over time, the Dow Jones should snake about the real amount of work." Twenty years later, a century's market and energy data shows that whenever the Dow Jones Industrial Average spikes faster than US energy consumption, it crashes: 1929, 1970s, the dot.com bubble, and now with the mortgage collapse.
Nicholas Georgescu-Roegen (a Romanian-born economist whose work in the 1970s began to define this new approach) models the economy as a living system. Like all life, it draws from its environment valuable (or “low entropy”) matter and energy, for animate life, food; for an economy, energy, ores, the raw materials provided by plants and animals. And like all life, an economy emits a high-entropy wake, it spews degraded matter and energy, that is... waste heat, waste gases, toxic byproducts, the molecules of iron lost to rust and abrasion. Low entropy emissions include trash and pollution in all their forms. Matter taken up into the economy can be recycled, using energy; but energy, used once, is forever unavailable to us at that level again. The law of entropy commands a one-way flow downward from more to less useful forms. Thus, Georgescu-Roegen, paraphrasing the economist Alfred Marshall, said: “Biology, not mechanics, is our Mecca.”
See also 
- http://web.mac.com/biophysicalecon/iWeb/Site/About%20Me.html Retrieved November-3-09
- http://www.nytimes.com/gwire/2009/10/23/23greenwire-new-school-of-thought-brings-energy-to-the-dis-63367.html?pagewanted=all N.Y. Times article featuring Hall Retrieved November-3-09
- http://www.greenpeace.org/international/about/deep-green/deep-green-jan-2009 Greenpeace article Retrieved November-3-09
- http://www.nytimes.com/2009/04/12/opinion/12zencey.html?pagewanted=1&_r=2&ref=opinion N.Y.Times article on energy systems Retrieved November-3-09
- C.A.S.Hall's website at State University of New York
- The EROEI Institute [dead link]