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Thermodynamic Considerations In Determining World Carrying Capacity

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2009 Annual Conference & Exposition


Austin, Texas

Publication Date

June 14, 2009

Start Date

June 14, 2009

End Date

June 17, 2009



Conference Session

Sustainability in Engineering Courses

Tagged Division

Environmental Engineering

Page Count


Page Numbers

14.1267.1 - 14.1267.18



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Paper Authors


Scott Morton University of Wyoming

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Scott Morton received his Bachelor and Master degrees in Agricultural Engineering from the University of Wyoming in 1972 and 1978 respectively. He worked as an engineering consultant, a self-employed business owner, and a plant engineer before joining the University of Wyoming Mechanical Engineering faculty as a Research Scientist in 1999. He holds four patents and has two pending. Current research activities are in the areas of wind and solar renewable energy and computer aided laboratory instruction. Some of his many projects include radial flow and augmented flow small wind turbines, an electric car, and restoring his home, which was built prior to 1894.

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M.P. Sharma University of Wyoming

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M.P. Sharma is Professor of Chemical and Petroleum Engineering at the University of Wyoming. He received Ph.D. in Mechanical Engineering from the Washington State University in 1977. His current areas of teaching/research interest are thermodynamics, drilling/production of oil and gas, enhanced and thermal oil recover, air pollution control and emissions from coal fired power plants. He has published and taught courses in pollution prevention, life cycle analysis and sustainability including complex interaction between energy, entropy and environment. He has published and given ASEE short courses on how to develop and teach online courses and active learning courses.

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NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

Thermodynamic Considerations in Determining World Carrying Capacity Abstract

Applying knowledge of thermodynamic systems and laws (laws of mass, energy and entropy) to the overall the earth system and to individual human systems, leads to the concept of a minimum-sized control volume (called “transition control volume”). Such a control volume is the minimal control volume that is theoretically needed to cycle all mass, energy and entropy flows required by the open system of an individual human. Such processes and fluxes are necessary for an individual human to exist without environmental limitations on life.

Using simplified assumptions of just two out of many necessary components, energy fluxes, the carbon cycle, and heat rejection, this thermodynamic model analysis is used to estimate the human carrying capacity of the earth with current non-renewable energy usage. If all the earth’s inhabitants were to use non-renewable energy at the same rate as the average Unite States citizen, the carrying capacity of the world would be about 770 million people. If the average energy consumption is limited to around 40 gigajoules per year (1200 watts) and is derived primarily from renewable energy sources and if natural background heat flux from the core of the earth is supplemented by 5%, the carrying capacity is estimated to be 3.8 billion. These estimates are based on using very simplified assumptions and limited input data (like using just three fluxes mentioned above) for performing the calculations using the thermodynamic model proposed. The model, however, is capable of more accurate and comprehensive calculations and predictions, if the quality and extent of input data is improved.

Observations of problems related to energy sources and sinks in human societies show more chronic sink-related problems than source-related problems. To think that energy sink-related problems can be solved by the increased use of supplemental, non-renewable energy is erroneous. If the entropy and temperature of the earth system are to remain at reasonably low level (natural level), the thermodynamic analysis presented in this paper, shows that use of supplemental non-renewable energy increases the entropy production, making the energy sink- related problems worse. Analyses of energy fluxes through the environment from this standpoint lead to the conclusion that the human carrying capacity is more likely limited by the transport of energy and entropy to single sink for the earth system and ultimately by the sink itself than it is by energy sources.


Many authors have addressed the question of the human carrying capacity of the world, proposing various bases to estimate carrying capacity. Most rely on energy source or resource limitations, mainly food production, to establish maximums as illustrated by the following eight estimates1.

1. 5.994 Billion E. G. Ravenstein, 1891, food production limitations, 2. 15.634 Billion Albrecht Penck, 1924, food production limitations, 3. 146 Billion C. T. De Wit, 1967, non-agricultural land use limitations,

Morton, S., & Sharma, M. (2009, June), Thermodynamic Considerations In Determining World Carrying Capacity Paper presented at 2009 Annual Conference & Exposition, Austin, Texas. 10.18260/1-2--5839

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