EMERGY evaluations of and limits to forest production

TitleEMERGY evaluations of and limits to forest production
Publication TypeThesis
Year of Publication1995
AuthorsDoherty, SJ
UniversityUniversity of Florida
Accession NumberLUQ.141
KeywordsEMERGY, forest production, systemdinamics
Abstract

To replace the nonrenewable sources of fuel and electricity as their availability declines, research continues for renewable alternatives. One of the main possibilities is solar-based, organic biomass from agriculture forestry. Major theoretical and practical questions include: 1) what are the best possible net yields from biomass; 2) are there biophysical limits to biomass production; and 3) how is time related to net resource yield? In this dissertation, energy systems methods are used to evaluate production and multiple-use of a wide range of agroforest systems under different management schedules from temperate and tropical latitudes. Net emergy measures are used to compare biomass fuels with current alternatives in the generation of heat and electricity. Energy-based meassures are compared with market values for forest profucts. An effort is made to determine the thermodynamic maximum production of biomass. By considering full cycles of growth, harvest and regrowth, net yields are related to the rotation period. Computer simulation is used to relate inputs, cycle time, and yield. The discussion considers the implications of biomass limits for the world reforestation, human carrying capacity, and global environmental-energy policy. Forest systems worldwide are increasingly being reorganized by human interactions. Old growth forests are cleared and replaced with managed old ones; silvicultural practices are reducing the turnover time of forest biomass; forests are often burned or are replaced by some other land-use. Following a century of forests exploitation, now global in scale, new and old systems of utilization are needed that are both productive and sustainable. Further, as the availability of fossil fuels decreases, the controversy increases over what is the maximum sustainable conversion of biomass and fuels from renewable solar energy. Recognition and quantification of the full range of values forests provide, including those outside the market economy, are needed in order to determine best uses of forests ecosystems worldwide. Issues such as these require new and comprehensive assessments if scientists, land managers and ultimately policy makers are to make sound decisions regarding our forest resources and their roles in future questions of energy supply and global processes.

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