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Can the Earth Produce the Biomass We Demand

Lyman Handy Colloquium presentsProfessor Tadeusz W. PatzekDepartment of Civil and Environmental Engineering
University of California - BerkeleyAbstractTo demonstrate the utter impossibility of sustained, industrial-scale production of biofuels anywhere and from and source, I consider the local,
field-scale sustainability of a productive industrial maize agrosystem that has replaced a fertile grassland ecosystem. Using the revised Second Law approach of Svirezhev, I show that currently this agrosystem is unsustainable in the US (and anywhere else), with or without tilling the
soil. The calculated average erosion rates of soil necessary to dissipate the entropy produced by US maize agriculture, 23 -- 45 t/ha-yr, are bounded
from above by an experimental estimate of mean soil erosion by conventional agriculture worldwide, 47 t/ha-yr. Between 1982 and 1997, US agriculture
caused an estimated 7 -- 23 t/ha-yr of average erosion with the mean of 15 t/ha-yr. The lower mean erosion rate of no till agriculture, 1.5 t/ha-yr,
necessitates the elimination of weeds and pests with field chemicals -- with the ensuing chemical and biological soil degradation, and chemical runoff -- to dissipate the produced entropy. The increased use of field chemicals that replace tillers is equivalent to the killing or injuring of up to 300 kg/ha-yr of soil flora and fauna. Additional soil degradation, not discussed
here, occurs by acidification, buildup of insoluble metal compounds, and buildup of toxic residues from field chemicals. The degree of unsustainability of an average US maize field is high, requiring 6 -- 13 times more energy to remediate soil degradation, etc., than the direct energy inputs to maize agriculture. This additional energy, if spent, would
not increase maize yields. The calculated ``critical yield'' of ``organic'' maize agriculture that does not use field chemicals and fossil fuels is only 30 percent lower than the average maize yield of 8.7 tons per hectare (140 bushel/acre) assumed here. Immediate attention should be devoted in the US to more sustainable alternatives to the current industrial agriculture. I will also discuss the implications of my findings to the current wholesale destruction of the tropical ecosystems. URL: http://petroleum.berkeley

Location: Olin Hall of Engineering (OHE) - 122

Audiences: Everyone Is Invited

Contact: Petra Pearce Sapir