「食べ物をバイオ燃料に」の愚さ：人は食べないと死ぬ、この「当たり前」を忘れるエリート達

バイオ燃料で疲弊した農業振興と言う大義名分は、短期的な救済策としては理解できるが、中長期的には大変な間違いである。人類から食料を奪う話であり、またエネルギー収支からみても、多くは非合理的である。
穀物からのバイオ燃料はやってはいけない。ブラジルのサトウキビからのエタノールのＥＰＲは８程度と高いが、アメリカなどでのコーン、穀物からのＥＰＲは低い、そして土壌、環境破壊を伴うからである。

「水田を油田に」は以前、朝日新聞に掲載された記事である。日本のエリート層、その意味を考えないで、温暖化対策になる、脱石油戦略になるなどと言うようだ。いまではバイオ燃料は流行の先端ともなった感がある。だが、本当にそれでよいのか。
識者、大学、研究者は国民の立場、真に地方の側に立って問題を科学的に考える必要がある。自民大敗を念頭に、地方、庶民、中小企業、社会的弱者の立場で本気で思索すべきなのでは。
単にアメリカでコーン・エタノールが盛ん、それに遅れないようになどでは無邪気過ぎるのでは。企業はお金が儲かればそれでよいが、国民、庶民、世界の普通の人々、そして今も飢える人々にとっては、そうは行かない。
拝金主義はもう止めにしたい、そのようなことに税金を使ってはならない。昔からの教訓、「お金で幸せは買えない」を思い出そう。そこで、

１）「もったいない学会」は10月16日午後、東大の弥生講堂・一条ホールで、シンポジウム　「自動車用燃料をどうするか」を開催。
２）コーネル大学のＰｉｍｅｎｔｅｌ，カルフォルニア大学バークレー校のＰａｔｚｅｋ等の見解（下記Ｍｏｒｅ）を参照されたい。またＰａｔｚｅｋには長い論文、「Thermodynamics of the Corn-Ethanol　Biofuel Cycle」などがある。




Editorial: Green Plants, Fossil Fuels, and Now Biofuels
November 2006

For 700 million years, green plants contributed to the formation of soil, oil, natural gas, and coal. As the human population　increases, so too does the consumption of soil and fossil energy. If this trend continues unabated, humans will consume most of these precious resources within the next few hundred years.

By 1850, when wood accounted for 91 percent of US energy consumption and the US population was less than 10 percent of the current 300 million, serious wood shortages already existed. Now, with only about 4.5 percent of the world population, the United States accounts for a quarter of total fossil fuel use, the largest per capita consumption of any country. Between 1850 and 2000, 90
percent of the US oil endowment was mined.

Converting grain or other biomass into ethanol is currently a popular idea, but it is not a new one. It requires fertile soil, large quantities of water, and sunlight for green plant production. Green plants in the United States collect about 53 exajoules of energy per year from sunlight. Americans consume slightly more than twice that amount, however. Enthusiasts suggest that ethanol produced
from corn and cellulosic biomass could replace much of the oil used in the United States. Yet the 18 percent of the US corn crop that is now converted into 4.5 billion gallons of ethanol replaces only 1 percent of US petroleum consumption. If the entire corn crop were used, it would replace only 6 percent. And because the country has lost over a third of its agricultural topsoil, no large increase in the corn crop is possible.

Our up-to-date analysis of the 14 energy inputs that typically go into corn production and the 9 invested in fermentation and distillation operations confirms that 29 percent more energy (derived from fossil fuels) is required to produce a gallon of corn ethanol than is contained in the ethanol. Ethanol from cellulosic biomass is worse: With current technology, 50 percent more energy
is required to produce a gallon than the product can deliver. Investigators differ over the energy value of the by-products of making corn ethanol, but the credits range only from 10 percent to 60 percent. In any event, biomass ethanol is a bad choice from an energy standpoint.

Moreover, the environmental impacts of corn ethanol are enormous. They include severe soil erosion, heavy use of nitrogen fertilizer and pesticides, and a significant contribution to global warming. In addition, each gallon of ethanol requires 1700 gallons of water (mostly to grow the corn) and produces 6 to 12 gallons of noxious organic effluent.

Using food crops, such as corn grain, to produce ethanol also raises major ethical concerns. More than 3.7 billion humans in the world are currently malnourished, so the need for grains and other foods is critical. Growing crops to provide fuel squanders resources; better options to reduce our dependence on oil are available. Energy conservation and development of renewable energy
sources, such as solar cells and solar-based methanol synthesis, should be given priority.

David Pimentel
College of Agriculture and Life Sciences, Cornell University

Tad Patzek
Department of Civil and Environmental Engineering,
University of California–Berkeley