One problem is that even though the raw materials used in industrial biotechnology may not be derived from fossil fuels, they are still capable of stirring up some difficult ethical questions.

其中的一个问题是，尽管工业生物技术中使用的原材料不来自矿物燃料，但仍会引起难以解决的道德问题。

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Because biodiesels can be made from materials derived from plants, which use carbon dioxide to grow, they potentially have a much lower carbon footprint than petroleum-based fuels.

由于生物柴油的原料都是来自与植物，而植物本身就会转化为二氧化碳，所以这样的话使用生物燃料的碳排放相对来讲比使用化石燃料的碳排放要小。

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To have a pure hydrogen economy, the hydrogen must be derived from renewable sources rather than fossil fuels so that we stop releasing carbon into the atmosphere.

为了获得清洁的氢燃料经济，必须采用可再生的原料来分离出氢气，而不是石化燃料，这样我们就能够阻值二氧化碳进入大气。

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Fischer-Tropsch derived fuels for aviation have been produced recently for the Department of Defense by U.S. based Syntroleum, and have been successfully tested by the US Air Force in a B-52 jet with all eight of its engines fueled by the mixture.

FORBES: Flight of Fancy? British Airways to Purchase $500M of Biofuels

Certainly, greenhouse gas emissions are not the only consideration to be borne in mind in choosing a particular biofuel, and there is the matter of production-costs and the feasibility of making the fuel on the large scale, if any significant substitution for petroleum-derived fuels is to prove practical.

FORBES: Land Use Changes Are Main Factor In Carbon Emissions From Biofuels

The air force is working to certify all its aircraft to use synthetic fuels made from gas derived from coal or biomass, using the Fischer-Tropsch method used by Germany during the second world war.

ECONOMIST: Monitor