Biofuels from Electricity

先日のブログで「Biofuels from Electricity」というプロジェクトのタイトルだけ書いたら「何の事やら分からん」というおしかりを受けました。そこで、DOE(Department of Energy)のサイトとか、ハーバード大学のサイトとかによっかかって、分かる範囲で解説してみます。

  • 電気からバイオ燃料を生産
    • 現在のバイオ燃料生産技術は結局「植物の光合成反応」に依存している。すなわち、植物そのものを燃料に変換するか、藻などの光合成生物を利用して燃料を作らせているかのどちらかである。
    • このプロセスでは、太陽光を燃料(=化学エネルギー)へ変換する効率は1%に満たない。
    • 一方、このElectrofuelのアプローチでは、有機体を利用して太陽由来の資源から燃料(=化学エネルギー)を抽出する。
      • ここでいう「太陽由来の資源」とは太陽光や太陽熱を使って作った電気
      • Electrofuel(エレクトロフュエル)と言葉を無理に訳すと「電気から作成した燃料」?
    • 理論的にいえば、このアプローチは現行のバイオマスを利用して燃料を作成するアプローチより、10倍以上も効率的である。

(DOEのサイトより)“Electrofuels” - Biofuels from Electricity --- Today’s technologies for making biofuels all rely on photosynthesis; either indirectly by converting plants to fuels or directly by harnessing photosynthetic organisms such as algae. This process is less than 1% efficient at converting sunlight to stored chemical energy. Instead, Electrofuels approaches will use organisms able to extract energy from other sources, such as solar-derived electricity or hydrogen or earth-abundant metal ions. Theoretically, such an approach could be more than 10 times more efficient than current biomass approaches.

(DOEのサイトより)This project would develop a bacterium to use electricity (which could come from renewable sources like solar or wind) to convert carbon dioxide into gasoline. The bacterium would act like a reverse fuel cell: where fuel cells use a fuel to produce electricity, this bacterium would start with electricity and produce a fuel.

(ハーバードのサイトより)The goal of the proposed research is to engineer a bacterium to absorb electrical current as an input and convert this energy into chemical energy in the form of a biofuel. The bacteria will be engineered to accept electrons in the form of current, to fix carbon dioxide, and to produce a biofuel, specifically octanol. Finally, a device that combines features of an electrochemical cell and a microbial fermenter will be developed.


(ARPA-Eのサイトより)ARPA-E is seeking new ways to make liquid transportation fuels - without using petroleum or biomass - by using microorganisms to harness chemical or electrical energy to convert carbon dioxide into liquid fuels. Many methods of producing advanced and cellulosic biofuels are under development to lessen our dependence on petroleum and lower carbon emissions. Most of the methods currently under development involve converting biomass or waste, while there are also approaches to directly produce liquid transportation fuels from sunlight and carbon dioxide. Although photosynthetic routes show promise, overall efficiencies remain low. The objective of this topic is to develop an entirely new paradigm for the production of liquid fuels that could overcome the challenges associated with current technologies. ARPA-E requests innovative proposals which can overcome these challenges through the utilization of metabolic engineering and synthetic biological approaches for the efficient conversion of carbon dioxide to liquid transportation fuels. ARPA-E specifically seeks the development of organisms capable of extracting energy from hydrogen, from reduced earth-abundant metal ions, from robust, inexpensive, readily available organic redox active species, or directly from electric current. Theoretically such an approach could be 10 times more efficient than current photosynthetic-biomass approaches to liquid fuel production.