Synergy between Biofuel & Fuel Cells

[Kingfish]

Recently on another thread the conversation steered into a discussion about sources of alternative energy other than plugging in. Two tangents that spun out were dynamic generation of biofuel and employment of fuel cells using LPG. Both fuel sources are carbon-based and produce carbon-related by products. I would like to explore whether it was possible to use biofuel in a fuel cell using common components, i.e. forms of sugar or possibly other widely available sources of fodder.

In the past week there have been three interesting announcements in the news.

• MSNBC - Biofuel cells may turn cockroaches into cyborgs
  This article discussed the research how certain types of life were able to withstand long periods of dormancy, particularly related to dehydration and subsequent resuscitation. The target creature of interest in this case was the cockroach which produces a particularly organized disaccharide called Trehalose that inhibits cell membrane reduction during periods of low hydration; extends life in times of hardship. The enzyme Trehalase is naturally used to reduce Trehalose “into two simpler sugars” (Glucose), and then “A second enzyme oxidizes the simple sugars, releasing electrons that ‘can then be funneled together to electrodes where they are captured and delivered to oxygen’".

What is the second enzyme? Interestingly enough, another similar article caught mine eye, this time using microorganisms to convert sugar into electricity directly:

• Space.Com - How NASA May Use Microbes to Power Space Robots
  

  "The bacterial colony will live as long as you give it food — in our case, sugar — or one of the other biomass fuels we're looking into. The colony will be able to survive pretty much indefinitely."
  … Their current microbes consist of Geobacter sulfurreducens, a bacterium that does not require oxygen.
  … "There are planetary protection concerns, as well as concerns about protecting the microbes themselves from radiation," Scott said. "Sometime down the road we also have to consider whether the microbes we're looking at are most effective for radiation environments or extreme temperatures."

Backfilling on the technical, there are a few references on Geobacter sulfurreducens used in Radiochemistry, and I believe it has been studied extensively for employment of reducing hazardous waste before considered as an electron-donor.

From MicrobeWiki:

Geobacter sulfurreducens is of considerable ecological importance due to its wide range of biotechnologically exploitable bioremediation capabilities. The organism is involved in carbon cycling, can precipitate soluble metals, and has the ability to generate electricity. Insoluble materials like iron, magnesium, and uranium oxides, that can’t be broken down into soluble subunits can be metabolized by Geobacter (and is) is capable of an anaerobic respiration using one or another of these solid oxides as the terminal electron acceptor.

Now we have identified linkage between long-living natural organisms and methods to extract energy from them in a perhaps macabre-Matrix sort of way. I don’t think G. sulfurreducens is the electron donor in the cockroach study, although it sheds clues on how it is conceivable. The possibilities of fuel sources though opens up widely when there is a natural bacteria capable of digesting (reducing) heavy metal wastes into usable forms, and at the same time creating power.

Bringing the two genomes together to create a bio-digester cum generator, a biofuel cell in portable form, able to run on sugarcane as well as depleted Uranium (and obviously a practical compromise in-between) would go a very long way to unhitch from fossil fuels. When you think about it, we have two natural sources of renewable energy: Photosynthesis and Oxidation. What’s to say five years from now we are filling our tanks with rusty sugar water? I can see it now: My bike pooping out little iron ingots… :lol:

But seriously, if we could manufacture a bio-machine that shortens the link between consumption and production in one unit, outputting usable waste instead toxins or Carbon Dioxide, well – we would be miles ahead.

Hmmm, now I'm watching where my feet land. Wouldn't want to kill off a potential generator... 8)
~ KF

 

[deVries]

... When you think about it, we have two natural sources of renewable energy: Photosynthesis and Oxidation. What’s to say five years from now we are filling our tanks with rusty sugar water? I can see it now: My bike pooping out little iron ingots… :lol:

But seriously, if we could manufacture a bio-machine that shortens the link between consumption and production in one unit, outputting usable waste instead toxins or Carbon Dioxide, well – we would be miles ahead.

Hmmm, now I'm watching where my feet land. Wouldn't want to kill off a potential generator... 8)
~ KF

Kingfish, you have my vote as the most entertaining writer on ES.

I hope you might agree that for the next several years or decades recycling-fermenting straw, sugar cane, corn, whatever for ethanol is a good liquid fuel solution vs Foreign Oil sourcing we are addicted to now. The Sun is going to keep Earth producing carbon based life forms in unstoppable amounts for a few more billion years... it all adds-up... we're going to have to recycle it whether we drill it out or burn it off the surface. At least surface harvest burning of cleaner ethanol in recirculation doesn't input much more carbon above ground vs going underground. I'd rather have productive local farmers & distillers than rich troublesome desert rats overseas corrupting our political & financial systems.

We have to compromise for now until we can be nearly pure electric with wind, solar, hydro, ocean forces, etc.

I hope to use as little of the liquid fuels as is possible transitioning to wind, solar, hydro, ocean as much as I personally can do.

 

[deVries]

Better than bacteria?

June 10, 2011

Swiss team creates gasoline from water, CO2 and sunlight

Tokyo (SCCIJ) - A research team from ETH Zurich, PSI, and Caltech has developed a novel thermochemical reactor that uses sunlight to convert carbon dioxide and water into precursors of gasoline at an unachieved efficiency. The feat is a breakthrough toward using solar energy to produce much-needed liquid fuels more efficiently. The process also does not produce any new carbon dioxide.

Search for Energy Carrier

Scientists ask themselves: how can we get hold of the vast, yet intermittent and unevenly distributed, solar energy resource such that it can be stored and transported from the sunny and uninhabited regions of the earth’s sunbelt to the world’s industrialized and populated centers, where much of the energy is required?

This question has motivated the search for recipes to transform sunlight into chemical energy carriers in the form of storable and dispatchable liquid fuels, such as gasoline and jet fuel, usable to propel not only our cars, airplanes and ships, but the entire world economy. This would ensure the goal of a sustainable energy future.

New recipe and cooking pot

A research team around Aldo Steinfeld, Professor of Mechanical and Process Engineering at ETH Zurich and Head of the Solar Technology Laboratory at Paul Scherrer Institute, in collaboration with the California Institute of Technology (Caltech) in Pasadena, USA, has recently developed a promising recipe and associated reactor technology.

Their idea is based on a solar-driven thermochemical cycle for splitting CO2 and H2O using metal oxide redox reactions. “The operation at high temperatures and the utilization of the entire solar spectrum provide a thermodynamically attractive path to solar fuel production at high kinetic rates and energy conversion efficiencies”, says Steinfeld.

The solar reactor consists of a cavity-receiver with a small windowed aperture for the access of concentrated solar radiation. The selected dimensions ensure multiple internal reflections and efficient capture of incoming solar energy. A porous, monolithic ceria cylinder is placed inside the cavity and subjected to multiple heat-cool cycles under appropriate gases to induce fuel production.

Efficient heat transfer

With this arrangement, the porous ceria cylinder is directly exposed to concentrated solar radiation impinging on its inner walls, providing efficient radiative heat transfer directly to the reaction site. Reacting gases flow radially across the porous ceria cylinder, while product gases exit the cavity through an axial outlet port.

Experimentation was carried out at PSI’s High-Flux Solar Simulator with a 2000 Watt solar reactor prototype subjected to solar concentration ratios exceeding 1,500 suns. The measured solar-to-fuel energy conversion efficiency, defined as the heating value of the fuel produced divided by the solar radiative power input, reached 0.8 percent.

“This efficiency value is about two orders of magnitude greater than the one observed with state-of-the-art photocatalytic approaches for CO2 dissociation”, says Philipp Furler, doctoral student in Steinfeld’s group, who is currently working on the reactor optimization with help of fluid mechanics and heat transfer simulation models. Efficiencies above 15 percent are attainable.

500 cycles without interruption

Beyond efficiency, material stability is a crucial criterion for a viable thermochemical process. Using the differential reactor system, 500 cycles of water dissociation were performed without interruption, yielding stable fuel production at constant rates.

In the meantime, Steinfeld and his team are currently focusing on optimizing the solar reactor technology with the aim of scaling it up for megawatt solar towers, such as those already applied commercially for electricity generation.

When asked about the timetable towards industrial implementation, he is cautious and rather conservative: “By 2020 we should be able to witness the first industrial solar fuel plants coming into operation”.