Microbial Hybrids: Connecting solar energy and electric vehicles via biobatteries

September 24, 2015 |

ElectrofuelsAn end to EV range anxiety, endless battery re-charges, and the infrastructure cost of electric vehicles?

In a word: biobatteries. Here’s the why and how.

In the long-term, the advantage of molecules over electrons is that they store more energy with less weight than traditional electrical battery systems.

When it comes to transportation, the longer the trip, the more that the cost of transporting the energy along with the vehicle becomes a factor.  electric batteries are really, really heavy. And, the amount of time that it takes to recharge an electric battery becomes a source of aggravation.

That’s why long-range marine, heavy-duty trucks and aviation have been especially fertile areas for biofuels and traditional fossil fuels. And why light-duty, local transportation has been the best fit so far for electric vehicles.

One of the newer branches of research is a hybrid technology — not the kind of hybrid that sometimes uses gasoline, sometimes use electricity to power a car. Rather, this hybrid uses renewable electricity to generate a stable fuel that can be stored more efficiently, or use dense organic material to generate renewable electricity to power an electric motor.

At the same time, it swaps the electric battery re-charge for a re-fuel that can be accomplished in seconds, not hours.

An array of technology options

There are more than a dozen technologies somewhere in development with a dizzying array of acronyms. Microbial fuel cells, microbial electrolysis cells, microbial methanogenesis cells, microbial reverse electrodialysis electrolysis cells, microbial struvite production cells, and microbial desalination cells among them. To those in the field, known as MFCs, MECs, MMCs, MRECs, MSCs and MDCs.

Here’s a recent summary of the state of those technologies from Penn State’s Bruce Logan and colleagues — Logan, the High Muck-a-Muck of Microbial Fuel Cells, lo these many years.

The two major fundamental breakthroughs

Microbial fuel cells and their brethren have been discussed and toyed with for a long time. In recent years, we’ve discovered that we can directly use wastewater or any biodegradable material to produce electricity, no need for specialty chemicals to assist. More about that here.

And, at the University of Massachusetts it was discovered that “some microorganisms can feed on electricity. The microorganisms live on the surface of electrodes, consuming the electrons released from the electrode as their energy source. The microorganisms use carbon dioxide in the same way that humans use oxygen. The microorganisms “breathe in” in the carbon dioxide and convert it to organic compounds that the microorganisms then “breathe out”. More about that here.

With these, you have platforms for new technologies.

How do the fuel cells work?

Logan’s group explains:

“When bacteria are placed in the anode chamber of a specially designed fuel cell that is free of oxygen, they attach to an electrode.  Because they do not have oxygen, they must transfer the electrons that they obtain from consumption (oxidation) of their food somewhere else than to oxygen– they transfer them to the electrode. In a MFC these electrons therefore go to the anode, while the counter electrode (the cathode) is exposed to oxygen. At the cathode the electrons, oxygen and protons combine to form only water.  The two electrodes are at different potentials (about 0.5 V), creating a bio-battery (if the system is not refilled) or a fuel cell (if we constantly put in new food or “fuel” for the bacteria).”

What can you do with these technologies?

One, you can convert solar energy to a stable fuel, using Microbial Electrosynthesis. They can produce acetic acid, ethanol, even butanol. Eventually, even valuable speciality chemicals such as BDO (butanediol). That fuel can be stored — overnight, for example, something solar technology can’t do today without expensive batteries or energy storage schemes. Or, even for the long term. This was the broad goal of ARPA-E’s Electrofuels project, which completed two years back, and you can read more about that here.

Two, you can clean up wastewater with it, as you use bacteria to produce electricity, via the microbial fuel cell.

Three, you can produce hydrogen with it, to fuel the hydrogen economy and the more traditional hydrogen fuel cell.

Four, you can tun a car using an electric motor with the electricity supplied by a microbial fuel cell, and the fuel in turn supplied by, say, a solar power facility. That way, you can take advantage of electric motor technology but overcome the limitations of traditional battery technology, and the problems of re-charge time. These are limitations and aggravations imposed not by electric motors, but by electric batteries.

What’s new in the field?

A team of researchers led by Elizabeth S. Heidrich at the University of Newcastle in England have completed 12-month pilot-scale operation of a 100-liter microbial electrolysis cell “producing an average of 0.6 L/day of hydrogen. Gas production was continuous though decreased with time. An average 48.7% of the electrical energy input was recovered, with a Coulombic efficiency of 41.2%.”

As the research team noted, “This research has established that the biological process of an MEC will to work at low temperatures with real wastewater for prolonged periods. Testing and demonstrating the robustness and durability of bioelectrochemical systems far beyond that in any previous study, the prospects for developing MEC at full-scale are enhanced.” More about that here.

The bottom line – could we really bypass electric batteries, using biobatteries, and use solar energy to power EVs with vast ranges?

In a word, yes.

How would that work?

In a practical sense, the best place to produce solar fuels is right next to a good solar electricity source. Once a target fuel with the desired energy density is produced, it is simply a matter of shipping it via any number of common infrastructures — no need to build a grid connection — to the re-fueling station. Once loaded into the vehicle in a matter of seconds, the microbial fuel cell converts fuels to electricity, powering the electric motor.

Is this a route to a solar plane?

Well, yes it is. You see, there isn’t anything particularly inefficient about an electric turbofan. In fact, aircraft engines and wind turbines have commonalities. The problem is the battery weight.

How is this related to solar fuels like Joule and Algenol might produce?

In the case of Joule and Algenol, they are producing fuels photosynthetically — though their engineered microorganisms achieve much more photosynthetic efficiency that traditional plants. So, they aren’t produced using solar electricity — they cut out the middleman and produce fuels directly from sunlight. They are not quite as solar-efficient as solar panels, but having one technology is much cheaper than having two, and that’s why they are aiming to be cost competitive with $50 oil.

But the back-end technology could be the same. In other words, feeding a Joule or Algenol fuel to a fuel cell to produce electricity, that can be done. There are direct-ethanol fuel cells, and a vehicle using an early-stage of this technology competed in a Shell Eco-marahon in France in 2007.

State of play, today

This is all very early-stage, low on the technical readiness scale but absolutely making material and credible progress. It’s such an attractive technology platform, if the reactor science comes along as hoped, that we might think of this is as the long-term global transportation technology for the 21st and 22nd centuries. Given that it uses a fueling infrastructure already in place, and solves the most pressing problem of EVs, there’s much to commend this pathway to researchers and policymakers.

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