Can electrofuels and electrosugars save the day?

May 24, 2013 |

mighty-mouseIs the ultimate industrial fuel system going to be based on electricity, waste CO2 and brackish water – to return society to the days of energy abundance?

It will take a mighty production microorganism, but R&D is well underway and a path is becoming clearer.

In yesterday’s Digest, we explored new research at UCD that may create a new pathway to making fuels and chemicals using the problematically abundant supply of CO2.

One of the reasons to pay attention is that the use of waste CO2 is a component in what you might call biofuels’ Holy Grail. That could be described as a technology that uses a modified production microorganism to directly create targeted molecules using only brackish or saline water, waste CO2 and electricity.

The electrofuels and their promise

It’s an end-goal of ARPA-E’s Electrofuels project, which is scheduled to complete its first phase by years end.

As the Electrofuels manifesto states:

“Most biofuels are produced from plant material that is created through photosynthesis, a process that converts solar energy into stored chemical energy in plants. However, photosynthesis is an inefficient process, and the energy stored in plant material requires significant processing to produce biofuels. Current biofuel production methods are also intensive and require additional resources, such as water, fertilizer, and large areas of land to grow crops. Electrofuels bypass photosynthesis altogether by utilizing microorganisms that are self-reliant and don’t need solar energy to grow or produce biofuels. These microorganisms can directly use energy from electricity and chemical compounds like hydrogen to produce liquid fuels from carbon dioxide (CO2).”

In all, 14 Electrofuel projects are expected to complete this year under their ARPA-E grants. But work continues outside of ARPA-E, too. In February, we reported on a project from the University of Minnesota’s BioTechnology Institute. As Phys.org related:

“By adding marine oxidizer Mariprofundus ferrooxydans PV-1, along with some nutrient medium to an electrode, the bacteria was tricked into consuming electrons as if it were in its natural, iron-saturated environment. The bacteria absorbed electrons directly from the electrode, which enabled it to capture carbon dioxide and multiply.”

The problem of photosynthetic inefficiency

The limitation that Electrofuels seek to overcome is the problem of photosynthetic inefficiency. Few plants utilize more than 4 percent of available solar radiation, and the theoretical limit has been placed at around 10 percent, no matter what efficiencies are developed through microbial engineering. By contrast, solar PV systems have captured up to 25 percent, and one day will do more.

Yet, liquid fuels have a place – both for reasons of energy storage and energy density. Electric cars have proven a tough sell, and one reason is range anxiety and the huge cost of battery-based energy storage.

And the problems of energy storage and energy abundance may be uniquely linked.

SynGest CEO Jack Oswald once told the Digest it’s a mistake to be thinking about simply shifting from an energy-starved world based on fossil fuel reserves, to an energy-starved world based on clean energy.

“What we need is energy abundance,” he said. “If you have enough energy, you don’t have to think twice about pumping the water of some some gigantic Lake Tahoe two thousand feet further up the mountain, and using that proven system for energy storage. We don’t have the abundant, affordable energy to do it now, so we end up with ARPA-E prescribing outcomes by setting up energy storage as a critical national technology goal. Scarcity makes us think and act in different ways, not always to our advantage.”

A production microorganism that uses waste CO2, saline water and electricity is yet to be found. It is not entirely different from the class of organisms under development by Joule, Proterro and others – excepting that those companies use photosynthesis, and Proterro’s microorganism likes freshwater.

But Joule’s and Proterro’s goals are universally admired — even if they are very early in their development — for they aim to make, respectively, renewable fuels & chemicals, and low-cost sugars. Sapphire Energy is expecting to use waste CO2 and brackish water, as well — to make algae, from which fuels can be recovered. So, there’s a class of technologies that are heading very much in this direction.

Sourcing waste CO2, water, and process heat and steam

Sources of feedstock? It may well be that an ideal system would place a production microorganism in close proximity to a power generation station that uses gas or coal. Those stations produce electricity, of course — but also residues of immense interest in the form of waste CO2, process heat and steam and water (used as coolant).

Even a super-advanced power plant will produce 1,000 pounds of CO2 per megawatt-hour – as much as 25 million tonnes of CO2 per year. To put this in context — using a conventional algae production process, that’s enough CO2, onsite, to produce more than 1 billion gallons of fuel.

We can hear the “tut-tut” already: “but natural gas is not a renewable resource, it is not a renewable fuel.” To which we would point out that existing biorefineries already use large amounts of non-renewable electric power, and use gas or coal to generate own process heat. Moreover, the goal of the renewable fuels movement is to reduce the overall carbon footprint — if using gas-fired power and waste CO2 and steam accomplishes that goal: that’s super.

The missing piece, then, is a scalable production microorganism that can make targeted fuels, chemicals or sugars fast enough, and continuously for long run times. That’s something different from identifying a microcritter in a lab that can create industrial fuels & magic in a shake flask.

An ideal industrial system

It may well be that an ideal industrial system would have as many as three production units — one producing sugars, one producing isobutanol, one producing diesel. The latter two can blend directly into the fuel stream.

The former would provide — along with some process heat and steam — a welcome source for co-located production units of the Amyris, Solazyme, Genomatica, and LS9 class. Capable of making a wide range of products using, for example, Amyris’ biofene or Solazyme’s tailored oils. Fragrances, flavors, lubricants, food oils, nutraceuticals — as well as fuels.

industrial-system

Or, a catalysis project of the Virent class or fermentation projects by the likes of Avantium or Gevo — capable of making renewable jet fuels, as well as the elusive paraxylene, the missing molecule in the quest for a plastic bottle made completely from residues and renewable products.

What’s renewable, what’s not?

Now, somewhere out there amongst the Digesterati, someone is fast figuring out that a sugar produced from waste CO2 generated ultimately from natural gas — is not as renewable as a sugar produced from, say, sugarcane.

Or, is it?

Who’s really to say where the sugarcane obtained its own supply of CO2? It’s not as if molecules come with signs around their necks – cane will use ambient CO2 from any source, and we know a lot of those molecules come from burning fossil fuels. Using waste is a good thing.

As long as no one is burning fossil fuels strictly to generate waste CO2. Just as using recycled paper waste is a good thing, so long as no one generates garbage strictly to make feedstocks for recycled paper. Or recycling cans is a good idea so long as no one makes cans in order to recycle them. The point of a residue is that it has to be a true residue — a consequence of an action that already would have been taken.

How much power gen is out there – how much waste CO2 at such facilities? According to the IEA, in 2008, we generated around 13.5 petawatt hours of power from coal, fuel oil or natural gas — that’s something on the order of 6.7 billion tons of CO2. Enough, using conventional algae processes, to make some 3.3 billion tons of biomass — expressed in liquid terms, more than 800 billion gallons of fuels. That is to say, more than enough to substantially alter the future of energy production and usage — and monstrously reduce the carbon footprint.

Where are we in the knowledge quest?

The waste is there, and increasingly we have the knowledge to build industrial-scale facilities of the Solazyme, Genomatica or Amyris class. The production microorganisms that can truly transform waste CO2, waste and saline water and electric power into base products such as sugars, and drop-in fuels such as isobutanol and diesel — well, those have a ways to go.

And they do not reduce the urgency of researching the limits on photosynthetic efficiency — not only to address the problems of fuel, but food and fiber as well.

But the pathway to a sustainable, affordable, reliable, available stream of new fuels becomes increasingly clear.

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