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Joule’s solar fuels process can produce up to 15,000 gallons of renewable diesel/acre/year; 5-50X greater conversion efficiency than any biomass-dependent process

Schematic comparison between direct photosynthetic (top) and algal biomass (bottom) processes. Source: Robertson et al. Click to enlarge.

Joule Unlimited’s direct, single-step, continuous process for the production of solar hydrocarbon fuels (earlier post) can produce the areal equivalent of up to 15,000 gallons of diesel per acre annually, according to a new open access paper by a Joule team published in the journal Photosynthesis Research. Harvard Medical School Professor of Genetics George Church, Joule co-founder and chairman of its technical advisory board, is a co-author.

The paper, which examines Joule’s advances in solar capture and conversion, direct product synthesis and continuous product secretion, finds that the solar-to-product conversion efficiency of the direct, continuous process for producing diesel, ethanol and chemicals is between 5 and 50X greater than any biomass-dependent process, and gains additional efficiencies by avoiding downstream refining. In addition, the analysis counters prior assumptions about the viability of industrial photosynthesis, addressing the barriers overcome by Joule to achieve unprecedented photosynthetic efficiency.

Joule was formed not to improve upon existing biofuel processes, but to create a new and transformational process altogether. We have channeled photosynthesis, the most productive energy-capture process on earth, at efficiencies previously thought unattainable. At the same time we’ve eliminated dependence on biomass, the Achilles heel of biofuel production, and the prohibitive costs, processing and logistics it entails. The result is a new paradigm for renewable fuel production with unrivalled productivity targets that are fully supported by actual, measurable gains we’ve achieved at every layer – from photon capture through product synthesis, secretion, separation and collection.

—Bill Sims, President and CEO of Joule

Joule’s process, called Helioculture, combines an engineered cyanobacterial organism supplemented with a product pathway and secretion system to produce and secrete a fungible alkane diesel product continuously in a SolarConverter designed to efficiently and economically collect and convert photonic energy. The process is closed and uses industrial waste CO2 at concentrations 50–100 times higher than atmospheric. The organism is further engineered to provide a switchable control between carbon partitioning for biomass or product.

Sum of individual contributions and accumulated photon losses for two fuel processes and a theoretical maximum for energy conversion. Log scale. Source: Robertson et al. Click to enlarge.

The engineered microorganisms thus function as biocatalysts that use only sunlight, waste CO2 and non-fresh water to directly and continuously produce diesel-range hydrocarbons, which are compatible with existing infrastructure. The paper says that Joule’s combined advances in genome engineering, solar capture and bioprocessing result in photosynthetic conversion efficiency of more than 7% relative to available yearly solar energy striking the ground, many times greater than prior industry assumptions.

The paper compares the efficiencies for an algal pond biomass-to-biodiesel and a cyanobacterial direct-to-fungible diesel process, presenting a theoretical maximum and computed practical maximum efficiencies. Both processes convert solar energy into fuel, but unlike the direct process, the indirect production of fuel from algal biomass requires the costly culturing, harvesting and processing of algal biomass. Moreover, Joule’s process directly yields hydrocarbons that are fungible with existing diesel infrastructure.

By using the photosynthetic efficiency calculated above, the extrapolated metric of barrel energy equivalents (bble) is equal to 6.1 x 109 joule) and any product density expressed in kg/m3 and energy content, e.g., heating value in MJ/kg, the output of this analysis can be converted to areal productivity for any molecule produced from either an endogenous or an engineered pathway.

For example, the direct process, operating at the calculated 7.2% efficiency would yield 350 bble/acre/year. This equates to 15,000 gal alkane/acre/year where a C17 alkane has a heating value of 47.2 MJ/kg and density of 777 kg/m3. Given the flexibility of genome engineering to construct production organisms that make and secrete various fuel products, a similar calculation can be applied for any product synthesized via a recombinant enzymatic pathway and a productivity value extrapolated.

By comparison on an energy basis, the practical efficiency of the algal biomass process would equal about 3,500 gal/ acre/year of the target triglyceride (71 bble; heating value 41 MJ/kg; density 890 kg/m3). Note that 1 gal/acre/year is equivalent to 9.4 l/hectare/year.

The areal productivity estimate for the direct process surpasses the best estimates for fuel productivity potential by any biomass-derived fuel process, e.g., for grain or cellulosic ethanol, for algal or vegetable oils for biodiesel, or biomass gasification and Fischer–Tropsch reforming for hydrocarbons. The photon energy densities and process productivities, plus the advantage of no arable land or freshwater displacement, create a scenario in which a minimal dedication of marginal land can serve to meet US renewable fuel standards.

—Robertson et al.


  • Dan E. Robertson, Stuart A. Jacobson, Frederick Morgan, David Berry, George M. Church and Noubar B. Afeyan (2011) A new dawn for industrial photosynthesis. Photosynthesis Research doi: 10.1007/s11120-011-9631-7



Very interesting. If this process materializes and can be used on a massive scale, it could put an end to corn based ethanol. Captured CO2 from coal fired and NG/SG power stations could be used.


Massive scale is the key phrase. The gallons/acre/year figure is nice but if the initial setup costs are 50x more than an agricultural biofuel operation then who really cares? There has to be a high probability to make big money in order to incentivize venture capitalists and other investors to build massive scale operations...government mandates & incentives will only go so far.


I'll believe it when I see it.


"15,000 gallons of diesel per acre annually.." sounds great - so what's the catch?

"The process is closed and uses industrial waste CO2 at concentrations 50–100 times higher than atmospheric." + "an engineered cyanobacterial organism supplemented with a product pathway and secretion system to produce and secrete a fungible alkane diesel product continuously in a SolarConverter.." equals(ballpark):

How much per gallon, at what scale, at what initial outlay, at what operating costs, yielding what investment rate of return, etc


The 'earlier post' states, "The entire process produces more net energy than it consumes". Something sounds fishy.


danm, they're not counting solar energy (who does?).

This system is going to require closed photobioreactors, because otherwise the hydrocarbon emissions will cause so much smog it'll have to be shut down. That makes it REALLY expensive.

If these cyanobacteria can be given the same electrons-to-energy pathway as the archaea used in the electricity plus CO2 to methane trick, this will allow the production of diesel directly from e.g. excess wind power.


EP, thanks.
Expensive to build the reactors but if diesel can be produced at $30/barrel it would be worth it.


Nothing new proposed here, but they must aim to use atmospheric CO2 rather than waste CO2, even if that means a capture step requiring some energy.


Agree with clett. As described here, this is a one-time re-use of CO2 emissions from a fixed source. After the produced fuel is used in cars, trucks, aeroplanes, ships, the CO2 is released into the atmosphere and can't be used anymore as input for this process.


30 dollars a barrel

If it is ever built it will be selling for about 10 dollars a barrel less the normal diesel


Around here, diesel retails for about $150/bbl.


And around here (Aberystwyth, UK) diesel is retailing at $348/bbl.


" around here (Aberystwyth, UK) diesel is retailing at $348/bbl." This price would collapse present US trucking.


I like the idea of using excess electricity (off peak wind and nukes) to create some sort of liquid fuel. But its got to be easier and cheaper just to use that electricity to displace liquid fuel at point of use especially for heating.

Building energy efficiency (esp heating and lighting) is the real low hanging fruit, many energy efficiency projects pay back within a couple of years

Henry Gibson

A nuclear power plant can be built on the same acre and produce a lot of electricity at lower cost even if a few ton of thorium have to be bought. ..HG..


3PS: that works if you have an immediate need for heating. Right now I'm in the middle of chinook conditions (high winds and sunny, just a few degrees below room temperature) so zero need for heat. What would I do with the wind power (well, besides running my DHW tank up to 180°F so it can coast for a while)?

The electric-CO2-to-methane trick is claimed to be 80% efficient. (I'd love to know what those bugs are doing with the oxygen.) If one can get 60% electricity-to-diesel and surplus wind power goes for 2¢/kWh, you'd get diesel for an energy cost of about $1.40/gallon (add cost of CO2, amortization and O&M). That's not that bad.

Henry Gibson

The word "can" is misused, but like Scuderi and an ultra capacitor maker, keep the computers running even if an ounce of oil has not been produced.

It is already 15 times more efficient to use solar cells to produce electricity to run a car with 40 percent efficient solar cells and 90 percent efficient electric batteries and motors compared to 33 percent efficient diesel engines and 7 percent efficient organisms. It just costs too much. Bruce Bastian, wealthy from the early success of WordPerfect, responded to the denouncing of the building of a tunnel between buildings as impossible, was reported to say "It is not impossible it is just very expensive."

There is a lot of people funding a lot of research about solar produced fuels to pretend that there is a chance to use the sun to avoid the use of crude oil. Much of this work is funded by the wealth produced by the oil and coal industries. They are doing well to avoid the disaster to those industries in France by distracting people from a fifty year old solution.

Solar energy is free, so is coal energy, wood energy, gas energy and nuclear energy, and perhaps the person who seems to control the ground where this free energy is available gets some money for it, the real cost of energy is the money required to get it from the earth and taken to where it is used.

Solar energy in California and Arizona is free to the residents, and it costs a lot of money to get rid of it. The main reason people can live in Arizona and California is air conditioning and imported food and water which all depends mostly on fossil fuels delivered as kilowatt hours on power lines.

The sun is highly honored by people who do not know engineering. The right catalyst could combine the oxygen in the air with the nitrogen and water from the ocean and produce excess energy and a lot of nitric acid. When it happens in our engines we do not use it to fertilize the ground but eliminate it and spend a lot of energy making it from natural gas to put on the farms.

Every atom in a human body and found anywhere on the earth was made in a nuclear reaction.

Every cellphone could be made to be disabled if it received a simple signal. And every automobile could be made to give out such a signal when the engine is running and the car is moving and no other persons are in the vehicle. Magnets or magnetic coils could target the driver alone.

Spending billions to protect someone millions of years from now from nuclear "waste" is foolish if texting is done by drivers; especially if the radiation from the "waste" can be reduced to that already naturally present from similar or equivalent energy natural atoms and sources in many places. If the radiation from nuclear "wastes" diluted in the oceans is a fraction of a percent more than from the uranium, radium and radon already there, the chance or damage from such atoms is an even smaller fraction of the possible damage from the radiation from the natural potassium in our own bodies, 500 gamma rays per kilogram per second at least. The repair mechanisms that repair the damage done, if any, by these rays are far busier repairing the damage from oxygen and other chemicals in the body including excess iron.

If you think that any amount of radio activity is too dangerous, move to the shore of the dead sea and build a very large tank of distilled water and live most of the time in a tiny submarine made of plastic ten feet from any surface. Don't smoke; the Navaho miners in uranium mines mostly got lung cancer if they smoked, but not if they did not. ..HG..


Henry, you jumped the shark..


True EP, but pumped storage can be uprated if the situation was to happen regularly. On a domestic side it could be possible to have seasonal thermal storage but the house needs to be built around it, but it does make a good match for domestic solar thermal.

Phase changing material is a bit of a wildcard here, if you could store lots of heat in a small volume that would be pretty handy.


In our area:

Diesel fuel has gone up to CA$1.32/l or CA$4.96/US gal or US$5.02/US gal.

Regular unleaded gas is now CA$1.26/l or CA$4.74/US gal or about US4.80/US gal.

Both could go up another CA$0.05/l shortly if cities get the extra tax they want to pay the public transport drivers $120,000+/year.

If the trend continues, taking a city bus to work may cost more (over $5 total per ride) and pollute more than using a BEV with a single person on board.

We really need driverless reduced maintenance electric city buses.


Correction...the total cost per driver is over $122,000/year.


3PS, pumped storage (of water) runs into geographic limitations.  Converting electricity to heat is essentially irreversible.  I'm not too hot on the losses involved with making motor fuel either, but given the high value of diesel and relatively high efficiency of its use (up to 40%), that may be one of the best out of a set of far-from-ideal options.


I agree, although dual fuelling LNG in a diesel engine would allow you to use the off peak electricity to liquify the LNG

Henry Gibson

See new article about this company.

Perhaps they can engineer an organism that also extracts CO2 out of a solution of potassium carbonate or bicarbonate and part of the land area can be devoted to a potassium carbonate-bicarbonate-hydroxide solution lake.

The potassium is needed by most plants and organisms, but all natural potassium is radioactive, even that in humans; so the lake, like any natural salt lake, would be radioactive. ..HG..

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