Artificial photosynthesis

I’ve been thinking about alcohol-powered cars.

As far as I understand, to fuel them you have to:

  1. plant a lot of sugar-rich plants
  2. grow them for weeks or months
  3. harvest them
  4. extract the sugar
  5. brew the sugar into alcohol

From what I understand, the process takes a lot of land, time and effort and produces only slightly more fuel than it uses.

So, I was thinking, can we build a device that artificially reproduces photosynthesis, taking air plus water plus sunlight (or other energy), and making sugar? Could it be done on an industrial scale, producing large quantities of sugar, quickly? Should also be non-polluting.

And as for brewing, could we do that artificially too? Just add a few artificially produced enzymes, and quickly turn sugar into alcohol faster than using yeast?

Why or why not?

We can do all of those things abiotically, but we can’t do it cheaper than we can biologically. The big catch is going to be in where you get the carbon: Plants get it from the atmosphere, but that’s always going to be slow, because there just isn’t very much carbon dioxide in air. If you want a more concentrated source of carbon, like for making plastics, you usually get it from oil or other fossil fuels… but that kind of defeats the purpose for making fuel, because you might as well just burn the oil itself instead of turning it into ethanol.

TL;DR response: photosynthesis is more complicated than you think.

What the o.p. is describing is the fuel production cycle for first generation biofuels. Because these only use the sugar- and starch-rich parts of the plant they are fairly inefficient in carbon use and as a fuel, and primarily serve as octane boosters for existing petrocarbon fuels so internal combustion engines can operate at higher compression and thus operate with greater efficiency and/or specific power output. They also take away from arable land and effort that could be used for food production, notwithstanding the amount of water needed to produce them which often strains non-renewable reservoirs.

Second generation biofuels would actually make use of lignocellulosic biomass (the woody parts and stems/leaves of plants) which is widely considered to be waste material or for low nutrient mash filler. This has less energy per mass or volume, but since it is essentially all waste material (and often burned or allowed to decay, producing methane and other greenhouse gases) converting it into alcohols is a net benefit even if the efficiencies are low. Although most fuel-grade methanol is produced from syn gas, producing methanol from pulp by fermentation is a feasible method for mass production, albeit one requiring a large footprint for yield. Methanol has been demonstrated with good efficiency in Otto-cycle combustion engines, and dimethyl ether from dehydration of methanol offers good potential in diesel-cycle engines and potentially rotating detonation engines without requiring cryogenic or high pressure storage. However, even at maximum yields it would still only replace a small portion of current petrocarbon fuel use, and the logistics of collecting and processing pulp into a mash may make it non-competitive as a large scale fuel production method.

Third generation biofuels, e.g. “algae fuel” is from the cultivation of oil-rich algae. It offers the advantage of providing more complex (and therefore energy dense) hydrocarbon fuels which can be grown in any wastewater or other nutrient-rich water environment. The advantages of scaleability and being able to use wastewater as a growth medium are appealing, especially as the algae can also draw carbon dioxide directly from water (where it is more densely concentrated and absorbed than in respiration with air). Bulk extraction may be logistically challenging, and the costs are not favorable compared to current oil production and first-generation biofuels. However, the future potential as a highly scaleable and viable method of hydrocarbon fuel production, especially with genetically modified organisms optimized for high yield under variable temperature conditions and nutrient content. It also offers the greatest potential of atmospheric carbon sequestration.

There is also the potential for a glucose-based energy economy (using glucose to power fuel cells or biomechanical devices) with a lower overall carbon exchange footprint than any combustion fuel per energy release. However, glucose fuel cell technology is in its infancy and is currently only suitable for very low specific power output.

As for photosynthesis, it is a very complicated process that we still don’t fully understand, and that some biophysicists have postulated to involve macroscopic non-trivial quantum mechanical effects, albeit so localized and transient that they are very difficult to observe directly. We are nowhere near being able to reproduce photosynthesis artificially, and while we can produce sugars through synthesis process it is very inefficient and not suitable to mass energy production.


One advantage is that it will be able to take advantage of low-value or wasted parts of crops. Like the stalks of oats or wheat – after the grain is picked off the top of these, the remainder is either chopped & plowed back into the ground, or cut & baled into straw, which sells for low prices. If this could be fermented in ethanol, it might have more sales value. And that’s additional income for the farmer, after selling the grain.

Also, there is marginal land that doesn’t produce enough to be used as cropland. For example, marshy areas or creekside setoffs have to be kept for drainage reasons, but aren’t worth planting because common crops won’t grow in them. But things like cattails grow there naturally – if they can be harvested and turned into ethanol, that’s some income from these ‘waste’ areas. In the western haslf of the USA, there are many areas that are too dry to grow commercial crops. But prairie grass is evolved to handle such conditions. That could be harvested, nd growing it prevents dust-bowl type erosion.

So the hope is that eventually we can get energy from waste land or waste parts of crop,

This month’s Scientific American has an item that discusses this very question. No. 2 on their list of Top Ten Emerging Technologies is "Fuel from an artificial leaf (page. 32). If you believe the hype, they are zeroing in on the technology.

A few years back, i lead a project for a major wood product manufacturer, looking at feasibility of converting ligono cellulosic biomass into fuel or energy. Liguno cellulosic biomass is technically known as hog fuel or worse than hog fuel for the wood products industry.

Here’s what we found that most scientific researchers (using a lot of government and private grant money) ignore in their “research “:

Most of the wood industry (many prefer to call themselves fiber industry), take a tree and strip out all the branches and only use the trunk of the tree. The leftover branches and twigs (hog fuel or ligono cellulosic biomass) is :

  1. Very labor and cost intestive in collection because they are scattered all over the place and need to be cut because of odd shapes.
  2. Very transportation cost intesive. Trees grow in hard to access places and transportation is expensive. Because branches and twigs are odd shapes, a full truck of branches and twigs will weight a third to a fifth of a truck loaded with trunks.
  3. Very moisture intestive : About 50 to 70 percent of the mass is just water. So you are just transportation water in a way.
  4. Almost all the scientific publications assume clean biomass. In reality, these are always contaminated with dirt, rocks, insects etc. etc.
    I think most researchers ignore all these aspects (confirmation bias perhaps) when evaluating the efficacy of their process. But commercially , none has been successful without a subsidy in some form.

Wouldn’t electrolysis of water using a solar cell be more efficient than making sugars and converting the sugars to alcohol? Hydrogen storage has its own issues, sure, but there’s room for technology maturation there.

There is as much room for technology maturity as for cold fusion.

Hydrogen has been around for ages since the first balloons and Ammonia plants. It’s just not a good fuel for the following reasons :

  1. It’s very very low density fuel. It also takes a lot more work to compress Hydrogen than to say Natural gas for the same pressure. And their are issues with leaks and explosively. It’s energy density will never come close to coal or oil - so you spend significant energy and costs transporting it around. Same are the limits when trying to store hydrogen in MOFs or matrices.

  2. Except fuel cells (which is a boutique application) - no combustion process likes Hydrogen because it burns too hot and makes a lot more NOX pollutants than oil. Gas turbines, which are very efficient on oil or natural gas, give poor efficiency on Hydrogen because it has very low Molecular weight. The dew point of hydrogen combustion products is very high - so traditional HRSGs (steam power) gets limited efficiency too.
    All fertilizer, chemical and refining industries use Hydrogen on a regular basis but not as FUEL but a chemical feedstock like for Ammonia, Hydrogenating Vegetable Oil or Upgrading. In fact some early Hydro plants used to electrolyze water to make hydrogen for Ammonia fertilizer.

Thanks for the replies so far. some interesting stuff, but …

Aren’t these saying opposite things?

I can’t speak for Chronos, but while we can sequester carbon dioxide and construct sugars from basic constituants, we can’t do it by simulating the process of photosynthesis.

As for using hydrogen as a fuel, am77494 is adroit in his criticisms for pretty much any terrestrial application, and he is correct that hydrogen is more useful as a feedstock than as a fuel (although most hydrogen produced today is through steam reforming of natural gas or methane rather than the thermodynamically inefficient electrolysis). The one application for which hydrogen is a good fuel is upper stages of space launch vehicles, where the low molecular mass of the products gives better propulsive efficiency, especially when run hydrogen-rich.


That’s clear, thanks.

Thanks Stranger, and fully agree with you. Even for space applications, Hydrogen as a fuel is driven more by its molecular size than its energy content. Per kilogram, Hydrogen contains about 130 MJ of energy (in simple terms not considering LHV, HHV, etc). Even considering no energy is needed in producing it - you need about 40 MJ to liquefy a Kg of it. Then maybe another 20 MJ are lost due to heat losses in transportation, storage and launch delays. So roughly, half of its energy is needed from external sources (aka fossil fuels)
Although Steam reforming is the preferred method of Hydrogen production (syngas production more approximately) in the world, gasification/partial oxidation is not far behind. The advantage with gasification lies with the use of heavier hydrocarbons/coal like Bitumen, Petcoke or coal.

And if your final goal is alcohol (ethanol or methanol), it’s even easier, if you don’t have any microbes doing your work for you, to just produce those directly than to make sugars.

I guess the reason there was so much “hydrogen economy” talk is that it seemed pretty simple. You just need excess electrical energy from your <insert sustainable power source>, use that to split water through simple hydrolysis, store the hydrogen, and burn the hydrogen later. The only waste product is water. And this could be done in a very decentralized way, because any little solar panel anywhere could have a little hydrogen generation system.

Except it isn’t that easy. Hydrogen is hard to store. It’s not a great fuel. It’s a pain in the ass. And it’s not true that the only pollutant would be water.

I’m pretty sure that in the future we’re going to have some method of storing energy from whatever energy sources we use. But it’s not going to be tanks of compressed H2.

So on a related subject, there’s all this natural gas around. CH4. And you can use it to run your vehicles and so on. But it’s a pain in the ass, because you have to compress the stuff. Why isn’t there an industry to convert methane to methanol, which is liquid at STP? Seems like you’d solve all sorts of problems since liquid fuels are so much easier to deal with.

There are lot of factors that go into this:

  1. The first is that the Methane molecule is thermodynamically very stable. What’s Iron or Lead to nuclear decay, methane is the same for hydrocarbons. So if you take any hydrocarbon - heat it up or pass it over a catalyst - most likely you will end up making methane. The reverse is not true - I.e. if you try to make two methane molecules join and make another bigger hydrocarbon, it will stubbornly refuse - no matter the heat or pressure :). You have to trick the methane molecule by reacting it with Oxygen (or some very reactive elements) and make CO (Carbon Monoxide), CH3OH (Methanol) or HCHO (Formaldehyde) etc.

  2. Small scale Gas to Methanol (GTM) or mini Gas to Liquids is the holy grail for chemical engineers, catalyst scientists etc. This is specially attractive for fracking because the wells are remote and they flare the gas that comes up with the oil. There are a few companies with Pilot scale demonstrations like Velocys, GasTechno, CompactGTL etc. but the technology is not mature. These technologies have the following big challenges :
    a. These technologies are like scaling down a nuclear power plant to a home power generator. They don’t scale well at all - the costs are very high, and the operability is very finicky.
    b. As stated above, these technologies compete with age old technology of pipelines. Once a well is connected to a pipeline, the need for flaring goes away. This is why, you’ll see a lot of new pipelines all over the place.
    c. Gas production from a well is not constant - it decays (sometimes exponentially). Investing in a GTM plant versus a pipeline is a lot more cost effective.

  3. Large scale Gas to Methanol is a mature technology and many companies like LyondellBasell, Methanex, Valero etc have plants in operation or going into production. Again, this is limited by demand of Methanol and supply by China which makes a lot of Methanol from coal.

  4. Although Methanol can be used in cars (race cars already use it), its a whole different ball game to have the distribution network. If you buy a

Sorry for the mess up:


  1. Although Methanol can be used in cars (race cars already use it), its a whole different ball game to have the distribution network. gasoline is already cheap plus you have the Ethanol lobby. As far as I am aware, for the US consumers, Methanol has only appeared in chafers for party trays and DME in wart / skin-tag freezers. In China DME is used for cooking “gas” and Volvo has introduced Methanol powered semis/ trucks.

So Methanol will play a very small part as a fuel in the world market while the price of oil is so low. The Chinese coal-liquids market is highly subsidized, so that’s another matter.