[Nizzle (OP)]

http://wattsupwiththat.com/2011/03/29/the-greens-worst-nightmare-a-co2-to-oil-process/

If we would be able to make oil from CO₂ using only bacteria and sunlight, wouldn't that make all cars zero emission vehicles?
What are those greenies complaining about?

[CliffordK]

I think it is a joke.
The ultimate sustainable cycle would be organic fuel --> vehicles --> CO₂ --> organic fuel.
Of course, we're talking about doubling the CO₂ now.  Halving it could be a much more serious issue.

There has been an effort to make biodiesel out of algae.  The biofuels from bacteria would be similar.  Cyanobacteria?  or some transgenic bacteria?

They often do best with a concentrated CO₂ source, for example getting coal plant exhaust to feed your little bugs... 

Is there a risk of developing, and releasing the next super-bug on Earth?

[imatfaal]

Nizzle

Firstly - which greens are complaining?   This is an article on a clearly climate-skeptical site with a mocked up photo.  The ability of algae (and any green plant) to convert CO2 back to an energy rich format by utilising the power of sunlight would be great - but there are problems.

If we use the algae-created hydrocarbon (rather than sequester it) then the whole plan is at best carbon neutral - which is a great way of running cars but no good in tackling raised CO2 levels.  Many people, like myself think we just use far too much energy  and the way to tackle the globe's problems is to lower usage first.

With very rough calculations - if the algae could convert 50 pct of available sunlight to chemical energy then a country like Belgium would need about 5-10pct of its land area covered with algae to cover energy needs.  So it's a good stop gap and a method to store sunlight energy for later and make it usable is always good - but it isnt a single solution to our energy needs or CO2 levels.

[Bored chemist]

"With very rough calculations - if the algae could convert 50 pct of available sunlight to chemical energy then a country like Belgium would need about 5-10pct of its land area covered with algae to cover energy needs.  "
So?
Does Belgium currently produce all its own oil?
Why would it be different if it were to import algae derived fuel, rather than oil?

[CliffordK]

Keep in mind that there are different types of energy & fossil fuel requirements.

• Large fixed installations for generating electricity such as coal plants and natural gas generators.  These would be best replaced with direct generators, solar, wind, hydro, nuclear, tidal, etc.  An exception might be biological natural gas production from landfills and agricultural waste where it is most efficient to do local power generation rather than transporting the gases.
• Automobiles.  These require generally easily transportable, high density fuels, and thus gasoline or diesel.  However, if alternative electricity sources become available, they may be replaced to some extent with battery vehicles, especially for local driving.  However, it remains to be seen if battery power will become economical.  Nonetheless, this is a good target for biofuels.
• Trains and light rail.  Largely converted to electric in Europe, but still very much diesel powered in the USA.  What about installing track-side solar?
• Shipping.  Not discussed a lot, but the ships are very power hungry.  Perhaps small nuke plants, but hydrocarbon fuels may in fact be safer than nuclear.  High energy density is required.
• Aircraft.  For the foreseeable future, I don't see the use of hydrocarbons being replaced, unless they would be powered on pure H₂ Hydrogen.  The high energy density and weight requirements preclude batteries for the majority of aircraft.
• Plastics.  This is actually a very large portion of the oil usage.  Better recycling?

Anyway, it would be pretty silly to replace coal electric plants with organically derived oils.  However, perhaps one would choose to extract the oil, then burn the remaining solids. 

It would take a lot of effort to convert to organic vehicle fuels on a large scale, but not impossible.

Currently we should have pretty much adequate land capacity to supply organic vehicle fuels, but increased population growth will make that more and more difficult as fuels will compete with foods.

There are also inorganic methods for generating methane and short chain hydrocarbons from Carbon Dioxide.
http://en.wikipedia.org/wiki/Sabatier_process
http://phys.org/news155471367.html
http://www.greenoptimistic.com/2009/02/18/titania-nanotube-co2-methane/

[Geezer]

It's a big if, but if gasoline, diesel, or some other hydrocarbon fuel could by synthesized entirely from renewable (non-fossil) energy sources, it would, from a Global perspective, be just as good as any other, so called, "green" fuel.
 
It might not be so popular in some places because it wouldn't allow large metropolitan areas to export a local pollution problem elsewhere. Personally, I think that's a benefit.

[dontremember]

To my knowledge it still isn't quite feasible at the moment, at least there's no scientific proof for that.

Even if you're able to produce bacteria and sunlight indirectly via oil, they are still too "weak" in terms of car energy.