# Propane from bacteria



## Cynnergy (Sep 3, 2014)

Oh, I really wish this can get scaled-up.  I really like cooking with propane/natural gas, so I want a sustainable source for the future.  An electric stovetop powered by solar just won't be the same...

http://www.theguardian.com/environment/2014/sep/02/propane-renewable-sources-ecoli-genes


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## Cynnergy (Sep 3, 2014)

Lol I love how they avoided the term 'genetically modified bacteria' in the article - I'm pretty sure that's exactly what they are.


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## maverick06 (Sep 4, 2014)

of course they are modified bacteria, but who cares.... have to break a few eggs to make breakfast.

I saw this done a few years ago, bacteria that output nearly perfect diesel fuel. Problem was that they couldnt reproduce. Doesnt do much good if you have to spent millions to make 3 or 4 cells....

now, if you could get them to reproduce then you are onto something (fuel so cheap its not economical to meter it, or a life ending plague.... either way...


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## Cynnergy (Sep 4, 2014)

I have some issues with how GM technology has been applied in our current world, but for this sort of application I'm all for it.  It's just another example of the spin-doctors at work though - the Guardian is a leftie newspaper and I would imagine the majority of their readers would be anti-GM but pro-renewable energy, so they had to walk a fine line with this one!  Can't escape spin.


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## TradEddie (Sep 4, 2014)

They explicitly state that it's genetically engineered, no cover up. I worked briefly on this type of process more than 20 years ago, when tools for genetic modification were prohibitively expensive. Now it could really take off.

TE


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## begreen (Sep 5, 2014)

We have been genetically modifying plants and animals since we first planted seeds and made friends with wolves.


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## Doug MacIVER (Sep 5, 2014)

begreen said:


> We have been genetically modifying plants and animals since we first planted seeds and made friends with wolves.


can't agree more with that statement. how did they ever get pears and apples from one tree? just don't add salmon to the apples and pork to the pears.


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## fossil (Sep 5, 2014)

There's a difference between genetic modification (relatively new science) and selective breeding (very old science).  Genetic modification can involve inserting DNA from an entirely different species, whereas this is clearly precluded in selective breeding.


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## dougstove (Sep 5, 2014)

Actually, multiple crop plants (wheat...) are derived from selective crosses between more than one parental species.
Modern genetic modification is faster, more precise and allows transfers across wider ranges.


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## Grisu (Sep 7, 2014)

Cynnergy said:


> Oh, I really wish this can get scaled-up.  I really like cooking with propane/natural gas, so I want a sustainable source for the future.  An electric stovetop powered by solar just won't be the same...
> 
> http://www.theguardian.com/environment/2014/sep/02/propane-renewable-sources-ecoli-genes



Not sure if I would really call that "sustainable energy source". At first glance, it sounds nice but in the end what the bacteria are doing is converting nutrients into propane. There is no energy gain in that as the energy in the propane was already contained in the nutrient source the bacteria receive. Would we be as excited about some bacteria which convert crude oil into propane? Certainly not for reasons of having a sustainable or renewable energy source. 

A much more promising avenue may be to develop algae that produce fossil fuels like propane or diesel. Those would use at least some of the energy from sunlight. Still, a far cry from the free energy we receive by just drilling in the ground.


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## begreen (Sep 8, 2014)

There is nothing "free" about the energy that comes from drilling in the ground. As this energy becomes more difficult to extract the physical and environmental cost gets higher and higher.


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## Grisu (Sep 9, 2014)

"Free" in the sense that it costs us only a small amount of energy to get a large amount back: http://en.wikipedia.org/wiki/Energy_returned_on_energy_invested
And yes, compared with how people had to use their "labor energy" to do everything up to about 200 years ago, fossil fuel energy is free. I doubt that propane made by bacteria will ever get significantly above 1 meaning we will not get more energy out than we put in.


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## woodgeek (Sep 9, 2014)

The real issue is that biomass fuels cannot displace any significant fraction of current global energy use, even if you got a lot more efficient and dedicated ALL agriculture to its production.  The numbers are just not there.  Humans already use more energy in a year than is captured by all the green plants on earth and in the seas, and demand for energy services will surely grow in the future.

Photosynthesis under ideal conditions (hermetically sealed algae bioreactor with special gas cocktail) approaches 2% conversion efficiency, With vascular plants, the typical conversion eff for crops is <0.2%, about 1/100 that of a PV panel.  If you want chemical fuel from renewable energy, you need to start with electrolytic hydrogen from renewable electricity.  Whether you convert the H2 to more useful fuels with a chemical or a biological process is 'dealers choice'.  Energy conversion in biological systems from one compound to another is often very efficient, its just photosynthesis that sucks.

One real possibility is to use energy crops just as a relatively cheap method to collect non-fossil carbon.  Burn it and use the energy for process heat or electricity (not the point), but then take the CO2 output and combine it with PV-derived H2 (which is where most of the final fuel energy comes from).  Voila, zero (fossil) carbon hydrocarbon fuels for special purposes like aviation.  If you use chemoautotrophic archea bacteria, they can convert CO2 and H2 to protein and lipid biomass, suitable for animal feed. This would allow the production of human food in a much less agriculture dependent manner, which would be a real benefit for the natural ecosystem.


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## dougstove (Sep 9, 2014)

I think sugarcane in Brazil can get a solar energy conversion efficiency of ~2%, it can carry a nitrogen fixing symbiont so the soil requirements are very low, and it can grow nearly year around.
And, as part of that conversion, it regenerates itself, so no manufacturing costs, and low capital costs.
Of course, raw sugar cane requires transport and processing.
So in some situations agricultural biofuels may have a role in a future energy mix.

Fungal protein is already on the market (Quorn), and could be used to upgrade marginal feedstocks to human consumability.


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## woodgeek (Sep 10, 2014)

dougstove said:


> I think sugarcane in Brazil can get a solar energy conversion efficiency of ~2%.



Let's push this around a little.

On the interwebs:

I found that Brazil can make 662 gal EtOH/acre/year, with the process heat coming from the cane waste material, so its 'net'.  This works out to be 50 million BTU, MMBTU/acre/year.  Sounds about right, enough to heat a house for a year.

I also found that a PV solar farm with an area of 2.8 acres can deliver 1 GWh/year, which is 1/2.8 = 357,000 kWh/acre/year

Now, 50 million BTUs is equal to 14,600 kWh, so that is 14,600/357,000 = 0.041 or about 1/25th that of the solar farm.

Let's call sugar cane EtOH ~1% eff all in.   

Of course electricity is more useful that EtOH, in a COP=3 ASHP I will get enough heat from an acre of panels to heat 75 homes, rather than just 1 home.  In an EV, versus an E85 ICE car, I am about >3x more efficient too, so I will get >75x as many passenger miles from the PV as the 'cane.


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## dougstove (Sep 10, 2014)

woodgeek said:


> Let's push this around a little.
> I found that Brazil can make ... 50 million BTU, MMBTU/acre/year. ... equal to 14,600 kWh, so that is 14,600/357,000 = 0.041 or about 1/25th that of the PV solar farm at 357,000 kWh/acre/year...
> 
> Agreed.
> ...


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## woodgeek (Sep 10, 2014)

dougstove said:


> Agreed.
> But: What is the ROI on the manufacturing, installation and pollution externality cost for the solar panels?
> That is going to lower the ratio considerably.



Ok, let's see. Energy payback on conventional silicon PV is 12-18 mos, versus a cell lifetime of 30 years.  Most of the materials are Silicon and Aluminum (and glass), which are what most of the earth's crust is made out of (after oxygen), recyclable, and not particularly toxic in metallic or oxide forms.  The 'cane has carbon emissions related to soil carbon depletion, requires a LOT more fresh water to grow, and leads to topsoil depletion rendering it unsustainable on some (perhaps long) timescale.

IMO, the biggest externality (after CO2) is habitat destruction and land use. In terms of land use, the 1/75th acre of PV to get energy for ~1 house, versus 1 acre for the 'cane suggests biofuel solutions would require enormous (perhaps tropical) plantations for energy in addition to the space occupied by the houses, perhaps 1000s of miles away, while the PV solution could get to zero-net energy on site with something like a rooftop area (in suitable locations, but including much of the US 48) at something like existing suburban housing density, perhaps even a bit higher.

As for money payback, both clearly pay back. The 'cane solution appears at first glance to be less capital intensive, requiring just seed cuttings, but in practice in developed countries, all the processing would have to mechanized with heavy equipment, which with grinder/fermenter/distillery also represents a lot of capital investment.


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## dougstove (Sep 11, 2014)

This is all interesting.  I will be teaching a unit on this in November, and was going to use the Brazil sugarcane as a comparator to N.American maize bioethanol (Brazil is vastly better, because of higher productivity, and because their sugarcane can fix nitrogen, as opposed to fertilized maize).  But now I will include the PV comparator as well.  Thanks!
I think your argument for the embodied processing energy in fossil fuels, applies as strongly (or more) to biofuels.


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