Turning CO2 into Ethanol

[Moonbeam]

The water consumption piece is definitely pertinent. While it's true that re-consumption of the ethanol will place more H20 back into the environment, it's a sideways point because we then have to collect (and I'm assuming purify) that water again to re-utilize it. It's the same problem with our water supply now. We don't drink it and have it disappear. We pee it back out into our toilets.

I do not think that the issue of water consumption is actually pertinent here due to the differences in value of water vs ethanol so I tried to find evidence to support that and found this:

"Depending on local energy prices, 1,000 gallons of desalinated seawater can cost around $3 or $4. Although that might not seem like much, it is still cheaper in many places to pump water out of the ground or import it from somewhere else."

"As of September 2016, the rack price of ethanol was $1.51 versus $1.75 for unleaded 87–octane gasoline—a difference of 24 cents per gallon."

So if a thousand gallons of ethanol sells for $1510.00 and desalinated seawater costs 3 to 4 dollars, I think any supply problems with water won't be a factor.

 

[interchange]

I do not think that the issue of water consumption is actually pertinent here due to the differences in value of water vs ethanol so I tried to find evidence to support that and found this:

"Depending on local energy prices, 1,000 gallons of desalinated seawater can cost around $3 or $4. Although that might not seem like much, it is still cheaper in many places to pump water out of the ground or import it from somewhere else."

"As of September 2016, the rack price of ethanol was $1.51 versus $1.75 for unleaded 87–octane gasoline—a difference of 24 cents per gallon."

So if a thousand gallons of ethanol sells for $1510.00 and desalinated seawater costs 3 to 4 dollars, I think any supply problems with water won't be a factor.

Although your math is significantly simplified in your favor in this argument, I fully agree that the balance of the terms (cost of water vs cost of energy) are lopsided enough to make that alone irrelevant at this exact time.

I am ignorant to the environmental impacts or projections on future supply/demand characteristics of fresh water. If this were a massive scale operation so as to replace our current gasoline industry (for example -- to be close to greenhouse gas neutral), those environmental concerns and supply/demand characteristics I think would shift quite dramatically.

I am also curious about a scenario where, perhaps, this becomes a process employed in some scale by a nation where there is insufficient access to clean water for people presently. What would happen to those people if the government demanded even 10% of the drinkable water supply?

 

[werepossum]

Another possibility is that if that ethanol is used in centralized power generation rather than point source combustion such as replacing gasoline, then massive closed loop pollution controls become practical, so we may be able to recapture the CO2 using a fraction of the original capture energy.

 

[interchange]

Another possibility is that if that ethanol is used in centralized power generation rather than point source combustion such as replacing gasoline, then massive closed loop pollution controls become practical, so we may be able to recapture the CO2 using a fraction of the original capture energy.

Burning ethanol in order to generate power to "recapture the CO2" would undoubtedly lead to more CO2 being released than obtained. There is no point in using greenhouse gas producing energy to accomplish this process unless it was overproduction in the first place.

 

[werepossum]

Burning ethanol in order to generate power to "recapture the CO2" would undoubtedly lead to more CO2 being released than obtained. There is no point in using greenhouse gas producing energy to accomplish this process unless it was overproduction in the first place.

On the contrary. CO2 capture is already being done - in fact, under Obama, the EPA is considering CO2 a pollutant which MUST be captured. https://www3.epa.gov/climatechange/ccs/index.html
It's a short step from capturing for sequestration to capturing for ethanol manufacturing to replace or supplement petroleum. It is of course dependent on the technology, but capturing CO2 from power generation is likely to be significantly less energy-intensive than starting from scratch capturing it in the wild. Just as a heat pump can give more heat than the equivalent energy powering it, so too can fuel cells potentially be ultra high efficiency devices, assuming the right catalysts and material structures can be devised. The new fields of meta material creation, nano technology, and quantum effects engineering are being geared toward this end. Things that seem to break common sense, such as heat pumps or containers that hold more of a specific substance than an empty container of the same volume, result from such knowledge.

https://www.technologyreview.com/s/411848/efficient-ethanol-fuel-cells/
http://www.alcohol4fuel.com/id30.html
http://www.autonews.com/article/201...anol-fuel-cells-to-jump-infrastructure-hurdle

Generally speaking, I prefer methanol or hydrogen fuel cells over ethanol. However, if we can make ethanol from excess CO2 and avoid more fossil fuel mining and consumption, especially if we recapture and reuse the exhaust components, then ethanol begins to look much more practical. It's not usually practical to capture the exhaust in automobiles, but it might be in static power generation. If so, then we may eliminate most of the cost of gathering and processing the feed stock.

 

[Paratus]

On the contrary. CO2 capture is already being done - in fact, under Obama, the EPA is considering CO2 a pollutant which MUST be captured. https://www3.epa.gov/climatechange/ccs/index.html
It's a short step from capturing for sequestration to capturing for ethanol manufacturing to replace or supplement petroleum. It is of course dependent on the technology, but capturing CO2 from power generation is likely to be significantly less energy-intensive than starting from scratch capturing it in the wild. Just as a heat pump can give more heat than the equivalent energy powering it, so too can fuel cells potentially be ultra high efficiency devices, assuming the right catalysts and material structures can be devised. The new fields of meta material creation, nano technology, and quantum effects engineering are being geared toward this end. Things that seem to break common sense, such as heat pumps or containers that hold more of a specific substance than an empty container of the same volume, result from such knowledge.

https://www.technologyreview.com/s/411848/efficient-ethanol-fuel-cells/
http://www.alcohol4fuel.com/id30.html
http://www.autonews.com/article/201...anol-fuel-cells-to-jump-infrastructure-hurdle

Generally speaking, I prefer methanol or hydrogen fuel cells over ethanol. However, if we can make ethanol from excess CO2 and avoid more fossil fuel mining and consumption, especially if we recapture and reuse the exhaust components, then ethanol begins to look much more practical. It's not usually practical to capture the exhaust in automobiles, but it might be in static power generation. If so, then we may eliminate most of the cost of gathering and processing the feed stock.

If you capture the exhaust from combustion, (cars, fossil fuel plants, etc), where are you getting the power to reform the captured CO2 into ethanol?

 

[interchange]

On the contrary. CO2 capture is already being done - in fact, under Obama, the EPA is considering CO2 a pollutant which MUST be captured. https://www3.epa.gov/climatechange/ccs/index.html
It's a short step from capturing for sequestration to capturing for ethanol manufacturing to replace or supplement petroleum. It is of course dependent on the technology, but capturing CO2 from power generation is likely to be significantly less energy-intensive than starting from scratch capturing it in the wild. Just as a heat pump can give more heat than the equivalent energy powering it, so too can fuel cells potentially be ultra high efficiency devices, assuming the right catalysts and material structures can be devised. The new fields of meta material creation, nano technology, and quantum effects engineering are being geared toward this end. Things that seem to break common sense, such as heat pumps or containers that hold more of a specific substance than an empty container of the same volume, result from such knowledge.

https://www.technologyreview.com/s/411848/efficient-ethanol-fuel-cells/
http://www.alcohol4fuel.com/id30.html
http://www.autonews.com/article/201...anol-fuel-cells-to-jump-infrastructure-hurdle

Generally speaking, I prefer methanol or hydrogen fuel cells over ethanol. However, if we can make ethanol from excess CO2 and avoid more fossil fuel mining and consumption, especially if we recapture and reuse the exhaust components, then ethanol begins to look much more practical. It's not usually practical to capture the exhaust in automobiles, but it might be in static power generation. If so, then we may eliminate most of the cost of gathering and processing the feed stock.

You cannot violate the laws of thermodynamics. In combustion reactions where a hydrocarbon's bonds are broken + O2 to produce CO2 and H2O, the reaction is exothermic. In any reaction where you take CO2 + H2O to produce hydrocarbon + O2 again, the reaction is equally endothermic. A 100% efficient process would be able to neatly exchange the 2.