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Educated" opinions on climate change - Part 5 11

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Agreed, although CNG might make a tolerable fuel for large civilian aircraft, probably in diesels/turboprops. I imagine cruisng speed will drop, there again I've never seen the point of shipping strawberries or RAM at M0.85.




Cheers

Greg Locock

SIG:please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
 
GregLocock said:
Agreed, although CNG might make a tolerable fuel for large civilian aircraft, probably in diesels/turboprops. I imagine cruisng speed will drop, there again I've never seen the point of shipping strawberries or RAM at M0.85.
Click to expand...

That is what I expected. Apparently, there is no difference in engine performance. I would not be surprised if you didn't see a major effort, in the coming years, to switch US commercial air transport to these fuels. Decoupling their largest expense from the world oil market could be the only way to save the industry.


Link 1

Link 2
 
I hate those absolutes... how can you say that bio-fuels will never be possible? On a large scale perhaps, but if you are off of the grid and don't have huge energy needs, it is indeed possible, as is solar. In this type of situation, nuclear may well be considered impossible.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]
 
Fischer-Tropsch coal based hydrocarbons are an approved blendstock for military jet fuel, and good strategically being a domestic source. Uncoupling from crude oil pricing should be good long term. Negatives include 7 tonnes of CO2 per tonne of liquid hydrocarbon product according to Wikipedia. So CO2 collection, compression, and burial will need to be part of the cost structure. I don't know much about F-P coal but maybe the CO2 is relatively easy to capture.

HAZOP at
 
ewh said:
23 Oct 09 9:28
I hate those absolutes... how can you say that bio-fuels will never be possible? On a large scale perhaps, but if you are off of the grid and don't have huge energy needs, it is indeed possible, as is solar. In this type of situation, nuclear may well be considered impossible.
Click to expand...

I classify bio-fuels as an impossibility because it needs to be reasonably scalable and the amount of available energy needs to be vastly greater to our requirements, even if only in a geographically limited area such as geothermal.

Biofuels are all indirect solar. Compared to photovoltaic, you could say that biofuels are incredibly inefficient but chemically convenient. The Earth's total bio-energy production is only ten times the global energy consumption of humanity. That is to say that the total energy produced through the photosynthetic conversion of solar energy to chemical energy is not vastly greater than our requirements. Keep in mind, our agricultural production is only a sliver of the global crop. Most of that is algae and wild plants.

Your point about the feasibility of moving off grid is indeed true if only a few people do it. However, you cannot divorce the feasibility of energy sources from the fact that everyone needs/wants energy. In this case, they also want to eat.

Nuclear, on the other hand, could conceivably last us well beyond the point that other "hypothesized" sources would have come on line. With reprocessing and non-traditional extraction technologies, nuclear power could last for thousands if not millions of years. I would hope by that point we have solved all problems related to fusion, orbital solar, or some other comic book energy source.

Keep in mind, geothermal is indirect nuclear!
 
If we do away with (most of) the stationary wasters of fossil fuels by a combination of conservation, renewables with storage, and nuclear, we'll have plenty of options for transportation including for aircraft. You can do F-T, which makes lovely zero-sulphur diesel and jet fuel, from ANYTHING that has carbon in it- including biomass. It's just a lossy process-much less lossy than burning the biomass for stationary energy production.

I'm with the "withouthotair" guy: just don't propose an energy mix unless it adds up. And don't talk about the issue at all unless you're willing to pay for it.
 
Pushed send on that one too soon: burning is LESS lossy than making a gas, then a liquid, and THEN burning. In essence, that is what gasification plus F-T equates to.
 
Why is biomass, which could include several things, always brushed off without consitering the different technologys. They are different and have differering efficienies.

I do agree they probally won't be a large percentage of our fuel mix, but they should be consitered for some locations.

Wood and woody byproducts is a mature technology used in cogeneration of electricty and steam. And it works well to supply secondary heating for homes, or fireing of boilers.

Methane retrieval from land fills reduces a powerful green house gas.

Corn ethonol so far just rases the price of corn so the goverment pays less subusities.

Making biodiesel from pig and cow fat is less talked about, so I can't comment much.
 
cranky108 said:
Why is biomass, which could include several things, always brushed off without consitering the different technologys. They are different and have differering efficienies.

I do agree they probally won't be a large percentage of our fuel mix, but they should be consitered for some locations.
Click to expand...

They will be considered, where they are a natural choice and extremely cheap. However, as part of a national energy policy they are a complete disaster. I live in a major ethanol state. Even the people who are(were) profiting from it know that it is nothing more than another farm subsidy.

To use, on the order of, 50 percent of our crop land to provide less than half of our transportation fuel is not sustainable, period. Additionally, there is going to be a big reckoning coming to the US in the coming years pertaining to our incredible water consumption. Unless massive desalination projects are undertaken, we simply won't have the water.

It would be better to take the $5 Billion plus we spend annually subsidizing Ethanol production and buy 5000 MW of photovoltaics, which are 10 to 100 times more efficient with the suns energy than biofuels.
 
Speaking of biomass Cranky108 wrote "I do agree they probably won't be a large percentage of our fuel mix, but they should be considered for some locations."
That is exactly the trap. They get big subsidies for for some locations based on the expectation that they will get better and not need subsidies in the future. BUT THEY ONLY WORK IN SOME LOCATIONS. So they only provide a little bit of energy and never achieve the economies of scale that are necessary to get better. Canada and Alberta just committed about $900 million to scrub CO2 out of a coal plant stack and pump it underground in the neighbourhood. But it only works for power plants near underground space where there used to be oil or gas. It also does not work for oil sands with their multiple sources of CO2. We are heading towards lots of CO2 pipelines with a few breaks and clouds of suffocating CO2 lying around. Sorry I got carried away there.


HAZOP at
 
When did CO2 go from this wonderful gas that plants NEED to survive to this gas that is as deadly as chlorine gas and will end the world?
 
NomLaser said:
When did CO2 go from this wonderful gas that plants NEED to survive to this gas that is as deadly as chlorine gas and will end the world?
Click to expand...

When we almost doubled the amount of it in the atmosphere. I know that is a bit terse. It isn't a poison, we just need to find a way to reach a new equilibrium and understand what it means to our long term climate situation. On the up side, we probably interrupted the glaciation cycle!

There is also an underlining energy supply issue here, which I feel is far far more disastrous then climate change. The era of cheap oil is winding down due in part to production issues and in a large way to increased consumption in developing countries. More people are chasing the same barrel of oil. Additionally, fossil fuels are simply to valuable to burn. They have enabled an agricultural revolution and the feedstock of our chemical/materials industries. We can create other energy systems. However, synthesizing replacements for non-fuel uses will be very difficult.

 
"However, synthesizing replacements for non-fuel uses will be very difficult. "

Which non-fuel uses are you thinking of?



Cheers

Greg Locock

SIG:please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
 
So exactly why are we subsidizing any of the alternative technologys? And at the same time the oil, gas and coal are heavly taxed, and they are proposing more taxes.

At what point is the tax enough, and the subsidizies to much?

Also notice that nucular is also heavly taxed, although it could solve many more problems than solar and wind ever can.
 
GregLocock


Which non-fuel uses are you thinking of?

The first ones that come to mind are fertilizers and plastics.
 
BTW, we haven't doubled the atmosphere's CO2 levels. From 1884 to now it has went from 0.0284% to 0.0384% in 2007. That's less than 1/2% of the atmosphere is CO2, even a small fraction of that CO2 is actually anthropogenic. Do you realize how ridiculous man-made warming sounds when you put it in actual percentages of the atmosphere that CO2 composes?
 
"The first ones that come to mind are fertilizers and plastics. "

For fertilisers isn't the oil being used as a source of hydrogen?

The ubiquity of plastics is just another symptom that the price of oil is too low.

In both case coal+water would be a rather grungey but widely available feedstock.



Cheers

Greg Locock

SIG:please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
 
Aren't plastics also made from coal?

I believe most lubricants are presently made from oil. Also mineral oil which is used as an electrical di-electric/coolant.

What ever happened to the clorniated compounts that were suposely caused a hole in the ozone. We quit using them, the UN never pushed the issue, and we still have a hole in the ozone?
 
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