Naked Science Forum
Life Sciences => The Environment => Topic started by: Nascent on 08/08/2014 16:11:01
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I'm curious with all the news in recent days whether or not it would be possible to capture methane and co2 from the atmosphere and use them for continued energy?
i.e. Burn methane, capture co2 (as well as pulling from the atmosphere), then making more methane from the co2, burning that onward and onward.
If such things were possible, would that at all be enough to make an impact on the increasing levels in the atmosphere?
Thanks in advance for answers.
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I don't know how easy it is to capture methane from the atmosphere (it is lighter than air, boils at –164 °C and is non-polar, which limits its solubility)
Capturing CO2 is much easier because it is heavier than air and has a reasonable solubility in water (even though it is non-polar it is polarizable and contains very polarized bonds). CO2 is very soluble in alkaline solutions (pH >9).
Unfortunately it is still reasonably expensive to capture CO2 from the atmosphere (it's only about 400 ppm, so one has to filter huge volumes of air to remove any appreciable amount of CO2) Luckily the sea already does this for us--this is bad for many sea organisms as the dissolved CO2 acidifies the oceans, but it means that we can extract the CO2 by processing much, much smaller volumes.
The US navy is experimenting with technology that can extract >99% of the dissolved CO2 from sea water, and then convert it to jet fuel. (see feasibility study from 2010, just search "feasibility and current estimated capital costs of producing jet fuel at sea" in google and the pdf should be the first link to appear)
Of course the energy to do this conversion has to come from somewhere. The navy happens to have many nuclear reactors, so energy is not an issue on the scale they propose, but if we wanted to do this on a climate-changing scale, I see solar power as the only viable option (obviously using coal or oil for this process would be counterproductive, or neutral at best).
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Indeed, thanks for that, quite enlightening. Though it might not be the most productive in terms of energy returns from the collection etc. I wonder if it would at all be viable in a situation of "Do this or everything heats up, snowball etc".
But I still wonder what the chances are of capturing methane from the atmosphere. In the most simplistic of terms, to filter it from the air just as dust, dirt and such from an auto filter. My lack of understanding in this should be quite evident, but nice to learn with a back and forth.
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Extracting CO2 from the air and turning it into a burnable fuel is dead easy. Plants do it all the time. Live plants are called "animal food", and dead plants are called "fossil fuel". So if you want less CO2 in the atmosphere, grow more trees and breed fewer humans and animals. Costs nothing, achieves everything, and no new technology required.
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Yeah, my initial thoughts were (if it were easy to do), use it as an alternate source by making more methane whilst taking it (methane) from the atmosphere. Short of some materials I've seen in some searches though, it seems methane capture from the air is difficult.
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Extracting CO2 from the air and turning it into a burnable fuel is dead easy. Plants do it all the time. Live plants are called "animal food", and dead plants are called "fossil fuel". So if you want less CO2 in the atmosphere, grow more trees and breed fewer humans and animals. Costs nothing, achieves everything, and no new technology required.
Just because plants can do it doesn't mean it's easy. There is also a problem of scale--there is no way for the plant life on this planet to keep up with the rate at which we are burning fossil fuels.
I refer to this chart of atmospheric CO2 concentration (http://www.mongabay.com/images/2006/graphs/co2_mauna_loa.jpg). All of the parts of the curve with negative slope are due to photosynthesis--there are more plants in the Northern hemisphere, so more carbon dioxide is absorbed April–September. I am slightly optimistic by how steeply sloped downward these portions of the curve are, but then the portions where the curve goes back up again are because of the decay of leaves and fruit etc. during the fall and winter, so unless we have some way of collecting all of the plant material and turning it into fuel, plants are not the way to go. Overall this cycle is roughly carbon neutral (ever so slightly carbon negative--absorbing a little more than is released, but only because of organic matter that gets subducted before it can decay--making fossil fuels), and the overarching trend of increasing CO2 is largely due to burning of fossil fuels.
There is a lot of carbon still in the ground (every molecule of oxygen in the atmosphere corresponds to an atom of carbon stored somewhere), but this took billions of years, and at the rate we're going (~200 ppm/century), it would only take 100,000 years to burn all of that, so we are releasing carbon almost 4 orders of magnitude faster than it is being sequestered.
Maybe some serious bio-engineering can help the plants catch up, but I doubt it.
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The scale of CO2 absorption is not greatly affected by human activity: most of the green bits of the planet are either intensively farmed (and therefore absorbing CO2 as rapidly as we can achieve) or wild forest. The rate of consumption of fossil fuel depends on the energy demand per capita (which will continue to increase for the next 50 years) and the number of humans. That is the one variable over which we have absolute control (at no cost), and the only one that nobody seems to be interested in controlling. For as long as politicians and economists derive their living from an increasing population, and people assume that it is inevitable, we are doomed to eventual extinction.
The Mauna Loa curve is particularly interesting because it is counterintuitive. The greatest uptake of CO2 by growing plants actually occurs in April - August but the release is mostly due to the activity of temperature-sensitive microbial and cold-blooded animals, which also peaks in August.
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There have been proposals to use algae in conjunction with power plants to recover the carbon dioxide at much higher concentrations than what is in the air, then producing fuel from the algae. It may be rather intense with the land area and sunlight requirements, as well as water requirements. However, I have no doubt that within the next decade or two we'll see more CO2 use, and perhaps an increase in the value of reclaimed CO2.
As far as plant growth, there are two types of plants, C3 and C4. The C4 plants hit their maximum growth at about our current 400 ppm CO2 concentration. The C3 plants continue to have growth improvements over a wider range of CO2 concentrations.
It is quite possible that greenhouses growing C3 plants would benefit from receiving concentrated CO2 from power plants.
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would be possible to capture methane ... from the atmosphere and use them for continued energy?
Landfill produces large volume of methane, as organic compounds decay under anaerobic conditions. If you cover an old landfill with clay soil, and drill some collection pipes into it, you can collect much more concentrated methane than you could collect from the atmosphere.
As a potent greenhouse gas, it is better to collect and burn methane to CO2 before it reaches the atmosphere.
There are a number of landfill gas (http://en.wikipedia.org/wiki/Landfill_gas#Landfill_gas_use) projects around the world.
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As Chiral wrote. Too difficult, expending too much energy. And plants and trees do not generally, as some texts commonly used to assume, thrive under more carbon dioxide. There have been several studies confirming this. Doesn't mean that there aren't plants that will though. We still have some diversity left on Earth, although we are doing our best to confine those to botanical gardens and zoos. We're a very destructive species.
I agree with Hansen. We should have done something at 350 ppm, but we didn't. Now we need to do something at 400 ppm. But we won't.
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According to Hansen, him using a combination of climate and earth science, the truly pivotal change should be at around 450 ppm. Because it was at that concentration that ice sheets, the Arctic and Antarctica started to develop. So passing that, as some new magical number, then means the opposite. No more Arctic, no more Antarctica, and a possible massive methane release, worse than the PETM 55 million years ago, (the Paleocene-Eocene thermal maximum). Why? because the methane reservoir has been filled up following global cooling over tens of millions of years.
"methane hydrate models that are consistent with the limited data suggest a total inventory of about 5,000 gigatons of carbon in the form of methane ice and methane bubbles. Thus, unfortunately, not only is the methane gun now fully loaded, but it also has a charge larger than the one that existed prior to the PETM blast."
We've had other methane releases between PETM and now, but not from fully loaded reservoirs.
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the point is that we really need to stop it, now. But even if we do.
"Given the atmospheric lifetime of carbon dioxide is many hundreds to thousands of years, we can now understand that long-lived greenhouses will also continue to exert a warming influence on the worlds oceans for a very long time. Indeed, climate models suggest that ocean warming will continue for at least a thousand years even if CO2 emissions were to completely stop. "
That CO2 tail in the atmosphere has no easily defined life cycle, but millenniums are a sure guess.
“My model indicates that about 7% of carbon released today will still be in the atmosphere in 100,000 years. I calculate a mean lifetime, from the sum of all the processes, of about 30,000 years. That's a deceptive number, because it is so strongly influenced by the immense longevity of that long tail. If one is forced to simplify reality into a single number for popular discussion, several hundred years is a sensible number to choose, because it tells three-quarters of the story, and the part of the story which applies to our own lifetimes.”
The main point should be that when we pass 450 ppm we won't be returning to any stable environment for a civilization to exist, at least not ours. Hansen also rightly points out that what has allowed civilization is a stable environment without too many fluctuations. But now we're introducing oscillations in the Earth system, forcing it from one semi stable state to another. The other not being a state in where we will prevail.
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You might find those articles interesting.
Warm climates of the past—a lesson for the future? (http://rsta.royalsocietypublishing.org/content/371/2001/20130146.full.pdf+html)
Climate sensitivity, sea level and atmospheric carbon dioxide. (http://rsta.royalsocietypublishing.org/content/371/2001/20120294.full.pdf+html)
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We are one he* of a strange species. We think more of a undefinable theoretical quantity, somehow expected to defining our individual worth, called 'money', than we think about our kids? We need to become stewards of this earth, or as I call it 'care takers', but as we don't find a individual profit in it, we refuse. We kiss ass as soon as we meet someone of 'more worth' economically, unable to see that they too came from the same place, and will end exactly as us, not able to take anything with them. And those thinking that they by gathering this money also protect their kids are for the moment destroying us all as a species.
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What Green Revolution? Coal Use Highest In 44 Years. (http://oilprice.com/Energy/Coal/What-Green-Revolution-Coal-Use-Highest-In-44-Years.html)
Coal to surpass oil as top global fuel by 2020 -Woodmac. (http://www.reuters.com/article/2013/10/14/coal-demand-idUSL4N0I202320131014)
"In 2009, the world relied on renewable sources for around 13.1% of its primary energy supply, according to IEA statistics. Renewables accounted for 19.5% of global electricity generation and 3% of global energy consumption for road transport in the same year."
Then take a look at this graph. Mauna Loa Observatory, Hawaii. (http://www.esrl.noaa.gov/gmd/ccgg/trends/)
Now tell me when you think we will pass 450 ppm?
(my guess, somewhere between two to three decades. If we continue as now)
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Intriguingly, everyone avoids discussing the obvious solution: fewer people. Why?
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I see three ways of reducing the human population:
1) exodus--some (or all) people leave the Earth for someplace else
2) deathrate increase
3) birthrate decrease
Option one isn't really practical with our technology today. The second option conjurers images of war, disease, ethnic cleansing and euthanization... ie not a pretty picture. The third option appears most reasonable to me, but there are enough people out there who find this option as repulsive as option 2 that no one really talks about population control without facing severe backlash.
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Option 3 is the only feasible one. So far, less than a hundred people have ever left the planet and most of them returned. Two hugely expensive wars in the last century, and umpteen genocides, have had almost no effect on the global population and the additional expenditure of greenhouse gases in wartime pretty much offset whatever was achieved by killing a few million people. Plus the damage done to agriculture in wartime means less CO2 sequestration by food plants.
Not making babies must be the easiest answer to most of the world's problems. Since it involves (a) doing nothing and (b) receiving an immediate benefit in terms of money, food, and career opportunities, it is difficult to see why anyone finds it "repulsive". Each child costs the UK taxpayer about £1000 per year: if I were to offer every British woman £1000 for every year she was not pregnant, what "backlash" would I face? From whom?
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True Alan. I'm as confused as you to why people don't find this one of the best partial solutions we have. And it doesn't involve governments, it just involve deciding it by oneself. Although I have no specific profs for it, I think one kid per person should be a very nice idea for the next hundred years or so.
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If you do the arithmetic, a one-child policy increases the working-age fraction of the population, leading to bigger pensions or earlier retirement for all. If pursued to the point that the population reaches one fifth of its present level (in about 100 years' time) , all our descendants could enjoy a Western standard of living indefinitely as there would be sufficient cultivable land to feed everyone and provide around 5 kW per capita of biofuel. No traffic congestion, no unemployment, no overcrowding.....and at no net cost whatever.
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I read an article and it said a coal power plant in the state of New Jersery, USA was emitting ~440 tons of CO2 a day. Quite an amount of CO2.
The problem I see --- as I could put anything of concentration and mass to good use for half a dollar any day of the week --- is getting the power plant to concede to the CO2 being taken. You need some industrial desire for the stuff.
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I read an article and it said a coal power plant in the state of New Jersery, USA was emitting ~440 tons of CO2 a day. Quite an amount of CO2.
Here's a neat thought experiment. Switch off the power plant and see how many people die. Not immediately, but eventually, from a lack of heating, refrigeration, medical equipment, cooking facilities, falling over in the dark, starvation resulting from unemployment, inability to walk up to the 49th floor of their home or office.....
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Not to mention the fires started by alternative cooking methods (processed food is even worse when eaten raw). An article I once read stated that the biggest kept secret in Saudia Arabia at the time was the population. Seems the practice of polygamy was resulting in a non-increasing population. Probably Reader's Digest propaganda, but still, many (okay, men) would see this as a viable way to cut down the populace to manageable numbers. Not specifically forbidden by the Bible, and allowed by that other book, so would seem to be more palatable to the religious cohort (the main opposition) than most other methods.
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Seems the practice of polygamy was resulting in a non-increasing population.
Someone slept through Biology 101, I think. On my planet, one male can fertilise thousands of females, and marriage merely increases the probability of doing so.
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It's unlikely one man could fertilise thousands of females in one year, but thousands of men could, year after year, which seems to be the problem.
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One young man can happily (and I mean happily) fertilise three or four women a day, say a thousand a year, by traditional means, and still find time for employment and other recreations. Hence the irrelevance of polygamy - it doesn't matter whether you have one husband or a thousand, you will still get a thousand offspring from a thousand wives.
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The success rate under ideal conditions is only about 1 in 12, so, unless you are Bill Clinton, you may be waiting a while for those thousand offspring. It's not a biology problem, it's a math problem.
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The traditional method may well be that inefficient, but farmers and lesbians have developed technologies that make 99.9% of males redundant.
That said, we do seem to be straying from the subject.