I empathize with people who are trying to help by reducing their footprint. Though I fear it'll all be in vain when a machine is invented that can suck a lifetime's worth of frugality out of the air in a fraction of a second.
I have spent a not inconsiderable amount of resources reducing my footprint and I will be thrilled to death if we can manage our way out of this crisis and people get "free lunches". This is just trivial game theory and the sunk cost fallacy.
Regrettably, the numbers involved make me pessimistic. I think your idea of some deus ex machina technology is ungrounded optimism, wishful thinking, or denial. Nothing in the linked article gives any cause for such optimism.
Climate change math is like the ballistics equation. It is just a cold hard reality check. There is no free lunch in terms of the energy of a chemical reaction.
We are all getting really, really close to failing here. I think it's imperative not to be hopeless about it, but we should be honest with ourselves that we may not have modern human civilization as we understand it within a generation or two [edit: unless we act immediately, not soon]
There is a non-negotiable entropy cost associated with removing CO2 from the atmosphere: you need to either pump it, so P0 = 0.0004 atm; if P1 = 5 atm (liquid CO2) then E = M R T ln(5 / 0.0004) / 44 => E/M = about 500 J/kg, or you need to absorb it chemically, which requires a chemical with a vapor pressure of CO2 < 0.0004 atm, (e.g. NaOH) itself generally energy-intensive to produce.
I expect that we will eventually develop technology for CO2 extraction, but it's not going to be easy or convenient. 500 joules per kilogram is a lot and I doubt chemical methods will beat it. Currently there are about 3.5 trillion tonnes of CO2 in the atmosphere, or about 3.5 * 10^15 kg. To decrease the concentration by 1/3, returning us to preindustrial CO2 levels, you'd need about 600 petajoules or 170 terawatt-hours of input energy assuming thermodynamically perfect isothermal compression (which is impossible to actually achieve). Global world electricity consumption per year is about 21000 TWh.
No current method of CO2 extraction comes close to this limit and it's very unlikely that any ever will. Nonetheless, we have several orders of magnitude of wiggle room to let real-life methods work out okay. But the energy cost is not small and the negative effects of present-day CO2 emissions should not be considered easily curable.
And just for the fun of it, a human being releases about 4 * 10^5 kg of CO2 during their lifetime, requiring about 2 * 10^8 J. So the most efficient CO2 pump possible would require at least 200 million watts of power (about a thousand Tesla Roadsters at maximum output) to confine this CO2 within a second.
I integrated the PV curve at constant temperature, so P = nRT/V and dW = P dV = nRT dV/V. Then we can write W = nRT log(V0 / V1) = nRT log(P1 / P0), and n = M / 44, the molar mass of CO2.
Also, you can't restore the initial pressure because at the initial pressure the CO2 takes up a whole atmosphere of space!
Thanks. You've calculated the energy required to pressurize the gas. You can get that energy back if you make the gas doing work; if you pressurize it quasi-statically, you at least won't lose energy while compressing...
I didn't get your last line though. I assume you compress "dirty" air.
You can't get the energy back because I assumed you have a magical compressor that only compresses carbon dioxide. I didn't include any terms for compressing air. You get a slightly cheaper term (ca 420 J/kg) if you set the upper pressure to atmospheric but then you're storing gaseous CO2 which is not practical. But recovering energy by restoring the original [partial] pressure of 0.0004 atm is not possible unless you somehow jettison the CO2 into outer space.
To be clear: all real processes probably require many times more energy than this. There is no way I know of to selectively compress one component of a gas mixture. But if you did, this would be the energy cost.
Ok, let's take 500 J/kg of CO2. Do you think it's a lot? To get 1 kg of CO2 you'll need to process roughly a ton of air. There are ~5e15 tons of air in the atmosphere, so it's 3e18 J to process all the air. We produce annually 75e18 J annually on the planet - can we handle this expense?
I'm afraid it will be more than that - but how much more exactly?
Using PSA can reduce the energy cost of CO2 extraction significantly relative to direct compression technology. But because we know that the adsorbent is used in a cyclic process, we have dW[compression] = p dV + dE[adsorbent] and the long-time integral of dE[adsorbent] is effectively zero because the adsorbent cannot absorb or release energy forever, so ΔW[compression] = int[p dV] and thus any technology, compression-based or not, incorporating some finite amount of external components, is subject to the work limit.
This is also why, for example, thermodynamic analyses of engine types are always concerned about the possible compression ratio. You could consider the partial pressure of atmospheric and stored CO2 as the compression ratio of a hypothetical compressed-air motor, which can then be run to extract thermal energy (i.e. violate the second law of thermodynamics) from any process more efficient than 500 J/kg CO2, since again W[motor] = int[p dV]. You can improve the compression ratio by taking advantage of the P-T curve and performing the whole compression at the South Pole, which saves you about 100 J/kg.
Also, I was off by a factor of ten when I plugged in the vapor pressure of CO2. Correcting this is left as an exercise to the reader.
Technologies not subject to the work limit include e.g. olivine crushing, somehow inhibiting volcanic activity (???), planting trees, etc. Another technology I just thought of would be to to form CO2@H2O clathrates in seawater starting with air, which would also lower the compression ratio, and extracting the (solid) clathrates to recover CO2 and desalinated water. Here the pressure required is much lower and additionally desalinated water is produced; this only works if we form the clathrates in a cold environment and decompose them in a warm one, which is kind of inconvenient. Then again, shipping gigatons of fresh water to LA might become necessary anyway!
> Though I fear it'll all be in vain when a machine is invented that can suck a lifetime's worth of frugality out of the air in a fraction of a second.
In the same way that a year's worth of health insurance is wasted if you don't get sick. So, not wasted.
The article links to a website where you can calculate your footprint, and buy offsets in various programs to negate that footprint (projectwren.com). It would cost me USD 17 / month to offset my (larger than average for my country) footprint. Why do I even bother with my reusable coffee cup and paper straws for that kind of money? I just don't understand. If an extra charge of $10 / month for everyone in Europe would 'solve' the problem, why don't we do it?
Reducing the use of disposable plastics isn't supposed to prevent climate change, it's about reducing the amount of trash. While any trash that you put in the bin in a western country is highly unlikely to end up in the world's oceans, it still sends a signal against ubiquitous single-use products. That the two are so often treated as one is really unfortunate. Because if people actually cared about reducing their individual carbon emissions, they'd have to give up things like flying and eating meat, not disposable plastics. But that involves actual changes in behaviour, so it's not exactly popular and many people find the mere suggestion offensive.
But they do make you feel like you're doing your part. I wonder how many people are just satisfied with that and whether it wouldn't have made more sense to push other solutions instead.
>If an extra charge of $10 / month for everyone in Europe would 'solve' the problem, why don't we do it?
Considering how much excise taxes Europeans pay on their gasoline, you would think that climate change would already be a solved issue. Taxes are a larger part of the cost of gasoline than the gasoline itself. Yet somehow there isn't enough money to fight climate change?! The Netherlands pays $3.53 per gallon purely in excise taxes.[0] Bulgaria, a country with an average income of $9000 a year[1], pays $1.61 a gallon in excise taxes.
I think at a certain point you need more than offsets. We once had a forested world, with oil in the ground.
We cut forests, and burned oil. Offsets help revert one of these things. But, we’d need to do more than that to reverse the change.
So the offsets you can buy now are low hanging fruit. Actual carbon sucking costs vastly more than wren’s offsets.
Though still achiveble? Would be about $10,000 usd per person at average european emissions. About $20,000 usd per person at average american emisisons. Includes children.
If those costs go down, the costs become realistic. I don’t mean politically realistic, just possible to do.
Fwiw I use both wren and climeworks. And maybe if enough people used wren they might find non-forest offsets that are achievable at low cost. But right now it wouldn’t obviously scale if all did it.
Reusable cups and paper straws aren't for climate change. They're for the quite unreasonable landfill scare. The people who subscribe to that belief have no idea beyond "plastic = bad" and "landfills = bad". Sometimes they try to link it to climate change for added credibilty though.
> The people who subscribe to that belief have no idea beyond "plastic = bad"
So... you're saying that there's not an accumulation of plastic waste / microplastics in the environment, or that we know any impacts or benign or negligible?
Good news if true, would like to know what position there's the most credible evidence for.
> and "landfills = bad".
I'm a fan of consumer goods, so naturally it's convenient for me if landfills == good, but I also tend to wonder (a) exactly how effectively they isolate waste issues from, say, groundwater or other environmental circulation and (b) if there might be some volume threshold past which landfills aren't an adequate solution for addressing waste streams.
Most western countries have proper regulation regarding waste disposal. Plastic pollution is a big is a big issue, but wont be solved while big economies decide to export their waste to places with less strict regulations. This is - in my opinion - the point that needs pressure from conscious citizens.
We are only now starting to measure up the microplastics impact and their origin. Switching to reusable cups is a drop in the ocean, when tons of the stuff is released by simply washing clothes or makeup off your face.
They do. Keep in mind, most of the produced residues arent recyclable or compostable. What gets exported is a small fraction of it. Could legislation be better? That was my point.
