And replaced with what? While coal is dirtier than natural gas the calorific value is far greater so you get a lot more heat and electricity per unit of combustion by-product. If these coal plants were replaced by gas-burners then emissions haven't been eliminated, only reduced. If we really want to ELIMINATE emissions we need to be looking at base-load sources that emit zero carbon such as nuclear.
Based on https://www.eia.gov/energyexplained/us-energy-facts/
So in 2011 we had:
Coal at 19.66 quadrillion BTU
Natural Gas at 24.95 quadrillion BTU
Petroleum at 34.63 quadrillion BTU
Nuclear at 8.27 quadrillion BTU
Renewables at 9.20 quadrillion BTU
In 2019 we had:
Coal at 11.31 quadrillion BTU (-8)
Natural Gas at 32.10 quadrillion BTU (+7)
Petroleum at 36.72 quadrillion BTU (+2)
Nuclear at 8.46 quadrillion BTU (+0.2)
Renewables at 11.45 quadrillion BTU (+2)
Basically we replaced the use of Coal with natural gas, and used Renewables to add on new capacity. Indeed not exactly a rosy picture of lowering our emissions. And what’s not captured here is that we dropped our fuel use drastically during the 2007-2009 financial crisis and only just recovered from that drop. But our Real PCE (Personal Consumption Expenditures) went up 30% in that same time frame. While it’s not a 1-1 correlation or anything, increased consumption without increased electricity use probably means we’ve just off-shored a lot of our usage to less developed countries in the last 13 years anyway.
Natural gas is a net benefit as it releases significantly less carbon per kWh than coal. Coal is almost entirely C + 02 = C02 but with natural gas you also get energy from 4H + 02 = water. Even better it’s far more flexible easily accommodating a renewable heavy grid.
Natural gas is also in vastly shorter supply than coal, naturally forcing a transition away from it fairly soon.
To add to this: if you burn one mol (16g) of CH4 you get one mol of CO2 (44g) and water and 900 KJ of energy. If you burn one mol (12g) of C you get the same mol of CO2 (44g) and only 400 KJ of energy. Overall you get more than twice the same thermal energy for the same amount of emitted CO2. What's more, the most efficient power plant can only convert 42% of the thermal energy into electricity, while the most efficient gas power plant can convert 62%.
In terms of climate change, natural gas is comparable to using coal. The CO2 emissions from a natural gas plant are much lower than a coal plant, but it isn't clear that if you account for methane releases during production/transporting/storage that it is better for climate change than coal.
>...Back in August, a NOAA-led study measured a stunning 6% to 12% methane leakage over one of the country’s largest gas fields — which would gut the climate benefits of switching from coal to gas. We’ve known for a long time that methane is a far more potent greenhouse gas than carbon dioxide (CO2), which is released when any hydrocarbon, like natural gas, is burned. But the IPCC’s latest report, released Monday (big PDF here), reports that methane is 34 times stronger a heat-trapping gas than CO2 over a 100-year time scale, so its global-warming potential (GWP) is 34. That is a nearly 40% increase from the IPCC’s previous estimate of 25. ...The IPCC reports that, over a 20-year time frame, methane has a global warming potential of 86 compared to CO2, up from its previous estimate of 72. Given that we are approaching real, irreversible tipping points in the climate system, climate studies should, at the very least, include analyses that use this 20-year time horizon. Finally, it bears repeating that natural gas from even the best fracked wells is still a climate-destroying fossil fuel. If we are to avoid catastrophic warming, our natural gas consumption has to peak sometime in the next 10 to 15 years, according to studies by both the Center for American Progress and the Union of Concerned Scientists.
As we use more and more natural gas, we can expect more and more methane disasters like the leak from Aliso Canyon in CA which was the largest methane leak in US history. This released over 100,000 tons of methane into the atmosphere and required 11,000 residents to be evacuated.
>...Natural gas is also in vastly shorter supply than coal, naturally forcing a transition away from it fairly soon.
Not really. The U.S. Energy Information Administration estimates in the Annual Energy Outlook 2020 that as of January 1, 2018, there were about 2,828.8 trillion cubic feet (Tcf) of technically recoverable resources (TRR) of dry natural gas in the United States. Assuming the same annual rate of U.S. dry natural gas production in 2018 of about 30.6 Tcf, the United States has enough dry natural gas to last about 92 years.
Methane’s global warming impact is front loaded, it breaks down in the atmosphere so in a steady state future leaks only maintain but don’t increase the amount of methane in the atmosphere. In other words there are significant benefits from eventually moving to something else, but little long term advantage due to methane from doing so sooner.
“technically recoverable resources“ is what’s possible to extract at any price making it a very poor measurement of economically viable reserves. Considering natural gas is already more than twice as expensive as solar power it’s primary benefit is flexibility and the limited amount of solar manufacturing currently available.
Further the absolute worst case from known reserves of 92 years worth of natural gas is the equivalent of less than 28 years worth of coal production at those rates. Which means any coal offset with natural gas is at worst equivalent to zero coal in 2048 and very likely significantly better than that.
PS: 1998 methane levels are 5% lower than current levels because we have significantly increased output over the last 20 years. But looking at the graph it’s nothing like a linear increase.
Methane is 34 times stronger a heat-trapping gas than CO2 over a 100-year time scale. This is the timeframe we need to worry about right now to avoid the worst affects of climate change.
>...“technically recoverable resources“ is what’s possible to extract at any price making it a very poor measurement of economically viable reserves.
Yes, but technology improves and all of sudden they are viable. People knew of those big oil deposits in North Dakota for decades and then with fracking it became feasible to extract it. As I pointed out, even today China is going forward with making synthetic natural gas from coal (which is even worse for climate change than just burning methane.)
>...Considering natural gas is already more than twice as expensive as solar power it’s primary benefit is flexibility and the limited amount of solar manufacturing currently available.
The major weakness of solar is that having 100% capacity at noon in July on a sunny day in Arizona, doesn't help at midnight when you want to run medical equipment.
It is possible grid storage will become feasible in the future to cover the daily and seasonal variations of capacity for wind/solar, but if we end up having the grid rely on natural gas will make it very difficult to avoid the worst problems associated with climate change.
34 = (86/5) + 4x/5 so Average from years 20 to 100 = 21.
You can graph it based on in initial GWP and final GWP. CH4 = 16.04246 g/mol and CO2 = 44.0095 g/mol. So after breaking down it’s 2.75x the global warming potential of CO2 which is almost exactly the GWP from years 60 to 100.
PS: Now sure that’s greater than 1, but compared to the scale of CO2 released vs accidental methane releases it might as well be.
Part of the Hacker News guidelines is to assume good faith.
As the IPCC says:
>..There is no scientific argument for selecting 100 years compared with other choices (Fuglestvedt et al., 2003; Shine, 2009). The choice of time horizon is a value judgement since it depends on the relative weight assigned to effects at different times.
I chose 100 years since you seemed to imply that since methane was "front loaded" then "...there are significant benefits from eventually moving to something else, but little long term advantage due to methane from doing so sooner."
Trying to ignore the problems of methane in the atmosphere is not helpful. As the Think Progress article says
>...The IPCC reports that, over a 20-year time frame, methane has a global warming potential of 86 compared to CO2, up from its previous estimate of 72. Given that we are approaching real, irreversible tipping points in the climate system, climate studies should, at the very least, include analyses that use this 20-year time horizon.
>...If we are to avoid catastrophic warming, our natural gas consumption has to peak sometime in the next 10 to 15 years, according to studies by both the Center for American Progress and the Union of Concerned Scientists.
I chose 100 years since you seemed to imply that since methane was "front loaded" then "...there are significant benefits from eventually moving to something else, but little long term advantage due to methane from doing so sooner.
Ahh, ok I genuinely assumed you understood what that number meant and chose to use it incorrectly.
As to 86 for 20 years still being important. These methane leaks from natural gas are nowhere near 1/86th of global CO2 production. They are not even 1/86th of the displaced CO2 from reduced coal use age.
Compare ~10 megatonnes of methane leaks worldwide from all sources of natural gas with global Fossil CO2 emissions at ~37,000 megatons per year and 740,000 over 20. Except your natural gas emissions don’t stack linearly for 20 years with past emissions. So natural gas power plants are easily a net reduction in global warming over your 20 year timetable.
>...Compare ~10 megatonnes of methane leaks worldwide
It isn't clear we fully understand the extent of methane leaks in the US and probably have less info on many other countries.
This is illustrated in the Aliso Canyon leak:
>..The authors believe there are important lessons to be learned from the leak - particularly the need to monitor oil and gas facilities more carefully.
They say that there has been little co-ordinated oversight of the biggest oil and gas leaks in recent years. They point to Aliso Canyon, the BP spill and the Total Elgin rig blowout in the North Sea as examples where luck more than intent ensured the impacts on the environment were monitored.
In the case of Aliso Canyon, the surveying aircraft was working on another project searching for pipeline problems, when the scientists were asked to overfly the leaking well.
"The state's response to Aliso Canyon was teed off by the first measurement we took, at that point no-one had any clue that this was 50,000kg per hour of gas," said Dr Conley.
This report discusses the overall level of uncertainty in this area:
>...However, given limited current evidence, it is likely that leakage at individual natural gas well sites is high enough, when combined with leakage from downstream operations, to make the total leakage exceed the 3.2% threshold beyond which gas becomes worse for the climate than coal for at least some period of time.
Using coal for fuel is almost a crime against humanity considering the health costs, so switching to natural gas is harm reduction. The amount of reduction in GHG production though is more uncertain due to lack of investments in monitoring and reducing methane leakages.
That’s from 2012, we currently have vastly better satellite monitoring of leaks. This provided dual benefits of better measurement and reduction in the number of active leaks thus reducing emissions.
I hate to say it but based on this source it looks like global power sourced from coal power has gone UP every year since 2011. I found this source on google and am know nothing about its political agenda, however the slider it provides to see total coal power by year seemed very handy.
Historically it was common to make a useful "town gas" which could be used to make heat and light in homes or factories. Often "coal gas" was the town gas used, you make it by processing coal, so, unsurprisingly, the carbon emissions are worse than coal. When it was discovered that the planet has a whole bunch of natural methane we could harvest that's a natural gas you can use instead. It's cheaper, it burns cleaner, once you discover it there's nothing not to like...
Coal gas is also poisonous and its density means it's inclined to lay in a room, so when e.g. Britons mostly cooked with coal gas ovens that's where you get the phrase "Put your head in the oven". The idea isn't that you could somehow suicide by cooking yourself, but instead that the poisonous gas will kill you.
These days if you have a gas oven (they're rarer) and try this it won't work, the gas isn't poisonous and will escape from most spaces - although you might if you're unlucky manage to collect the right amount of methane somewhere to cause an explosion.
The reduction in suicide from upgrading from town gas to natural gas is a success story and a model for other interventions. It showed very clearly that "displacement" isn't a big deal. People didn't go "Huh, my oven didn't kill me. Oh well I'll jump off a building". Thus, other interventions can be expected to be effective, such as anti-suicide fencing on bridges or platform screen doors at railway stations.
My house was built in 1914, which is fairly old for Portland. It's been heated by 5 different technologies:
1) Manufactured Gas, which I assume is the same as coal gas. The pipe for this is about 3 times as large as natual gas.
2) Wood chips (still a spot in the concrete floor where the "octopus" furnace (called because of the vents coming off
it) sat. This was a byproduct of the timber industry.
3) Oil. The underground tank in the side yard was filled in.
4) Natural gas
5) Air heat pump powered by electricity (partially fed by solar panels)
I'm not sure of the exact order but I think that's basically correct, as the development of trucks meant it was possible to drop off a big bunch of wood chips or later a tankful of oil.
I've read that some towns are not allowing new natural gas connections because of pollution issues. With the explosion yesterday in Maryland and our problems keeping up infrastructure, it seems like a reasonable approach to me.
> I've read that some towns are not allowing new natural gas connections because of pollution issues. With the explosion yesterday in Maryland and our problems keeping up infrastructure, it seems like a reasonable approach to me.
Yes. In Britain there was a three way choice offered to central government towards the end of last century. They could discontinue household natural gas service (perhaps gradually over time) and shut the delivery network of pipes under roads across much of the country OR they could replace the entire network of cast iron pipes which are gradually failing so as to prevent explosions OR they could accept that gradually gas explosions would become more and more common as the pipes fail.
The last mile gas delivery is notionally in the hands of private company National Grid, because Tory ideology holds that this is better, but of course the private company exists only to collect profits, government must pay for all the inevitable costs of delivering the service, and thus had to make this decision. In the event they picked replacing all the pipelines, section by section ever since the cast iron gas pipes are being dug out of roads and replaced with plastic pipes expected to last many more decades.
Given that burning gas helps force climate change we don't want, in hindsight probably switching off the network would have been a wiser choice. The plastic pipes may last until say, 2100 but burning natural gas to heat UK homes in even 2050 will be very obviously stupid.
It's called natural gas because it's naturally occurring. The term was used long before humans understood the effects fossil fuels had on the environment.
Combustion of natural gas produces essentially only CO2 and H2O. Combustion of coal produces these, along with many other harsh molecules. Compared to coal-powered plants, they are a good thing.
More specifically, Brayton cycle with a Rankine bottoming cycle (combined cycle). Open cycle gas turbines are about as efficient as supercritical steam plants (but are much cheaper to build).
I don't think natural gas is actually a carbon-neutral alternative to coal, my understanding is that methane leakage makes it almost as bad as coal in the long term.
True, but it doesn't have the incredibly horrific non-carbon pollution problems of coal. The things almost every coal plant in the world does to nearby rivers would nauseate most people. Fly ash produced by coal plants releases one hundred times the radiation into the environment as a nuclear plant of the same capacity.
"A lot" is relative. From what I can tell, coal ash contains about the same amount of uranium and thorium as granite and slightly more than ordinary soil. (Of course, it's less concentrated in the coal itself, which is largely carbon and hydrocarbons that gets burnt off.) The main reason coal power releases so much radiation compared to nuclear because there's a lot of coal burnt and normal operation of nuclear power plants also releases very little.
What's more scary is the production of things like rare earth minerals - that quite heavily concentrates the uranium and thorium as part of the extraction process, producing large quantities of relatively radioactive mining waste.
Natural gas is way cleaner than coal overall. It does not release particles that kill people over the long term either. It's a pretty clear cut between the two.
Coal leaks methane too. A while ago there were people here pointing that even more than natural gas; I'm not convinced, but both are on the same ballpark.
Anyway, methane is a short term problem. It's CO2 that is long term.
It isn't neutral at all, it's merely less-intensive.
Leakage is a problem with straightforward extant solutions, but well operators are poorly incentivized to implement those solutions—the loss is often too small to substantially impact their profit, and the leak is invisible (natural gas being colorless) so it's easy to turn a blind eye and not implement effective monitoring.
I'm not sure how we would implement any more effective monitoring of natural gas leakage. We have gas detectors all over the facility and personnel walk around with gas detectors on their coveralls. Flowmeters are generally not accurate to <1%.
I would expect the only credible thing we can do is design it out, e.g. by running seal vents to flare rather than safe location, improving reliability, flareless operation etc.
I imagine the majority of "leakage" must be unburnt hydrocarbon in flare and GT exhausts.
But when you say "straightforward extant solutions" what are you referring to? In the industry, nobody particularly assesses "leakage" or really designs for minimising leakage per se.
> In the industry, nobody particularly assesses "leakage" or really designs for minimising leakage per se.
An interesting perspective.
You sound as if you have relevant first-hand experience. From your knowledge, what is the state of aerial/satellite detection? Those are the solutions that I've seen cross my news feeds in recent years.
I work for an operating company rather than a design contractor, and I'm involved in topsides. I can't quite imagine what benefit aerial/satellite detection would have. Before we start up a process system, the last stage of commissioning is to pressurise with a nitrogen-helium mix and get a contractor to go round with a very sensitive helium detector to catch any tiny leaks.
To put it in perspective, we have another low-tech approach where you put tape around a potential leak point, spray a soapy mixture, then count the bubbles. The pass/fail criterion is measured in bubbles per minute. Yet inside the pipe you measure the flowrate in tens or hundreds of tonnes of gas per hour.
Possibly unburnt hydrocarbon in the flare could contribute to this "leakage" but flares are designed for complete combustion so I can't imagine it would make any difference in terms of GHG emissions compared to the already-considerable CO2.
We already have plenty of fixed gas detectors and personal gas monitors around site that are sensitive to about 0.04% methane (I think) so I can't really picture a satellite doing anything better.
I'd like to interrogate those ideas, if you don't mind? I'm truly curious here. Somewhat skeptical from the impression my reading has given me, but I don't mean to be hostile.
The initial testing is all very well, and I have no reason to expect it's at all ineffective, but I imagine it would be more interesting to look at the consequences of wear/weathering over time.
I suppose my biggest question is the mechanism by which those (fixed and personal) detectors work. I know that the aerial solutions work via lidar, and I expect satellite similarly looks for absorption in particular wavelengths.
Also, as you can probably tell from my comment already, I know very little about satellite surveillance for methane leakage, only that it is not common practice for operating companies.
I recently saw an intriguing software engineer job posting for a company in Montreal & Ottawa that deploys satellites for testing/surveying for methane leakage. I was tempted.
It could be mandated that all facility pressures be below atmospheric pressure. Then all leaks would lead to air getting into the pipes rather than gas getting out.
Clearly with that being the case, one needs much bigger more expensive pipes.
That would easily solve the problem, by making any gas processing facilities completely uneconomic to operate ;)
I am quite interested in the idea of methane leakage though. There seems to be a growing consensus online that it exists and is significant, but within industry it is really not recognised.
that graph is the simplest possible way to think about "dealing with climate change". Its a checklist: #1 coal. #2 oil. #3 gas.
Gas has been a "transitional" fuel in the sense that its made the last decade less bad than it would have been, but given the timeline left* its already too late to build new gas infrastructure, assuming you intend to finance it with 30 year bonds.
* per the ipcc in order to stay under 2C emissions need to hit zero somewhere between 2040 for rich/western countries and 2055 for the whole planet, and then be followed by negative emissions for the rest of the century
With the current cost of solar and wind, coal->natural gas conversions aren't a slam dunk for utilities or investor owned generators.
> Coal power plants in the US have been retiring at an average clip of 10 gigawatts per year as the clean energy transition takes hold. That may sound impressive, but it’s not nearly quick enough, considering that climate change is already buffeting the Earth. The pace has to pick up quickly in order to avoid more catastrophe. That’s where a new thing called solar-for-coal swaps comes in. The “swap” part is a bit complicated, but if the idea catches hold it could speed up coal power plant retirements and skim more than 20 gigawatts right off the top.
> In a new white paper, the clean energy group Energy Innovation has identified some low hanging coal fruit, in the form of 179 gigawatts that can’t compete on cost with solar any more. These coal units are still operating for various reasons even though solar saves money, but Energy Innovation has picked out a group of 22.5 gigawatts that could be rolled over in short order.
From the article, only 49 of 316 GW (16%) of coal capacity was replaced in eight years.
This is Detroit and fuel efficiency all over again. Look how good we are doing dragging our feet! (Even though the results allow a lot of cool things).
Natural gas conversion mostly reduces particulates. The EIA data says natural gas produces more CO2/MkWh than coal:
Electricity generation CO2 emissions
million kWh million metric tons million short tons pounds per kWh
Coal 1,124,638 1,127 1,240 2.21
Natural gas 1,246,847 523 575 0.92
Petroleum 21,860 21 23 2.11
Ironically, particulates decrease insolation and actually slightly reduce warming (CO2's half life is a lot longer than particulates, so the "cooling" is short-lived and will go away when you stop burning coal, net warming, overall). Natural gas doesn't produce as many particulates, so I would expect that converting to natural gas would increase global warming in the short and long term compared to continue to burn coal.
It's far better to switch to solar/wind/geo/nuclear than natural gas in the long run, but there are health benefits to removing the coal particulates:
"Coal impacts: air pollution
When coal is burned it releases a number of airborne toxins and pollutants. They include mercury, lead, sulfur dioxide, nitrogen oxides, particulates, and various other heavy metals. Health impacts can range from asthma and breathing difficulties, to brain damage, heart problems, cancer, neurological disorders, and premature death." https://www.ucsusa.org/resources/coal-power-impacts#:~:text=....
I presume that the primary driver of this conversion isn't the environment, but economics. The price of coal/kWh is more expensive than the volume of gas required to generate the same kWh. The Total system LCOE is usually the number people want to minimize.
https://www.eia.gov/outlooks/aeo/pdf/electricity_generation....
tl;dr: No. Burning gas is worse from a climate perspective.
You are correct, parent commenter misunderstood the table they are referring to.
That table says there's slightly more kWh generated from natural gas (1,246,847) than from coal (1,124,638). I assumed they read this wrongly and thought this was CO2 emissions per kWh.
The best number to read from that table is the last column, "CO2 emissions - pounds per kWh":
Natural Gas: 0.92
Coal: 2.21
So yeah, natural gas's CO2 emissions are much lower.
https://www.electricitymap.org/map illustrates this for the world, it offers estimates for types of electricity generation in each country and where a country or region offers real-ish time data on power generation it reflects that.
Countries/ regions that show dark brown are mostly relying heavily on coal. Getting on for 1 gram per watt-hour of CO2, which is ludicrous.
In a few cases they've managed to find something even less environmentally responsible to burn than coal, such as oil or the most pants-on-head crazy electrical generation method - peat†, which unless somebody starts a national project of shooting endangered animals and then burning the corpses as fuel ought to stand as the least responsible way to make power.
† In theory burning wood could be sustainable because you really could grow enough wood quickly enough to power a not insubstantial electricity plant forever. You probably shouldn't but you could. Peat does not form quickly enough for that to ever be practical.
It's definitely economics; and that's before you factor in carbon cost and looming potential for expensive law suits because of people filing for damages (think tobacco industry). Any remaining coal plants will be under a lot of scrutiny in a few years.
Gas plants are much better from that point of view but still too expensive. Renewables are really killing it on the cost front and with viable energy storage solutions coming online even a role as peaker plants is not going to be a long term thing for gas plants.
Economics are also the reason nuclear is not happening. It's just too expensive and risky for operators to get involved in. When prices below 0.02$/kwh are becoming normal for new solar bids, that kind of puts the squeeze on everything else. Even gas. And there is no sign of this being a final price, this will likely dip well below 0.01$ at some point.
The only reason for investments like this is short term gains while production capacity for clean energy simply can't cover the whole market just yet. So converting coal plants makes sense to replace expensive capacity with slightly less expensive capacity while enough cheap capacity to replace it is short term just not there yet.
>It's far better to switch to solar/wind/geo/nuclear than natural gas in the long run...
Solar and wind require gas plants as balance when the sun is not shining and the wind is not blowing. All other "infinite" energy sources such as coal or nuclear don't have enough dispatchability to perform solar/wind load following. Hydroelectric has a high dispatchability but is not infinite (the lake level gets too low and you have to wait for the next rain).
source: https://www.eia.gov/todayinenergy/detail.php?id=40212