00:00:20.830 okay so we will we were talking about 00:00:25.24000:00:25.250 last time about about fossil fuels and 00:00:29.13000:00:29.140 we talked about coal and we started 00:00:32.65000:00:32.660 talking about oil but there's some more 00:00:35.50000:00:35.510 stuff about oil I want to show you and 00:00:37.32900:00:37.339 then I want to tell you a little bit 00:00:38.71000:00:38.720 about natural gas and then we'll sort of 00:00:42.70000:00:42.710 try you know across the boundary in this 00:00:45.10000:00:45.110 lecture into chapter 10 I think it is 00:00:47.59000:00:47.600 when we start talking about the climate 00:00:50.97900:00:50.989 impact of methane because natural gas is 00:00:52.66000:00:52.670 methane so it's kind of a natural segue 00:00:55.11900:00:55.129 there so oil a big question that always 00:01:08.41000:01:08.420 comes up about oil if you read about it 00:01:10.81000:01:10.820 in the newspapers or whatever is how 00:01:12.60900:01:12.619 long is it going to last and there's one 00:01:24.82000:01:24.830 way to sort of calculate how much how 00:01:26.88900:01:26.899 long it will last that sort of takes 00:01:29.23000:01:29.240 advantage of our newfound prowess at 00:01:33.76000:01:33.770 thinking about units at putting together 00:01:36.37000:01:36.380 a formula to calculate what we want just 00:01:39.10000:01:39.110 by letting the unit's sort of guide us 00:01:41.29000:01:41.300 and it looks like this the lifetime of 00:01:47.22900:01:47.239 the oil era is equal to reserves so how 00:01:55.83900:01:55.849 much oil there is in the ground and the 00:01:57.94000:01:57.950 units of that would be a Giga tons we 00:02:02.02000:02:02.030 could call it or you know kilograms or 00:02:05.91900:02:05.929 barrels or however you know whatever 00:02:07.69000:02:07.700 sort of unit you want and so the 00:02:11.65000:02:11.660 lifetime is we want something in years 00:02:14.49000:02:14.500 so reserves and then to convert Giga 00:02:21.67000:02:21.680 tons per year 00:02:22.72000:02:22.730 we'll use the production rate how fast 00:02:27.36900:02:27.379 we're consuming it and the production 00:02:30.22000:02:30.230 rate is in say Giga tons per 00:02:33.09000:02:33.100 year so in order to cancel out this 00:02:34.92000:02:34.930 gigatonnes on the top we need gigatonnes 00:02:36.84000:02:36.850 on the bottom so we will assemble our 00:02:45.18000:02:45.190 our formula this way one over production 00:02:48.12000:02:48.130 so now the units of this will be years 00:02:53.42000:02:53.430 on top and gigatonnes on the bottom 00:02:56.34000:02:56.350 instead of Giga tons per year one over 00:02:58.32000:02:58.330 it is years per Giga ton and so Giga 00:03:00.45000:03:00.460 tons cancel out and we got years on on 00:03:02.43000:03:02.440 both sides this is what they call a in 00:03:07.28000:03:07.290 the sort of petroleum industry the heart 00:03:12.30000:03:12.310 2p ratio there's a figure in the 00:03:20.91000:03:20.920 textbook which I would have liked to 00:03:23.25000:03:23.260 have shown you today except I just 00:03:24.95000:03:24.960 stymied by this work of this cable have 00:03:27.60000:03:27.610 possibly gone it doesn't make sense but 00:03:31.68000:03:31.690 it should just vanish but it's I can't 00:03:33.42000:03:33.430 find it there's a plot of this R to P 00:03:40.89000:03:40.900 ratio as calculated by British Petroleum 00:03:46.07000:03:46.080 BP publishes these reports online every 00:03:49.20000:03:49.210 year this is these energy fact books 00:03:53.22000:03:53.230 that have lots of tables of numbers like 00:03:55.95000:03:55.960 how much oil there is in the ground and 00:03:57.45000:03:57.460 stuff and they've been calculating this 00:03:59.22000:03:59.230 r2p ratio over time so sort of from 50 00:04:05.73000:04:05.740 years ago what they find is that the r2p 00:04:12.57000:04:12.580 ratio has been sort of steady throughout 00:04:17.78900:04:17.799 the years at about 40 years so it's 00:04:22.08000:04:22.090 saying that in 6 1960 or 1980 or 00:04:24.63000:04:24.640 something like that there was 40 years 00:04:26.37000:04:26.380 left and it's saying there's 40 years 00:04:28.92000:04:28.930 left today so that must mean that 00:04:31.05000:04:31.060 they're finding more you know to kind of 00:04:33.42000:04:33.430 keep up with how much they're taking out 00:04:35.16000:04:35.170 of the ground so that makes it sound 00:04:37.26000:04:37.270 like you know 40 years that's a long 00:04:38.97000:04:38.980 time kind of right I mean on a sort of 00:04:41.96900:04:41.979 political timescale that's a long that's 00:04:44.04000:04:44.050 a long time it's not something that's 00:04:45.51000:04:45.520 going to affect 00:04:46.32000:04:46.330 right away but there's another way to 00:04:49.32000:04:49.330 look at this which is called peak oil 00:05:06.71000:05:06.720 which is a also called Hubbert's peak 00:05:17.30900:05:17.319 after a geological survey petroleum 00:05:21.42000:05:21.430 geologist named Hubbard who originally 00:05:23.52000:05:23.530 came up with this idea he found that if 00:05:27.62900:05:27.639 you look at the production rate as a 00:05:35.79000:05:35.800 function of time for some oil field so 00:05:41.96900:05:41.979 he first did this for some Texas to some 00:05:44.61000:05:44.620 field in Texas and then and then applied 00:05:47.52000:05:47.530 it to the continental US as a whole and 00:05:51.89900:05:51.909 it worked both times that the production 00:05:56.51900:05:56.529 rate how much oil you get out of the 00:05:59.04000:05:59.050 ground per time goes as kind of a bell 00:06:01.68000:06:01.690 curve so there's an initial part where 00:06:05.51900:06:05.529 it kind of looks like exponential growth 00:06:14.83900:06:14.849 but it doesn't keep growing 00:06:17.39900:06:17.409 exponentially so the exponential growth 00:06:19.17000:06:19.180 part maybe is about you know building 00:06:23.45900:06:23.469 the infrastructure you know learning how 00:06:25.35000:06:25.360 to do it learning where the oil is it 00:06:27.30000:06:27.310 sort of tends to take off like that but 00:06:29.51900:06:29.529 then it sort of label levels out and 00:06:32.24900:06:32.259 plateaus at the top of a bell curve and 00:06:34.80000:06:34.810 then follows the curve back down again 00:06:38.39900:06:38.409 so where the where this really got 00:06:40.92000:06:40.930 famous was there were data from 00:06:46.35900:06:46.369 the continental US that sort of looked 00:06:51.46900:06:51.479 like it was still kind of in the 00:06:52.96900:06:52.979 exponential growth phase and it looked 00:06:55.27900:06:55.289 like you know the sky's the limit where 00:06:56.83900:06:56.849 we're golden forever at the time but he 00:06:59.49900:06:59.509 estimated how much oil is going to be in 00:07:03.13900:07:03.149 the earth in the continental US overall 00:07:07.85000:07:07.860 and then he fit a curve this bell curve 00:07:11.29900:07:11.309 so that it fit the data that already had 00:07:14.08900:07:14.099 you know happened the past and the total 00:07:17.77900:07:17.789 area under the curve is the total amount 00:07:25.33900:07:25.349 of oil so this is this is like barrels 00:07:32.38900:07:32.399 per year is the production rate sort of 00:07:35.20900:07:35.219 unit or you know could be Giga tons per 00:07:37.54900:07:37.559 year or whatever and then you know so 00:07:40.90900:07:40.919 this many barrels per year times this 00:07:43.57900:07:43.589 many years gives you just barrels and so 00:07:45.82900:07:45.839 the total inventory sort of constrains 00:07:49.10000:07:49.110 the total size of the curve the total 00:07:51.25900:07:51.269 inventory was was was twice as big you 00:07:53.83900:07:53.849 might have a curve that sort of looks 00:07:55.39900:07:55.409 like that or if it was half as big you 00:07:56.98900:07:56.999 might have to fit a smaller curve to the 00:08:01.04000:08:01.050 data but so in at about this part of the 00:08:06.04900:08:06.059 curve in I forget what year it was but 00:08:08.95900:08:08.969 but had a fairly sort of early part of 00:08:12.11000:08:12.120 the curve he said that the u.s. is going 00:08:14.83900:08:14.849 to reach the peak just a few years later 00:08:20.42000:08:20.430 and it seemed like a ridiculous 00:08:23.01900:08:23.029 prediction you know it's like those 00:08:24.85900:08:24.869 people that predict that you know the 00:08:26.57000:08:26.580 universe is going to the economy is 00:08:28.75900:08:28.769 going to collapse when you know such and 00:08:30.58900:08:30.599 such happens he's kind of like one of 00:08:32.44900:08:32.459 these sort of Looney theories but it 00:08:34.57900:08:34.589 turned out that he was exactly right and 00:08:37.10000:08:37.110 the real the real peak for the 00:08:40.93900:08:40.949 continental US came right when he 00:08:42.49900:08:42.509 predicted it would so you're going to be 00:08:46.91000:08:46.920 playing with a model one of the three 00:08:49.99900:08:50.009 for next week that's that's new to you 00:08:51.93900:08:51.949 that lets you kind of do this kind of 00:08:54.55900:08:54.569 curve fitting and and and see what the 00:08:57.47000:08:57.480 implication is for when 00:08:59.42000:08:59.430 peak oil will happen for the whole world 00:09:03.44000:09:03.450 so you'll put in you'll have data and 00:09:06.47000:09:06.480 and you'll get to fit a curve to the 00:09:08.69000:09:08.700 data and you have some estimate of the 00:09:10.85000:09:10.860 total amount of petroleum in the world 00:09:12.59000:09:12.600 and and then from that it'll give you 00:09:14.99000:09:15.000 when when the peak should come and then 00:09:17.72000:09:17.730 you can try to figure out how much kind 00:09:19.19000:09:19.200 of wiggle room there is in that now one 00:09:22.75000:09:22.760 fairly fundamental objection to 00:09:26.66000:09:26.670 Hubbert's peak is that it's not a 00:09:29.38000:09:29.390 theoretical sort of a thing it's not 00:09:32.03000:09:32.040 like blackbody radiation from quantum 00:09:35.09000:09:35.100 mechanics you can you can calculate 00:09:36.76900:09:36.779 exactly that curve and it's you know it 00:09:40.16000:09:40.170 you can trace it back to the fundamental 00:09:42.14000:09:42.150 you know physics of a blackbody and 00:09:45.95000:09:45.960 quantum mechanics and all that so that's 00:09:47.45000:09:47.460 real solid that's that's like you know 00:09:49.82000:09:49.830 the the gold standard in science is to 00:09:52.91000:09:52.920 go all the way back to the fundamental 00:09:54.56000:09:54.570 mechanisms but here the rate of oil 00:09:57.44000:09:57.450 extraction depends on all kinds of 00:10:01.10000:10:01.110 things like you know a extraction in 00:10:04.43000:10:04.440 iraq sort of plummeted when the war 00:10:06.35000:10:06.360 started extraction in venezuela depends 00:10:10.46000:10:10.470 on you know how chavez is feeling 00:10:12.73000:10:12.740 there's all kinds of sort of social and 00:10:15.47000:10:15.480 political things that go into it and so 00:10:17.84000:10:17.850 this curve is not a theoretically you 00:10:20.75000:10:20.760 know solid thing it's what they call 00:10:22.67000:10:22.680 empirical or sort of observed or just 00:10:28.31000:10:28.320 kind of the way things you know tend to 00:10:30.89000:10:30.900 be so it's perfectly possible that the 00:10:34.40000:10:34.410 the rate of extraction for the whole 00:10:36.56000:10:36.570 world oil may not follow this curve 00:10:39.14000:10:39.150 exactly Hubbert's peak can be wrong it's 00:10:41.57000:10:41.580 just kind of a way to guess or a way to 00:10:44.96000:10:44.970 bet if you had to make a bet on walk on 00:10:48.38000:10:48.390 it what it says is that well there's two 00:10:52.49000:10:52.500 sort of salient conclusions one is that 00:10:57.94000:10:57.950 the peak comes 00:11:02.90000:11:02.910 when when when the oil is half gone so 00:11:12.03000:11:12.040 this this r2p ratio that's essentially 00:11:16.17000:11:16.180 trying to estimate when the last drop of 00:11:21.24000:11:21.250 oil comes out of the ground and says 00:11:23.61000:11:23.620 forty years from now barring finding any 00:11:25.95000:11:25.960 more oil or changing the rate of 00:11:27.48000:11:27.490 extraction or whatever just keeping 00:11:28.92000:11:28.930 everything sort of as it is this is kind 00:11:32.55000:11:32.560 of a different thing the the peak 00:11:34.50000:11:34.510 extraction and shortage comes when the 00:11:37.62000:11:37.630 growth in demand demand is continuing to 00:11:45.09000:11:45.100 grow sort of exponentially and the if 00:11:49.38000:11:49.390 the bell curve sort of flattens out and 00:11:51.03000:11:51.040 lays ecla and lays over like that then 00:11:53.67000:11:53.680 the shortage is actually kind of around 00:11:57.87000:11:57.880 the time of the peak the time when the 00:12:01.65000:12:01.660 rates of extraction can't get any higher 00:12:03.84000:12:03.850 when they were sort of pumping it out as 00:12:05.55000:12:05.560 high as much as you can so if you talk 00:12:07.65000:12:07.660 to all company executives or somebody 00:12:09.57000:12:09.580 like that analysts Daniel Yergin the guy 00:12:11.82000:12:11.830 who wrote the prize is not a believer in 00:12:14.16000:12:14.170 peak oil theory he will say well the 00:12:16.38000:12:16.390 rate of extraction of oil today is 00:12:18.27000:12:18.280 entirely because you know they didn't 00:12:19.86000:12:19.870 invest in infrastructure the refineries 00:12:22.08000:12:22.090 and we could easily you know bring out 00:12:23.58000:12:23.590 more oil if we wanted to so he 00:12:25.53000:12:25.540 personally doesn't buy the empirical 00:12:27.78000:12:27.790 Hubbert's peak model but still it's a 00:12:29.94000:12:29.950 very interesting thing to watch what you 00:12:31.86000:12:31.870 find when you start to get to the peak 00:12:34.89000:12:34.900 and start to get shortages is that 00:12:36.63000:12:36.640 prices tend to get they go up for one 00:12:38.94000:12:38.950 thing because of supply and demand but 00:12:40.71000:12:40.720 they also get spiked year so you know 00:12:44.64000:12:44.650 the spikes in oil prices last year may 00:12:47.79000:12:47.800 have been kind of a harbinger of peak 00:12:50.88000:12:50.890 oil and if I could get my computer 00:12:53.82000:12:53.830 plugged in I would show you that uh the 00:12:58.01000:12:58.020 there was a there's a nifty figure of 00:13:01.41000:13:01.420 peak oil for a whale oil that I found on 00:13:04.92000:13:04.930 the internet and put in the textbook so 00:13:06.75000:13:06.760 the rate of extracting oil from whales 00:13:11.07000:13:11.080 which they used for lighting before they 00:13:14.22000:13:14.230 started using like me loyal 00:13:16.41000:13:16.420 as this amazing cupboard speak sort of a 00:13:18.90000:13:18.910 shape to it also so that's kind of the 00:13:29.61000:13:29.620 story of oil as far as as far as it goes 00:13:38.96000:13:38.970 and then the third kind of fossil fuel 00:13:43.17000:13:43.180 is natural gas which is mostly methane 00:14:00.43900:14:00.449 so the amount of natural gas in 00:14:08.57900:14:08.589 traditional sort of deposits we already 00:14:10.50000:14:10.510 talked about it's sort of a few hundred 00:14:15.76900:14:15.779 billion metric metric tons or Giga tons 00:14:18.50900:14:18.519 so it's comparable to oil and and less 00:14:21.30000:14:21.310 than coal by something like a factor of 00:14:22.98000:14:22.990 50 so coal is the heavy hitter oil and 00:14:27.38900:14:27.399 natural gas by themselves wouldn't be 00:14:30.24000:14:30.250 enough carbon to just totally cook the 00:14:32.00900:14:32.019 planet really the big question you know 00:14:33.90000:14:33.910 I can't stress enough is is coal natural 00:14:38.73000:14:38.740 gas is kind of funny in a you know the 00:14:42.87000:14:42.880 the energy infrastructure in that it's 00:14:45.72000:14:45.730 difficult to transport because it's a 00:14:56.51900:14:56.529 gas so you can either have compressed 00:15:01.86000:15:01.870 natural gas 00:15:08.14000:15:08.150 in a like in a cylinder like a scuba 00:15:11.14000:15:11.150 tank and you know it's very high 00:15:13.87000:15:13.880 pressure in their 3000 psi or something 00:15:16.39000:15:16.400 like that pounds per square inch if you 00:15:18.10000:15:18.110 were to you know break it it would 00:15:19.84000:15:19.850 explode it's it takes a very heavy you 00:15:22.54000:15:22.550 know walls to hold in that much pressure 00:15:24.78000:15:24.790 or there's also liquid natural gas where 00:15:32.56000:15:32.570 they cool it down enough to make it into 00:15:34.84000:15:34.850 a liquid and you and then you you still 00:15:37.00000:15:37.010 have to sort of hold it under pressure 00:15:38.32000:15:38.330 and you don't want heat to getting there 00:15:40.24000:15:40.250 because you know at room temperature it 00:15:42.34000:15:42.350 doesn't want to be a liquid it wants to 00:15:43.72000:15:43.730 be a gas and so there's these are sort 00:15:46.06000:15:46.070 of the two ways of transporting natural 00:15:49.24000:15:49.250 gas around and they're both expensive so 00:15:52.03000:15:52.040 the price of natural gas depends very 00:15:56.95000:15:56.960 strongly on on where you are on earth 00:16:02.82900:16:02.839 and there are some places where natural 00:16:07.69000:16:07.700 gas is worth noting because the markets 00:16:11.26000:16:11.270 are so far away where you can sell it 00:16:13.24000:16:13.250 but to transport it from where it comes 00:16:15.55000:16:15.560 out of the earth like Siberia is a good 00:16:17.59000:16:17.600 example of this and so a lot of times if 00:16:20.07900:16:20.089 there's you know natural gas that is 00:16:22.60000:16:22.610 associated with with oil and it's not 00:16:26.92000:16:26.930 economical to capture and transport and 00:16:29.47000:16:29.480 then sell the natural gas they just burn 00:16:31.66000:16:31.670 it in place it's called flaring so price 00:16:39.93000:16:39.940 depends on location price I guess value 00:16:45.96000:16:45.970 and some places not really worth 00:16:58.21000:16:58.220 anything 00:16:58.75000:16:58.760 and so it's flared which is a burned to 00:17:06.97000:17:06.980 co2 and then just release to the 00:17:08.62000:17:08.630 atmosphere as co2 so there's one last 00:17:18.75000:17:18.760 sort of point of comparison among the 00:17:21.93900:17:21.949 three different kinds of fossil fuel 00:17:23.47000:17:23.480 that I want to make and then we're going 00:17:25.66000:17:25.670 to talk about methane in the atmosphere 00:17:28.69000:17:28.700 as a greenhouse gas and that has to do 00:17:36.37000:17:36.380 with this sort of spectrum of oxidation 00:17:41.08000:17:41.090 states of carbon so co2 is oxidized the 00:17:50.71000:17:50.720 most oxidized form of carbon and in an 00:17:53.05000:17:53.060 oxygenated atmosphere like ours it's the 00:17:55.63000:17:55.640 stable form of carbon ch4 methane is the 00:18:03.79000:18:03.800 most reduced form of carbon so if you 00:18:11.44000:18:11.450 bond that carbon with all hydrogen's 00:18:13.18000:18:13.190 that's as you know that's that's giving 00:18:15.94000:18:15.950 it as many electrons as it can possibly 00:18:18.18000:18:18.190 take it's got four in its outer shell 00:18:21.27000:18:21.280 hydrogen's give it you know one more 00:18:24.19000:18:24.200 each four of them total so then it's got 00:18:26.68000:18:26.690 eight in its outer shell it doesn't want 00:18:28.18000:18:28.190 any more than that so you can't possibly 00:18:29.59000:18:29.600 make it any more reduce than that so 00:18:31.51000:18:31.520 this is sort of the spectrum and then in 00:18:34.09000:18:34.100 the middle of the spectrum we had 00:18:36.06000:18:36.070 biomass what gets produced by 00:18:43.56000:18:43.570 photosynthesis 00:18:44.90900:18:44.919 which is kind of at an intermediate 00:18:48.19000:18:48.200 oxidation state so let's see a minus two 00:18:52.00000:18:52.010 for each oxygen the carbon here has to 00:18:53.95000:18:53.960 be plus four here the carbon 00:18:58.54900:18:58.559 - for here the carbon is equal to zero 00:19:02.22000:19:02.230 the oxidation state of the carbon 00:19:05.24000:19:05.250 because you know it's losing two 00:19:08.76000:19:08.770 electrons to the oxygen but it's getting 00:19:11.07000:19:11.080 getting one each from the two two 00:19:12.75000:19:12.760 hydrogen's now 00:19:14.51900:19:14.529 coal is is mostly just elemental carbon 00:19:18.29900:19:18.309 so we just sort of write that as see a 00:19:21.12000:19:21.130 whole bunch of C together you know in 00:19:24.12000:19:24.130 some sort of a blob kind of a you know 00:19:26.10000:19:26.110 amorphous random messy sort of structure 00:19:29.02900:19:29.039 diamond is also pure carbon or graphite 00:19:31.47000:19:31.480 but those are crystals and ordered and 00:19:33.63000:19:33.640 and a little different but they're all 00:19:35.10000:19:35.110 sort of carbon so coal kind of has an 00:19:43.01900:19:43.029 oxidation state of about zero and then 00:19:45.99000:19:46.000 oil is long chains of carbon and the 00:19:52.91900:19:52.929 ones in the middle which is most of them 00:19:56.45000:19:56.460 are catch-22 carbons and also each one 00:20:00.14900:20:00.159 to two hydrogen's so oil is probably so 00:20:04.50000:20:04.510 the average carbon and oil is something 00:20:06.72000:20:06.730 like let's see where I put it right here 00:20:11.13000:20:11.140 oil the average carbon in a chain of oil 00:20:14.03900:20:14.049 is sort of ch2 so the oxidation state of 00:20:20.72000:20:20.730 this carbon right here for example is a 00:20:27.23000:20:27.240 it is it is a minus two because it's 00:20:31.20000:20:31.210 getting one hydrogen one electron from 00:20:33.99000:20:34.000 each of the two hydrogen's but it's not 00:20:35.82000:20:35.830 really doing anything with with the 00:20:37.64900:20:37.659 carbons that it's bonded to so that's 00:20:39.41900:20:39.429 there's no base sort of share equally 00:20:42.18000:20:42.190 the two carbons the electrons there's no 00:20:44.01000:20:44.020 contribution to the oxidation state 00:20:45.89900:20:45.909 there so we have this sort of spectrum 00:20:48.41900:20:48.429 of oxidation states of the fossil fuels 00:20:53.06000:20:53.070 where coal is here and then oil is here 00:20:59.19000:20:59.200 and then natural gas is there and the 00:21:03.75000:21:03.760 more reduced it is the more energy you 00:21:06.21000:21:06.220 get by by oxidizing it back to co2 so 00:21:12.71000:21:12.720 less energy burning the coal and more 00:21:18.12000:21:18.130 energy burning the natural gas so one 00:21:27.00000:21:27.010 way to think of it is the number of 00:21:28.26000:21:28.270 electrons that go to the carbon another 00:21:31.50000:21:31.510 way to think of it which is equivalent 00:21:32.82000:21:32.830 is that if you burn just coal you get 00:21:45.45000:21:45.460 energy because you're making co2 whereas 00:21:52.47000:21:52.480 if you burn natural gas you make co2 00:21:57.15000:21:57.160 plus the hydrogen's there get get a get 00:22:02.37000:22:02.380 get made into water and you get energy 00:22:04.68000:22:04.690 from that too so I don't know if you 00:22:06.69000:22:06.700 ever made hydrogen and like you know 00:22:08.85000:22:08.860 science class by electrolysis and then 00:22:10.83000:22:10.840 you then you stick a a stick in there 00:22:14.31000:22:14.320 that's got a flaming em but I've got a 00:22:15.90000:22:15.910 hot ember on it and it makes the 00:22:17.37000:22:17.380 hydrogen explode it was a real formative 00:22:19.53000:22:19.540 experience for me in like middle school 00:22:21.03000:22:21.040 because you make explosions in science 00:22:22.65000:22:22.660 class so making hydrogen making water 00:22:25.53000:22:25.540 out of hydrogen gives you energy 00:22:26.79000:22:26.800 so making water as well as co2 is more 00:22:32.19000:22:32.200 energy it turns out that you get about 00:22:36.63000:22:36.640 twice as much energy per carbon molecule 00:22:39.27000:22:39.280 carbon atom by burning gas than by 00:22:42.27000:22:42.280 burning coal so there's sort of they 00:22:44.61000:22:44.620 talk about methane gas natural gas as 00:22:47.25000:22:47.260 being a cleaner fossil fuel than coal 00:22:50.85000:22:50.860 and it is in several ways one coal when 00:22:54.15000:22:54.160 you burn it releases all these sulfate 00:22:56.52000:22:56.530 aerosols that affect the climate and 00:22:58.71000:22:58.720 then become acid rain as always mercury 00:23:01.47000:23:01.480 coal mining is intrinsically an ugly 00:23:04.16900:23:04.179 process you know especially when they do 00:23:05.64000:23:05.650 these like mountaintop removal things 00:23:07.43000:23:07.440 natural gas you get more less carbon for 00:23:12.69000:23:12.700 the amount of energy that you produce 00:23:13.95000:23:13.960 and it's also you know it doesn't have 00:23:15.84000:23:15.850 as much sort of other baggage like the 00:23:18.41900:23:18.429 sulfur and the mercury and stuff with it 00:23:20.34000:23:20.350 yes a mercury 00:23:25.13000:23:25.140 likes to form a sulfide there's there's 00:23:31.44000:23:31.450 a whole suite of elements that if 00:23:33.87000:23:33.880 there's no oxygen and the sulfur is 00:23:37.83000:23:37.840 turning into sulfide sulfide hydrogen 00:23:41.46000:23:41.470 sulfide is is some of the stinkiest 00:23:43.50000:23:43.510 stuff in the world you can smell better 00:23:45.18000:23:45.190 hydrogen sulfide than any detector can 00:23:47.19000:23:47.200 tell because it's very poisonous and it 00:23:48.65900:23:48.669 sort of comes up in our in our 00:23:49.74000:23:49.750 environment you know that we evolved in 00:23:51.81000:23:51.820 so in a place where you're preserving 00:23:55.14000:23:55.150 coal there's no oxygen air that's why 00:23:57.93000:23:57.940 the organic carbon from the the 00:23:59.58000:23:59.590 photosynthesis gets preserved and that 00:24:01.50000:24:01.510 also tends to make sulfide and that 00:24:03.78000:24:03.790 tends to trap elements like mercury and 00:24:07.68000:24:07.690 cadmium and lead and others like that so 00:24:10.35000:24:10.360 it's n tends to travel it tends to 00:24:12.24000:24:12.250 concentrate in those sort of dark smelly 00:24:15.81000:24:15.820 anaerobic places where the where we get 00:24:18.57000:24:18.580 the fuels from 00:24:25.55000:24:25.560 okay so natural gas is cleaner than coal 00:24:30.92000:24:30.930 for energy but natural gas is still a 00:24:35.00000:24:35.010 source of carbon and in fact the methane 00:24:37.64000:24:37.650 itself is a greenhouse gas so just to 00:24:47.84000:24:47.850 kind of review what we learned when 00:24:50.75000:24:50.760 you're talking about greenhouse gases it 00:24:53.84000:24:53.850 is something like 30 times more powerful 00:25:03.19000:25:03.200 than co2 sort of comparing one molecule 00:25:07.40000:25:07.410 of methane to one molecule of co2 and 00:25:09.95000:25:09.960 that's because there's much more co2 in 00:25:12.89000:25:12.900 the air so co2 is more band saturated 00:25:16.22000:25:16.230 than methane is so the methane the way 00:25:24.41000:25:24.420 it behaves when it's released to the 00:25:26.84000:25:26.850 atmosphere is it is a transient gas it 00:25:37.61000:25:37.620 gets released to the air and then it has 00:25:40.73000:25:40.740 a lifetime of about a decade in the 00:25:44.27000:25:44.280 atmosphere before it before it reacts to 00:25:51.11000:25:51.120 make co2 after about a decade the ch4 00:26:03.94000:26:03.950 reacts to make co2 and when it does that 00:26:06.65000:26:06.660 it loses most of its the carbon atom 00:26:08.72000:26:08.730 loses most of its greenhouse power 00:26:10.37000:26:10.380 because it's now a co2 molecule instead 00:26:13.55000:26:13.560 of a methane molecule so 00:26:32.03900:26:32.049 so the source of methane to the 00:26:40.77900:26:40.789 atmosphere is is it's sort of like a 00:26:45.49000:26:45.500 driver and the the seat where the 00:26:53.35000:26:53.360 methane goes depends on the methane 00:27:01.72000:27:01.730 concentration so this should look sort 00:27:10.24000:27:10.250 of familiar to you actually this is this 00:27:12.70000:27:12.710 is yet another example of where we can 00:27:16.12000:27:16.130 apply our wonderful sink analogy so 00:27:18.81000:27:18.820 there's the faucet 00:27:21.06000:27:21.070 there's the sink you have sources of 00:27:26.47000:27:26.480 methane that are putting methane into 00:27:28.57000:27:28.580 the atmosphere and then the sink depends 00:27:31.99000:27:32.000 on how much methane is in the atmosphere 00:27:34.29900:27:34.309 because if you're the high concentration 00:27:36.01000:27:36.020 of methane that means you're reacting 00:27:38.20000:27:38.210 more molecules per second or whatever 00:27:41.02000:27:41.030 then if there's you know no methane in 00:27:43.36000:27:43.370 the atmosphere so the the the the water 00:27:51.13000:27:51.140 level in the sink represents here the 00:27:56.83000:27:56.840 methane concentration in the air and 00:27:58.81000:27:58.820 then the going down the drain that's a 00:28:04.28900:28:04.299 reaction in the atmosphere making co2 00:28:20.11000:28:20.120 so let's say that we had the the methane 00:28:26.57000:28:26.580 concentration in the air as a function 00:28:29.36000:28:29.370 of time and let's say that we started 00:28:41.87000:28:41.880 out with sort of a steady concentration 00:28:44.72000:28:44.730 of methane in the atmosphere so it's not 00:28:47.00000:28:47.010 changing as a function of time and now 00:28:49.43000:28:49.440 we're going to at this time we're going 00:28:52.91000:28:52.920 to add some new sources of methane what 00:29:04.76000:29:04.770 happens is so say the source goes up 00:29:08.39000:29:08.400 like this and then the concentration 00:29:16.61000:29:16.620 will will sort of rise until it is 00:29:23.00000:29:23.010 enough to to make the the sink for 00:29:26.81000:29:26.820 methane let's see so we'll call this a 00:29:29.35000:29:29.360 methane rate and we'll put the methane 00:29:38.39000:29:38.400 concentration get another plot kind of 00:29:41.36000:29:41.370 up here 00:29:55.33000:29:55.340 so we suddenly increase the source and 00:29:58.09000:29:58.100 then you know at that point after you've 00:30:00.07000:30:00.080 increased the source the there's more 00:30:02.20000:30:02.210 going into the air than going out and so 00:30:04.62900:30:04.639 your your concentration is going to rise 00:30:06.90900:30:06.919 and as the concentration Rises the 00:30:09.73000:30:09.740 reaction rate of converting it to 00:30:12.10000:30:12.110 burning it essentially to co2 Rises 00:30:14.32000:30:14.330 until it sort of balances the source 00:30:17.08000:30:17.090 rate and the time scale for this is 00:30:19.91900:30:19.929 about the 10-year life time of methane 00:30:26.20000:30:26.210 in the atmosphere so just like in the 00:30:33.31000:30:33.320 sink analogy two ways of changing the 00:30:35.76900:30:35.779 the water level in the sink one is with 00:30:37.86900:30:37.879 the faucet the sources that's what we 00:30:39.85000:30:39.860 just heared here the other is with with 00:30:42.34000:30:42.350 the sink if you change the chemistry of 00:30:44.04900:30:44.059 the atmosphere in some way and it turns 00:30:47.56000:30:47.570 out that most of the discussion about 00:30:53.12900:30:53.139 the methane concentration in the air and 00:30:59.70000:30:59.710 how it has changed involved new sources 00:31:16.77000:31:16.780 sources of methane there are natural 00:31:22.29900:31:22.309 ones there are human caused ones and 00:31:33.43000:31:33.440 there's also the possibility of sort of 00:31:37.21000:31:37.220 climate feedback sources so the biggest 00:31:48.40000:31:48.410 natural source of methane is swamps 00:31:54.18000:31:54.190 methane is called swamp gas so if you 00:31:57.15900:31:57.169 step in some really muddy yucky gross 00:31:59.37000:31:59.380 swamp or you know shallow water lake mud 00:32:03.58000:32:03.590 sediment or something a lot of times 00:32:05.38000:32:05.390 you'll see all these bubbles coming out 00:32:06.70000:32:06.710 and that's methane methane Catching Fire 00:32:12.61000:32:12.620 in swamps is you know that's the 00:32:16.68000:32:16.690 explanation you always hear for UFO 00:32:18.70000:32:18.710 sightings 00:32:19.36000:32:19.370 it's just swamp gas and so it burns 00:32:21.34000:32:21.350 because it's methane there are other 00:32:23.62000:32:23.630 sort of natural sources that are much 00:32:25.36000:32:25.370 smaller termites and and ruminant 00:32:32.35000:32:32.360 animals like natural ones deer moose or 00:32:37.41900:32:37.429 something like that as part of their 00:32:40.06000:32:40.070 digestive strategy they they they Harbor 00:32:45.46000:32:45.470 a consortium of bacteria that can digest 00:32:48.19000:32:48.200 cellulose which is something that we 00:32:51.46000:32:51.470 can't I mean we can't eat wood and and 00:32:53.16900:32:53.179 and and the digestive even though 00:32:54.90900:32:54.919 there's energy in that wood that you 00:32:57.19000:32:57.200 know you've burned wood in a campfire 00:32:58.53900:32:58.549 and get energy from it but you can't eat 00:33:00.94000:33:00.950 it because we don't have the enzymes to 00:33:02.56000:33:02.570 digest that so or grass for examples the 00:33:05.68000:33:05.690 way that cows eat grass is they have 00:33:10.04900:33:10.059 bacteria that they that they host that 00:33:12.97000:33:12.980 have the enzymes and they sort of do 00:33:15.22000:33:15.230 some of the digestion for them as part 00:33:17.14000:33:17.150 of that process it releases methane so 00:33:20.49000:33:20.500 under human 00:33:22.41900:33:22.429 one of the one of the sources are our 00:33:26.04900:33:26.059 livestock so it's not strictly speaking 00:33:33.58000:33:33.590 cow farts I told people for a long time 00:33:37.99000:33:38.000 the cow farts were this source and this 00:33:40.18000:33:40.190 was a question that nobody ever ever 00:33:41.88900:33:41.899 ever missed on the exam it was just the 00:33:44.88900:33:44.899 astonishing thing 00:33:45.82000:33:45.830 so once you've heard that it's in your 00:33:46.99000:33:47.000 mind forever there's nothing you can do 00:33:48.46000:33:48.470 about it but it's actually not true 00:33:50.23000:33:50.240 because where the methane comes out in a 00:33:52.53900:33:52.549 cow is is an exhale you know from the 00:33:55.14900:33:55.159 front end rather than the back end as it 00:33:57.37000:33:57.380 turns out so you know the one fact that 00:33:59.04900:33:59.059 I was very successful at conveying was 00:34:01.89900:34:01.909 wrong I just have to live with that 00:34:03.73000:34:03.740 truth there's an that human sort of 00:34:08.26000:34:08.270 analog to swamps which is a rice farming 00:34:14.70000:34:14.710 it turns out that rice doesn't you know 00:34:17.43000:34:17.440 require living in a swamp but if it 00:34:21.46000:34:21.470 tolerates standing water better than a 00:34:25.00000:34:25.010 lot of the weeds that that can confound 00:34:27.63900:34:27.649 rice agriculture so a lot of times rice 00:34:30.76000:34:30.770 is grown in sort of standing water and 00:34:32.64900:34:32.659 this makes a big source of methane to 00:34:34.59900:34:34.609 the to the atmosphere 00:34:36.94000:34:36.950 there's also methane released from 00:34:39.60900:34:39.619 fossil fuel industry like we talked 00:34:43.48000:34:43.490 about a flaring natural gas well maybe 00:34:46.69000:34:46.700 they don't always you know get around to 00:34:48.25000:34:48.260 burning it maybe something's just 00:34:49.72000:34:49.730 released you walk down 57th street 00:34:55.21000:34:55.220 there's this apartment building called 00:34:56.64900:34:56.659 the muse and they've got these very 00:34:58.08900:34:58.099 fancy gas lights out on the by the 00:35:01.35900:35:01.369 sidewalk these little Mantle's and they 00:35:03.46000:35:03.470 glow and sometimes a little mantle which 00:35:06.88000:35:06.890 is a little bag of string breaks in that 00:35:10.48000:35:10.490 case the fire goes out and you can smell 00:35:12.52000:35:12.530 as you walk down the street this natural 00:35:14.17000:35:14.180 gas coming out and it just really 00:35:15.67000:35:15.680 irritates me that they would that they 00:35:17.38000:35:17.390 would just cavalierly put methane in the 00:35:19.35900:35:19.369 atmosphere but we would call that I 00:35:20.77000:35:20.780 guess fossil fuel fossil fuel source and 00:35:24.43000:35:24.440 then there's a potential for climate to 00:35:28.07900:35:28.089 change things in ways that may add 00:35:31.93000:35:31.940 methane to the atmosphere 00:35:33.43000:35:33.440 and the most prominent source is a 00:35:41.52000:35:41.530 permafrost melts that has a with peat 00:35:51.57000:35:51.580 so there are peat deposits that are 00:35:54.73000:35:54.740 accumulating in the high latitudes today 00:35:57.13000:35:57.140 in Canada and Siberia and places like 00:35:59.83000:35:59.840 that and they're preserved by being 00:36:01.60000:36:01.610 frozen so you can put some you know 00:36:04.36000:36:04.370 leftover food or something in your 00:36:05.71000:36:05.720 freezer and it will preserve it they'll 00:36:07.39000:36:07.400 keep things keep bacteria from eating it 00:36:09.25000:36:09.260 so I've even heard about somebody 00:36:11.74000:36:11.750 finding an intact woolly mammoth that's 00:36:15.19000:36:15.200 been frozen for 20,000 years up in the 00:36:17.44000:36:17.450 high you know somewhere and it was 00:36:20.50000:36:20.510 thawing out and they they they they 00:36:23.38000:36:23.390 actually ate a stake of this and it was 00:36:25.99000:36:26.000 kind of gross but you know it was still 00:36:27.94000:36:27.950 perfectly edible it was still preserved 00:36:29.68000:36:29.690 freezing sort of preserves organic 00:36:31.72000:36:31.730 carbon 00:36:32.26000:36:32.270 so these permafrost soils have been 00:36:34.45000:36:34.460 preserving organic carbon for thousands 00:36:36.43000:36:36.440 of years and now if they start melting 00:36:38.38000:36:38.390 it may decompose and start releasing 00:36:41.02000:36:41.030 methane to the atmosphere and then 00:36:44.71000:36:44.720 there's also on very long time frames 00:36:46.90000:36:46.910 these hydrates that we mentioned last 00:36:50.40000:36:50.410 time so these are these ice deposits and 00:36:54.64000:36:54.650 ocean sediments and to to melt these and 00:36:58.06000:36:58.070 release carbon or methane it would take 00:37:00.70000:37:00.710 sort of thousands of years 00:37:09.48000:37:09.490 so those are the sources of methane the 00:37:18.64000:37:18.650 sink is this chemical reaction it's very 00:37:21.73000:37:21.740 interesting chemistry because it's it's 00:37:23.98000:37:23.990 a it all has to do with these radical 00:37:28.66000:37:28.670 compounds so ch4 gets attacked by this 00:37:40.35900:37:40.369 radical which is called HS if it's Oh H 00:37:46.83000:37:46.840 so oxygen really wants to be h2o it 00:37:51.82000:37:51.830 doesn't it's not happy being Oh H that's 00:37:54.01000:37:54.020 a very unstable it's a radical compound 00:37:56.10900:37:56.119 it's only found where there's sunlight 00:37:58.06000:37:58.070 that sort of blows molecules apart and 00:38:00.46000:38:00.470 it has a lifetime of you know 00:38:05.55000:38:05.560 microseconds or something like that 00:38:07.15000:38:07.160 before it finds some way to steal 00:38:09.31000:38:09.320 another hydrogen and go back to being 00:38:10.96000:38:10.970 water and one of the things it can steal 00:38:13.83900:38:13.849 hydrogen from is is methane so so now 00:38:22.81000:38:22.820 the oxygen there and that hydrogen are 00:38:25.03000:38:25.040 happy because they've made water you 00:38:26.95000:38:26.960 know a nice sort of little family there 00:38:29.05000:38:29.060 a nice stable molecule and now this one 00:38:33.42000:38:33.430 the ch3 is a radical so someone asked 00:38:36.57900:38:36.589 the other day if you can have three 00:38:37.72000:38:37.730 bonds to carbon instead of four you can 00:38:40.21000:38:40.220 but it's a very unstable compound it's a 00:38:42.57900:38:42.589 radical and so once this ch3 is formed 00:38:46.90000:38:46.910 it then attacks somebody else and it 00:38:49.51000:38:49.520 very very very quickly through a series 00:38:52.96000:38:52.970 of reactions gets oxidized to two co2 00:38:58.44000:38:58.450 but this is sort of the first step and 00:39:01.12000:39:01.130 then after it happens you know the rest 00:39:03.13000:39:03.140 of it is all just is all just very 00:39:05.47000:39:05.480 quickly now the thing about this 00:39:10.90000:39:10.910 chemical reaction is that this Oh H 00:39:13.59900:39:13.609 radical 00:39:17.80900:39:17.819 has the potential to be affected by all 00:39:21.90000:39:21.910 kinds of other changes that have 00:39:23.70000:39:23.710 happened in the atmosphere so OAH is 00:39:36.55900:39:36.569 produced from ozone which you know 00:39:44.55000:39:44.560 there's more ozone in the sort of lower 00:39:47.70000:39:47.710 atmosphere especially in sort of smoggy 00:39:51.50000:39:51.510 urban environments there are these ozone 00:39:53.94000:39:53.950 alert days in the summer they tell us 00:39:55.68000:39:55.690 not to go outside running because it's 00:39:57.72000:39:57.730 worse for you than sitting there 00:39:59.16000:39:59.170 watching television I guess because 00:40:00.59900:40:00.609 there's this ozone in the atmosphere and 00:40:02.76000:40:02.770 it messes up your lungs so ozone is 00:40:05.49000:40:05.500 changing it's also produced by these 00:40:10.71000:40:10.720 nitrogen compounds called NO X so this 00:40:15.48000:40:15.490 is a family of N oh and no.2 which come 00:40:21.69000:40:21.700 from car exhausts and it's one of the 00:40:29.64000:40:29.650 components of urban smog so you get this 00:40:34.70000:40:34.710 nitrogen compounds coming out of 00:40:36.75000:40:36.760 tailpipes and then you shine Sun on it 00:40:39.99000:40:40.000 and it makes this sort of brew of nasty 00:40:43.47000:40:43.480 chemicals in the atmosphere and make 00:40:44.91000:40:44.920 ozone and another thing that affects OAH 00:40:47.33900:40:47.349 is carbon monoxide which comes from 00:40:56.22000:40:56.230 things like fires so there are you know 00:41:01.82900:41:01.839 more fires in the world than there would 00:41:03.66000:41:03.670 be naturally because people cut down 00:41:05.81900:41:05.829 trees and burn them in order to to do 00:41:10.17000:41:10.180 agriculture so all of these things seem 00:41:15.08900:41:15.099 like they ought to be changing 00:41:20.83000:41:20.840 the concentration of Oh H which should 00:41:24.02000:41:24.030 be changing the lifespan the lifetime of 00:41:26.54000:41:26.550 methane in the atmosphere and so that 00:41:29.63000:41:29.640 would be like messing around with the 00:41:31.34000:41:31.350 the drain of the sink analogy but it 00:41:35.78000:41:35.790 doesn't seem like like there have been 00:41:37.91000:41:37.920 any big changes in the lifetime of 00:41:39.77000:41:39.780 methane in the air and I you know it 00:41:42.62000:41:42.630 just it seems like there's there's all 00:41:44.84000:41:44.850 these sort of factor of two changes in 00:41:48.14000:41:48.150 these drivers for methane that seem to 00:41:50.42000:41:50.430 sort of cancel each other out by by sort 00:41:53.33000:41:53.340 of coincidence so what the methane has 00:41:56.03000:41:56.040 actually done in the air is a it has 00:42:01.45000:42:01.460 sort of doubled from the pre-industrial 00:42:11.00000:42:11.010 value of from-from the year 1750 but it 00:42:19.76000:42:19.770 it it sort of stopped rising actually in 00:42:23.15000:42:23.160 about the year 1993 so it was going up 00:42:26.87000:42:26.880 and it looked like it was going to keep 00:42:28.10000:42:28.110 going up and then it sort of defied all 00:42:31.10000:42:31.110 expectations and kind of leveled off and 00:42:33.47000:42:33.480 it's not clear why it did that one 00:42:36.11000:42:36.120 theory is that this was around the time 00:42:38.63000:42:38.640 of cleaning up the the the former 00:42:43.22000:42:43.230 Eastern Bloc leaky oil or gas pipelines 00:42:46.88000:42:46.890 and inefficient industry and things like 00:42:48.77000:42:48.780 that 00:42:49.12000:42:49.130 decreasing the source another theory is 00:42:52.04000:42:52.050 that the planet has been sort of drier 00:42:54.26000:42:54.270 since then so maybe there's less of a 00:42:57.20000:42:57.210 source from from swamps but at any rate 00:42:59.87000:42:59.880 it's kind of a mystery and it's not 00:43:01.85000:43:01.860 clear it looks like it's actually 00:43:04.28000:43:04.290 started going back up again just in the 00:43:06.35000:43:06.360 last since about 2007 but it's not clear 00:43:10.01000:43:10.020 what you know it is this sort of a loose 00:43:14.27000:43:14.280 cannon in the whole climate system it's 00:43:17.48000:43:17.490 not clear why it stopped going up or why 00:43:21.20000:43:21.210 it started again so we'll leave it at 00:43:24.29000:43:24.30000:43:25.67000:43:25.680 you 00:43:35.03000:43:35.040
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