17
Jan 2008

Oil companies and Climate Change

UPDATE 20-03-2008: A significant error has been revealed in a section of the following post (relating to the amount of CO2 that would have been captured by BP’s Miller Field CCS project). For details of this error, please read the correction / apology: Oil companies and Climate Change Redux. For the calculation estimating the quantity of CO2 emitted by a single barrel of oil, please see: Carbon dioxide emissions per barrel of crude.

This article, therefore, remains as merely a cautionary example about placing too much faith in published figures, and should be disregarded.


Merrick‘s writing an article about the use of hydrogen as fuel (sneak preview: he’s not uncritical of the idea. Update: here’s that article.) and encountered this particular proposal by BP. Now, while the project won’t be going ahead, the proposal itself makes fascinating reading. The basic idea goes something like this…

Instead of building a new Natural Gas power station, BP proposed to build a two-stage plant. Stage 1 would extract the hydrogen from the Natural Gas. Stage 2 would burn the hydrogen to generate electricity. The only emission from burning hydrogen is pure water. Notch one up for the fight against Climate Change, and drinks are on me! BP go so far as to claim this process results in 90% less CO2 emissions than through burning the Natural Gas directly. Which by any standards is pretty damn impressive.

Except. Well… except it’s not really. Because if you step back to Stage 1 of the process, it turns out that extracting hydrogen from Natural Gas leaves you with large amounts of waste, in the form of… you guessed it… CO2 gas. Makes you start wondering what the hell Stage 1 is actually achieving, right? But hey, chill out, all is not lost. Rather than release this CO2 into the atmosphere (which would make the whole hydrogen extraction process singularly pointless) BP instead proposed to capture it. They’d simply pump it into one of their old oil wells that was entering decline, and Bob’s your rather expensive, but nonetheless low-carbon, uncle.

You know what? As a way to reduce the carbon emissions of a Natural Gas power station, that’s really not a bad idea. The electricity produced would be a good deal more expensive (that hydrogen extraction process doesn’t come for free, energetically speaking, and nor does compressing and pumping CO2 deep underground) but it would be far less of a contributor to Climate Change. Based on the planned capacity and lifetime of the plant proposed by BP, there’d be 1.3 million tonnes of CO2 captured that would otherwise have been emitted as a result of burning Natural Gas.

I’ll go on record and state that in principle this is an interesting way to exploit Natural Gas if you are committed to using Gas in the first place*. And if that were the end of the story, this would be an article praising an oil company for getting something right. Which are few and far between in this neck of the woods.

Think like an Oil Company

But that’s not the end of the story. So I’m afraid my praise shan’t be forthcoming. BP have added a little kicker to sweeten the deal for themselves. In what is — and I say this without hyperbole — one of the most astonishing examples of Orwellian doublethink in corporate literature, this kicker appears under the heading “Industrial-scale decarbonized fuels project”:

… the carbon dioxide would be transported by an existing pipeline and injected for enhanced oil recovery and long-term geological storage in the Miller Field. Injecting the carbon dioxide into the Miller Field reservoir more than three kilometers under the seabed could extend the life of the field by about 20 years and enable additional production of about 40 million barrels of oil that are not currently recoverable.

When operational, it is planned that DF1 will create 350 megawatts of carbon-free electricity, enough to power a quarter of a million homes in the UK. The project would also permanently store 1.3 million tonnes of carbon dioxide, the equivalent of removing 300,000 cars from the roads.

See that? The way they just slipped it in there? In return for the 1.3 million tonnes of carbon captured, they’re getting to extract 40 million barrels of oil that would otherwise have remained underground and consequently in very little danger of being converted to atmospheric CO2. Suddenly this isn’t looking like such a great deal for the environment after all. But let’s not be too hasty, how much atmospheric CO2 will be produced from 40 million barrels of oil? If it’s less than 1.3 million tonnes, then we can perhaps, albeit grudgingly, still accept the proposal as better than just burning the Natural Gas. After all, it’s not like we really expected an oil company to be doing something for the greater good. If we’re honest with ourselves, we were always looking for the ulterior motive even as we hoped against hope that it might not be there this time.

So, all that’s left is to find out how much CO2 would get emitted by 40 million barrels of oil, and we’ll know just how much this industrial-scale decarbonized fuels project is benefiting the fight against Climate Change.

It was at this point that Merrick emailed me with the question, “how much CO2 gets emitted when we consume a barrel of oil?” And it got me thinking…

How much carbon per barrel?

I’m afraid there’s no precise answer. No simple formula.

Crude oil is (almost) never used directly. Instead it’s refined into all manner of interesting chemicals, most of which we burn in various engines, but some of which never get converted into CO2 (lubricant oils, plastics, asphalt, etc.). Different grades of crude oil will produce significantly different amounts of each. So a barrel of light / sweet crude might produce lots of petrol and kerosene but only a small amount of asphalt (as a very simple example). But a barrel of heavy / sour crude would produce more asphalt (still less than the amount of petrol produced, but more in comparison with the sweeter oil). This means that, ironically, less of the heavier and more sulphuric stuff, although it’s called sour (and sometimes “dirty”) oil tends to end up as atmospheric CO2 (we coat our roads with it instead).

While we could, no doubt, work out a figure for the CO2 emitted by burning a given barrel of crude oil, it would be very much a red-herring as it almost never happens. To get any meaningful figure for CO2 emitted per barrel we’re going to need to do our calculations on the products of crude oil.

First up, let’s be clear that this is real back-of-the-fag-packet stuff and I welcome input and corrections to this calculation. That said, let’s see if we can’t get some kind of number.

The oil being discussed here is from a North Sea field, so I’m going to assume that it is at least average quality (i.e. we’re not talking about some kind of heavy sulphuric sludge or tar-sand here). Taking betting tipsRiegel’s Handbook of Industrial Chemistry as our guide, we know that the average barrel (~159 litres) of crude oil to pass through U.S. refineries in 1995** yielded the following products…

1. Gasoline: 44.1% (70.12 litres)
2. Distillate fuel oil: 20.8% (33.07 litres)
3. Kerosene-type jet fuel: 9.3% (14.79 litres)
4. Residual fuel oil: 5.2% (8.27 litres)***

Percentage values from Riegel’s Handbook of Industrial Chemistry, 2003 edition (Page 515, Fig. 15.6). Litre values based upon conversion rate of 159 litres per barrel.

I’m going to be very charitable to the BP project and assume that none of the other products**** will end up as atmospheric CO2. They all have sufficient alternative uses to make this possible even if not 100% plausible. Of the four grades of fuel listed above, however, it’s fair to say all of it is destined to be burnt.

The litre values are no good to us by themselves. Each of the fuels has a different specific gravity (a different weight per litre), and it’s the weight of carbon we’re looking for, not the volume. Once we’ve multiplied the volume of each fuel by it’s specific gravity we’ll have a rough “kilogram per barrel” number for each fuel.

1. Gasoline: 70.12 litres x 0.74 = 51.89kg
2. Distillate fuel oil: 33.07 litres x 0.88 = 29.10kg
3. Kerosene-type jet fuel: 14.79 litres x 0.82 = 12.13kg
4. Residual fuel oil: 8.27 litres x 0.92 = 7.61kg*****

Overall, this suggests that the average barrel of crude refined in the United States in 1995 yielded a shade over 100kg of liquid fuels (that’s an uncannily round number… 100.73kg to be exact). Now, we know that a carbon-based fuel will emit 3.15 times its own weight in CO2 when burnt (Source: Calculating the Environmental Impact of Aviation Emissions, Oxford University Study, PDF file). This may seem anti-intuitive at first glance, but it’s a result of each atom of carbon reacting with two atoms of oxygen to produce CO2. The “extra” weight is being drawn from the air (hence why a fuel fire will die out if deprived of oxygen).

Using the 3.15 multiplier, we see that the combined liquid fuels from an average barrel of crude oil will produce roughly 317kg of CO2 when consumed. This means that 40 million barrels will produce 12,680,000,000kg. Or 12.68 million tonnes of CO2. That’s almost ten times the 1.3 million tonnes BP said would be captured.

As an attempt to reduce atmospheric CO2, it’s utterly risible. And describing it as an “industrial-scale decarbonized fuels project” is surely against some kind of trades-description legislation.

Even if this were the lowest grade North Sea crude imaginable, I’m confident that it would be producing at least 75% of the liquid fuels cited in the above “average” barrel. And if it’s higher than average quality, they might even get an extra 10%. So to be absolutely fair, we should calculate a likely range depending upon the crude. Take the 12.68 million tonnes figure, first reduce it by a quarter to get the potential minimum (9.51 million tonnes of CO2). Second increase it by 10% for the potential maximum (13.95 million tonnes of CO2).

9.51 to 13.95 million tonnes of CO2. That’s certainly a wide range, and it can’t be narrowed without knowing the specifics of the oil in question. But even the lowest number is far higher than the 1.3 million tonnes of CO2 that would have been sequestered by the project.

I’m hardly the first person to do the maths on this; surely it’s occurred to somebody at BP already. Surely they’re aware that describing the project as an “industrial-scale decarbonized fuels project” is, in every sense that actually matters, a bare-faced lie. That at a minimum, the extra oil gained in the project would emit over 7 times the CO2 as was captured.

In May 2007 BP cancelled the plan, citing governmental delays in approving the project and in providing adequate incentives. The Miller oil field is reaching the end of its life, and they needed the CO2 in a hurry to extend it. The capturing of 1.3 million tonnes of carbon was never a goal in itself; it was merely a way to falsely paint the project as a way to combat Climate Change. In doing so, BP would then be in a position to drain public money ear-marked for just that purpose (in the form of planning short-cuts, tax-relief and whatever else can be clawed from the pot to incentivise investment in carbon-reduction technologies).

Let’s be very clear about this. BP attempted to dupe the public into backing a project on the basis that it would combat Climate Change, despite (surely!) being well aware that in reality it would demonstrably increase emissions. That’s about as low, as craven… as anti-human as it’s possible to get. And while that may well be normal behaviour for a corporation, we’re complete fools if we consider it acceptable.

* It goes without saying that given the natural resources available to us in this part of the world, all investment in new generating capacity should be in wind and sea.

** I don’t have more recent numbers, but there’s no reason to assume 1995 wasn’t a representative year.

*** 1: automobile grade fuel. 2: includes home heating oil and transportation diesel. 4: industrial grade fuel oils; used in ships and oil-burning power plants.

**** Still gas, coke, asphalt, road oil, petrochemical feed stocks, lubricants, etc.

***** Specific gravities taken from this list. The value of 0.92 is an educated guess for what is a mixture of heavy oils with a range of specific gravities. I will gladly accept correction if someone can point me towards a more accurate number.

UPDATE (16:10): The original date for the cancellation of the project was given as February 2007. In fact it was May 2007. The second-last paragraph has been updated to reflect this. Also, the final two paragraphs were substantially rewritten at the same time. The phrasing was pretty clumsy first time round.
UPDATE (22-01-2008): Although the project proposed by BP for the Miller Field in the North Sea has been cancelled, the principle is clearly an attractive one to oil companies. The government of Abu Dhabi appears to be contemplating just such a scheme, though on an even larger scale. This line from the BBC article made me smile: “The CO2 can be pumped underground, either simply to store it away permanently or as a way of extracting more oil from existing wells, using the high-pressure gas to force more of the black gold to the surface.” Hmmm… is anyone really dumb enough to believe the third largest oil producer in the Gulf won’t use the captured carbon as a tool to extract more oil? So, given what we know from the above calculation, Richard Black, the BBC’s Environment Correspondent, is dangerously wrong when he introduces carbon sequestration as a “technolog[y] likely to be important in a low-carbon future”.

Posted in: Opinion