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My chemistry is not good enough to solve this problem, and it's driving me crazy.

At my job, a sales agent approached me to be their representative in my area for their product. It's a product that when mixed with diesel or gasoline, it reduces carbon emissions in the vehicle to almost 0.

Now this seems impossible to me. The burning of hydrocarbons necessarily creates $\ce{CO}$ or $\ce{CO2}$, and the $\ce{CO}$ can be converted to $\ce{CO2}$ in the catalytic converter by oxidizing it.

In the test results, $\ce{CO}$ dropped to almost 0, and $\ce{CO2}$ stayed the same or went down (also my own calculations show the change in $\ce{CO2}$ was not statistically significant with the small sample size - 3 before and 3 after tests on 3 cars).

I've seen the test results (yes, they could have been faked, but they filmed the testing process). My buddy also personally tested it on his car and got the same results.

Anecdotal evidence shows that the car's mileage is the same.

Can anyone point me to somewhere to try and figure out what is going on here? It sounds too good to be true, and as such, there is no way I'm going to recommend my company represent this product until I know what's going on.

Here are the mean test results (ppm). Some of them have high variance. The only statistically significant changes are $\ce{CO}$ reduction in all cars, and all changes in the first car. The $\ce{NOx}$, $\ce{CO2}$, and $\ce{CxHy}$ changes in car2 and car3 are not significant.

        Before                          After
        CO    CO2    CxHy    NOx        CO    CO2    CxHy    NOx
Car1    3491  9.4    0.39    46.7       33.3  7.8    0.07    9.7
Car2    164   11.5   0.13    2.7        12.9  11.4   0.37    0.7
Car3    2868  11.1   0.18    14         123   10.9   0.06    39.3

I'm suspicious this may just be ethanol, but the manufacturer swears it isn't.

The advertised ratio is 1 oz to 12.5 gallons of fuel which is less than 0.1% (I believe they used double that in the tests). Too low to be ethanol anyway, right?

Follow-up:

I have confirmed that I was originally mistaken in that all measurements are ppm. I received a new copy of the original results, and $\ce{CxHy}$ and $\ce{CO2}$ are indeed measured in percent, rather than ppm. It was incorrectly rewritten in the report. The numbers are the same, though.

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  • $\begingroup$ Hang on - you state that the product is supposed to make carbon emissions drop to almost zero, and then state that the CO2 emissions did not drop statistically significantly (ignoring CO for the time being). Can you please clarify what the observations were in terms of total carbon? $\endgroup$ – Richard Terrett Nov 30 '12 at 2:53
  • $\begingroup$ I think the CO2 sensor might have been faulty. Those CO2 concentrations are several orders of magnitude too low, and lower than ambient atmosphere (currently around 391 ppm). $\endgroup$ – Richard Terrett Nov 30 '12 at 3:30
  • $\begingroup$ The sensor was certified calibrated (although still could be faulty). It was inserted into the exhaust pipe of the car. "For accurate readings, the O2 readings must be lower than 20.5% and gas temperature must be more than 5 degrees hotter than ambient temperature. The analyzer was purged with ambient air prior to each set of readings." Would that make a difference? $\endgroup$ – Bryan Nov 30 '12 at 3:38
  • $\begingroup$ Regarding your original comment - catalytic converters produce more CO2 than normal exhaust because one of their functions is to convert CO and unburnt fuel to CO2. The total amount of carbon going in and coming out must be the same. Regarding CO2 measurements - if wikipedia is to be trusted, the concentration of CO2 in petrol engine exhaust is about ten thousand times higher than the 'before' figures you have listed, which leads me to believe that the CO2 sensor is reporting % CO2 rather than ppm CO2. $\endgroup$ – Richard Terrett Nov 30 '12 at 4:06
  • $\begingroup$ You are right, I edited to reflect this. The report I have was incorrect. The units for CxHy and CO2 are %, not ppm. I understand about catalytic converters. My issue is determining how this product can possible achieve these results. It would be horribly unprofessional of me to recommend this product to my bosses (possible scam?), but at the same time it's hard to let it go. $\endgroup$ – Bryan Nov 30 '12 at 4:15
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With reference to the discussion in the question comments, this product does not appear to appreciably reduce carbon emissions in total. It does however appear to reduce carbon monoxide emissions. As carbon monoxide is a product of incomplete combustion, it is plausible that the additive is helping the fuel burn more completely. Broadly speaking, you would hope that the majority of the carbon in your exhaust gas would come out as carbon dioxide, which is 'merely' a greenhouse gas and not truly nasty like CO or PAHs. Prior to the advent of catalytic converters, carbon monoxide poisoning by vehicle exhaust was a much greater risk.

It should be noted that conservation of mass tells us some powerful things about what to expect from an engine - namely that the carbon that goes in to the engine as a component of fuel must come out as exhaust gasses, particulates, polycyclic aromatic hydrocarbons etc., or else be sequestered inside the engine (though the latter is achievable by putting a banana into the exhaust pipe, it is generally done as a prank).

Reduction of carbon emissions in general is achieved through obtaining more work per mass of fuel burnt, which, when coupled with the mass and other design features of the car confers the fuel efficiency. Unfortunately, the data provided don't tell us anything about that. The more complete burning of the fuel, evinced by the reduction of CO concentration in the exhaust gas does imply some increase in efficiency, however CO is a very small component of exhaust gas, indicating alongside the low concentration of unburnt hydrocarbons that the fuel is already burning virtually to completion.

Without knowing the specific claims made by the manufacturer of the additive, I will not make any judgment of good or bad faith, however my distilled conclusions are:

  • The product does not dramatically impact total carbon emissions

  • The product appears to appreciably reduce carbon monoxide emissions

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  • $\begingroup$ @Bryan - sorry, my answer does sort of walk through some points that I see the edit to your question evinces a good understanding of, however I'll leave my answer unmodified for the potential edification of other future readers. $\endgroup$ – Richard Terrett Nov 30 '12 at 5:14
  • $\begingroup$ Thanks for the reply. Going with what I already know, and your's and permeakra's comments, I'm going to have to decide to either leave this product (somehow it's just trapping the carbon in the engine), or do some some tests to see if it is meaningfully increasing the efficiency and work output of the reaction. I didn't consider PAH emission... $\endgroup$ – Bryan Nov 30 '12 at 5:55
  • $\begingroup$ @Bryan - I was sort of joking about carbon sequestration inside the engine. It is not practical to just store away the carbon without a radical re-imagining of the internal combustion engine (for instance attaching something like a rebreather to it, which would require frequent replacement). My conclusion is that it's difficult to say whether the additive is doing anything at all to total carbon emissions, and the chances are good that it is not. $\endgroup$ – Richard Terrett Nov 30 '12 at 6:10
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I think the entire claim by the sales representative, the question itself, and the ensuing discussions in comments and answers can be distilled down to two items:

1) The claim that "It's a product that when mixed with diesel or gasoline, it reduces carbon emissions in the vehicle to almost 0" is nonsense, as the OP and further discussions stated. The desirable net chemical reaction taking place in an internal combustion engine is simply:
$$\ce{hydrocarbons + O2 -> CO2 + H2O}$$

2) The only useful measure of a fuel additive's ability to decrease carbon emissions is a comparison of distance traveled per volume of fuel, with and without the additive. This was only addressed in the statement "Anecdotal evidence shows that the car's mileage is the same." Thus, the total carbon emissions were essentially unchanged by the additive, as $\ce{CO}$ and unburned hydrocarbons represent a negligible fraction of the total carbon emissions.

Clearly, the "Reduces carbon emissions" catch-phrase is unfortunately an untruth distracting from what the additive appears to possibly do well: reduce $\ce{CO}$ and possibly unburned hydrocarbon and $\ce{NOx}$ emissions.

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