Black Smoke ... and Diesel Engines

Information on diesel engine emissions and a breakdown of the events and subsequent research that led me to write the Diesel Engine Emissions Calculator program.
(See <Tech Stuff>)

Smokey Engine











I wrote the emissions calculator program while I was working on a seismic crew in Oman.

A government agency had come to the crew to carry out emissions tests on the crew generators that supplied our electricity. If our emissions were not within spec the crew could be shut down.

While a shut-down would be very expensive Oil companies will comply with regulations. They have quite rightly taken on responsibility for environmental protection and take regulation breaches seriously.

The agency came and took their measurements. The generators were deemed to be emitting 50% more carbon dioxide than is allowed and the crew were given two weeks to fix them.

At great cost a Volvo engineer was flown in specially from Europe and spent two days working on the generators. He left saying they were now in top condition.

The emissions agency returned and said the generators were still 10% over the allowed CO2 emissions and a final notice was issued.

Now I am as keen as anyone to ensure we minimise pollution of our planet but I was amazed at this result and asked to see the test equipment calibration certificate and results printout.
As the Oil Company representative it was my job to ensure the field work was carried out as efficiently as possible. To my mind this included any external agencies wanting to shut the crew down. The emissions agency representatives flatly refused to give me any information about their test equipment or their methods.

During this time I had been researching emissions and emissions measurement and one most crucial point that came out was that of measurement accuracy. In recent times allowable quantities of emissions have become relatively small. This puts a severe strain on the accuracy of emissions measurement devices. As measurement devices are required to measure smaller and smaller volumes of gas the accuracy of different types can vary considerably. Accuracy figures can be seen quoted to as high as +-30%.

So the agency measurement of 10% excessive emission could in fact mean that the generators were 20% under the limit. Their uncertain and unexplained tests could result in unnecessary and expensive work being carried out on equipment that was in fact within specification.

I put in a formal complaint explaining my reasons and stating that when any emissions measurement carried out by an agency results in hardship for those under scrutiny (maintenance cost or even closure), the agency should be asked to provide procedural details of the measurement as well as accuracy and recent calibration evidence for their measuring instruments. Without this information the measurement is clearly unproven and invalid.
The agency did not return to the crew and we continued working.


The Program Research

The research for my program is based on a couple of studies carried out in the States. The program gives a very close approximation of the hazardous emission quantities for any size diesel generator and for any load.

It uses fuel consumption as the basis for its calculations. Clearly, the larger the generator and/or the larger the load, the greater the fuel consumption and hence pollution will be. And poorly maintained engines tend to use more fuel and hence produce more emissions.

Calculations based on engine specifications and varying load factors may be a more scientific approach, but even these must still be an approximation.

Load factors will vary on a second by second basis so it would be impossible to provide precise data for calculations based on load.

On top of this, the general condition of the generator will affect the results, and how would you quantify this factor?

So, this is not a precise science and if you try to get figures accurate to the nth degree you are simply wasting your time.

Therefore approximate calculations based on fuel consumption must be as good as any.


------------------------ RESEARCH 1: Based on Fuel Consumption -------------------------------
From the County of Santa Barbara Air Pollution Control District come these calculations for the emissions from a diesel generator.

They are for a 70 horsepower engine which runs a 40kW generator.
The figures are for every 1,000 gallons of diesel fuel consumed.

If you are running a different sized generator base your calculations on fuel consumed and you will come very close as factors such as load and ambient temperature will juggle the figures some.

Generally for every 1,000 gallons of diesel fuel consumed the following emissions occur:

11.9 Tons of Carbon Dioxide.
575 Pounds of Nitrous-Oxides.
22 Pounds of Total Suspended Particulates (TSP)
49 Pounds of Hydrocarbons.
28.5 Pounds of Sulfur Dioxides.
812 Pounds of Carbon Monoxide.

And don't forget the use and generation of motor/hazardous waste oils.

-------------------------- RESEARCH 2: A more scientific approach? ----------------------------
Calculating CO2 emissions based on molecular weights.

The Intergovernmental Panel on Climate Change (IPCC) guidelines for
calculating emissions inventories require that an oxidation factor be
applied to the carbon content to account for a small portion of the fuel
that is not oxidized into CO2. For all oil and oil products, the oxidation
factor used is 0.99 (99 percent of the carbon in the fuel is eventually
oxidized, while 1 percent remains un-oxidized.)[1.]

Finally, to calculate the CO2 emissions from a gallon of fuel, the carbon
emissions are multiplied by the ratio of the molecular weight of CO2 (m.w.44)
to the molecular weight of carbon (m.w.12): 44/12.

CO2emissions from a gallon of gasoline = 2,421 grams x 0.99 x (44/12)
= 8,788 grams = 8.8 kg/gallon = 19.4 pounds/gallon

CO2 emissions from a gallon of diesel = 2,778 grams x 0.99 x (44/12)
= 10,084 grams = 10.1 kg/gallon = 22.2 pounds/gallon

Note: These calculations and the supporting data have associated variation
and uncertainty. EPA may use other values in certain circumstances, and in
some cases it may be appropriate to use a range of values.



If you look at the two independent research results for CO2 emissions you
will see that they are not that much different.

Research 1: Santa Barbara Air Pollution Control (used in my program)

Generally for every 1,000 gallons of diesel fuel consumed the following
emissions occur- 11.9 Tons of Carbon Dioxide.

Research 2: Intergovernmental Panel on Climate Change (not used, verification only)

CO2 emissions from a gallon of diesel = 2,778 grams x 0.99 x (44/12)
= 10,084 grams = 10.1 kg/gallon = 22.2 pounds/gallon

So 1000 gallons will produce 22,200 pounds of CO2

1 US Ton is 2000 pounds so 22,200 pounds is 22,200 / 2000 = 11.1 tons of Carbon Dioxide.



The two results are not the same, but they are fairly close - 11.9 and 11.1 US Tons
that's less than 8% difference

This adds support to the idea that using fuel consumption as a base for calculating emissions is going to give a fairly close approximation. And as I said previously, if you are looking for nth degree accuracy then you may have a long wait.





Smokey Engine