How CO2 Emissions Factors Are Calculated (and Why They are Wrong)

A lot of people ask why SailPlan’s direct CO2 emissions measurements differ so significantly from fuel-based CO2 estimates. Let’s take a look at how CO2 emissions factors are created.

How is CO2 created?

CO2 is formed by the combustion of fuel. Carbon atoms from the fuel combine with oxygen atoms from the air to form CO2. The atomic weight of carbon is 12. The atomic weight of oxygen is 16. Now you can add them up. Combine those, you get 12(C) + 16(O) + (16)O = 44. So 44 divided by 12 = 3.67. CO2 is approximately 3.67 times heavier than carbon.

Diesel fuel is about 86% carbon₁ and other types of marine fuels have more or less carbon content. Using our basic chemistry formula from above, we know that 1 kg of carbon produces approximately 3.67 kgs of carbon dioxide. So one metric ton of diesel fuel creates approximately 3,150 kgs of carbon dioxide when combusted. And for each ton of fuel we burn, we therefore generate about 3.15 kgs of carbon dioxide₂.

Voila! 3.15 is your emissions factor!

So that’s how the CO2 emissions factors were created. It’s basic chemistry. The emissions factors that you use to report CO2 emissions from fuel were created this way. Depending on the carbon content of your fuel, you may be +/- this number but it’s directly due to the carbon content of the fuel you are combusting.

But there is a problem with CO2 emissions factors  

If you report CO2 emissions by using emissions factors, you’re automatically reporting the worst case CO2 emissions for your ship. Say what?!

Your ship could be operating more efficiently than these CO2 factors assume. In fact, it likely is! Your engines likely don’t combust fuel into CO2 at the same rate across their load ranges. In fact, we know they don’t. 

But wait, there is hope!

Direct CO2 Measurements are accepted by both IMO DCS and EU MRV for reporting accurate CO2 emissions from ships. Measuring CO2 emissions allow you to report your actual CO2 emissions, not the worst case estimates. On average, CO2 emissions tend to be about 8-10% lower than the emissions factors suggest. And with the Carbon Intensity Indicator (CII) and EU ETS in effect, 10% is a big change. 

Find out more about how we can help you measure and report accurate CO2 emissions for your ship fleet by getting in touch today!

Sources:

1. EPA Emission Facts
2. Basic math