Virgin Atlantic Airlines and their partner LanzaTech believe making jet fuel from ethanol that came from carbon monoxide in a steel mill is green. I do not have to repeat the ethanol from carbon monoxide story as I have beaten that one to death. Now let’s look at making jet fuel from ethanol. Jet fuel is typically 10 carbons long but could be as low as 5 or as high as 15 carbons long. For simple math let’s use 10 carbons as the chain length of jet fuel. At this length it will also have 22 hydrogen atoms (to be a saturated paraffin). As ethanol has 2 carbon atoms, 6 hydrogen atoms and one oxygen atom we first have to remove some H2O from the ethanol, then we have to polymerize 5 of the C2s to get C10 and then we have to add hydrogen to saturate any unsaturated bonds. The resulting chemical balance is as follows:
5 C2H5OH + H2 = C10H22 + 5 H2O
Assuming we do this in a pound mole basis we have 230 pounds of ethanol plus 2 pounds of hydrogen yielding 142 pounds of jet fuel plus 90 pounds of water. The input energy of the ethanol plus hydrogen on a lower heating value basis is 2.748 million BTU, the output on the same lower heating value basis is 2.627 million BTU. Approximately 4.4% of the energy in the ethanol and hydrogen is lost in producing the jet fuel. If one were to make the C5H12 jet fuel the heat balance would be a little improved and approximately 3.1% of the energy would be lost. For our purposes let’s stay with the C10 jet fuel.
Now we have 20 moles of CO2 being emitted at the steel mill that produces the ethanol and when the jet fuel is burned on plane another 10 moles of CO2 will be emitted for a total of 30 moles of CO2. Had the CO simply been flared at the steel mill, 30 moles of CO2 would be emitted at the steel mill. Had the C10 jet fuel been produced from crude oil another 10 moles of CO2 will be emitted when the fuel is burned aboard the plane for a total of 40 moles of CO2. From this analysis we can see that at best 10 moles out of 40 (25%) is the savings in CO2 emissions by propelling a plane by jet fuel derived from CO from a steel mill. When all the other emissions associated with cooling the reactors, and purifying the chemicals the CO2 savings will be less than 25%
Virgin has claimed a 60% reduction of CO2 emissions for planes using the LanzaTech technology . This comes from a quote in the article linked below. “According to Virgin Atlantic, the fuel has the potential to cut emissions by 60 per cent compared to conventional aviation fuels, while fitting the technology to all steel plants globally could produce enough biofuel to meet 19 per cent of global demand.”
I guess we now have three greenwashers involved in this steel mill off gas to ethanol and jet fuel scam - Virgin, Siemens, and Lanzatech.