Amyris: Can their renewable jet fuel ever be affordable?

June 27, 2013 |

In the Digest mailbag, we’ve been getting a fair amount of feedback to our coverage of Amyris’s advances in renewable jet fuel.

In our article, we pointed out the growing gap between the price of sugar and jet fuel over the past ten years — giving credence to the use of sugar as a feedstock for fuel production.

Some of our more astute readers ask, calculators in hand, how is it going to be ever economically possible to make jet fuel from Amyris biofene?

One reader writes:

“Theoretical yield for farnesene from sugar (glucose) is about 30% by weight (compared to 51% for ethanol, which is a much shorter-chain molecule than farnesene or other fuel-grade oils).  However, actual yields will typically be on the order of <50% of that, so probably more like 15% (0.15 g farnesene/ g sugar) or even less.  

“From there the math makes it fairly easy to calculate the cost of a gallon of “jet fuel” or “diesel” from any cost of sugar (using a density like ethanol of about 3 kg/gal).  In addition, farnesene is not the final molecule — farnesane is — which means Amyris will need to use a source of hydrogen to hydrogenate farnesene, further adding to the cost.

“At an actual yield of 20% (giving them the benefit of the doubt), it would take 5 lbs of sugar to make 1 lb of jet fuel.  So using your number of $0.17/lb for sugar, the cost of farnesene would be 5*0.17 or approximately $1/lb just for raw material (forgetting the need for H2 and of course all other raws and capex) – which is more than 2x the market value of jet fuel, which you put at ~$0.40/lb.”

It’s an interesting question — and frankly beyond the Digest staff’s abilities with a calculator — so we asked Joel Velasco at Amyris for some help.

He writes:

“We don’t disclose current yields. But as we describe in at least one of our patents (See here.) the max theoretical yield for our Farnesene strains is about 30%.

“We have always offered the figure of about 3 kilos of sugar for a liter of farnesane (jet fuel/diesel) for our analysis of target production.

“So, at current sugarcane TRS pricing in Brazil (R$ 0.44/TRS kg according to public market data, here), the feedstock cost of producing a liter of fene at these targets (and R$/$ exchange rate) would be about $0.61 per liter or $2.35 per gallon.”

Now, that’s just feedstock costs using current local prices in Brazil, and not the sale price of fuel, but it does continue to add credence to the concept that — so long as the cost of the underlying sugars continues to trend south of rising priceline of jet fuel — there are reasons to continue to be optimistic regarding renewable jet fuels made via the Amyris process.

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