The Compelling Case for Biojet Fuel

April 1, 2019 |

By Jess Hewitt and Jonathan Lewis, Lee Enterprises Consulting

Special to The Digest

Biojet is in the news a lot lately, with one carrier after another announcing a test flight. But widespread use by most airlines just does not seem to be happening. Why? Let’s look at the case for Biojet and determine its real status in today’s jet fuel marketplace.

Many people are confused by the term “biojet,” and the many other terms used to describe this “new fuel”. There is a standard specification that describes this product. Turbine (jet) fuels are covered by the American Society of Testing Materials Standard, (ASTM) D-7566. Actually, the title of this specification is: “Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons”. Specifically, D-7566 refers to two types of Aviation Turbine Fuel: “Jet A” and “Jet A1”. (Note that there are several different aviation turbine fuels available (e.g. “Jet B”) of which the above are only two).

The ASTM standard focuses on synthefirsized hydrocarbons, and not all synthesized hydrocarbons can be considered “biojet” or “Renewable Jet (RJ)” fuels. The specification allows for synthesized hydrocarbons produced from renewable as well as non-renewable feedstocks, such as natural gas and coal, both of which are fossil fuels. There are also different production processes, including, but not limited to: Fischer-Tropsch [F-T] processing and Hydrotreated Esters and Fatty Acids [HEFA] processing. There is also Alcohol to Jet (ATJ). All of these produce synthesized hydrocarbons for Aviation Turbine Fuel.

In Section 6 – “Materials and Manufacture” – the Standard specifies that the maximum blend ratio of petrojet to biojet is 50/50:

“6.1.1 Conventional blending components or Jet A or Jet A-1 fuel certified to Specification D 1655; with up to 50 % by volume of the synthetic blending component defined in Annex A1.”

Most, if not all, airlines testing or using biojet have decided to blend at much higher ratios of petrojet to biojet.

Gulf Hydrocarbon has worked with air carriers and jet fuel suppliers to determine optimal blend percentages and to determine how to realize the maximum economic benefits from biojet utilization.

In general, biojet can is considered to be “synthesized hydrocarbons from renewable sources”, such as biomass – or products produced from biomass. Feedstocks might include organic oils from plants and animals as well as gasified biomass. It is important to note that most renewable synthesized hydrocarbons (biojet fuels) are covered by D-7566, Annexes 2 and 5.


Biojet fuels offer several advantages over petro-jet fuels:

  1. When biojet fuel is used for aviation, the Green-House Gas (GHG) emissions can be reduced by 90%, relative to petrojet, a huge environmental benefit. (NREL)
  2. Biojet tends to have significantly higher “Net Heats of Combustion”, another way of saying that the fuel has a higher energy density. Here’s what ASTM D-7566 says about Net Heat of Combustion:

“X1.5.2 Net Heat of Combustion—The design of aircraft and engines is based on the convertibility of heat into mechanical energy. The Net Heat of Combustion provides a knowledge of the amount of energy obtainable from a given fuel for the performance of useful work; in this instance, power. Aircraft design and operation are dependent upon the availability of a certain predetermined minimum amount of energy as heat. Consequently, a reduction in heat energy below this minimum is accompanied by an increase in fuel consumption with corresponding loss of range. Therefore, a minimum net heat of combustion requirement is incorporated in this specification.”

We can therefore infer that the inverse is also true, i.e. that an increase in heat energy above this minimum is accompanied by a decrease in fuel consumption with corresponding increase in range. Moreover, less fuel means less fuel weight, allowing for more profitable (increased) utilization of Payload/ZFW. Thus, we can immediately see the financial benefits of going farther with a lower fuel consumption rate.

  1. Renewable jet fuels, in conformity with the Renewable Fuel Standard (RFS), are eligible for RIN credits which significantly impact fuel expenses.


There are disadvantages to the use of biojet fuel (or any jet fuel containing synthesized hydrocarbons), mostly relative to the logistics surrounding its utilization:

  1. Most synthetic hydrocarbons are produced in relatively small amounts and represent a very small quantity in comparison to their petrojet counterparts. For example, Diamond Green indicates that their St. Charles facility in Louisiana can produce around 275 mmgpy of Renewable Diesel (RD)/Renewable Jet. By contrast, note that Valero’s, Houston refinery (by most standards “a mid-sized plant”) has a daily throughput of 235,000 barrels, which, generally speaking, would be a production of about 3.29 mm gallons per day of petro-diesel and petrojet fuels.

To put the above numbers in their proper perspective, note that U.S. airlines alone consumed 17.3 billion gallons of jet fuel in 2017, with worldwide consumption of about 90 billion gallons. Broken down, this indicates that U.S. airline fuel consumption averages about 47 million gallons daily. Thus, even if all of its daily production were jet fuel, a refinery like Valero’s could only produce about 7% of the airlines’ daily consumption, and the Diamond Green plant would be more like 2%. Of course, at maximum blending percentages, these amounts would double, but that would imply an equal utilization of petrojet vs biojet. At the maximum blend percentage of 50/50, we would need over thirty plants with capacities similar to the Green Diamond plant, and as of 24 October, 2018, there were only three.

  1. The next issue is transporting the new biojet fuel. Even at miniscule amounts, biojet fuel must be transported to airports’ fuel storage facilities. In the case of petrojet, virtually all major airports have pipeline access. Thus, petrojet refineries can simply inject the various pipelines with their petrojet fuels for delivery to airports around the country. This is by far the most cost-effective means of transporting fuels. But many, if not all biojet producers are located close to their feedstock sources as it is much more cost-effective to transport the commodity with the highest energy density; i.e., the biojet fuel. Often these biojet production facilities are far away from pipelines and other petroleum infrastructure, necessitating transportation by truck, rail or ship (in order of descending transport expenses). Assuming good access and the necessary infrastructure, loading rail cars and ships is relatively efficient. But trucks are a different story. Normally, a large over-the-road tanker truck can carry around 7,500 gallons (depending on the density of the fuel transported). Thus, if it didn’t have rail, seaport or pipeline access, even the facilities like Diamond Green would need 106+ truckloads per day to transport their fuels. The logistical nightmare and infrastructure needed to refuel 106 trucks per day would be overwhelming.

A major hurdle for pipeline access is likely to be receiving permission for biojet to be shipped via pipeline. While biojet is much more widely accepted today, the necessity to prove that the biojet molecules are the same as the petrojet molecules still exists. This same problem may appear at airports also, as in many of the airport fuel communities, biojet may still be viewed as a “contaminant”. (Biojet has its own ASTM Fuel Standard because aircraft engine warranties are based upon ASTM fuel specifications). If D-7566 fuel is not expressly covered in the warranty, an airline will likely not want to risk possible warranty invalidation by using this biojet.

  1. The last and biggest hurdle facing widespread commercial utilization of biojet is price. Airlines are particularly vulnerable to fuel pricing. In January 2019, the Gulf Coast Spot Price for [petro] jet fuel averaged $1.79/gallon. At this writing (second week of March 2019), the price is $1.92, a $0.13/gallon increase. Assuming average fuel consumption of 2900 gallons per hour and 4000 hours per year of flight time, the fuel cost increase for one year amounts to more than $1.5 million dollars for one aircraft. Last week, petro-jet fuel was selling for about $1.86 per gallon. Yellow Grease (a common renewable biomass feedstock for RJ production) was selling for about the same price, before production and refining to biojet fuel. (The NREL estimates production costs at about $5.00/gallon, all in.)


Can biojet ever compete with petro-jet economically? Why would any carrier want to spend more for the biojet option? The first part of the answer lies with the RINs (credit for transportation fuels blending). Biojet (like Renewable Diesel) can qualify for non-ester renewable fuel RINs with equivalence values of 1.6-1.7. With today’s cellulosic fuel RINs at about $1.80, a gallon of this fuel could qualify for a total [cash] credit of $3.06. Furthermore, if the fuel is eligible for the CARB LCFS credits, depending on the fuel’s energy density and CO2 reduction, at today’s LCFS price of about $192, biojet could qualify for another $0.99/gallon credit. Now, even at $5.00/gallon, biojet then becomes much more interesting at its net cost of $0.95/gallon – especially given the increased range and payload capabilities with less overall fuel consumption.

The second part of the answer involves the enhanced performance characteristics of a fuel with an increased energy density. More energy per kilo means less fuel weight and more capacity available for paying passengers or cargo.

Taken together, the advantages of biojet fuel utilization are compelling, especially today when fuel prices for both are virtually at parity, and in an era where airlines have been forced to the point where every single service is an additional cost, the advantages of biojet fuel could have very positive impacts on operating expenses.

Biojet is the fuel of the future and there are experts available to work with carriers and engine manufacturers to determine optimum blend percentages for optimal performance and maximum economic advantages.

About the Authors: Jess Hewitt and Jonathan Lewis are independent consultants and member of Lee Enterprises Consulting Group. Hewitt is the President and CEO of Gulf Hydrocarbon, and Lewis is Gulf Hydrocarbon’s technology associate. The opinions expressed herein are those of the authors and do not necessarily reflect the opinions of Lee Enterprises Consulting.

Lee Enterprises Consulting is the world’s premier bioeconomy consulting group, with over 100 highly qualified experts serving in all these areas. We can assist show clients in obtaining maximum advantages performance-wise and economically from biojet fuels that appear to cost more at first glance. Take a look at our experts and the services we provide. In smaller projects, we have just the right expert. In larger projects, we have the advantage of assembling full service, interdisciplinary teams with one point of contact. Call us at 1+ (501) 833-8511 or email us for more information.


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