aviation fuel

Under the Clean Air Act (CAA) the EPA is responsible to protect the Public from toxic pollutants including lead in motor vehicle exhausts.  The EPA is also responsible for the Federal ‘renewable fuels standard’  program and setting annual Transportation ethanol blending-consumption targets.  Lead in the form of ‘tetraethyl lead’ (TEL), has been added to gasoline as an octane (increase) additive since the 1920’s.  To initially address this very toxic pollutant, the EPA banned all TEL from ‘light duty vehicle’ (LDV) petroleum gasoline.  This required the Auto Industry to develop the LDV ‘internal combustion engine’ (ICE) technology upgrades required to operate reliably on the new unleaded gasoline produced by the Oil Industry.

Although all lead was removed from LDV gasoline before 1996, lead continues to be used in ICE powered aircraft ‘aviation gasoline’ (avgas), fuels.  Despite numerous LDV ICE technologies developed to eliminate the need for leaded gasoline in the past, lack of aircraft ICE technology innovations and alternative fuels development apparently continue to be barriers to eliminating the need for leaded avgas.  One of the most feasible alternatives to leaded avgas is ethanol.  Despite a history of aggressively forcing the Commercial and Industrial sectors to develop the necessary technologies required to substantially reduce most vehicle tailpipe emissions and replace increasing volumes of petroleum gasoline with ethanol, why has the EPA failed to ban lead from avgas in recent years?

Health Effects of Lead

There is no question that lead is extremely toxic to humans.  The Federal Government began substantially eliminating this known health hazard back in 1977 when leaded paint was banned, followed by totally banning LDV leaded gasoline by 1996.  Children are most at risk to lead exposure since inhaled/consumed lead is absorbed into the young’s growing tissues and organs, which causes numerous mental-physical health problems.   Unlike most other pollutants such as SO2, lead is retained in our bodies and is carrier into adulthood.  Childhood and long-term lead exposure also adversely effects adults in their retirement years.  While the current debate surrounding leaded avgas is apparently based on exposure concentration-effects, there is no question that less, shorter term, or better yet no lead pollution exposure is best for all children.

History of High Octane Leaded Gasoline

All early LDV’s and aircraft were initially powered by gasoline ICE’s.  Past technology advancements in civilian and military LDV/aircraft began to rapidly increase ICE performances (increased torque-horsepower (hp), increased acceleration and speed).  These vehicle/aircraft performance improvements were achieved by many advancements in ICE technology designs that included increased displacement (motor size/hp), higher compression ratios, fuel/ignition system upgrades, and the installation of turbo/super chargers.  To fuel these new high performance ICE technology advancements required increasing the ‘research octane number’ (RON) of gasoline fuels. 

Meeting the growing demand for higher octane gasoline required petroleum refinery process technologies (reforming, alkylation, etc.) advancements/upgrades and the increased use of TEL additives.  While ethanol based fuels were definitely a high octane alternative or option to meet the growing market demand, leaded petroleum gasoline became the market supply standard apparently due to more favorable economics.  As the higher performance ICE technologies continued to develop, gasoline fuel octane requirements increased up to the 100 (RON) level and use of TEL increased almost proportionally.  The lead content of LDV gasoline and avgas increased up to about 5 gram/gallon (+/-) by 1970.  After Congress amended the CAA 1970-1990 the EPA was required to substantially reduce all LDV tailpipe emissions, including a 90% reduction of SO2 and NOX, and 100% reduction of lead for LDV’s.  

Substantially reducing all LDV tailpipe emissions was an extremely, technologically challenging task for the Auto and Oil Industries.  Despite the huge technology gaps and challenges, the EPA still established very aggressive LDV tailpipe emission standards that required developing new and highly innovative emission control technologies that did not exist anywhere in the world prior to 1970.  This historic EPA regulatory strategy was commonly called ‘technology forcing’ (or ‘action forcing’)   

The required and major LDV tailpipe emission reduction technology breakthroughs were very successfully developed by the Auto and Oil Industries.  These included developing new catalytic converters, and lower sulfur, unleaded gasoline.  The EPA strategy for reducing/eliminating lead emissions was to ban its use as a gasoline additive.  This no lead gasoline solution was also required due to the fact that lead would poison the newly developed catalysts used in the LDV exhaust catalytic converters.  Lead poisoning would severely reduce converter catalyst life needed to continuously meet all tailpipe emission standards over the useful life of the LDV.

Clearly during the 1975-1995 period, forcing the development of LDV tailpipe emission reduction technologies and producing 100% unleaded LDV gasoline was the EPA’s priority.  Aviation leaded avgas, however, was apparently not an EPA focus priority until recent years.  Interestingly, during the phase-out of leaded gasoline, owners of high performance street, muscle, or hotrod LDV’s that required 100 RON leaded gasoline temporarily made the switch to leaded avgas during the interim, until unleaded race car (such as NASCAR) fuels became available.

Brief Ethanol and Flex Fuel Vehicle Technology History

The use of ethanol as a LDV fuel began with the Ford Model ‘T’.  Even though Model T’s were originally designed to operate on ethanol, market demand quickly switched to petroleum gasoline.  ‘Flex fuel vehicles’ (FFV) and associated technology did not become significantly available until The Energy Policy Act (EPAct) of 1992 was passed by Congress to encourage the production of alternatives to petroleum.  Alternative fuels included ethanol, and as a result of EPAct 1992 manufacturers began producing FFV’s designed to operate on alternative ethanol fuels.  Auto Industry incentives such as CAFE compliance credits for selling FFV’s were fairly successful in creating the current U.S. FFV fleet of up to 8+ million vehicles today.  Unfortunately, due to a combination of limited E-85 fueling stations and relatively poor fuel efficiency/increased operating cost compared to petroleum gasoline, very few FFV’s routinely operate on E-85 today.

The octane of E-85 is typically 100-105 RON, which is generally wasted in average FFV’s that often only require regular 87 RON.  However, high performance vehicle owners-drivers have discovered that their 500+ hp, super-charged race cars and motorized vehicle toys that have ethanol FFV designed capability can be much more economically operated on E-85 vs. most available 100 RON race car petroleum gasoline.

Recent Leaded Avgas Regulatory and Legal Actions

Following World War II high-leaded avgas with octanes up to typically 100/130 (RON/turbo octane rating) were commonly used in high performance and many older aircraft.  Following the EPA regulatory standards that eliminated all leaded LDV gasoline, the Aircraft and Oil Industries began slowly developing lower/no lead avgas fuels and aircraft ICE technologies required to operate on unleaded avgas.  High lead 100/130 avgas was largely replaced by 100 RON low lead (100LL) avgas and slowly increasing amounts of unleaded (UL) avgas (82 (RON) UL, 85UL and 91UL). The Federal Aviation Administration (FAA) currently projects that the majority of existing aircraft probably can operate safely on UL avgas.  Only the very high performance and older aircraft apparently are not certified to operate on avgas fuels other than 100LL.

The EPA did not appear to put much priority on addressing leaded avgas until the mid 2000’s.  The lack of EPA focus on avgas lead was apparently due to insufficient data to reasonably address the public health endangerment.  This statement was surprising, particular since it represents a huge departure from past EPA regulatory practice.  This EPA’s current position of not addressing and reducing 50% of all known and readily controllable U.S. man-made lead emissions and its harmful impact on children is very concerning. 

As a result of the EPA’s failure to address avgas lead and its potential health impacts, the Friends of the Earth (FoE) petitioned them in 2006 to address this issue.  The EPA’s initial response to the FoE’s petition was that addressing avgas lead was not scheduled for completion until late 2015.  In 2010 the EPA issued notice of proposed rulemaking to potentially address ICE aircraft leaded avgas (in response to the FoE’s 2006 petition).  Despite the fact that any significant level of lead exposure from avgas can be significantly harmful to children, the EPA continued to delay any possible action until (at least) 2015.  The FoE’s response to this EPA delayed action was to sue.  Despite the EPA’s continued delay of very likely needed actions to ban leaded avgas, the Court recently found that no organization can force the EPA to evaluate and make (a more timely) determination on the health effects of leaded avgas.

Technical Barriers to Unleaded Avgas

The ICE Aircraft Industry faces some of the same technical challenges as the Auto Industry faced 1975-1995, but significantly less complex.  Unlike the required LDV upgrades that included 90% tailpipe reductions of all pollutants (plus the new CAFE standards compliance), the largest ICE aircraft technical challenges appear to be conversion to unleaded avgas only.   Dealing with the need for unleaded avgas largely includes finding alternative fuels to replace current 100LL avgas and making aircraft ICE upgrades necessary to reliably and safely operate on 100 RON or possibly lower octane UL avgas. 

Unlike some early LDV ICE conversions from leaded to unleaded gasoline and problems that caused premature engine wear/failures that may have stranded some (land based) motorists, the reliability of aircraft is a much greater safety concern.  That is why the FAA is responsible to thoroughly evaluate-certify all aircraft ICE modifications and 100LL replacement fuels to ensure the approved changes do not risk in-flight engine stalling-failures, causing potential aircraft catastrophes.  To complete this task the FAA has formed a committee of the primary stakeholders including the EPA, AOPA, FAA specialists, Aircraft Manufacturers, and existing avgas Suppliers.  The FAA has also developed a fairly comprehensive and detailed plan to carry out the critical work necessary to safely remove lead from current avgas.  

The Aircraft Owners and Pilot Association (AOPA) is very active in the development of alternatives to leaded avgas.  A couple recent articles by the AOPA on this issue (Lead is King I and Lead is King II) cover many of the most important issues for the ICE aircraft Industry and owners. 

As with the past LDV ICE conversion to unleaded gasoline, the conversion of ICE aircraft to unleaded avgas will require similar technology upgrades.  These ICE upgrades will likely include replacing obsolete ICE cylinder heads/valves required for UL operation, ICE modification to possibly operate on lower octane UL avgas and upgrades needed to reliably operate on alternative avgas fuels such as ethanol.  Most of these ICE aircraft technology upgrades can be based on existing LDV ICE technology innovations made since the 1970’s.  The existence of many required ICE technology upgrades should make the ICE aircraft conversions to UL avgas far less challenging then faced by the Auto Industry 30-odd years ago.

100LL Avgas Alternative Fuels

The AOPA reports that about 70% of existing ICE aircraft can safely operate on 91/96 or lower RON UL avgas.  The 30% balance of existing (high performance and older) ICE aircraft will likely continue to require 100 RON avgas.   Producing lower octane UL avgas should not be too challenging since removing all the lead from 100LL basically yields a 91/96UL avgas with only minor petroleum formulation adjustments.  Producing 100UL avgas will be more challenging, but still very feasible based on existing fuels production capabilities.  100UL can be produced by slightly upgrading current NASCAR 98 RON UL fuel or possibly by blending ETBE (ethyl tertiary butyl ether made from ethanol).   

‘Aviation gasoline ethanol’ (AGE-85) can be produced to readily displace 100LL.  AGE-85 is a 100+ RON UL fuel similar to E-85 and can be produced with currently available fuel production facility capabilities.  The existing mechanical upgrades needed to operate older aircraft on AGE-85 are almost identical to existing LDV E-85 FFV technology upgrades (mostly fuel line, seals and valve rubber/synthetic materials upgrades).  One unique technical issue that might need addressing is upgrading the ICE aircraft fuel systems and the airport fueling infrastructure to dry and prevent AGE-85 water contamination (a potential fuel icing issue at altitude). 

Future of Unleaded Avgas

Half of existing U.S. lead emissions can be readily reduced by banning all lead in avgas.  While the EPA must have the FAA approval to require this regulatory action, the needed technology upgrades should not be as challenging as the Auto Industry faced in the past.  The ICE Aircraft Industry has a huge advantage since nearly all of the required technology improvements have previously been developed by the Auto Industry.  Despite these factors the FAA apparently projects it could take another 10 years to develop a replacement for 100LL.  If true, this would mean the Aircraft Industry has required over 40 years to implement and certify primarily existing ICE unleaded technologies.  Taking 40 years to develop-approve needed unleaded ICE technologies would make the Aircraft Industry likely the slowest and least innovative business sector in recent U.S. history.

To more quickly reduce 50% of existing U.S. lead emissions and eliminate the associated threats to our children’s health, the Federal Government needs to be much more aggressive in banning leaded avgas.  It’s possibly time to restore the past EPA regulatory development strategy of ‘technology forcing’.  Due to the extremely slow progress the ICE Aircraft Industry has made in recent decades, the EPA/FAA need to substantially increase their motivation to make the needed technology upgrades and certifications. 

AGE-85 alternative fuels can readily be produced within a year or so utilizing existing processing-production capabilities of the U.S. Oil or Ethanol Industries.  Such an action would have the duel benefit of substantially reducing the lead exposure health risk to numerous children, but also help increase the Transportation sector’s ethanol consumption in compliance with future ‘renewable fuels standards’.  If converting older, high performance aircraft to unleaded avgas proves to be uneconomical, perhaps it’s time to start retiring these typically 30+ year old aircraft.