Global biofuels production is nearing 2 million barrels per day – an impressive number that ranks biofuels ahead of Libya among oil producing nations – but most of this consists of conventional biofuels derived from corn starch and sugarcane. While these fuels may meet ground transportation needs, they lack the performance characteristics required by jet engines.

For end-users such as commercial airlines and the U.S. Navy, demand is focused squarely on advanced drop-in biofuels, which are fungible with existing petroleum infrastructure and derived from non-food feedstocks. Led by industry stakeholders such as Boeing, Airbus, and Embraer, industry consortia involving airlines, nonprofits, government agencies, and trade groups have set a course to ramp up the use of advanced biofuels over the next decade. With the long shadow of rising oil prices and EU’s Emissions Trading System looming, for these players, market share and profitability are at stake. The U.S. Navy, which is focused more on security, has been at the vanguard in driving biofuels innovation and has set its sights on deploying the “Great Green Fleet” in 2016, composed of vessels and ships powered by advanced biofuels.

While advanced biofuels may skirt the image problems of conventional biofuels – a dubious connection to rising food prices and land use change – they have so far proven incapable of meeting end-user demand. The bruising road to commercialization has raised difficult questions about which pathways commercial airlines and the Navy should pursue. Eschewing conventional biofuels, and lacking a sufficient fuel supply from advanced pathways, these customers are caught between a rock and a hard place.

Enter alcohol-to-jet, or ATJ, which has gained traction as an alternative advanced biofuels pathway for meeting demand from aviation and military customers. By fermenting agricultural residues and woody biomass in an advanced process similar to conventional ethanol production, ATJ (along with its precursor, isobutanol) is emerging as an appealing pathway for advanced biofuels and biojet commercialization.

For ATJ to be viable, however, it all comes down to cost. As Jim Lane of Biofuels Digest notes, costs are only estimates at this point; price parity is a threshold that has yet to be realized. While ATJ holds significant promise, a number of competing pathways also show commercialization potential.

Advanced biofuels derived from oilseeds and algae, which fall within ASTM’s Bio-SPK jet fuel spec, are the only aviation biofuels pathway certified for commercial use today. While companies like Solazyme have delivered some gallons meeting ASTM’s Bio-SPK jet fuel spec, this is a far cry from the scale of supply needed to offset petroleum dependence in a significant way. Long-term, there are serious doubts as to whether oilseeds can supply demand at a cost competitive to petroleum-based jet fuel.

Scale is one advantage ATJ has over other pathways. Unlike camelina and jatropha – key feedstocks used in producing Bio-SPK fuels that depend on farmer’s willingness to plant the crop in the first place – agricultural residues and woody biomass are already available in abundance throughout the world. Companies like Virent, Gevo, and ZeaChem are targeting these feedstocks, with commercialization slated for mid-decade.

Regulatory hurdles must still be overcome. ASTM is currently testing ATJ with certification expected sometime in the next few years. Without this certification, these fuels have no pathway to commercialization.

Ultimately, ATJ is expected to play a key role in the aviation biofuels mix. There is no silver bullet, but ATJ should provide part of the advanced biofuels silver buckshot mix.