Biofuels and Renewable Fuels

Biofuels are liquid or gaseous fuels derived from recently-living biomass — distinct from fossil fuels by the carbon-cycle timescale. The principal commercial classes are ethanol (corn, sugarcane, cellulosic), biodiesel (FAME — fatty acid methyl esters), renewable diesel (HVO — hydrotreated vegetable oil), sustainable aviation fuel (SAF), renewable natural gas (RNG, biomethane), and emerging electrofuels / e-fuels (Power-to-Liquid via hydrogen and captured CO2). US policy under the Renewable Fuel Standard (since 2005, expanded 2007) and California’s Low Carbon Fuel Standard (LCFS, since 2009) drives volumes and prices. The Inflation Reduction Act of 2022 introduced the 45Z Clean Fuel Production Credit (effective January 1, 2025) and the 40B SAF Credit (2023-2024). The global biofuels market grew from approximately 16 billion liters in 2000 to over 165 billion liters in 2023, with the US (~62 Bliters ethanol + RD/biodiesel), Brazil (~30 Bliters ethanol), and the EU (~17 Bliters biodiesel) the dominant producers.

Corn ethanol

US ethanol production is overwhelmingly from corn starch via dry-mill fermentation. Process steps: corn → grind → liquefy → saccharify (alpha amylase, glucoamylase enzymes from Novozymes/DuPont/DSM) → ferment with Saccharomyces cerevisiae → distill → dehydrate via molecular sieve to 199.5 proof (~99.7% ethanol). The Renewable Fuel Standard (RFS), enacted in the Energy Policy Act of 2005 and expanded by the Energy Independence and Security Act of 2007, mandates blending biofuels into US transportation fuel via RIN (Renewable Identification Number) credits.

The 2007 expansion set a 36 billion gallon target by 2022 with sub-mandates:

• D6 conventional biofuels (corn ethanol, capped at 15 Bgal post-2015);
• D4 biomass-based diesel;
• D5 advanced biofuels (any non-corn-ethanol biofuel with ≥50% CI reduction);
• D3 cellulosic biofuel (capped well below original target due to commercialization failures).

US ethanol production peaked near 16 Bgal/yr in 2018-2019 from approximately 200 operating plants. Major operators:

• POET — privately held, ~33 plants ~3 Bgal capacity;
• Valero Renewable Fuels — ~14 plants ~1.7 Bgal;
• Archer-Daniels-Midland (ADM) — multiple corn-belt plants;
• Green Plains (NASDAQ:GPRE);
• The Andersons (NASDAQ:ANDE);
• Cargill;
• Marquis Energy;
• Flint Hills Resources (Koch subsidiary).

Output dropped to ~13.9 Bgal in 2020 from COVID demand collapse and rebounded to ~15.6 Bgal 2023. The EIA Petroleum Supply Monthly tracks weekly and monthly production by PADD region.

Coproducts dominate the economics. Dried distillers grains with solubles (DDGS) — the protein/fiber/fat residue after starch fermentation — are sold as cattle, swine, and poultry feed at roughly one-third of corn feed price by mass; about 17 kg DDGS per bushel of corn. Corn oil extracted at the back-end of fermentation feeds renewable-diesel feedstock supply at premiums of $0.30-$0.60/lb 2023-2024. Coproduct values typically supply 30-40% of plant revenue, and during periods of low ethanol prices coproducts have determined plant survival.

Brazilian sugarcane ethanol is the global low-cost producer. The sugar/ethanol “usina” sector centers on:

• Cosan Raízen (joint venture with Shell, ~30 mills, ~3 Bgal sugar and ethanol capacity);
• Petrobras Biocombustíveis (now divested);
• São Martinho;
• Adecoagro;
• Tereos Brasil (subsidiary of French Tereos);
• BP Bunge Bioenergia (joint venture with BP after 2019 BP-Bunge merger).

Brazilian production was ~30 billion liters (~8 Bgal) in 2023 split roughly 55% hydrous (E100) and 45% anhydrous (blended). Brazilian flex-fuel vehicles introduced 2003 (Volkswagen Gol TotalFlex) became >80% of new car sales by 2010 and made E25-E100 choice a price-driven daily decision at the pump — the most successful biofuels policy implementation globally. The RenovaBio program (effective 2020) extends sugarcane-ethanol’s role with tradeable CBIO decarbonization credits.

Cellulosic ethanol — the unfulfilled promise

Second-generation (2G) cellulosic ethanol from corn stover, switchgrass, wood, or sugarcane bagasse breaks down lignocellulose using either:

• Dilute acid + cellulase enzymes (Novozymes Cellic CTec, DuPont Accellerase);
• Steam explosion pretreatment;
• Organosolv pretreatment (alcohol-water lignin fractionation); then ferments hexose and pentose sugars (the latter requiring genetically engineered xylose-fermenting yeast or Z. mobilis).

The 2007 EISA RFS target was 16 Bgal/yr cellulosic by 2022. Actual production has been a small fraction of target, leading to repeated EPA cellulosic-mandate waivers.

The graveyard of cellulosic ethanol projects:

• POET-DSM Project Liberty (Emmetsburg IA, opened 2014, 20 MGal nameplate, joint venture with DSM) — never reached nameplate, shifted to anaerobic digestion 2019, DSM exited 2021;
• Abengoa Bioenergy Hugoton KS (25 MGal, opened October 2014) — Abengoa bankruptcy 2016, plant idled;
• DuPont Cellulosic Ethanol Nevada IA (30 MGal, opened October 2015) — closed November 2017, sold to Verbio (German), reconfigured to RNG from corn stover 2021;
• GranBio Bioflex Itúiba (São Miguel dos Campos, Alagoas, Brazil, 82 ML/yr nameplate ~22 MGal/yr, opened September 2014) — Brazilian flagship, intermittent operation; new GranBio AVAP technology promised next-generation cellulosic;
• Beta Renewables Crescentino Italy (Mossi Ghisolfi, 75 MLiters, opened 2013, parent bankruptcy 2017).

The collective cellulosic underperformance led to repeated EPA RFS waiver actions and the de facto retreat of the cellulosic mandate.

The economics never worked at oil prices below ~$80/bbl absent very heavy subsidies. Capital costs ran 3-5x first-generation corn ethanol per gallon of capacity. Enzyme cost despite Novozymes’s 90% reductions 2008-2018 remained a binding constraint.

Biodiesel (FAME) and renewable diesel (HVO)

Biodiesel is fatty acid methyl ester (FAME) produced by base-catalyzed transesterification of fats/oils (soybean, canola, palm, tallow, used cooking oil — UCO) with methanol producing FAME + glycerol byproduct. FAME blends from B5 to B100 are sold; cloud-point and cold-flow issues limit winter use of B20+. ASTM D6751 is the US specification, EN 14214 the European.

Renewable diesel (RD) is paraffinic diesel produced by hydrotreating triglycerides (HVO process) with hydrogen over a catalyst (typically NiMo or CoMo sulfided) at 300-400 °C and 30-180 bar. The reaction removes oxygen as water and produces C15-C18 normal paraffins, which are then isomerized for cold-flow improvement. RD is chemically a hydrocarbon meeting ASTM D975 — fully fungible with petroleum diesel including at 100% blends (R100). The Neste NEXBTL process and Honeywell UOP Ecofining process dominate commercially; Axens Vegan, Topsoe HydroFlex, and Haldor Topsoe HT-IsoCracking are alternative licenses.

Leading RD producers as of 2024:

• Neste Oyj (Finland) — operates Porvoo (Finland), Rotterdam (Netherlands), Singapore. The Tuas Singapore site is the largest single RD/SAF site globally, expanded 2023 to 1.3 Mt/yr capacity. Martinez California joint venture with Marathon Petroleum (730 M gal RD capacity 2024). Total Neste capacity ~6.8 Mt/yr (~2.3 Bgal/yr) of RD+SAF combined.

• Diamond Green Diesel (joint venture Valero Energy + Darling Ingredients). Norco Louisiana (700 Mgal capacity expanded 2021). Port Arthur Texas (470 Mgal opened 2022 + SAF unit 235 Mgal expected late 2025). Largest US producer at >1.2 Bgal capacity.

• Renewable Energy Group (REG) — acquired by Chevron June 2022 for $3.15B. Operates Geismar LA biodiesel/RD plant.

• Phillips 66 Rodeo Renewed — Rodeo California refinery converted to 800 Mgal RD/SAF capacity, fully online April 2024.

• Marathon Martinez — 390 Mgal RD via stand-alone; partnered with Neste at Diamond Green-style co-location.

• ENI (Italy) — Venice Porto Marghera converted refinery, 360 kt/yr capacity 2014, expanded 750 kt/yr 2024; Gela Sicily 750 kt/yr.

• HF Sinclair (formerly HollyFrontier) — Cheyenne WY and Artesia NM RD conversions; Sinclair WY.

• TotalEnergies La Mède France (500 kt/yr, opened 2019, converted from refining).

• Preem Lysekil Sweden (HVO co-processing).

Total US RD capacity reached ~4.5 Bgal/yr by mid-2024 — well in excess of US demand absent strong policy. California LCFS demand absorbs the bulk of US RD (~80% of California diesel-pool replacement by 2024). The capacity overhang led to D4 RIN price compression late 2023 and plant idling/curtailment by mid-2024.

Sustainable Aviation Fuel (SAF)

SAF is jet-range hydrocarbons (C8-C16 mostly) certified for blending up to 50% (ASTM D7566 Annex 1-7) with conventional Jet A-1. Eight currently-approved pathways:

1. FT (Fischer-Tropsch synthesis from syngas) — Annex 1, 2009. Biomass or waste gasified to CO+H2, then catalytically synthesized to hydrocarbons over Co or Fe catalysts (Velocys, Fulcrum BioEnergy, Sasol historical CTL).
2. HEFA (Hydroprocessed Esters and Fatty Acids) — Annex 2, 2011. Same chemistry as RD with fractionation to jet range; Neste MY SAF, World Energy Paramount CA (first US commercial SAF supplier, 2016).
3. SIP (Synthesized Iso-Paraffins from fermented sugars) — Annex 3, 2014. Amyris-Total farnesane.
4. FT-SKA (FT with aromatics) — Annex 4, 2015.
5. ATJ-SPK (Alcohol-to-Jet, from ethanol or isobutanol) — Annex 5, 2016. Gevo Lake Preston SD (Net-Zero 1 project, 65 Mgal SAF, FID 2022, startup expected 2027). LanzaJet Freedom Pines Soperton GA (10 Mgal nameplate, opened January 2024, world’s first commercial ethanol-to-jet, backed by Shell, BA, LanzaTech, Mitsui).
6. CHJ (Catalytic Hydrothermolysis Jet) — Annex 6, 2020. Applied Research Associates / Chevron Lummus ARA.
7. HC-HEFA-SPK (algae) — Annex 7, 2020. IHI Corporation.
8. ATJ from isobutanol — Annex 8, 2023.

SAF mandates and incentives:

• EU ReFuelEU Aviation Regulation 2023/2405 (entered into force October 2023): 2% SAF minimum 2025, 6% by 2030, 20% by 2035, 70% by 2050; sub-mandate for synthetic e-fuels 1.2% 2030 → 35% 2050.

• UK SAF Mandate (Renewable Transport Fuel Obligation Order 2024) — 2% 2025 → 22% 2040 with synthetic sub-mandate.

• US: SAF tax credit under IRA Sec 40B ($1.25-$1.75/gal for SAF with ≥50% CI reduction, sliding) covering 2023-2024. Transitioned to 45Z Clean Fuel Production Credit (up to $1.75/galSAF,upto$1.00/gal RD/biodiesel) effective January 1, 2025. Both require GREET-model-based CI calculation; Treasury/IRS guidance January 2025 finalized 45Z methodology including book-and-claim biogas, CCS, and farming-practice CI bonuses.

• ICAO CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation) — voluntary pilot phase 2021-2023, first phase 2024-2026, mandatory phase 2027-2035; SAF reduces offset obligation.

• Singapore SAF mandate (2026 implementation, 1% rising to 5% by 2030).

• Japan SAF target — 10% of jet fuel by 2030 (METI roadmap 2022).

Notable SAF supply deals and offtake agreements:

• United Airlines purchased equity in Cemvita Factory and Fulcrum BioEnergy (Fulcrum bankrupt 2024);
• American Airlines + Gevo (5 yr offtake);
• Delta + Gevo + DG Fuels Louisiana;
• Lufthansa + Neste;
• IAG (British Airways parent) + LanzaJet;
• Microsoft, Bank of America, JPMorgan, Boston Consulting Group corporate SAF certificate purchases via Sustainable Aviation Buyers Alliance (SABA).

Pathway feedstocks

US RD/SAF demand has strained the lipid feedstock market. Soybean oil prices doubled 2020-2022 partly on RD demand. The USDA-RFS scoring of new feedstocks created surges in used cooking oil (UCO) imports from Asia (China, Indonesia, Malaysia) and tallow imports from Brazil and Australia. The US Treasury’s 2024 sustainability-attribute rules required tighter UCO chain-of-custody to prevent virgin palm being re-exported as UCO — a recurring fraud concern flagged by the EU REDcert and ISCC certification systems.

Animal fats — yellow grease (~$0.40-$0.60/lb 2024), tallow, white grease — flow from rendering operations:

• Darling Ingredients (~30% of US rendering; owns half of Diamond Green Diesel);
• JBS Friboi;
• Tyson Foods;
• Smithfield Foods.

Cover crops (winter camelina, carinata, pennycress) are emerging dedicated oilseed feedstocks:

• Nuseed (carinata, Australian-listed) for SAF feedstock supply contracts with bp;
• Cibus (camelina, formerly Calyxt + Cibus merger);
• CoverCress (pennycress, joint venture Bayer-Bunge-Chevron) targeting 10 Mgal CI~25 feedstock production from 2026.

Coproducts and CI calculation

Carbon intensity (CI) — grams CO2e per megajoule of fuel energy — is the LCFS and 45Z scoring metric. GREET (Greenhouse gases, Regulated Emissions, and Energy use in Technologies) model, Argonne National Laboratory, is the US reference. ANL R&D-GREET (Renewable Energy and Decarbonization GREET, 2023 release for 45Z) is the regulatory model. California CARB CA-GREET 3.0 is the LCFS equivalent. EU Renewable Energy Directive (RED II) Annex V default values and JEC well-to-wheel analysis serve the European market.

Approximate CIs (2024 representative, gCO2e/MJ):

• Conventional gasoline: 94 (LCFS baseline 91)
• US natural gas: 78 (CARB baseline)
• US corn ethanol: 50-60 (with high-CI corn, dry-mill no CHP) to 25-40 (low-CI with regenerative-ag corn, CHP, CCS — POET CCS pilot Marcus IA; ADM Decatur IL CCS; Project Tundra ND)
• Brazilian sugarcane ethanol: 30-40 (favorable due to bagasse CHP supplying steam and electricity)
• Cellulosic ethanol: 20-40
• US biodiesel (soy): 50-65
• US biodiesel (UCO/tallow): 15-35
• US renewable diesel (UCO/tallow): 15-30
• US renewable diesel (soy): 40-55
• US SAF (HEFA UCO): 15-30
• US SAF (HEFA soy): 40-50
• US SAF (ATJ ethanol): 30-50
• US SAF (e-SAF from green H2 + DAC CO2): 5-15 (depending on electricity CI)

CCS bolt-ons to ethanol plants can cut corn-ethanol CI by 20-30 gCO2e/MJ, transforming RFS/LCFS economics:

• POET Marcus IA pilot;
• ADM Decatur ISGS (Illinois Storage Geological Sequestration) demonstration since 2017;
• Wolf Carbon Solutions ADM-DG Decatur sequestration;
• Summit Carbon Solutions Iowa-Dakotas multi-state pipeline (contested 2023-2024, eminent-domain authority litigated in Iowa and South Dakota);
• Navigator Ventures Heartland Greenway pipeline canceled October 2023;
• Tallgrass-Boer Heartland Greenway alternative routing.

RIN credits and the regulatory engine

Each gallon of biofuel produced or imported generates a RIN tracked by EPA-administered EMTS (EPA Moderated Transaction System). Obligated parties (refiners, importers) acquire RINs to meet annual Renewable Volume Obligations (RVOs) set by EPA each November-December.

RIN prices vary by category:

• D6 (conventional, corn ethanol) — typically $0.50-$1.50/RIN, has traded $0.20-$2.40 historically;
• D4 (biomass-based diesel) — typically $1.00-$2.00, hit $2.40 in 2021;
• D5 (advanced) — between D4 and D6, often tracking D4 as advanced obligated parties cross-purchase;
• D3 (cellulosic) — supplemented by Cellulosic Waiver Credits; $2-$3 range.

Small refinery exemptions (SREs) granted under §211(o)(9) became a Trump-era flashpoint with 88 SREs issued covering ~4.0 Bgal RVOs 2017-2019. The Tenth Circuit RFA v EPA (2020) constrained SREs. Biden EPA largely denied them since 2021. HollyFrontier Cheyenne Refining v RFA, 594 US ___ (2021) — Supreme Court held SREs need not be continuous extensions of pre-existing exemptions — shaped the regime. RIN fraud cases (Phillip Rivkin, Imperial Petroleum, Vitol/REG audit) drove the establishment of QAP (Quality Assurance Plans) for verified RIN generation.

Low Carbon Fuel Standard (LCFS)

California’s LCFS (CARB, AB 32 framework, adopted April 2009, fully implemented 2011) sets declining CI standards on California’s transportation-fuel pool. The 2030 target is 20% CI reduction from 2010 baseline. CARB’s December 19, 2024 amendments tighten the trajectory to a ~30% reduction by 2030 and ~90% by 2045. Credits trade on the OPIS LCFS index — prices ranged $190/MTCO2inearly2020to$216 (2020 high), collapsed to $40-$60 in 2023-2024 from oversupply driven by RD volume, recovering to ~$100 by mid-2025 anticipating the tightened standard.

Comparable programs:

• Oregon Clean Fuels Program (CFP, 2016, expanded 2022 to 37% CI reduction by 2035);
• Washington Clean Fuel Standard (CFS, effective January 1, 2023, 20% by 2038);
• British Columbia LCFS (2010, 20% by 2030);
• Canada Clean Fuel Regulations (CFR, federal, effective July 2023) — 14 gCO2e/MJ reduction by 2030;
• New York and New Mexico LCFS proposals 2023-2025 (legislative status varies).

The combined RFS+LCFS stacking gives a California-delivered RD gallon revenue from base diesel price + RFS D4 RIN (~$1.50)+LCFScredit($0.50-$2.00)+45ZPTC($1.00) — explaining the capacity build-out and helping rationalize Pacific Coast refinery conversions.

Renewable natural gas (RNG)

RNG is biogas upgraded to pipeline-quality methane (~96% CH4). Sources:

• Anaerobic digestion of dairy/swine manure (lagoons covered with HDPE membranes; the methane capture displaces field venting making CIs deeply negative — California CARB dairy RNG CIs are routinely -250 to -400 gCO2e/MJ);
• Municipal solid-waste landfills (LFG-to-RNG);
• Wastewater treatment plant digesters (BioCNG installations);
• Food-waste/agricultural-waste co-digesters.

D3 RIN credit values plus LCFS credit make dairy RNG the highest-value biofuel per BTU in the US market.

RNG players:

• BP-Archaea Energy (acquired by BP October 2022 for $4.1B; ~50 sites operating, multi-billion-dollar expansion 2023-2025);
• Clean Energy Fuels (NASDAQ:CLNE, T. Boone Pickens-founded, partnered with TotalEnergies on dairy RNG joint venture, BP on TotalEnergies dairy 2023);
• Vanguard Renewables (acquired by BlackRock-managed Global Infrastructure Partners 2022, food-waste co-digestion);
• Brightmark (multiple Indiana, Florida dairy projects);
• Aria Energy (acquired by Republic Services 2020);
• Waste Management Renewable Energy (LFG-to-RNG portfolio);
• Republic Services (LFG-to-RNG growing portfolio);
• TotalEnergies-Clean Energy dairy JV.

Major debt/equity backers: Equilibrium Capital, Generate Capital, Macquarie Asset Management, Brookfield.

US RNG production: ~50 Bcf in 2023 (~13 TBtu); projected to ~300 Bcf by 2030 if D3 RIN values hold. End uses:

• CNG (compressed) for heavy-duty trucking and refuse fleets (Republic, Waste Management, UPS limited);
• LNG (liquefied) for marine and select trucking;
• Pipeline injection for utility decarbonization (SoCalGas, PG&E, Atmos Energy, Dominion gas portfolios, NW Natural, Avista).

Gasoline blends and E15/E85

E10 (10% ethanol) has been ubiquitous in US gasoline since the late 2000s. E15 (15% ethanol) approved by EPA for 2001-and-newer vehicles 2011. Summer Reid vapor pressure (RVP) waiver for E15 contested and reinstated by EPA emergency rule annually 2022-2024. Permanent year-round E15 for eight Midwest states (Iowa, Illinois, Minnesota, Missouri, Nebraska, North Dakota, South Dakota, Wisconsin) approved February 2024 effective April 28, 2025. E85 (51-83% ethanol) for flex-fuel vehicles (FFVs). US FFV stock peaked around 21 million in 2017 then declined as automakers reduced FFV production absent CAFE credits beyond 2020.

Synfuels and e-fuels

Power-to-Liquid (PtL) e-fuels combine green hydrogen (from electrolysis of water using renewable electricity) with captured CO2 (DAC or industrial) to synthesize methanol, gasoline, jet, or diesel hydrocarbons. Synthesis routes:

• Methanol synthesis + MTG (methanol-to-gasoline; ExxonMobil MTG, used commercially by Sasol Mossgas);
• Methanol-to-jet (Honeywell UOP MTJ, Topsoe TIGAS+);
• Fischer-Tropsch synthesis followed by hydrocracking.

CIs depend critically on electricity source — 100% additional renewable electricity yields ~5-15 gCO2e/MJ; grid-average electricity is worse than petroleum on a lifecycle basis.

Key projects:

• HIF Global Haru Oni (Punta Arenas Chile, opened December 2022, ~130 kL/yr methanol demo, scaling to 550 ML/yr e-gasoline late 2020s; backed by Porsche, Siemens Energy, Baker Hughes, ExxonMobil). HIF USA Matagorda Texas project 1 Bgal/yr e-methanol/e-fuels (FID delayed to 2025+).

• Synhelion AG (ETH Zürich spinout) — DAWN industrial-scale solar thermochemical fuel demo Jülich Germany operational 2024. Produces jet-grade kerosene from CO2 + H2O + sunlight; Swiss International Air Lines offtake 2025.

• Sunfire (Dresden, SOEC electrolysis) with Norsk e-Fuel Mosjøen Norway and Climeworks DAC; eFuels GmbH consortium.

• LanzaJet — biological/chemical ATJ pathway, qualifying for SAF mandates.

• Topsoe MeOH-to-Jet pilot 2024.

• Microsoft, Stripe Climate, Frontier Climate buyer coalitions purchased early e-SAF certificates 2023-2024 as advance market commitments to scale supply.

E-fuel economics 2025: levelized cost ~$3-$6/L equivalent versus Jet A ~$0.70/L wholesale. Only viable with deep policy support (ReFuelEU synthetic sub-mandate, US 45Z PTC, voluntary corporate buyers).

Marine methanol and ammonia

Methanol as marine fuel has gained momentum post-2022 IMO MARPOL Annex VI tightening. Major orderbook commitments:

• Maersk ordered 25 dual-fuel methanol container ships (first deliveries 2023-2024);
• COSCO ordered 12;
• MSC and CMA CGM following.

Engine technology:

• MAN Energy Solutions ME-LGIM methanol two-stroke engine series;
• Wärtsilä dual-fuel methanol designs;
• WinGD X-DF-M.

Methanol bunkering infrastructure is expanding in Rotterdam, Singapore, Pearl River Delta. Green methanol supply remains scarce — Maersk’s bio-methanol offtake from Goldwind Tongliao (Inner Mongolia) and CIMC Enric is small relative to fleet demand.

Ammonia (NH3) as zero-carbon marine fuel. MAN B&W and Wärtsilä ammonia-engine designs (commercial 2024-2026). Mitsui OSK, NYK, Korean shipowners ordering ammonia-ready vessels for 2026-2028 delivery. Chemistry challenges: high-NOx emissions, unburnt NH3 slip, toxicity (LC50 ~5000 ppm for 1 hr), and lower energy density vs heavy fuel oil (~18.6 vs ~40 MJ/kg).

Critique — food vs fuel and ILUC

The 2007-2008 global food price spike intensified the food-vs-fuel debate around corn ethanol. The OECD-FAO Agricultural Outlook and World Bank papers (notably Mitchell 2008 World Bank policy research) attributed 30-75% of the price spike to biofuel demand. Later academic work (Babcock 2011 CARD, Wright 2011 Annual Review of Resource Economics 3:139) attributed less, with macroeconomic and weather factors playing larger roles.

The induced land-use-change (ILUC) literature — Searchinger et al (Science 319:1238, 2008) controversially modeled high ILUC penalties for corn ethanol and palm biodiesel. This drove the EU’s 2015 ILUC Directive (EU 2015/1513) capping food-based biofuels at 7% of transport-fuel energy. RED II (2018) reinforced the cap and identified palm oil as high-ILUC-risk (phase-out by 2030).

Cellulosic biofuels were positioned as the food-vs-fuel resolution but largely failed to commercialize at scale. Animal-fat and used-cooking-oil RD/SAF sidestep the dispute but face supply ceilings:

• Global tallow and yellow grease ~10 Mt/yr;
• UCO ~5-10 Mt/yr collectible.

The current frontier of biofuels policy debate centers on:

• Cover-crop oilseeds (carinata, camelina, pennycress) that supplement rather than displace food crops;
• Algae feedstocks (intermittent commercial interest);
• Lignocellulosic 2G via pretreatment improvements (slow progress);
• E-fuels (massive cost gap remains);
• Sufficiency framing — reducing aviation and shipping demand vs replacing fuel.

Adjacent

• natural-gas-oil-markets
• electricity-markets
• climate-mitigation-and-adaptation
• electrochemistry
• carbon-capture-and-removal
• global-agriculture-systems