Why don’t cars run on biofuel?

Many cars already do—most gasoline sold in places like the United States and Europe contains biofuel—but widespread use of high-biofuel blends is limited by economics, infrastructure, vehicle compatibility, sustainability concerns, and policy. In short: low-percentage blends are common, high-percentage biofuels are not. The reasons span fuel chemistry and engine design, distribution systems and pump rules, and shifting strategies as automakers and policymakers prioritize electrification.

What counts as “biofuel” in road transport?

Biofuel is an umbrella term for fuels made from biological sources (crops, waste, residues) that can substitute for petroleum in combustion engines. Not all biofuels are the same: some are “blendstock” that must be mixed with petroleum, others are “drop-in” fuels that can fully replace fossil counterparts without engine changes.

• Ethanol (mostly from corn or sugarcane) blended into gasoline at E10 (10%), E15 (15%), or E85 (51–83% for flex-fuel vehicles)
• Biodiesel (FAME) typically blended into diesel as B5 or B20; higher blends face cold-flow and warranty limits
• Renewable diesel (HVO), a drop-in diesel chemically similar to fossil diesel, compatible up to 100% in many engines
• Biogas/renewable natural gas (RNG) upgraded from landfill or manure methane, used mainly in trucks/buses
• Advanced “drop-in” renewable gasoline/jet components from cellulosic residues or waste oils, currently limited in volume

These categories matter because they determine which vehicles can use the fuel, how much can be blended, and what changes fueling infrastructure and regulations require.

Where cars already use biofuel

Contrary to the premise, biofuels are common in light-duty transport—just not usually at very high blends outside a few countries.

In the United States, more than 95% of gasoline contains up to 10% ethanol (E10). E15 is approved for 2001-and-newer vehicles, and beginning in 2025, eight Midwest states can sell E15 year-round under a permanent EPA rule; elsewhere, summer sales have periodically relied on temporary waivers. E85 remains a niche product used by flex-fuel vehicles at a limited network of stations. On the diesel side, fleets use biodiesel blends (often B5–B20), while renewable diesel has grown rapidly on the West Coast under Low Carbon Fuel Standards.

In Brazil, most new light-duty cars are flex-fuel and routinely run on high-ethanol blends or hydrous ethanol (E100), supported by decades of infrastructure and policy. Across the European Union, E10 gasoline and B7 diesel are standard in many markets, with strict caps on crop-based biofuels and growing emphasis on advanced feedstocks. India is rolling out E20 nationwide by mid-2020s, pairing new engine compatibility with expanded ethanol production.

Why higher-biofuel cars aren’t the norm

The barriers to ubiquitous high-biofuel use are a mix of chemistry, cost, logistics, regulation, and strategic priorities in a world pivoting toward electrification.

• Energy density and performance: Ethanol has about one-third less energy per gallon than gasoline, so E85 usually delivers 20–30% lower miles per gallon unless engines are optimized for it. Biodiesel also has slightly lower energy density and can have cold-flow limitations; renewable diesel avoids many of these issues but is supply-constrained.
• Vehicle compatibility and warranties: Most gasoline cars are certified for E10; many can use E15, but E85 requires flex-fuel hardware and calibration. Diesel passenger cars often limit biodiesel to B5–B20. Automaker warranties and emissions certifications hinge on specific blends.
• Fueling infrastructure and the “blend wall”: Dispensers, storage tanks, labeling, and vapor-pressure rules complicate E15/E85 rollout. Many stations aren’t equipped or incentivized to carry multiple biofuel grades, and consumer demand is uncertain.
• Seasonal and regional constraints: Ethanol’s volatility affects summertime gasoline blending; biodiesel can gel in cold climates. Regulators have issued seasonal waivers for E15 in some years, but permanent solutions are patchy geographically.
• Lifecycle emissions and land use: Greenhouse-gas benefits vary widely. Waste- and residue-based fuels can be very low-carbon, while crop-based fuels face debates over land-use change, fertilizer use, and water. These uncertainties influence policy caps and investment.
• Economics and policy volatility: Biofuel competitiveness depends on feedstock prices and credits (e.g., U.S. Renewable Fuel Standard, state LCFS, and new 45Z clean fuel production credits starting 2025). Policy swings and oil price volatility deter long-term infrastructure bets.
• Market direction and R&D focus: Automakers are channeling resources to hybrids and EVs to meet tightening CO2 standards (e.g., EU 2035 zero-emission target with narrow e-fuel exceptions). That reduces momentum for dedicated high-biofuel powertrains in mainstream markets.

Taken together, these hurdles make low blends easy and cheap, while high blends require sustained policy, optimized engines, and infrastructure that many markets haven’t prioritized.

The blend wall and infrastructure problem

For gasoline, the “blend wall” refers to the practical limit of how much ethanol the system can absorb given vehicle approvals and pump logistics. E10 became ubiquitous because it fit within existing cars, stations, and refinery blending strategies. Moving beyond that is harder.

• Regulatory constraints: Vapor-pressure (RVP) limits restrict E15 summer sales in many regions; the EPA finalized year-round E15 for eight Midwest states from 2025, but nationwide rules are uneven, leading to seasonal uncertainty.
• Retail economics: Adding E15/E85 requires new tanks or dispenser certifications, labeling, and staff training. Station owners weigh those costs against uncertain demand and potential misfueling risks.
• Supply chain alignment: Refineries, terminals, and pipelines are optimized for standard grades. Extra logistics complexity raises costs for distributors and retailers.

Without clear, stable national rules and strong financial incentives, most retailers stick to the easiest blends their customers know—typically E10 for gasoline and up to B5 for diesel.

Environmental and sustainability debates

Biofuels can cut transport emissions, but how much depends on feedstock, farming practices, land-use change, and processing energy. That variability drives divergent policies and public opinion.

• Lifecycle emissions vary: Waste-based fuels (used cooking oil, animal fats, agricultural residues) often deliver large CO2 reductions. Corn ethanol’s benefits depend on farming inputs, co-product credits, and process energy; estimates range from modest to significant reductions.
• Land and biodiversity concerns: Expansion of cropland for biofuels can drive indirect land-use change, potentially offsetting carbon gains and impacting biodiversity.
• Air quality trade-offs: Ethanol blends can reduce some tailpipe pollutants but increase others (e.g., certain aldehydes); biodiesel can cut particulate matter but raise NOx in some conditions. Modern aftertreatment mitigates much of this.
• Policy responses: The EU caps crop-based biofuels and promotes advanced ones. U.S. programs reward low-carbon-intensity fuels; new credits from 2025 aim to steer production toward cleaner pathways.

Because impacts aren’t uniform, governments tend to encourage specific feedstocks and pathways rather than blanket expansion—limiting how far and fast biofuels scale for light-duty cars.

Economics and consumer behavior

Even when stations offer higher blends, consumers often stick with familiar fuels unless the savings per mile are clear and consistent.

• Price-per-mile math: Ethanol may be cheaper per gallon but often isn’t cheaper per mile given lower energy content, unless local incentives or discounts are strong.
• Range and convenience: E85 cuts range between fill-ups; drivers with limited time or sparse station coverage may avoid it.
• Trust and warranties: Mixed messages about compatibility, along with conservative dealership advice, suppress adoption beyond E10/E15.

Consumer economics ultimately determine pump throughput; without persistent, visible savings and strong assurances, high-biofuel blends remain niche.

What would it take for more cars to run on biofuel?

Broader adoption is possible, but it requires aligned policies, technologies, and market signals—especially for sustainable, advanced biofuels that deliver clear climate benefits.

• Stable, nationwide rules enabling year-round higher blends and streamlined dispenser certifications
• Targeted incentives tied to measured carbon intensity (e.g., credits that reward waste- and residue-based fuels)
• More vehicles calibrated for high-ethanol operation or flex-fuel capability, ideally optimized to regain efficiency losses
• Investment in drop-in fuels (renewable gasoline/diesel) that bypass compatibility hurdles
• Feedstock diversification and better agricultural practices to minimize land-use and water impacts
• Clear consumer messaging, labeling, and consistent price-per-mile advantages at the pump

If these pieces align, high-biofuel usage could grow in light-duty fleets—though it will likely compete with rapid electrification and hybridization strategies.

Outlook: Biofuels’ niche in a battery-tilting market

Biofuels are poised to play their biggest role where batteries struggle: aviation (sustainable aviation fuel), long-haul trucking (renewable diesel), and potentially shipping. In light-duty cars, low blends will remain common worldwide, with high-ethanol markets like Brazil and expanding E20 use in India as notable exceptions. In the U.S. and Europe, as EVs and hybrids gain share, the incremental decarbonization role for car biofuels will focus on cleaner pathways, higher blends where practical, and drop-in fuels that integrate without friction.

Summary

Cars don’t run exclusively—or even mostly—on high-biofuel blends because of energy-density penalties, vehicle and warranty limits, fueling infrastructure and regulatory hurdles, sustainability debates, and uneven economics. Many already use low-percentage blends daily, and some regions (Brazil, increasingly India) support high-ethanol fleets. Going further would require stable policies, optimized engines, more drop-in fuels, and clear carbon benefits—while competing with the accelerating shift to electrified vehicles.

Is biodiesel cheaper than gasoline?

Biodiesel costs are currently 70% to 130% higher than petrol and diesel on the wholesale market depending on the crop used, a new study into the true cost of biofuels shows.

Can cars run on 100% biodiesel?

Biodiesel can be produced from*
It can be dispensed as 100% biodiesel or as a blend with petroleum diesel. Common blends include B5 and B20, a blend of 20% biodiesel and 80% diesel. Most diesel vehicles can run on biodiesel, but check with your vehicle manufacturer or warranty.

Can you run a car on biofuel?

You won’t be able to fill up your car on pure bioethanol or biodiesel, but most cars can run perfectly on blended unleaded and diesel as there are no compatibility issues at such low percentages.

Why don’t we use biofuel for cars?

burning biofuels in internal combustion engines is very inefficient. Up to 80% of the energy is wasted and ejected into the environment as heat. High ethanol biofuels like 80P require modifications to car engines. Biofuels take a lot of energy to produce and transport.