The Problems With Biodiesel: Where a Cleaner Fuel Still Falls Short

Biodiesel reduces petroleum use and can lower net greenhouse gases, but it faces persistent problems: land-use and biodiversity risks from some crops, widely variable climate benefits, potential NOx increases in certain engines, cold-weather and storage issues, material compatibility in older equipment, lower energy density, supply and cost volatility, and heavy dependence on policy and certification to ensure sustainability. These constraints shape how, where, and when biodiesel is actually a good choice—and why many fleets limit blends to B5–B20 or pivot to renewable diesel (HVO) where available.

Environmental and Climate Drawbacks

Not all biodiesel is created equal. Impacts can swing from strong climate gains to net harm depending on feedstock and land-use dynamics, which regulators in the U.S. and EU increasingly reflect in policy.

Key environmental concerns often cited by scientists, NGOs, and regulators include:

• Indirect land-use change (ILUC): When cropland shifts toward energy crops, food production can move elsewhere, causing deforestation or peatland drainage and releasing large carbon stores.
• High-risk feedstocks: Palm oil and some soy expansion have been linked to deforestation and habitat loss; the EU now restricts “high ILUC-risk” biofuels under RED II/III.
• Lifecycle GHG variability: Waste oils and animal fats typically offer deep emissions cuts, while crop-based fuels can underperform or even backfire when land-use change is included.
• Fertilizer and soil emissions: Nitrous oxide (N2O) from fertilizer use is a potent greenhouse gas and can erode climate benefits.
• Water use and runoff: Irrigation, pesticide, and nutrient runoff from oilseed cultivation can stress watersheds and drive eutrophication.
• Biodiversity trade-offs: Monocultures and land conversion reduce species richness and ecosystem services.
• Social impacts: Large-scale land acquisition can create land-rights conflicts and affect rural livelihoods if not responsibly managed.

These issues are far less severe when biodiesel is made from true wastes and residues (e.g., used cooking oil), but those feedstocks are limited and increasingly contested globally.

Air-Quality and Tailpipe Emissions

Compared with petroleum diesel, biodiesel generally lowers particulate matter, carbon monoxide, and unburned hydrocarbons. The picture is more mixed for nitrogen oxides (NOx) and certain secondary pollutants.

Important air-quality considerations include:

• NOx variability: Some engines and duty cycles show modest NOx increases at higher blends (B20–B100), though modern calibrations and aftertreatment systems can mitigate or eliminate this effect.
• Aldehydes and secondary chemistry: Certain biodiesel blends can increase aldehyde emissions, which may contribute to secondary organic aerosol and ozone formation under specific conditions.
• Aftertreatment interactions: Poor-quality biodiesel can introduce inorganics that increase diesel particulate filter (DPF) ash; some fleets note altered DPF regeneration frequency depending on blend, engine, and operating temperature.
• Cold-start emissions: In cold weather, poor atomization can worsen start-up emissions if the fuel is not properly winterized.

The net local air-quality outcome depends on fuel quality, blend level, engine technology, and controls such as selective catalytic reduction (SCR) and DPFs.

Engine Performance and Reliability

FAME biodiesel has different physical and chemical characteristics than petroleum diesel, which can pose operational challenges—especially at higher blend rates or in older equipment not designed for it.

Common technical problems include:

• Cold-flow properties: Higher cloud and pour points can cause gelling and filter plugging in cold climates without proper winterization or heated storage.
• Oxidation stability: Biodiesel can oxidize during storage, forming acids and sediments that foul filters and injectors if antioxidant additives and storage best practices are not used.
• Hygroscopicity and microbes: Biodiesel absorbs more water, raising risks of microbial growth and corrosion in tanks and fuel systems.
• Material compatibility: Certain older elastomers, seals, and hoses can swell or degrade; fleets sometimes need component upgrades when using higher blends.
• Deposits and contamination: Poorly processed fuel (e.g., excess glycerin, soaps, metals) can cause injector deposits and sticking; strict adherence to ASTM/EN specs is critical.
• Lower energy density: Roughly 7–10% less energy per liter than petro-diesel, leading to slightly reduced fuel economy at higher blends.
• Shorter shelf life: Compared with ultra-low sulfur diesel, biodiesel often requires tighter turnover and quality management.

Many of these issues are manageable at low blends (B5–B20) with high-quality fuel and fleet procedures, but they become more pronounced as blend levels rise toward B100 without dedicated systems.

Infrastructure, Supply, and Cost

Biodiesel’s market footprint is constrained by feedstock availability, quality control, and logistics, which affect price and reliability.

Key market and supply challenges are:

• Limited sustainable feedstocks: Waste oils, greases, and residues are finite and increasingly demanded worldwide, pushing prices up.
• Food-fuel competition: Diverting vegetable oils to energy can tighten food markets, adding social and political risks.
• Price volatility: Feedstock and policy-driven credit values (e.g., RFS RINs, LCFS credits) can swing costs for blenders and fleets.
• Quality variability: Inadequate adherence to specs (ASTM D6751/EN 14214) can trigger engine issues; not all suppliers meet the most stringent quality management programs.
• Distribution and storage: Separate tanks, heated lines in cold regions, and water management add complexity and cost.
• Blend limits and warranties: Many OEMs endorse up to B20 for newer models; B100 typically requires dedicated approvals and more rigorous maintenance.

These constraints mean biodiesel often occupies niche or regional roles, rather than serving as a universal diesel replacement.

Policy, Certification, and Credibility

The sustainability of biodiesel hinges on robust standards and enforcement; without them, alleged “green” fuel can carry hidden environmental costs.

Salient governance issues include:

• Certification complexity: Verifying origin and sustainability across global supply chains is resource-intensive and unevenly enforced.
• Fraud and traceability risks: Markets have seen cases of mislabeled feedstocks (e.g., virgin oils passed off as used cooking oil) and compliance fraud in credit systems.
• Policy uncertainty: Changes to the U.S. Renewable Fuel Standard (RFS), California’s LCFS, or EU RED targets can quickly reshape economics and supply.
• International leakage: Tight rules in one region can shift questionable production elsewhere unless standards are harmonized.

While certification schemes are improving, trust still relies on transparent auditing and consistent enforcement across borders.

What Mitigations Exist?

Industry and regulators have developed tools to reduce risks, though none fully eliminate the underlying constraints on biodiesel.

Notable mitigations include:

• Prioritizing wastes and residues: Used cooking oil, animal fats, and other true wastes deliver stronger climate benefits with fewer land-use impacts.
• Fuel quality programs: Compliance with ASTM/EN standards and participation in recognized quality-management schemes improve reliability.
• Engine and fleet practices: OEM-approved blends (often B5–B20), updated elastomers, regular tank maintenance, and cold-flow additives reduce operational issues.
• Advanced drop-in alternatives: Renewable diesel (HVO)—chemically distinct from FAME biodiesel—works in any diesel engine, has better cold-flow and storage properties, and avoids many engine-side problems, though it competes for the same limited waste fats and oils.
• Targeted deployment: Using biodiesel where winter severity is manageable, storage turns over quickly, and maintenance is rigorous helps ensure consistent performance.
• Stronger certification and monitoring: Digital chain-of-custody systems and cross-border enforcement reduce fraud and ILUC risks.

These measures can make biodiesel a useful transitional tool in specific contexts, but they also underscore its limits as a universal solution.

Outlook and Alternatives

Biodiesel will likely remain a regional, blend-focused option, strongest where waste feedstocks are abundant and winters are mild. Growth in renewable diesel (HVO) is outpacing FAME in many markets due to superior fuel properties, though feedstock scarcity remains a cap. Over the longer term, electrification of light- and medium-duty vehicles, battery-electric or hydrogen fuel-cell trucks on key corridors, and e-fuels for hard-to-electrify sectors are expected to take more of the decarbonization load, with biodiesel occupying a narrower role.

Summary

Biodiesel can deliver real benefits, but the problems are substantial: uncertain climate performance for crop-based fuels, land-use and biodiversity risks, possible NOx increases, cold-flow and storage challenges, materials compatibility in older equipment, lower energy density, supply and cost volatility, and heavy reliance on policy and certification to ensure sustainability. High-quality fuel, conservative blends, and a focus on waste-derived feedstocks mitigate many issues, yet structural limits—especially feedstock scarcity—mean biodiesel is best seen as a targeted, transitional solution rather than a one-size-fits-all replacement for diesel.

What are 5 disadvantages of biodiesel?

Cons of Biodiesel:

• Tailpipe Emissions. Assets that run on biodiesel still have tailpipe emissions.
• Can be More Expensive. The cost of biodiesel depends on the blend level and the feedstocks.
• Gels in Cold Weather. Higher blends of biodiesel gel in the engine in cold weather.
• Not Available Everywhere.

What are the risks of biodiesel?

Biodiesel blended with petroleum-based diesel is widely available. Potential hazards in biofuels production and handling include: Fire and Explosion Hazards of Biofuels. Chemical Reactivity Hazards in Biofuel Manufacturing.

What is the problem with biodiesel?

Biofuel production and use has drawbacks as well, including land and water resource requirements, air and ground water pollution. Depending on the feedstock and production process, biofuels can emit even more GHGs than some fossil fuels on an energy -equivalent basis.

Is biodiesel bad for a diesel engine?

Biodiesel isn’t inherently bad, but higher blends (like B100) can cause issues in some diesel engines, especially older ones, by loosening fuel system deposits, requiring more frequent filter changes. It can also degrade certain rubber seals and fuel lines, though newer engines often have compatible materials. While beneficial for lubricity and lower emissions, high concentrations of biodiesel can increase fuel consumption due to lower energy density and may cause cold-weather gelling issues. Using appropriate blends and being prepared for system cleaning is key. 
Potential Problems with Biodiesel

• Fuel Filter Clogging: Opens in new tabBiodiesel acts as a solvent, dissolving old deposits in the fuel tank and lines. This can clog fuel filters quickly, leading to power loss or engine shuddering. 
• Seal and Hose Degradation: Opens in new tabBiodiesel can degrade certain rubber and nylon seals, O-rings, and fuel lines, potentially causing leaks. 
• Cold Weather Gelling: Opens in new tabPure biodiesel or high blends have a higher tendency to gel or form crystals at low temperatures, which can restrict fuel flow. 
• Increased Fuel Consumption: Opens in new tabBiodiesel has a lower energy density than petroleum diesel, meaning you’ll use more of it to get the same amount of energy, resulting in lower fuel economy. 

Advantages of Biodiesel

• Better Lubricity: Biodiesel enhances the fuel’s lubricity, reducing wear on engine components. 
• Reduced Emissions: Biodiesel combustion produces less particulate matter and other harmful emissions compared to petroleum diesel. 
• Clean Out Engine Deposits: It helps to clean out the fuel system, although this requires careful fuel filter management. 

How to Mitigate Issues

• Use Approved Blends: Start with lower biodiesel blends (like B5 or B20), which are generally well-tolerated by most modern diesel engines. 
• Clean the Fuel System: If you are switching to a higher blend, it’s a good practice to clean the fuel tank first to remove accumulated deposits. 
• Carry Spare Filters: Be prepared to change your fuel filter more frequently, especially when first using biodiesel, to prevent clogging. 
• Inspect Seals and Hoses: Check that your engine’s seals and hoses are compatible with biodiesel or have them replaced with nitrile or other compatible materials. 
• Use Additives for Cold Weather: In cold climates, consider using fuel additives or blending with lower-temperature petroleum diesel to prevent gelling.