The Downsides of Biodiesel: What Drivers, Fleet Managers, and Policymakers Need to Know

Biodiesel’s main downsides are lower energy content (reduced fuel economy), cold-weather operability problems, potential increases in nitrogen oxides (NOx) and some aldehydes, shorter shelf life and oxidative stability issues, material compatibility concerns in older fuel systems, limited and sometimes unsustainable feedstocks, higher costs that can depend on subsidies, and logistical constraints in storage and distribution. While biodiesel can cut particulate matter and lifecycle greenhouse gases when made from the right feedstocks, these trade-offs affect how, where, and at what blend levels it performs best.

What Biodiesel Is—and What It Isn’t

Biodiesel typically refers to FAME (fatty acid methyl esters) produced by transesterifying vegetable oils, animal fats, or waste cooking oils. It is commonly blended with petroleum diesel (e.g., B5, B20) and governed by standards such as ASTM D6751 (B100) and ASTM D7467 (B6–B20) in the U.S., and EN 14214 in Europe. It is distinct from renewable diesel (HVO), a hydrotreated, “drop-in” diesel with superior cold-flow and storage characteristics. Many of biodiesel’s downsides are specific to FAME chemistry and become more pronounced at higher blend ratios.

Technical and Operational Drawbacks

The following points summarize the core technical limitations operators encounter with biodiesel in day-to-day use, especially at higher blend levels.

• Lower energy density: B100 has roughly 8–12% less energy per gallon than petroleum diesel; B20 typically yields about 1–2% lower fuel economy.
• Cold-weather operability: Higher cloud/pour points can cause gelling and filter plugging in cold climates, particularly with saturated-feedstock biodiesel (e.g., tallow). Additives and winter blending help but don’t eliminate risk.
• Oxidative stability and shelf life: Biodiesel can oxidize and form acids, gums, and sediments, clogging filters and injectors. Storage beyond about six months, especially in heat or with oxygen exposure, raises risks.
• Water affinity and microbial growth: Biodiesel can hold more water than ULSD, fostering microbes that produce sludge and corrosive byproducts if tanks aren’t monitored and treated.
• Material compatibility: FAME can degrade certain elastomers (e.g., natural rubber, some nitriles) and reacts with copper, zinc, and brass, accelerating oxidation. Modern Viton/PTFE components and stainless/steel lines mitigate issues.
• Solvent effect and deposits: B100 can loosen existing deposits in legacy fuel systems, leading to initial filter clogging after a switch-over.
• Emissions trade-offs: While PM, CO, and many PAHs drop, some engines see slight NOx increases on higher biodiesel blends, and aldehydes (e.g., formaldehyde, acetaldehyde) can rise.
• Potential impacts on aftertreatment: Differences in combustion and oxygen content can alter DPF regeneration frequency and, in some calibrations, engine oil dilution dynamics.

Taken together, these issues don’t preclude biodiesel use, but they require careful fuel selection, diligent storage and filtration practices, and adherence to OEM blend limits—especially in cold regions.

Engine Performance and Emissions Implications

In modern diesel engines with advanced aftertreatment, biodiesel blends up to B20 are widely used, but outcomes vary with calibration and duty cycle. Biodiesel’s oxygen content helps cut smoke and particulate matter, which can ease DPF loading. Conversely, some engines—particularly older models or those not calibrated for biodiesel—can exhibit modest increases in NOx. Fleet data and lab studies generally show:

• PM, CO, and unburned HC reductions relative to ULSD, improving local air quality.
• Potential NOx increases on older platforms and certain cycles; modern SCR systems and engine maps often neutralize or reverse this effect, but results are application-specific.
• Fuel economy penalties tracking energy density (small for B5–B20, more notable for B50–B100).
• Possible injector and deposit behavior differences at high blends due to FAME’s boiling characteristics and solvency, emphasizing the importance of fuel quality and detergency.

To minimize drawbacks, stick to OEM-approved blends, use high-quality fuel meeting ASTM/EN specs, and monitor emissions system health and oil condition during transitions or seasonal changes.

Environmental and Sustainability Risks

Biodiesel can deliver large lifecycle GHG savings when derived from waste oils or residues, but feedstock choices and land-use dynamics matter. These are the chief environmental downsides.

• Indirect land-use change (ILUC): Expanding oilseed cultivation can displace food production and drive deforestation, undermining climate benefits. Palm-based biodiesel is particularly scrutinized for high ILUC risk and biodiversity loss.
• Agricultural inputs: Fertilizer and pesticide use for soy/canola raise nitrous oxide emissions and water pollution (eutrophication), diminishing net climate and ecological gains.
• Water and soil impacts: Irrigation demand and soil erosion can be significant in some regions and crops.
• Feedstock limits: Truly sustainable feedstocks like used cooking oil (UCO) and animal tallow are finite; scaling beyond them can raise sustainability concerns or spur fraud in supply chains without robust traceability.
• Local air toxics mix: While many toxics fall, certain oxygenated aldehydes can increase, affecting near-roadway exposure considerations.

Regulatory frameworks (e.g., EU RED II/III) increasingly cap or phase out high ILUC-risk feedstocks and push for traceability, but supply constraints remain a structural challenge.

Economic and Market Downsides

From fleet budgets to biofuel investment planning, several market realities can make biodiesel less attractive than alternatives.

• Cost and volatility: Prices track feedstock markets and policy credits. Without incentives, biodiesel can be costlier than ULSD.
• Policy dependence: In the U.S., incentives have shifted from the Biodiesel Blender’s Tax Credit to the technology-neutral Clean Fuel Production Credit (45Z) for 2025–2027, rewarding low-carbon-intensity fuels. Plants using higher-CI feedstocks may face thinner margins.
• Competition from renewable diesel (HVO): HVO is “drop-in,” with better cold flow and storage stability. Many fleets prioritize HVO where available, limiting biodiesel’s blend share growth.
• Food-versus-fuel tension: When oilseed prices spike, biodiesel economics and food prices can both be affected, sharpening public scrutiny.
• OEM and market limits: Many on-road warranties cap blends at B20 (U.S.) or B7–B10 (Europe), constraining demand for higher blends that would otherwise move more volume.

These pressures don’t eliminate biodiesel’s role, but they tilt growth toward waste-based, low-CI pathways and regions with supportive clean-fuel standards.

Infrastructure and Logistics Constraints

Storage, blending, and transport considerations can add cost and complexity relative to petroleum diesel and HVO.

• Storage life and conditions: Heat, air, light, and water accelerate degradation. Best practice limits storage duration, uses antioxidants/biocides as needed, and avoids reactive metals.
• Cold-chain handling: Winter blending, heated tanks, and cold-flow additives may be necessary in freezing conditions, especially above B20.
• Pipeline limitations: FAME’s properties and contamination concerns (e.g., cross-contact with jet fuel systems) restrict pipeline movement in many regions; biodiesel often travels by truck or rail.
• Blending accuracy: Poor blending or low-temperature precipitation of saturated monoglycerides and sterol glucosides can cause filter plugging episodes if quality control lapses.

Robust quality assurance—from terminal blending to end-user tank maintenance—is essential to avoid operational disruptions.

Policy and Standards Context (2024–2025)

Standards and policies shape biodiesel’s risk–reward balance. In the EU, RED III tightens sustainability criteria and phases out high ILUC-risk feedstocks (notably certain palm pathways) by 2030, while many member states keep B7–B10 caps in road diesel. In the U.S., the EPA’s multi-year Renewable Fuel Standard “set rule” defines 2023–2025 volumes, and state low-carbon fuel programs (e.g., California’s LCFS) continue to favor fuels with low carbon intensity—but credit prices have been volatile. From 2025, the federal 45Z credit rewards producers for lower lifecycle CI, pushing the sector toward cleaner power, better logistics, and waste-based feedstocks to stay competitive against HVO and other low-carbon options.

Mitigations and Best-Use Cases

Many disadvantages can be managed with the right practices and blend choices tailored to climate, duty cycle, and equipment.

• Choose appropriate blends: Use B5–B20 in most climates and applications; reserve higher blends for warm regions or dedicated/controlled fleets.
• Buy to spec: Insist on ASTM D6751/EN 14214-compliant biodiesel and proper blended-fuel specs (ASTM D7467). Ask for certificates of analysis and cold-flow data.
• Improve storage: Use clean, dry tanks; avoid copper/brass; monitor water bottoms; apply antioxidants and biocides as needed; rotate stock within six months.
• Prepare for winter: Employ cold-flow additives, heated storage, and seasonal feedstocks/blends to prevent gelling and filter plugging.
• Follow OEM guidance: Adhere to manufacturer blend limits and service intervals; watch DPF/DEF systems and oil condition during transitions.
• Prioritize sustainable feedstocks: Favor UCO, tallow, and residue-based biodiesel with verified traceability to preserve climate benefits and meet compliance targets.

Deployed this way, biodiesel can complement renewable diesel and electrification as part of a portfolio approach to decarbonizing diesel use, especially in legacy fleets.

Summary

Biodiesel’s downsides center on physics (lower energy density), chemistry (cold flow, oxidation, water/microbe sensitivity, some material incompatibilities), emissions trade-offs (potential NOx and aldehyde increases in certain engines), sustainability limits (ILUC and finite waste feedstocks), market dynamics (cost volatility and policy dependence), and logistics (storage and pipeline constraints). These factors don’t negate biodiesel’s benefits—particularly when sourced from verified waste streams and used at moderate blends with good fuel management—but they do confine where it is most practical and cost-effective compared with petroleum diesel and renewable diesel.

Why are we not using biodiesel?

Biodiesel isn’t widely used because of its high cost, lower energy content, and susceptibility to cold weather, which causes gelling. Significant infrastructure is also missing, which makes it unavailable everywhere, and production often requires large amounts of land and water, potentially impacting food prices and security. Additionally, while some emissions are reduced, it doesn’t eliminate tailpipe pollutants and can contribute to other environmental issues.
 
Technical & Performance Drawbacks

• Cold Weather Gelling: Opens in new tabBiodiesel’s “cloud point” is higher than petrodiesel, meaning it freezes and solidifies in colder temperatures, making it unreliable for use in colder regions. 
• Lower Energy Content: Opens in new tabBiodiesel has less energy per gallon than petroleum diesel, so more fuel is needed for the same amount of work. 
• Corrosive Nature: Opens in new tabSome components in older diesel engines, made from natural rubber, can degrade upon contact with biodiesel. 
• Fuel Quality: Opens in new tabPoor quality biodiesel can lead to problems like oxidation and microbial fouling, which can damage storage tanks and clog fuel lines. 

Economic & Infrastructure Challenges

• High Cost: Biodiesel is often more expensive to produce than petroleum-based diesel, and market demand may not support the higher price. 
• Limited Availability: There isn’t widespread availability of biodiesel at all fuel stations, creating a barrier for consumers and fleets. 
• Fossil Fuel Infrastructure: The current energy infrastructure is built for fossil fuels, and a massive investment would be needed to transition to biodiesel. 

Environmental & Resource Concerns

• Land and Water Use: Opens in new tabGrowing crops for biodiesel requires significant amounts of land and water, which can compete with food production. 
• Food Prices and Security: Opens in new tabUsing more land for biofuel crops can reduce food crop availability, potentially increasing food prices and impacting food security. 
• Environmental Impact of Production: Opens in new tabThe entire process of producing biodiesel can release greenhouse gases and cause air and water pollution. 

Other Considerations

• Tailpipe Emissions: Biodiesel still produces tailpipe emissions, including nitrogen oxides (NOx), which contribute to smog. 
• Lobbying: The powerful oil industry actively resists the transition to alternative fuels like biodiesel. 

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.

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. 

Can you switch back and forth between diesel and biodiesel?

Can I go back and forth between petroleum diesel and biodiesel? You can use biodiesel and diesel fuel interchangeably, as well as blended. Biodiesel fuel can be used in any diesel engine in pure form or blended with petroleum diesel at any level.