The Limitations of Biodiesel

Biodiesel’s main limitations include reduced cold-weather performance, lower energy content (and thus slightly lower fuel economy), storage and oxidation stability issues, potential material compatibility problems and filter clogging at high blends, possible increases in NOx in certain engines without modern aftertreatment, constrained and variable feedstock supply, higher and more volatile costs, limited infrastructure for high blends, and sustainability trade‑offs depending on the source of the oils or fats. These constraints shape when, where, and how biodiesel blends—typically B5 to B20—are best used, and why alternatives like renewable diesel (HVO) are growing for all‑season, drop‑in performance.

What Biodiesel Is—and Isn’t

Biodiesel refers to fatty acid methyl esters (FAME) produced by transesterifying vegetable oils, animal fats, or used cooking oil. It is commonly sold as a blend with petroleum diesel: B5 (5% biodiesel) is widely accepted, while B20 (20% biodiesel) is common in fleets with appropriate controls. Pure biodiesel (B100) is a niche fuel. Biodiesel is distinct from “renewable diesel” (HVO), a hydrotreated, paraffinic fuel that meets diesel specs and typically avoids many biodiesel cold-flow and stability limits.

Technical Limitations in Engines and Fuel Systems

The chemistry of FAME fuels introduces specific engine and fuel-system constraints that differ from petroleum diesel and HVO. The points below summarize the most relevant technical drawbacks operators encounter.

• Lower energy content: B100 has roughly 7–10% less energy per liter than ultra-low sulfur diesel (ULSD), leading to proportionally lower fuel economy; at B20, expect around a 1–2% mpg decrease.
• Cold-flow performance: Cloud and pour points are higher than ULSD and vary by feedstock. Soy- and canola-based biodiesel can gel near freezing; tallow- and palm-based biodiesel can gel well above 10°C, necessitating cold-flow improvers, heated storage, or lower blend ratios in winter.
• Oxidation and storage stability: FAME is more prone to oxidation, polymerization, and acid formation. Without antioxidants and good storage practices, shelf life may be only a few months, raising risks of deposits and filter plugging.
• Water affinity and microbial growth: Biodiesel absorbs and holds more water (on the order of 1,000–1,500 ppm at 25°C versus tens to a few hundred ppm for ULSD), increasing the chance of microbes, corrosion, and sludge if tanks are not well maintained.
• Material compatibility: High blends can swell or degrade certain elastomers (e.g., natural rubber, some nitrile rubbers, polyurethanes). Fluorocarbon elastomers (e.g., FKM/Viton) are generally compatible.
• Solvency and filter clogging: Biodiesel’s detergency can clean existing deposits from tanks and lines, temporarily clogging filters after the first switch or blend increase.
• Emissions trade-offs: While biodiesel tends to reduce particulate matter (PM), CO, and unburned hydrocarbons, some engines—notably older ones without SCR—can see small NOx increases with higher blends. Modern SCR-equipped engines largely mitigate this.
• Interaction with DPF regeneration: In certain late-model engines that rely on post-injection for DPF regen, high biodiesel blends can increase fuel dilution of engine oil, shortening oil-change intervals.
• Deposit formation risk at high blends: Poor stability, improper additives, or unsuitable feedstocks can contribute to injector coking and piston deposits, especially with B50–B100 in engines not designed for it.

Collectively, these technical factors explain why many OEMs endorse B5 broadly and B20 with conditions, while reserving higher blends for purpose-built engines, warmer climates, or controlled fleet operations with strict fuel quality and maintenance.

Operational and Infrastructure Constraints

Beyond the chemistry, users face practical hurdles related to storage, handling, and fuel availability that can raise costs or limit where biodiesel is feasible year-round.

• Limited high-blend availability: Many retail stations offer B5 or B11; B20 access is regional, and B50–B100 are typically fleet or specialty fuels.
• Seasonal management: Winter conditions often require lower blend ratios, winterized biodiesel, or supplemental cold-flow improvers, plus heated or insulated equipment.
• Storage housekeeping: Tanks need regular water drainage, microbial monitoring, and periodic cleaning; biocides and antioxidants may be required for longer storage.
• Filter and maintenance planning: Expect initial filter changes after switching to higher blends and more frequent checks in humid or high-turnover environments.
• Quality variability: Feedstock diversity and producer practices can lead to variable cold-flow, stability, and contaminant profiles. Adherence to ASTM D6751 (B100) and ASTM D7467 (B6–B20), plus BQ-9000 accreditation, helps ensure consistency.
• Infrastructure compatibility: Some legacy seals, gaskets, and coatings in storage and dispensing systems may need upgrading to biodiesel-compatible materials.

These operational realities mean successful biodiesel programs pair vetted suppliers and specifications with disciplined storage, seasonal fuel planning, and maintenance protocols.

Economic and Supply Limitations

Biodiesel depends on feedstocks that are finite, geographically concentrated, and subject to competing uses—driving price swings and limiting scalable growth relative to diesel demand.

• Feedstock constraints: Availability of soybean oil, canola oil, animal fats, and used cooking oil is limited; rapid demand growth can strain supply.
• Price volatility: Feedstock prices follow agricultural and commodity cycles, often making biodiesel more expensive than ULSD without incentives.
• Competition with food and oleochemicals: Edible oils have established markets; policy shifts and crop yields directly affect biodiesel economics.
• Logistics and regionality: Used cooking oil is dispersed and costly to collect; animal fats can have poor cold-flow properties; palm-based fuels face sustainability scrutiny.
• Byproduct markets: Glycerin co-product values can fluctuate, affecting plant economics.
• Energy return: Biodiesel has a positive energy return on investment (often roughly 2–5:1 depending on feedstock and process), but typically lower than HVO made from the same wastes at large scale.

These supply-side factors cap how much biodiesel can economically and sustainably displace petroleum diesel, particularly absent supportive policy or credits.

Environmental and Policy Caveats

Biodiesel’s environmental performance hinges on feedstock origin and land-use effects, and its on-road use is shaped by evolving emissions regulations and OEM approvals.

• Lifecycle GHG variability: Waste and residue feedstocks (used cooking oil, tallow) generally deliver large GHG reductions; crop-based oils vary widely and can be undermined by indirect land-use change.
• Biodiversity and land-use risks: Expansion of oil crops (e.g., palm) can drive deforestation and peatland emissions without strict safeguards and certification.
• NOx compliance: Small NOx increases with higher blends in engines lacking SCR can challenge regional ozone strategies; modern aftertreatment largely resolves this.
• Blend and warranty limits: In many markets, B5 is universally approved; numerous light- and heavy-duty OEMs approve B20 under ASTM specs, but B100 is rarely warranted in modern on-road engines.
• Standards and certification: Compliance with ASTM D6751/D7467 and participation in programs like BQ-9000 and sustainability certifications (e.g., RSB, ISCC) are key to ensuring quality and environmental integrity.

When responsibly sourced and properly controlled, biodiesel can provide meaningful GHG and air-quality benefits; without those controls, benefits shrink and risks rise.

What Blends Are Practical Today?

Most fleets and drivers choose blends based on climate, engine technology, supplier quality, and warranty conditions. The options below reflect current mainstream practice.

• B5 (up to 5%): Generally approved by OEMs and allowed under ASTM D975 as “diesel.” Minimal operational changes; good lubricity benefits.
• B6–B20: Supported by ASTM D7467; widely used by public fleets, transit, and some trucking operations with seasonal management, quality controls, and OEM approvals.
• B30–B100: Niche use in warm climates or dedicated fleets with compatible engines, upgraded materials, rigorous housekeeping, and close monitoring.
• Renewable diesel (HVO) comparison: Drop‑in compatibility, excellent cold-flow and storage stability, and broad OEM acceptance make HVO a preferred option where available—often used neat (R99) or in blends with biodiesel for cost/credit optimization.

In practice, B5 is a low-friction starting point, B20 delivers larger carbon benefits with manageable trade-offs, and higher blends fit specific, well-managed use cases.

How to Mitigate Limitations

Organizations that succeed with biodiesel blend use pair robust fuel quality standards with practical steps to manage cold weather, storage, and equipment.

1. Source wisely: Favor waste/residue feedstocks and certified sustainable suppliers; request certificates showing ASTM compliance and BQ-9000 participation.
2. Match blend to season: Use winterized biodiesel, cold-flow improvers, or lower blends in cold months; insulate or heat storage and lines as needed.
3. Maintain tanks: Regularly test for water and microbes; drain bottoms, clean periodically, and use approved biocides and antioxidants when appropriate.
4. Plan filter changes: Replace filters shortly after switching to higher blends and monitor for clogging during early adoption.
5. Verify compatibility: Upgrade vulnerable elastomers and seals to biodiesel-compatible materials; consult OEM guidance on maximum blends and service intervals.
6. Monitor oil and injectors: In DPF-equipped engines, analyze oil for fuel dilution and watch injector performance at higher blends.
7. Consider HVO co-blending: Where available, HVO can improve cold-flow and stability while maintaining high renewable content.

These measures reduce operational risk, protect equipment, and preserve the environmental benefits that make biodiesel attractive in the first place.

Key Numbers at a Glance

The figures below help quantify the most commonly cited biodiesel limitations and how they show up in the field.

• Energy content (LHV): ULSD ≈ 35.8–36.6 MJ/L; B100 ≈ 33–34 MJ/L. Expected mpg change: B20 ≈ −1–2% versus ULSD (vehicle-dependent).
• Cloud point (typical ranges, °C): Canola-based ≈ −3 to 0; Soy-based ≈ 0 to +3; Tallow/Palm-based often > +10. Actual values depend on exact feedstock and processing.
• Oxidation stability: ASTM D6751 (B100) requires ≥3 hours (Rancimat, EN 14112); ASTM D7467 (B6–B20) requires ≥6 hours. Practical, additive-free shelf life is often 3–6 months; longer with stabilizers and good storage.
• Water solubility: Biodiesel saturates at roughly 1,000–1,500 ppm at ~25°C versus tens to a few hundred ppm for ULSD—raising microbial risks if tanks aren’t dry and clean.
• NOx tendency: Older engines without SCR may see up to a few percent NOx increase at higher blends; modern SCR systems largely offset this.
• Material compatibility: Natural rubber and some NBR and polyurethane components are susceptible; FKM/Viton and PTFE are generally compatible.

These benchmarks underline why climate, engine technology, and supplier quality determine how far and how fast fleets can scale biodiesel blends.

Summary

Biodiesel can cut petroleum use and reduce several tailpipe pollutants, but it carries real limitations: weaker cold-weather performance, lower energy density, oxidation and storage challenges, material compatibility and maintenance considerations at higher blends, constrained and variable feedstock supply, and sustainability and NOx caveats tied to feedstock and engine technology. With strong fuel quality controls, seasonal planning, OEM-aligned blend choices (often B5–B20), and good tank housekeeping—or by pairing with or substituting HVO where available—many of these constraints can be managed. Ultimately, biodiesel’s value depends on matching the right blend to the right engine, climate, and supply chain, and ensuring that the feedstock truly delivers the intended environmental benefits.

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.

What is biodiesel and its advantages and disadvantages?

Biodiesel is a domestically produced, renewable substitute for petroleum diesel. Using biodiesel as a vehicle fuel improves public health and the environment, provides safety benefits, and contributes to a resilient transportation system.

What are the limitations of biofuel?

Disadvantages of biofuels include deforestation, loss of biodiversity, increased food prices and potential food shortages, significant land and water requirements, high production costs, and the release of air pollutants like nitrogen oxides and fine particles that negatively impact public health and contribute to smog. Furthermore, the energy required for biofuel production and transport can be substantial, sometimes even exceeding the energy content of the fuel itself, and the quality and efficiency of these fuels can vary. 
Environmental & Land Use Concerns

• Deforestation and Habitat Loss: Opens in new tabGrowing crops for biofuels requires large amounts of land, which can lead to deforestation and destruction of natural habitats, reducing biodiversity. 
• Water Consumption: Opens in new tabBiofuel crop production often demands substantial water resources for irrigation, potentially straining local water supplies and disrupting ecosystems. 
• Soil Erosion: Opens in new tabLarge-scale monoculture farming for biofuels can lead to soil erosion and degradation. 
• Air Pollution: Opens in new tabBurning biofuels releases air pollutants, including fine particulate matter, ozone, and nitrogen dioxide, which can trigger respiratory problems, heart attacks, and contribute to smog. 

Socioeconomic Impacts

• Food Prices and Shortages: Opens in new tabUsing land to grow biofuel crops reduces the amount of land available for food production, which can drive up food prices and potentially lead to food shortages. 
• High Production Costs: Opens in new tabSignificant investments in infrastructure and technology are needed to produce biofuels, making them more expensive than traditional fossil fuels. 

Energy and Production Issues

• Production Energy Use: The process of producing, transporting, and refining biofuels can consume a large amount of energy, sometimes to the point where the energy input is not significantly less than the energy output. 
• Variable Quality and Efficiency: The quality of biofuels can vary depending on the feedstock and production process. Additionally, some biofuels are less efficient than other fuels, releasing more heat and less usable energy. 
• Technical Challenges: High-ethanol biofuels may require modifications to car engines, and higher blends of biodiesel can gel in cold weather, limiting their use.