Use of Algae-Based Biofuels in Marine Diesel Engines — Injector-System Modifications

Use of Algae-Based Biofuels in Marine Diesel Engines — Injector-System Modifications

1 — Executive summary (TL;DR)

Algae-derived fuels (typically processed to FAME biodiesel or hydrotreated/renewable diesel variants) can be used in modern marine diesel engines, but their different physical and chemical properties affect injector performance and durability. Key injector-system implications are: changed lubricity/viscosity/cetane, increased risk of injector deposits and filter plugging for some FAME fuels, elastomer/material compatibility issues, and altered atomization needs (pressure/timing). Practical countermeasures include selecting the right fuel type (HVO/renewable diesel preferred where possible), upgrading filtration and water separation, implementing fuel heating or viscosity control, verifying injector materials and seals, adjusting injection pressure/timing maps (or using manufacturer-approved hardware/ECU maps), and adding fuel conditioning/antioxidant additives plus robust fuel monitoring. MAN, Wartsila and major engine OEM guidance and recent research back these points. MAN Energy Solutions+2Nature+2

2 — What “algae-based biofuel” usually means in practice

• FAME (fatty-acid methyl esters) from microalgae oil — chemically similar to vegetable-oil biodiesel; higher oxygen content, potentially higher viscosity and different cold-flow and oxidative stability. Nature+1

• Hydrotreated vegetable/renewable diesel (HVO / “renewable diesel”) produced from algal oil — paraffinic, low oxygen content, often more similar to fossil diesel (better cold flow, stability); many OEMs treat HVO more favorably. Advanced BioFuels USA+1

Practical takeaway: where possible use HVO/renewable diesel or well-refined FAME conforming to standards; untreated raw algal oil is rarely suitable without substantial upgrading. MAN Energy Solutions+1

3 — Fuel properties that drive injector issues (what to watch)

1. Viscosity & density: FAME often has higher viscosity than marine distillate diesel → affects spray breakup and atomization; may require higher injection pressures or heating to reach target spray characteristics. ScienceDirect+1

2. Oxygen content & oxidative stability: FAME has oxygen in the molecule and can be more prone to oxidation and polymeric deposit formation (gumming) during storage or in hot parts of the injection system. NREL Docs+1

3. Cold-flow & cloud point: algae-derived FAME blends may gel/plug filters at lower temperatures unless treated or blended correctly. HVO has much better cold-flow. SAGE Journals

4. Lubricity: many biofuels have good inherent lubricity (good for high-pressure pumps) but the long-term chemistry (acid formation, detergency) can alter wear patterns and seals. Test elastomer compatibility before long deployments. NREL Docs

These fuel differences lead directly to injector-relevant problems: poor atomization, injector tip deposits, nozzle hole blocking, seat wear and changes in pump/nozzle lubrication regimes. ResearchGate+1

4 — Observed injector failure modes with biodiesel / algal FAME

• External and internal injector deposits (coking/gumming) on tips and needle seat, altering spray pattern and causing incomplete combustion or misfires. ResearchGate

• Clogged filters and nozzles from particulates, degraded glycerides or insoluble reaction products. NREL Docs

• Accelerated wear / scuffing in pump plunger/cylinder and injector needle due to different lubrication film behaviour and possible acidity issues. ResearchGate+1

• Elastomer swelling/embrittlement (seals, O-rings, diaphragms) if incompatible materials are present — leading to leaks and pressure loss. NREL Docs

(Extensive literature and reviews document deposit mechanisms and field/bench evidence for these failure modes.) ResearchGate+1

5 — Injector-system modifications & retrofits (detailed recommendations)

A. Fuel selection & pre-treatment (first line of defence)

• Prefer HVO / renewable diesel where available (paraffinic, low oxygen) for lowest injector risk; MAN and other OEMs explicitly accept HVO/renewable diesel when it meets EN15940/ASTM standards. Advanced BioFuels USA+1

• Limit FAME concentration for critical systems (use manufacturer guidance for allowed blends; many systems accept blends up to specific limits). Conduct engine OEM approval before use. MAN Energy Solutions

• Stabilize & polish fuels before use: store in inerted, temperature-controlled tanks; use fuel polishing to remove water and particulates and to reduce peroxide/oxidation products. NREL and others recommend careful storage & conditioning. NREL Docs

B. Filtration & water separation upgrades

• Raise filtration fidelity: use fine multi-stage filtration — e.g., primary 10–30 µm followed by polishing of 2–5 µm for sensitive common-rail or unit injectors (exact micron rating per OEM). Consider depth filters with water-separating capability. NREL Docs+1

• Install enhanced coalescer / water separators upstream of pumps; water accelerates hydrolysis and acid formation in FAME. NREL Docs

C. Fuel heating & viscosity control

• Add controlled fuel heaters or improve fuel temperature management so the fuel reaches optimum viscosity for designed nozzle atomisation at injection pressure. This is particularly important for higher-viscosity FAME blends. Avoid overheating that accelerates oxidation. ScienceDirect+1

D. Injection pressure, nozzle geometry & ECU / control changes

• Review/adjust injection pressure & timing: higher injection pressure can improve atomization of heavier fuels, but it also increases injector stress and can accelerate wear — OEM test/approval required. Studies show optimized pressure improves biodiesel combustion but must be balanced against component life. SSRN+1

• Consider nozzle type / hole size changes (if the engine allows): some nozzles designed for diesel oil may need different orifice geometries to maintain proper spray cone and penetration with FAME blends. Any nozzle change must be approved by OEM and validated on a testbed. SAE International

E. Materials, coatings & elastomer selection

• Upgrade elastomers & seals to FAME-compatible materials (fluoroelastomers / FKM, HNBR grades shown compatible in many studies); test all seals, diaphragms and hoses for swelling/compatibility before extended use. NREL Docs

• Consider surface treatments / harder materials for critical wear surfaces in pumps and injectors if long-term FAME use is planned — but this is an OEM-level redesign in many cases. ResearchGate

F. Filtration & monitoring instrumentation (online)

• Install inline pressure & differential gauges to monitor filter loading and nozzle back pressures.

• Use online particle counters / periodic microparticle tests and scheduled nozzle-coking inspections as part of preventive maintenance. ResearchGate

G. Additives & conditioning agents

• Use approved antioxidant / anti-gumming / detergency additive packages tailored for FAME blends to reduce deposition and protect seals. Marine additive vendors publish products for injector cleanliness — use only OEM-approved chemistries and monitor compatibility. ValvTect+1

6 — Control strategy & commissioning steps

1. OEM engagement & approval: Before broad use, obtain engine-manufacturer authorization and recommendations (many OEMs publish service letters and operation guidelines for biofuels). MAN’s service letter outlines accepted biofuel types and operational cautions — follow those instructions. MAN Energy Solutions

2. Engine bench testing / fleet pilot: Run controlled tests (bench and sea trials) with instrumented injectors to log spray patterns, pressures, and deposit formation rates before full-scale rollout. SAE International+1

3. Calibration & mapping: If using common-rail or electronically controlled systems, calibrate injection timing and quantity maps for the specific algae-fuel blend under expected ambient and load conditions — manufacturer assistance advised. SAE International

7 — Maintenance & inspection plan (recommended)

• Daily / weekly checks: fuel filter differential pressure, water separator drains, fuel temperature readings.

• Monthly: fuel polishing cycles if feedstock storage > 1 month; sample testing for acidity, water content and particle count.

• Quarterly / 6-monthly: nozzle spray pattern checks (bench), injector tip inspection during planned maintenance windows, and elastomer inspection/replacement as needed.

• Record keeping: store fuel batch certificates (fatty acid profile, oxidation stability), additive dosing logs and sample analytic results to support warranty and troubleshooting. NREL Docs+1

8 — Standards, OEM guidance & regulatory notes

• Engine OEM guidance: MAN and other OEMs have published service letters and approvals for renewable diesel / HVO and some FAME blends — always check the latest OEM guidance for allowed fuels and limits. MAN’s service letter (e.g., SL2023-741) is an important reference. MAN Energy Solutions+1

• Fuel specs: For HVO/renewable diesel, EN15940 and ASTM D975 are commonly referenced; for marine fuels ISO 8217 remains the baseline for distillate/residual marine fuels — biofuel blends require careful conformity checks. Advanced BioFuels USA

9 — What the literature & field trials say (short literature synthesis)

Bench and engine tests of algal FAME blends often show comparable combustion but sometimes slightly reduced power and higher NOx depending on blend and engine calibration; deposit formation and filter plugging are commonly reported concerns for higher FAME fractions unless fuel handling and additive strategies are applied. Lab reviews and experimental studies on algal methyl esters corroborate injector deposit risks and the need for filtration/heating/control strategies. Nature+2AIP Publishing+2