Marine Growth (Biofouling) - A Hidden Threat Beneath the Hull
- Paul Nijhof
- 6 days ago
- 3 min read
As your vessel moves through warmer or more bioactive waters, marine growth inside cooling systems and around the hull isn’t just a nuisance — it becomes a cost. And unless you have a clear plan, that cost will show up in fuel, maintenance, and negotiating power.
The Problem & Regulatory Context
Every voyage touches different environments, and with each port call or coastal transit, organisms like mussels and barnacles find a way into internal seawater systems (cooling lines, sea chests) and around hull appendages (rudders, thrusters, stabilisers). As water gets warmer, fouling can die, expand or shift and cause restriction in cooling systems—leading to degraded performance and operational risk.
During dry-dock cycles, it’s not uncommon to remove 20–30 tons of marine growth, and proper disposal and logging of this activity is increasingly mandatory. Divers conduct in-service cleaning of hulls, shafts, niche areas, and the cooling circuit to preserve vessel efficiency.
From a regulatory standpoint, the International Maritime Organization (IMO) has already addressed the risk of hull-borne invasive aquatic species via its “Guidelines for the Control and Management of Ships’ Biofouling to Minimize the Transfer of Invasive Aquatic Species” (Resolution MEPC.378(80), adopted 7 July 2023) which builds on the earlier Resolution MEPC.207(62). The Guidelines recommend a ship-specific Biofouling Management Plan (BFMP) and a Biofouling Record Book.
Why It Matters for Owners and Operators
Reduced cooling efficiency: Internal fouling increases resistance, raising fuel burn and reducing available power. Some studies show heavy fouling can increase fuel consumption by up to 20–85 %.
Shortened maintenance windows & higher CAPEX risk: Discovering heavy growth during dry-dock can trigger unexpected hull/sea-chest cleaning, niche-area work, anti-fouling system reapplication, all of which disrupt schedules and add cost.
Compliance and port state risk: As biofouling regulation tightens, failing to maintain logs, hull condition and cleaning records puts vessels at risk of port state delays, entry refusals or increased survey focus.
Operational and commercial impact: Beyond fuel and maintenance, fouling reduces speed margin, increases the cost of voyage & trim optimisation, and can weaken your negotiating position when charterers or regulators question performance.
What You Can Do On Board
Implement a ship-specific BFMP + Record Book – Align with MEPC.378(80) which requires a documented plan and cleaning/inspection regimes.
Focus on niche and internal water systems – Cooling lines, sea-chests, thrusters, stabilisers are high-risk areas.
Regular inspection & monitoring – Use a fouling rating system (e.g., 0–4) to trigger proactive cleaning rather than waiting for performance loss.
Ensure robust cleaning & disposal – In-water or dry-dock cleaning must be recorded, waste handled correctly, anti-fouling system condition verified.
Link to energy efficiency & emissions goals – Reduced fouling delivers not just operational savings but helps you meet GHG and efficiency targets under frameworks such as the MEPC.395(82) (2024 Guidelines for SEEMP) which connect hull condition to broader efficiency strategy.
Why It Ties Back to P&L
Biofouling isn’t just a maintenance headache; It hits your top and bottom line. You pay more fuel, lose speed, spend more in dry-dock, face inspection risk and erode commercial strength. Getting ahead of fouling means lower drag, fewer unplanned interventions, stronger performance claims and a better negotiating and financing position.
A Practical Way Forward: NIJHOF Central Intelligence Library (Maritime) | NCIL(M)
NIJHOF Central Intelligence Library (Maritime) | NCIL(M) is your vessel’s offline AI for compliance, evidence and daily decision-making. It ingests manuals, class approvals, IMO regulations (like MEPC.378(80)), SEEMP Parts I–III, training material, MRV/DCS exports, CMMS records, BDNs, routing and trim outputs, and enterprise data. Cleaned and structured, this data runs on a high-performance on-board unit. Crew get instant, accurate, procedure-true answers with no internet required. With this support you strengthen biofouling management, evidence certainty, operational discipline and fuel efficiency performance across your fleet.
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