Storage & Logistics — Campaign Duration and Port Operations

Draft Medium Research 3,631 words Created Mar 4, 2026

Storage Requirements & Logistics for Shipboard Plasma Gasification Outputs

Date: 2026-03-04 Scope: 10 TPD ocean plastic processing vessel — methanol storage, slag storage, water balance, campaign modeling, port infrastructure, revenue logistics

1. Methanol Storage at Sea

1.1 Regulatory Framework

Methanol (CH3OH) has a flashpoint of 11-12°C, classifying it as a low-flashpoint fuel under the IGF Code (International Code of Safety for Ships Using Gases or Other Low-Flashpoint Fuels), which entered force January 2017 under SOLAS Chapter II-1.

Current regulatory status (as of March 2026):

The IGF Code currently covers gases (primarily LNG). Specific mandatory provisions for methyl/ethyl alcohols are being finalized.
MSC 110 (June 2025) progressed draft amendments to SOLAS Chapter II-1 and the IGF Code introducing a new "gaseous fuel" definition alongside "low-flashpoint fuel."
Amendments expected for approval at MSC 111/112 in 2026, with entry into force targeted for 1 July 2028.
In the interim, methanol-fueled vessels operate under MSC.1/Circ.1621 — interim guidelines for methanol/ethanol as fuel.

Practical implication: The Claw vessel carrying methanol as cargo product (not fuel) falls under the IBC Code (International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk). Methanol is a Chapter 17 cargo with Ship Type 2 requirements.

1.2 Tank Specifications

Parameter	Requirement
Material	Stainless steel (316L preferred) or carbon steel with compatible coating. Galvanized steel is NOT suitable for methanol service.
Pressure	Atmospheric or low-pressure (design pressure typically 0.25-0.7 bar gauge). Methanol is stored as a liquid at ambient pressure.
Temperature	Ambient. Methanol freezes at -97.6°C, boils at 64.7°C. No heating/cooling required for tropical Pacific operations.
Venting	Pressure/vacuum (P/V) valves on all tanks, connected to vent mast minimum 3m above deck. Opening pressure not lower than 0.007 MPa below atmospheric. No shut-off valves in vent lines.
Inerting	Vapor space inerted at all times; oxygen content must not exceed 8% by volume in any part of the tank. Nitrogen blanketing system required.
Flame arrestors	Vapor outlets must have type-approved flame passage prevention devices.
Containment	Cofferdams required around methanol fuel tanks (exception: tanks adjacent to shell plating below lowest waterline, since methanol is water-miscible and biodegradable).
Location	Not in accommodation spaces or Category A machinery spaces.

1.3 Safety Systems Required

1. Nitrogen inerting system — continuous blanket on all methanol tanks 2. Gas detection — methanol vapor detectors in tank surrounds, cofferdams, pump rooms 3. Fixed fire suppression — alcohol-resistant aqueous film-forming foam (AR-AFFF). Standard AFFF is ineffective on methanol fires. 4. Flame arrestors on all vent outlets 5. Double-wall piping or pipe-in-pipe for methanol transfer lines 6. Emergency shutdown (ESD) — automated valve closure on leak detection 7. Drip trays under all connections and valve manifolds 8. SCBA stations near methanol handling areas (methanol vapor is toxic) 9. Spill containment — coamings around tank tops, deck drains to slop tank

Critical note: Methanol burns with a nearly invisible flame in daylight. UV/IR flame detectors are essential; visual detection is unreliable.

1.4 Methanol Accumulation Modeling

Yield basis: Research literature reports 0.7-1.35 kg methanol per kg of plastic feedstock depending on process configuration and plastic composition. The 1.35 kg/kg figure comes from optimized lab-scale conditions with clean polymer feedstock. For ocean-recovered mixed plastic with contaminants, salt, biofouling, and moisture, a conservative yield of 0.5-0.7 kg methanol per kg feedstock is more realistic after accounting for:

Feedstock moisture and salt content (15-25% by weight for ocean plastic)
Syngas cleaning losses
Imperfect H2:CO ratio requiring water-gas shift
Methanol synthesis single-pass conversion (~5-10% per pass, with recycle)

Working assumption: 0.6 kg methanol per kg of dry, processed feedstock. If 10 TPD is the raw collection rate, effective dry feedstock is ~7.5 TPD after moisture/salt removal.

Parameter	Value
Methanol production rate	~4.5 tonnes/day (4,500 kg/day)
Methanol density at 25°C	791 kg/m³
Daily volume produced	~5.7 m³/day

Accumulation over campaign durations:

Campaign	Methanol Mass	Methanol Volume	Tank Ullage (85% fill)
30 days	135 tonnes	171 m³	201 m³ tank needed
60 days	270 tonnes	341 m³	401 m³ tank needed
90 days	405 tonnes	512 m³	603 m³ tank needed

1.5 Chemical Tanker Reference Sizing

Small chemical tankers (3,000-5,000 DWT) typically carry methanol in parcels of 500-2,000 m³ across multiple segregated tanks. A single methanol cargo tank on a small chemical tanker is commonly 200-500 m³. This is the relevant size class — the Claw vessel's methanol storage would be comparable to one or two cargo tanks on a small chemical tanker.

2. Slag Storage

2.1 Physical Properties

Property	Value
Density	2.5-2.8 g/cm³ (typically 2.6 g/cm³)
Appearance	Black, glassy, sand-like material (resembles obsidian)
Leachability	Non-leachable, passes TCLP protocols for metals
Hazard classification	Non-hazardous (inert)
Carbon content	3-10% unconverted carbon
Volume reduction	~99% vs. original MSW feedstock

2.2 Slag Generation Rate

Plasma gasification of plastic waste produces significantly less slag than MSW gasification because plastic is overwhelmingly organic (C, H, O). Inorganic residue from ocean plastic comes from:

Entrained sand, sediment, biofouling organisms (~5-10% of collected mass)
Fillers and pigments in plastics (CaCO3, TiO2, etc. — ~2-5% of plastic mass)
Salt residue after washing (~1-2%)

Working assumption: 5-8% of feedstock mass becomes vitrified slag.

Parameter	Value
Slag production rate	0.5-0.8 tonnes/day (from 10 TPD raw feedstock)
Slag density (bulk, settled)	~1.8-2.0 t/m³ (granulated form, not solid block)
Daily volume	0.25-0.44 m³/day

Accumulation over campaign durations:

Campaign	Slag Mass	Slag Volume (bulk)
30 days	15-24 tonnes	8-13 m³
60 days	30-48 tonnes	17-27 m³
90 days	45-72 tonnes	25-40 m³

2.3 Storage Requirements

Vitrified slag is chemically inert and non-hazardous. Storage is straightforward:

Bulk holds: Yes, standard dry bulk holds are suitable. No special lining or containment needed.
Container option: Could also be stored in skip bins or 20ft containers on deck if hold space is needed for other purposes.
Moisture: Slag exits the gasifier through a water quench system (water-cooled slag shows better leachability resistance). It will be wet when collected. A dewatering step (vibrating screen or settling bin) is needed before storage.
Ventilation: Not required — slag is inert, no off-gassing.
Segregation: Keep separate from methanol areas (obvious, but worth noting for regulatory compliance).

2.4 Handling Equipment

Loading onto vessel: Not applicable (slag is generated on board)
Internal transfer: Conveyor or skip hoist from gasifier quench pit to storage hold
Offloading at port: Grab crane, clamshell bucket, or conveyor to dump truck. Standard dry bulk discharge equipment.
Shore handling: Dump truck to aggregate yard. No special hazmat handling.

Key advantage: Slag is the easiest output to manage. It is non-toxic, non-flammable, non-reactive, and has commercial value as construction aggregate.

3. Water Balance on the Vessel

3.1 Water Generation from Process

Water is produced at multiple stages:

A. Feedstock moisture removal:

Ocean plastic arrives wet. Pre-processing (shredding, washing, drying) drives off moisture.
Estimate: 15-25% of collected mass is water → 1.5-2.5 tonnes/day from 10 TPD feedstock.
This water is saline/contaminated — requires treatment before use.

B. Syngas condensate:

Gasification produces water vapor from hydrogen in the plastic reacting with oxygen.
Syngas cooling/cleaning condenses this water.
Research shows condensate is approximately 11.3% of total products by mass.
Estimate: ~0.8-1.1 tonnes/day of condensate from syngas cleaning.
This water contains dissolved organics, particulates — needs treatment.

C. Methanol synthesis byproduct:

The methanol synthesis reaction produces water as a stoichiometric byproduct:

- CO₂ + 3H₂ → CH₃OH + H₂O (1 mole water per mole methanol) - Molecular weights: methanol 32 g/mol, water 18 g/mol - Ratio: 0.5625 kg water per kg methanol

At 4.5 tonnes methanol/day: ~2.5 tonnes water/day from synthesis
This is relatively clean process water (distilled quality after condensation)

Total water generation: ~4.8-6.1 tonnes/day (4,800-6,100 litres/day)

3.2 Ship's Freshwater Demand

Consumer	Daily Demand
Crew domestic (25 crew × 150 L/person)	3,750 litres
Galley and laundry	500 litres
Engine cooling (closed loop, makeup only)	200-500 litres
Industrial processes (feedstock washing, slag quench, gas scrubbing)	2,000-4,000 litres
Total	6,450-8,750 litres/day

3.3 Water Self-Sufficiency Assessment

Source	Daily Volume
Process water generated	4,800-6,100 L
Ship's demand	6,450-8,750 L
Deficit	~1,500-3,500 L/day

Verdict: Not fully self-sufficient, but close. The process covers 60-80% of water needs. The deficit can be closed by:

1. Reverse osmosis desalination unit — a small 5-10 m³/day RO unit is standard equipment on vessels this size. Cost: $50-100K installed. Power: 3-5 kWh/m³. 2. Feedstock pre-wash water recovery — if the saline wash water is treated (membrane filtration), it could close the gap entirely. 3. Rainwater collection — supplementary in tropical Pacific, but unreliable.

Practical recommendation: Install a 10 m³/day RO desalination unit as backup. The process water covers domestic needs; RO covers the industrial deficit. This makes the vessel effectively water-independent for campaigns of any length.

4. Campaign Duration Modeling

4.1 Constraining Factors

The ship must return to port when the first storage limit is reached. Two possible constraints:

1. Methanol tank capacity — the dominant constraint (large volume, hazardous cargo) 2. Slag hold capacity — rarely the binding constraint (small volume, easy to store)

Fuel, provisions, and consumables (plasma torch electrodes, catalysts) are secondary constraints not modeled here.

4.2 Campaign Duration Matrix

Methanol-limited (5.7 m³/day production):

Tank Size	Usable Capacity (85%)	Days Until Full	Methanol Stored
100 m³	85 m³	15 days	67 tonnes
200 m³	170 m³	30 days	134 tonnes
500 m³	425 m³	75 days	336 tonnes

Slag-limited (0.35 m³/day production, mid-range):

Hold Size	Usable Capacity (90%)	Days Until Full	Slag Stored
50 m³	45 m³	129 days	84 tonnes
100 m³	90 m³	257 days	167 tonnes
200 m³	180 m³	514 days	334 tonnes

Conclusion: Methanol is always the binding constraint. Slag storage of 50 m³ is more than sufficient for any realistic campaign.

4.3 Optimal Campaign Length

Given a 7-8 day round trip to Honolulu:

Campaign	Processing Days	Round Trip	Total Cycle	Utilization	Methanol Tank Needed
15 days	15	8	23 days	65%	100 m³
21 days	21	8	29 days	72%	140 m³
30 days	30	8	38 days	79%	200 m³
45 days	45	8	53 days	85%	290 m³
60 days	60	8	68 days	88%	400 m³
75 days	75	8	83 days	90%	500 m³

Recommended configuration: 200 m³ methanol tank, 50 m³ slag hold for a 30-day campaign cycle.

Rationale:

79% operational utilization is good for a pioneering vessel
30-day cycles align with crew rotation, resupply, and maintenance windows
200 m³ is a standard chemical tanker tank size — proven designs exist
134 tonnes of methanol per delivery is a commercially meaningful parcel
Monthly port calls allow regular inspection and maintenance of plasma systems

Stretch goal: 400 m³ methanol tank for 60-day campaigns (88% utilization). This requires more vessel space but nearly doubles throughput efficiency.

5. Port Infrastructure Needed in Honolulu

5.1 What the Ship Needs at Port

A. Methanol offloading:

Berth: Pier with chemical cargo handling capability (liquid bulk transfer)
Transfer method: Ship-to-shore hose connection to either:

- Shore tank (if a local storage facility is established), or - Tanker truck (MC 307/DOT 407 stainless steel chemical tanker, ~20 m³ / 16 tonnes per truck)

Duration: At 100 m³/hour transfer rate, a 200 m³ tank empties in ~2 hours
Safety: Vapor recovery system, grounding/bonding, fire watch, AR-AFFF on standby
Permits: USCG Captain of the Port permission for hazardous cargo transfer

B. Slag offloading:

Method: Grab crane or ship's crane to dump truck
Duration: 20 tonnes into a standard 10-wheeler dump truck = 2 loads, ~1 hour total
No special permits needed — slag is classified as inert, non-hazardous

C. Reprovisioning:

Fuel (if not dual-fuel methanol/diesel)
Crew provisions and fresh water (if RO is insufficient)
Plasma torch electrodes and catalyst (minor consumables)
Nitrogen for methanol tank inerting (or onboard nitrogen generator)

5.2 Honolulu Harbor Facilities

Honolulu Harbor handles over 12 million tons of cargo annually including 22.52 million barrels of liquid cargo through pipelines (FY 2021). It operates as the hub of Hawaii's commercial harbor system.

Existing liquid bulk capability:

Fuel-handling operations occur at multi-use cargo piers
Petroleum transfer infrastructure exists (primarily for jet fuel, diesel, gasoline imports)
No dedicated methanol terminal exists — Hawaii does not currently import methanol in bulk

What would need to be established: 1. Shore tank: A 500-1,000 m³ methanol storage tank at or near Honolulu Harbor. This is a modest installation — equivalent to a large fuel station tank. 2. Transfer piping: From berth to shore tank, with appropriate methanol-compatible materials and safety systems. 3. Alternatively: Direct ship-to-truck transfer at berth, avoiding the need for a shore tank entirely. This is simpler but slower and requires truck scheduling.

Permitting pathway:

USCG Facility Security Plan and Operations Manual
Hawaii DOT Harbors Division berth assignment
EPA Spill Prevention, Control, and Countermeasure (SPCC) Plan
Hawaii Department of Health permits for chemical storage

5.3 Hazardous Waste Considerations

Output	Hazardous?	Handling
Methanol	Flammable liquid, Class 3	Standard chemical cargo protocols
Vitrified slag	Non-hazardous (passes TCLP)	Standard dry bulk / aggregate
Scrubber water	Potentially contaminated	Test for heavy metals, treat/dispose per CWA
Spent catalyst	May contain copper/zinc	Recycle through catalyst vendor
Plasma torch electrodes	Non-hazardous (copper, tungsten)	Standard metal recycling

The only output requiring hazmat protocols is the methanol itself. All other outputs are either inert or recyclable through standard channels.

6. Revenue Logistics

6.1 Methanol Market — Pacific Region

Current pricing (Methanex Asia Pacific Posted Contract Price):

H2 2025 range: USD 360-420/MT
Trending range for 2026: USD 350-400/MT

Green methanol premium: USD 200-400/MT above conventional methanol in 2025, reflecting renewable energy input costs and carbon credit value. Methanol from ocean plastic gasification could potentially command this premium as a "circular economy" product.

Revenue per campaign (30 days, 134 tonnes):

Pricing Scenario	$/tonne	Revenue per Campaign	Annual (10 campaigns)
Conventional	$380	$50,920	$509,200
Green premium (low)	$580	$77,720	$777,200
Green premium (high)	$780	$104,520	$1,045,200

6.2 Nearest Methanol Buyers

Option A — Marine fuel (most promising for Hawaii):

Maersk is deploying 25 dual-fuel methanol vessels by 2027 and has contracted 500,000 tonnes/year of green methanol globally.
Pacific container routes pass through Honolulu. The vessel could supply bunkering methanol directly.
This is the highest-value channel (green methanol for shipping commands the best premium).

Option B — Chemical/industrial:

Methanex is the world's largest methanol producer and trader, with distribution throughout Asia-Pacific. They purchase from third-party producers.
Nearest major methanol consuming markets: US West Coast (California has methanol demand for MTBE replacement, biodiesel, wastewater treatment) and Japan/South Korea (large chemical industry consumers).
Small parcels (100-500 tonnes) would likely go via chemical tanker from Honolulu to Long Beach, Oakland, or Yokohama.

Option C — Local Hawaii use:

Hawaii has limited industrial methanol demand. Potential local uses:

- Biodiesel production (small-scale on Oahu and Maui) - Wastewater treatment plants - Laboratory/pharmaceutical supply

Likely too small to absorb full production, but could take 10-20% at retail pricing ($500-800/tonne in drums/IBCs).

Typical contract structure: Methanol is sold on monthly or quarterly contracts indexed to Methanex APCP or ICIS assessed prices. A new small-volume producer would likely sell through a trading intermediary (e.g., Helm AG, Proman, or a regional chemical distributor) rather than directly to end users.

6.3 Methanol Transport from Honolulu

Destination	Method	Transit Time	Cost Estimate
US West Coast (LA/Oakland)	Chemical tanker parcel	5-7 days	$30-50/MT freight
Japan/South Korea	Chemical tanker parcel	10-14 days	$50-80/MT freight
Local Hawaii	Tanker truck / IBC	Same day	$10-20/MT

At 134 tonnes per campaign, the methanol parcel is small for a dedicated chemical tanker shipment. More practical options: 1. Accumulate in shore tank over 2-3 campaigns (400+ tonnes), then ship as a meaningful parcel. 2. Sell to a local bunkering operation that resells to methanol-fueled vessels calling at Honolulu. 3. Backhaul arrangement — negotiate space on container ships returning empty to the US mainland.

6.4 Slag — Hawaii Construction Market

Local demand is strong. Hawaii imports the vast majority of its construction materials at high cost due to shipping. Any locally-produced aggregate has a built-in advantage.

Key buyers/users:

Hawaiian Cement — produces up to 345 tph of aggregates, consuming ~60,000 tonnes/month on Oahu. Vitrified slag as supplementary aggregate would be readily absorbed.
West Oahu Aggregate (WOA) — processes recycled construction materials in Honolulu. Already handles crushed concrete, rock, and soil for reuse.
Grace Pacific Corporation — uses recycled materials including crushed glass as aggregate in paving.
Honolulu Department of Environmental Services — actively promotes buying recycled products for city construction projects.

Slag pricing reference:

Construction aggregate in Hawaii: $20-40/tonne (premium over mainland due to shipping costs)
Vitrified slag (comparable to blast furnace slag): $15-30/tonne as aggregate
At 20 tonnes/campaign: $300-600/campaign revenue from slag — negligible but covers handling costs
The real value of slag is in disposal cost avoidance — it is a zero-cost or revenue-positive waste stream, not a disposal liability.

6.5 Revenue Summary

Output	Annual Volume	Price Range	Annual Revenue
Methanol (conventional)	1,340 tonnes	$350-420/t	$469K-$563K
Methanol (green premium)	1,340 tonnes	$550-780/t	$737K-$1,045K
Vitrified slag	200 tonnes	$15-30/t	$3K-$6K
Total (conservative)			$472K-$569K
Total (green premium)			$740K-$1,051K

7. Key Design Recommendations

1. Methanol tank: 200 m³ minimum (30-day campaign). 400 m³ preferred if vessel layout permits (60-day campaign). 2. Slag hold: 50 m³ is more than sufficient. Could be a simple below-deck bin. 3. Water system: 10 m³/day RO desalination unit + process water recovery. Vessel will be ~80% water self-sufficient from process alone. 4. Nitrogen generator: Onboard PSA nitrogen generator for methanol tank inerting (eliminates dependency on shore nitrogen supply). 5. Shore infrastructure: Start with ship-to-truck methanol transfer (minimal investment). Build shore tank when volumes justify it. 6. Market entry: Target marine bunkering methanol market first (highest value, growing demand, Honolulu is a natural refueling stop).