Engineering Intelligence Model

Innovative solutions to complex technical challenges.

Run Analysis

First Report Free

The Process

Input a detailed technical challenge. Sparlo runs a systematic innovation methodology to generate a thorough problem analysis with solution pathways, and delivers the report in 30 minutes.

The Methodology

1Root Cause Analysis

2Problem Reframe

3Non-Inventive Solutions

4Cross-Domain Innovation

5Commercial Viability

6Sustainability Assessment

Example Reports

Explore real innovation intelligence reports across industries.

Electrochemical Ocean Alkalinity Enhancement: Marine Electrolyzer Architecture for 5+ Year Survival

Jan 4, 2026·16 min read

The Brief

Electrochemical ocean alkalinity enhancement produces NaOH at sea to absorb atmospheric CO2. But marine electrolysis faces severe corrosion, biofouling, and membrane fouling. Need electrolyzer architecture that survives 5+ years in marine environment at <$80/ton CO2 equivalent alkalinity cost.

Executive Summary

The Assessment

The desalination industry solved seawater fouling decades ago with electrodialysis reversal—polarity switching every 15-30 minutes that dissolves scale and kills biofilms before they mature. Mikhaylin & Bazinet's 2016 review documents 5-10x membrane life extension with this single intervention. The adaptation to alkalinity production isn't research; it's engineering integration with a philosophy shift: design for managed degradation with modular hot-swap electrodes rather than fighting for 5-year component survival in an environment that destroys everything.

Viability

Viable with high confidence using proven technologies

Primary Recommendation

Implement polarity reversal (5-15 minute cycles for seawater) combined with modular cartridge electrodes designed for 6-12 month replacement. This approach uses proven EDR physics, accepts that seawater will degrade components, and optimizes for $/kg-NaOH-lifetime rather than component longevity. Target $60-80/ton CO2 equivalent with 70%+ capacity factor. First validation: 3-month seawater exposure test with reversal protocol optimization, $50-100K.

Problem Analysis

What's Wrong

Seawater destroys electrochemical systems through three simultaneous attack vectors: chloride ions corrode metals and degrade membranes within weeks; biofilms establish within 24-48 hours and mature into impermeable layers within weeks; and at cathode pH >10, Mg(OH)₂ and CaCO₃ precipitate directly onto electrode surfaces, creating insulating scale that kills efficiency. Current approaches designed for purified brine fail catastrophically—chlor-alkali membranes tolerate <50 ppb divalent cations while seawater contains 400 ppm Ca²⁺ and 1300 ppm Mg²⁺, a 10,000x mismatch.

Why It's Hard

The fundamental challenge is thermodynamic: chlorine evolution (1.36V) is kinetically favored over oxygen evolution (1.23V) on most catalysts in chloride-rich solutions, despite oxygen being thermodynamically preferred. The 490mV window exists but requires precisely engineered catalyst surfaces to exploit. Simultaneously, the cathode operates at pH >10 where both Mg(OH)₂ (Ksp = 1.8×10⁻¹¹) and CaCO₃ (Ksp = 3.4×10⁻⁹) are supersaturated by orders of magnitude—precipitation is thermodynamically inevitable. And biofilm formation follows predictable kinetics: conditioning film (proteins, organics) in minutes, bacterial attachment in hours, mature community in days. You cannot thermodynamically prevent any of these; you can only manage them kinetically.

Governing Equation

E_cell = E°_OER - E°_cathode + η_OER + η_cathode + iR_solution + iR_membrane + iR_fouling

Cell voltage includes thermodynamic minimum (1.23V for OER) plus overpotentials at each electrode plus ohmic losses. The fouling resistance term (iR_fouling) grows exponentially with time in seawater, eventually dominating. At 100 μm biofilm thickness, mass transport resistance increases 10-100x.

First Principles Insight

Optimize for $/kg-NaOH-lifetime, not component longevity

The 5-year electrode life target may be self-imposed rather than economically optimal. If electrode replacement is cheap and fast enough (modular cartridges, quick-connect interfaces), designing for 6-12 month disposable electrodes might beat 5-year hardened electrodes on total cost. The offshore wind industry accepts regular blade inspections and component replacement; the question is whether the electrolyzer industry's longevity obsession reflects optimal economics or inherited assumptions from chlor-alkali plants that operate with purified brine.

What Industry Does Today

Adapted chlor-alkali cells with Nafion membranes and DSA anodes

Limitation

Designed for purified brine; membranes foul in days-weeks with seawater; DSA anodes preferentially produce chlorine over oxygen

Bipolar membrane electrodialysis (BPMED)

Limitation

30-40% lower energy than direct electrolysis but membrane life in seawater is weeks without aggressive pretreatment

Heavy pretreatment to chlor-alkali standards

Limitation

Adds $20-40/ton NaOH equivalent; defeats the purpose of using seawater directly

Selective OER catalysts (NiFe LDH)

Limitation

Lab-proven >99% selectivity but long-term stability in real seawater (with organics, suspended solids) unvalidated

Current State of the Art

Equatic (UCLA spin-out)

Approach

Flow-through mesh electrodes accepting chlorine co-production, downstream mineral neutralization

Current Performance

$100-150/ton CO2 at pilot scale (disclosed in DOE ARPA-E documentation)

Target/Roadmap

$50-70/ton CO2 at commercial scale by 2027

Source: DOE ARPA-E award documentation and company disclosures, 2022-2023

Ebb Carbon

Approach

Electrochemical ocean alkalinity enhancement with proprietary electrode design

Current Performance

Not disclosed; pilot operations in 2023

Target/Roadmap

Commercial deployment by 2026

Source: Press releases, unverified

Planetary Technologies

Approach

Electrochemical production of Mg(OH)₂ from industrial waste streams

Current Performance

Pilot scale; cost not disclosed

Target/Roadmap

1 Mt CO2/year capacity by 2030

Source: Company announcements

Kuang et al. (Stanford)

Approach

NiFe LDH catalyst achieving >99% OER selectivity in seawater

Current Performance

100+ hours stability at 400 mA/cm² demonstrated

Target/Roadmap

Academic research; no commercialization timeline

Source: PNAS 2019

Constraints

Hard Constraints
  • Must operate in seawater (~19,000 ppm Cl⁻, ~400 ppm Ca²⁺, ~1300 ppm Mg²⁺)
  • Must produce net alkalinity (NaOH, Mg(OH)₂, or equivalent)
  • Cannot release significant chlorine to environment (<5% of current as Cl₂)
  • Must be deployable offshore or coastal
Soft Constraints
  • 5+ year system life (component replacement acceptable)
  • <$80/ton CO2 equivalent (may be negotiable with carbon credit pricing)
  • Continuous operation preferred but intermittent acceptable
  • Minimal pretreatment preferred but some acceptable if cost-effective
Assumptions
  • Temperate coastal waters (~15°C average); tropical deployment would accelerate biofouling 2-3x
  • Grid-connected or offshore wind power at $30-60/MWh
  • Direct operational cost only; MRV costs excluded (would add $10-30/ton)
  • Electrochemical approach required; mineral dissolution alternatives noted but not primary focus
Success Metrics

Alkalinity production cost

Target: <$60/ton CO2 equivalent
Min: <$80/ton CO2 equivalent
Stretch: <$40/ton CO2 equivalent

Unit: $/ton CO2

Mean time between maintenance

Target: >6 months
Min: >3 months
Stretch: >12 months

Unit: months

Capacity factor

Target: >70%
Min: >50%
Stretch: >85%

Unit: percent

Energy consumption

Target: <3.0 kWh/kg NaOH
Min: <3.5 kWh/kg NaOH
Stretch: <2.5 kWh/kg NaOH

Unit: kWh/kg

Chlorine selectivity (OER vs CER)

Target: >95% OER
Min: >80% OER (with downstream neutralization)
Stretch: >99% OER

Unit: percent Faradaic efficiency

Challenge the Frame

Assumptions Challenged

  • Electrochemical approach is required

    Challenge: Passive mineral dissolution (olivine spreading) or enhanced weathering may achieve similar alkalinity at lower cost without electricity

    If passive approaches prove viable at scale, the entire electrochemical architecture may be unnecessary. Monitor Project Vesta and similar efforts.

  • 5+ year system life is the target

    Challenge: If component replacement is cheap enough, 1-2 year system life with annual replacement may be more economical

    The 'managed degradation' philosophy may extend further than we've proposed. Disposable electrolyzer cartridges replaced annually could beat hardened systems.

  • Direct seawater use is required

    Challenge: If desalination costs continue falling, pretreating seawater to chlor-alkali standards may become economical

    At $0.50/m³ desalination cost, pretreatment adds ~$5-10/ton NaOH—potentially acceptable if it enables proven chlor-alkali technology.

  • Chlorine must be prevented or neutralized

    Challenge: Low-level chlorine release may be environmentally acceptable in open ocean where dilution is rapid

    If regulatory framework permits <1 ppm Cl₂ in discharge, system design simplifies dramatically. This is a policy question, not a technical one.

Innovation Analysis

Reframe

Instead of asking 'how do we make components survive 5 years in seawater,' we asked 'how do we make component replacement so cheap and fast that survival doesn't matter.'

Domains Searched
Desalination (EDR polarity reversal)Geothermal (precipitation steering)Marine biology (Sharklet antifouling)Cathodic protection (sacrificial anodes)Chlor-alkali history (mercury cells)Battery industry (solid electrolytes)Microfluidics (membraneless flow cells)Pulp & paper (black liquor electrolysis)

Solution Concepts

Solution concepts use proven technologies requiring integration, not invention. These represent the lowest-risk path to meeting the $80/ton CO2 target. Start here.

Primary Recommendation

Polarity Reversal + Modular Cartridge Architecture

CATALOG·85% confidence
Bottom Line

Combine proven EDR-style polarity reversal (5-15 minute cycles for seawater) with modular cartridge electrodes designed for 6-12 month hot-swap replacement. The system accepts that seawater will degrade components and optimizes for total cost of ownership rather than component longevity.

What It Is

Polarity reversal works by periodically switching anode and cathode. When current reverses, the former cathode (where Mg(OH)₂ and CaCO₃ precipitated at high pH) becomes the anode (low pH), dissolving the scale. Biofilms lose the ion gradient cues they need for attachment and detach. The Mikhaylin & Bazinet 2016 review documents 5-10x membrane life extension with this single intervention in brackish water; seawater may require more frequent reversal (5-15 minutes vs. 15-30 minutes) due to higher divalent cation load. Modular cartridges use standardized quick-connect interfaces allowing tool-free electrode stack replacement without cell disassembly. This follows the black liquor electrolysis philosophy of 'managed degradation'—accept that electrodes will wear, design for easy replacement, and optimize $/kg-NaOH-lifetime rather than $/year-operation. Cartridge materials can be simpler (carbon, nickel) rather than exotic alloys because they don't need to survive 5 years.

Why It Works

CaCO₃ solubility increases ~100x from pH 10 to pH 4; Mg(OH)₂ dissolves completely below pH 9.5. When polarity reverses, the former cathode experiences acidic conditions that dissolve accumulated scale. Biofilm EPS matrix loses structural integrity when local ionic strength and pH oscillate—the Mikhaylin & Bazinet review documents 50-80% biofilm detachment per reversal cycle. The key is reversing frequently enough that scale and biofilm never reach the 'mature' stage where they become mechanically robust and difficult to remove.

The Insight

Periodic electrochemical stress disrupts fouling equilibrium before irreversible attachment occurs

Domain: Desalination industry (electrodialysis reversal)

How they use it: EDR systems reverse polarity every 15-30 minutes to prevent membrane fouling in brackish water treatment

Why it transfers: The physics is identical—scale dissolution at low pH, biofilm disruption from ionic oscillation. Seawater just requires more frequent reversal.

Why industry missed it: The electrolyzer industry inherited chlor-alkali assumptions about continuous operation with purified feed. EDR is standard in desalination but the communities don't overlap. The 5-year electrode life target may be self-imposed rather than economically optimal.

Expected Improvement

2.8-3.2 kWh/kg NaOH (5-15% energy penalty from reversal)

Timeline

6-12 months to pilot validation

Investment

$0.5-2M for pilot system

Why It Might Fail
  • Polarity reversal frequency required for seawater may be so high that energy penalty exceeds 20%
  • May not work in tropical/humid environments where drying is slow
  • Capacity factor loss (5-15%) may exceed fouling-related gains
Validation Gates
12

3-month seawater exposure test with polarity reversal protocol optimization

$50-100K

Method: Deploy test electrodes in real seawater; vary reversal frequency; measure electrode weight loss, surface morphology, electrochemical performance, fouling coverage

Success: Electrode performance degradation <30% over 3 months; scale thickness <50 μm; biofilm coverage <20% of surface area

If degradation >50% or scale >100 μm, increase reversal frequency or pivot to chlorine-accepting architecture

Supporting Concepts

Accept Chlorine + Downstream Mineral Neutralization

FALLBACK

Stop fighting chlorine evolution at the anode. Accept mixed Cl₂/O₂ production and react chlorine with olivine or limestone slurry downstream.

What It Is

This is the Equatic approach, commercially validated at pilot scale. At the anode, seawater electrolysis produces both O₂ and Cl₂ (ratio depends on catalyst and conditions). Cl₂ hydrolysis produces HOCl/HCl. This acidic stream contacts olivine (Mg₂SiO₄): 2HCl + Mg₂SiO₄ → MgCl₂ + H₄SiO₄. The net reaction consumes acid and produces dissolved cations that represent alkalinity when discharged to the ocean.

Why It Works

HOCl (pKa 7.5) and HCl from chlorine hydrolysis attack mineral surfaces. Olivine dissolution: Mg₂SiO₄ + 4H⁺ → 2Mg²⁺ + H₄SiO₄. Each mole of Cl₂ produces 2 moles of H⁺, which can dissolve ~1 mole of Mg from olivine. The Mg²⁺ released represents 2 equivalents of alkalinity. Net effect: chlorine becomes a positive contributor to alkalinity production.

When to Use Instead

If selective OER catalysts prove unreliable in real seawater, or if polarity reversal energy penalty is unacceptable, the chlorine-accepting architecture becomes primary. Also preferred if mineral co-benefits (silica for agriculture, Mg for ocean chemistry) have value.

Geothermal-Inspired Precipitation Steering

COMPLEMENTARY

Install sacrificial 'scaling targets' upstream of electrodes that preferentially nucleate Mg(OH)₂ and CaCO₃.

What It Is

Replace scaling targets on maintenance cycles while electrodes remain clean. This is standard practice in geothermal power plants like Wairakei (NZ), which has operated for 60+ years with severe silica and carbonate scaling. Heterogeneous nucleation of mineral scale preferentially occurs on surfaces with high surface area, surface defects/roughness, and favorable surface chemistry. By placing intentionally rough, high-surface-area targets in the flow path before electrodes, supersaturated Ca²⁺ and Mg²⁺ preferentially nucleate on these sacrificial surfaces.

Why It Works

Nucleation theory: critical nucleus formation requires overcoming an energy barrier that depends on surface energy. Rough surfaces with high defect density provide low-energy nucleation sites. If scaling targets provide 10-100x more favorable nucleation sites than smooth electrode surfaces, >90% of precipitation occurs on targets rather than electrodes.

When to Use Instead

This is complementary to all other approaches—should be included in any system design regardless of primary architecture. Low cost, low risk, proven physics.

Intermittent Drying Cycle Operation

COMPLEMENTARY

Optimize for intermittent operation with deliberate drying cycles rather than continuous submersion.

What It Is

When electricity is unavailable (renewable intermittency) or during scheduled intervals, drain cells and allow surfaces to dry. Biofilms die without moisture (90-99% mortality after 4-8 hours drying); mineral scale becomes brittle and spalls from thermal expansion mismatch. This turns the weakness of intermittent renewables into a fouling management strategy. The intertidal zone demonstrates this naturally—organisms in the splash zone face much lower fouling pressure than continuously submerged surfaces.

Why It Works

Biofilm EPS is 90%+ water; desiccation causes irreversible collapse of the hydrogel structure. Gram-negative bacteria (dominant marine foulers) are particularly sensitive. CaCO₃ scale has thermal expansion coefficient ~6×10⁻⁶/°C vs ~12×10⁻⁶/°C for metals; temperature cycling during drying creates interfacial stress that propagates cracks.

When to Use Instead

Complementary to polarity reversal. Particularly valuable for offshore wind-powered systems where intermittency is inherent. May become primary fouling management in tropical deployments where biofouling is most severe.

Innovation Concepts

Higher-risk explorations with breakthrough potential.

Innovation concepts offer higher ceilings with higher uncertainty. These are parallel bets on breakthrough outcomes that could transform the economics if successful.

Recommended Innovation

Sacrificial Magnesium Anode Architecture

Confidence: 50%

Flip the paradigm: instead of protecting electrodes from corrosion, design the anode to corrode productively. Magnesium sacrificial anodes dissolve to produce Mg(OH)₂ directly—the anode IS the alkalinity product. No membrane needed because there's no chlorine production. Pair with inert cathode for hydrogen evolution. Magnesium metal spontaneously oxidizes in seawater: Mg → Mg²⁺ + 2e⁻. At the cathode, water reduces: 2H₂O + 2e⁻ → H₂ + 2OH⁻. The Mg²⁺ and OH⁻ combine to form Mg(OH)₂ (brucite), which is sparingly soluble and disperses as alkaline suspension. This eliminates the membrane entirely—there's no chlorine to separate because there's no oxidation of water or chloride at the anode, only metal dissolution. It eliminates biofouling on the anode because the surface is constantly dissolving. It eliminates the chlorine selectivity problem because no chlorine can form.

Magnesium dissolution proceeds through direct electrochemical oxidation: Mg → Mg²⁺ + 2e⁻ (E° = -2.37V vs SHE). In seawater, the reaction is spontaneous and fast. The Mg²⁺ immediately hydrolyzes: Mg²⁺ + 2OH⁻ → Mg(OH)₂. Each mole of Mg produces 2 moles of OH⁻ equivalents = 3.4 g OH⁻/g Mg. No chlorine can form because there's no oxidation reaction at the anode—only metal dissolution. Energy requirement is theoretically zero (galvanic); <0.5 kWh/kg NaOH equivalent with enhancement current.

The Insight

The electrode can BE the product—dissolution is production, not failure

Breakthrough Potential

If it works: Eliminates membrane, chlorine, and fouling problems simultaneously. Simplest possible architecture.

Improvement: Energy consumption could drop from 2.5-3.5 kWh/kg to <0.5 kWh/kg (galvanic + enhancement)

First Validation Step
Gating Question: Can Mg(OH)₂ passivation be managed to sustain >5 mm/year dissolution with reasonable flow or current?·First Test: Buy marine-grade Mg anodes from cathodic protection supplier, deploy in seawater with inert cathode, measure dissolution rate under various conditions·Cost: $20-40K·Timeline: 8-12 weeks
Parallel Investigations

Electrochemical Olivine Weathering Cell

Confidence: 45%

Electrochemically accelerate olivine dissolution instead of splitting water

Ceiling: Lower energy than direct electrolysis; complete elimination of chlorine problem; mineral acts as both feedstock and buffer

Key uncertainty: Silica gel formation from H₄SiO₄ polymerization could clog reactors; mineral passivation by secondary precipitates could limit conversion

Elevate when: If silica management proves straightforward and energy consumption is <2 kWh/kg, this becomes primary path due to lower energy than direct electrolysis and elimination of chlorine problem.

NASICON Solid-State Membrane Architecture

Confidence: 35%

Replace polymer membranes with ceramic Na⁺ conductors impermeable to seawater

Ceiling: Eliminates biofouling, organic fouling, and chloride attack on cathode side entirely. Potential for very long membrane life.

Key uncertainty: Mechanical brittleness of ceramics makes large-area membranes challenging; sealing ceramic to housing in seawater environment is unproven

Elevate when: If polymer membrane costs or PFAS regulations become prohibitive, and if ceramic manufacturing scales, this becomes primary path for long-term durability.

Frontier Watch

Technologies worth monitoring.

Galinstan Liquid Metal Cathode

PARADIGM
TRL

2

Self-renewing liquid surface that cannot be permanently fouled

Why Interesting

Mercury cells operated reliably for 80+ years; abandonment was environmental, not technical. If Galinstan electrochemistry proves viable, this could be the ultimate fouling-resistant architecture.

Why Not Now

Sodium solubility in Galinstan (~0.5-1 at.%) may limit practical rates. Gallium embrittlement of structural metals requires careful material selection. Gallium and indium supply chains are constrained (~300 and ~800 tons/year respectively). Fundamental electrochemistry research needed.

Trigger: Publication demonstrating >1 at.% Na solubility in Ga-based alloy, or Ambri-style liquid metal battery commercialization proving large-scale liquid metal handling

Earliest viability: 5-7 years

Monitor: Prof. Michael Dickey, NC State (liquid metal electronics); Ambri (liquid metal batteries); Dr. Qian Wang, Chinese Academy of Sciences (gallium electrochemistry)

Membraneless Laminar Co-Flow Electrolyzer Array

EMERGING_SCIENCE
TRL

3

Eliminate membrane by using laminar flow to keep products separate

Why Interesting

Eliminates membrane failure mode entirely. Kjeang et al. demonstrated >1 W/cm² in membraneless fuel cells. If manufacturing scales, this could be the ultimate membrane-free architecture.

Why Not Now

Manufacturing millions of parallel microchannels at acceptable cost is a major challenge. Clogging from seawater particles is serious concern. 3-5 year timeline and $5-20M development cost. The physics works; the manufacturing doesn't exist.

Trigger: Cost of microchannel arrays drops below $100/m² (currently ~$1000/m²), or 3D printing of metal microchannels becomes viable at scale

Earliest viability: 5-10 years

Monitor: Prof. Erik Kjeang, Simon Fraser University (membraneless fuel cells); Microchannel heat exchanger manufacturers (Heatric, Alfa Laval); MEMS foundries with high-volume capability

NiFe LDH + ALD-Protected Electrodes

EMERGING_SCIENCE
TRL

4

Combine selective catalyst with atomic-layer protection for seawater durability

Why Interesting

Both components are independently proven. Kuang et al. demonstrated >99% OER selectivity for 100+ hours. Díaz et al. demonstrated 10,000+ hour corrosion protection with ALD. The combination could achieve chlor-alkali efficiency in seawater.

Why Not Now

Long-term NiFe LDH stability in real seawater (with organics, suspended solids) is less proven than lab demonstrations. ALD coating at electrode scale is more challenging than semiconductor wafers. Manufacturing integration is the gap.

Trigger: Publication demonstrating >1000 hours NiFe LDH stability in real seawater, or commercial ALD service offering electrode coating

Earliest viability: 2-3 years

Monitor: Prof. Hongjie Dai, Stanford (NiFe LDH catalyst development); Prof. Markus Antonietti, MPI Colloids (earth-abundant catalysts); ALD equipment manufacturers (Beneq, Picosun) for electrode-scale coating

Risks & Watchouts

What could go wrong.

Seawater variability (temperature, salinity, biology) may cause performance inconsistency across deployments

Technical·Medium severity
Mitigation

Design for operational flexibility; include sensors and adaptive control; test across multiple sites

Carbon credit pricing may not support $60-80/ton CO2 cost in near term

Market·High severity
Mitigation

Target voluntary carbon market premium buyers (tech companies, airlines); pursue government procurement; design for cost reduction pathway

Ocean discharge of alkalinity or chlorine may face environmental permitting challenges

Regulatory·High severity
Mitigation

Engage regulators early; develop robust MRV (monitoring, reporting, verification); start with pilot permits in favorable jurisdictions

Offshore deployment and maintenance requires specialized marine operations capability

Resource·Medium severity
Mitigation

Partner with offshore wind or oil & gas operators; design for shore-based maintenance where possible

Polarity reversal frequency required for seawater may be so high that energy penalty exceeds 20%

Technical·Medium severity
Mitigation

Validate reversal protocol early in pilot; have fallback to chlorine-accepting architecture if penalty is unacceptable

Self-Critique

Where we might be wrong.

Overall Confidence

Medium

High confidence in the physics of polarity reversal and precipitation steering (proven in adjacent industries). Medium confidence in the economics (seawater is harder than brackish water; energy penalty may be higher than estimated). Lower confidence in the paradigm-shifting concepts (sacrificial Mg, NASICON) which have clear mechanisms but unvalidated economics.

What We Might Be Wrong About

  • Seawater may be fundamentally harder than brackish water—10,000x higher divalent cation load may overwhelm polarity reversal

  • The 5-15% energy penalty estimate for reversal may be optimistic; real penalty could be 20-30%

  • Sacrificial Mg economics may never work due to Mg cost and carbon footprint constraints

  • Regulatory barriers for ocean alkalinity enhancement may be higher than anticipated

Unexplored Directions

  • Biological integration—cultivating beneficial biofilms rather than preventing all biofilms

  • Hybrid thermal-electrochemical approaches using waste heat to accelerate reactions

  • Capacitive deionization variants that shuffle ions without water splitting

Validation Gaps

Seawater may be fundamentally harder than brackish water

Status:Addressed

First validation step explicitly tests in seawater, not brackish water. 3-month exposure will reveal if polarity reversal is sufficient.

Energy penalty for reversal may be higher than estimated

Status:Addressed

Validation protocol includes energy consumption measurement. If penalty exceeds 20%, fallback to chlorine-accepting architecture.

Sacrificial Mg economics may never work

Status:Extended Needed

Parallel bench test on Mg anodes will validate dissolution rate, but full economics require lifecycle analysis including Mg sourcing. Recommend commissioning LCA if dissolution rate is promising.

Regulatory barriers may be higher than anticipated

Status:Accepted Risk

Regulatory engagement is outside technical validation scope. Recommend parallel workstream on regulatory strategy, but this doesn't gate technical development.

Final Recommendation

Personal recommendation from the analysis.

If This Were My Project

If this were my project, I'd start with the boring stuff that works. Get an EDR system from Evoqua or Suez, modify it for seawater with more frequent polarity reversal (start at 15 minutes, optimize down to 5 if needed), and add precipitation steering targets upstream of the electrodes. This combination addresses both biofouling and mineral scaling with proven physics and minimal development risk. Run it for 3 months in real seawater and measure everything—electrode weight loss, surface morphology, electrochemical performance, fouling coverage. That's your baseline.

While that's running, I'd set up a parallel bench test on sacrificial Mg anodes. This is the paradigm-shifting concept that could change everything, and it's cheap to test. Buy some marine-grade Mg anodes from a cathodic protection supplier, put them in seawater with a cathode, and measure dissolution rate under various conditions. The key question is whether Mg(OH)₂ passivation can be managed. If you can sustain >5 mm/year dissolution with reasonable flow or current, you've got something. If passivation kills it, you've spent $20K to learn that and can move on.

The one thing I would NOT do is chase the exotic materials (NASICON, Galinstan, membraneless microchannels) until the simpler approaches hit a wall. Those are 5-year bets with major manufacturing uncertainty. The polarity reversal + modular cartridge approach can probably hit $80/ton CO2 with existing technology—that's the near-term path. Save the paradigm shifts for the next generation.