Energy Balance — Does the Loop Close?
Energy Balance — The Critical Feasibility Question
This is THE question. If the energy loop closes, the station eats trash and powers itself. If it doesn't, supplemental power is needed forever.
The Question
Does the syngas energy output from plasma gasification of ocean plastic exceed the electricity needed to power the plasma torches, shredders, conveyors, dewatering, and station operations?
What We Know: Energy Content of Feedstock
| Feedstock | Energy Content | Source |
|---|---|---|
| Polyethylene (PE) | 46.3 MJ/kg | Standard thermodynamic data |
| Polypropylene (PP) | 46.4 MJ/kg | Standard thermodynamic data |
| Polystyrene (PS) | 41.9 MJ/kg | Standard thermodynamic data |
| Nylon (fishing nets) | 31.0 MJ/kg | Standard thermodynamic data |
| Mixed ocean plastic | ~30-40 MJ/kg | ACS Omega 2024 |
| Crude oil (comparison) | 42-47 MJ/kg | — |
| Coal (comparison) | 24-35 MJ/kg | — |
What We Know: Energy Consumption
Plasma Torch Power Consumption
| Scale | Torch Consumption | Total Plant Consumption | Source |
|---|---|---|---|
| 10 TPD | 0.817 MWh/ton | 1.14 MWh/ton | ResearchGate academic study |
| 100 TPD | 0.447 MWh/ton | ~0.6 MWh/ton (estimated) | ResearchGate / economies of scale |
| Westinghouse claim | 2-5% of total energy input | — | Westinghouse/NETL |
Other Power Consumers
- Shredders/grinders
- Dewatering centrifuges
- Feed conveyors
- Gas cleaning systems
- Station operations (lighting, nav, comms, crew)
- Collection systems
What We Know: Energy Output
Syngas Production from Plastic
| Metric | Value | Source |
|---|---|---|
| Syngas composition | H₂ (43.86 vol%) + CO (30.93 vol%) | ACS Omega 2024 |
| Syngas LHV (plastic waste) | 13.88 MJ/Nm³ | ACS Omega 2024 |
| Syngas LHV (biomass) | 10.23 MJ/Nm³ | ACS Omega 2024 |
| Oil yield from plasma | 0.8 kg oil per 1 kg plastic | ACS Omega 2024 |
| Pyrolysis oil energy | 39.6 MJ/kg | ACS Omega 2024 |
| System output efficiency | 81% | ACS Omega 2024 |
| Electricity output per ton MSW | ~816 kWh | Westinghouse/NETL |
| Conventional gasification | ~685 kWh/ton MSW | For comparison |
| Cold gas efficiency | 47.8% (CO₂ plasma, medical plastic) | PMC study |
Electricity Generation from Syngas
- Gas turbine generators convert syngas to electricity
- Typical gas turbine efficiency: 30-40%
- Combined cycle (gas + steam turbine): 45-55%
Real-World Operational Data
Utashinai Plant (Japan) — The Best Data Point
The only large-scale plasma gasification plant with published energy balance data:
| Metric | Value |
|---|---|
| Capacity | 200-220 TPD (MSW + auto shredder residue) |
| Peak throughput | ~300 TPD (2007) |
| Gross electricity generated | 7.9 MWh |
| Electricity exported to grid | 4.3 MWh |
| Electricity consumed internally | 3.6 MWh |
| Export ratio | 54% |
| Internal consumption | 46% |
| Plasma torches | 2 gasification islands × 4 Westinghouse torches each |
InEnTec Columbia Ridge — Hydrogen Focus
- Processing 25 TPD of mixed waste into hydrogen
- Uses approximately half the energy of electrolysis for hydrogen production
- Expected to improve to one-quarter of electrolysis energy
- Different metric (hydrogen, not electricity) but shows positive energy balance
Hurlburt Field (US Air Force) — Military Scale
- Processing 3,100 metric tons/year (~8.5 TPD)
- 420 kW output via internal combustion engine running on syngas
- Small scale, but confirmed: syngas from unsorted waste powers engines
Energy Balance Scenarios for The Claw
Scenario A: Prototype (5 TPD)
Input:
- 5 tonnes ocean plastic per day
- Energy content: ~35 MJ/kg × 5,000 kg = 175,000 MJ/day = 48,611 kWh/day
- 1.14 MWh/ton × 5 tons = 5,700 kWh/day
- Torch: 5,700 kWh
- Shredders: ~500 kWh
- Dewatering: ~800 kWh
- Conveyors: ~200 kWh
- Station operations: ~1,000 kWh
- Total: ~8,200 kWh/day
- 48,611 kWh × 0.81 × 0.35 = ~13,800 kWh/day
Scenario B: Full Scale (100 TPD)
Input:
- 100 tonnes ocean plastic per day
- Energy content: ~35 MJ/kg × 100,000 kg = 3,500,000 MJ/day = 972,222 kWh/day
- Torch: 0.447 MWh/ton × 100 = 44,700 kWh
- Shredders: ~5,000 kWh
- Dewatering: ~8,000 kWh
- Conveyors: ~2,000 kWh
- Collection systems: ~5,000 kWh
- Station operations: ~3,000 kWh
- Total: ~67,700 kWh/day
- 972,222 × 0.81 × 0.35 = ~275,700 kWh/day
Scenario C: Pessimistic (Wet, Salty Feedstock Penalty)
What if ocean-sourced plastic loses 30-40% energy efficiency due to:
- Water content (energy needed to evaporate)
- Salt contamination (reduces syngas quality)
- Marine organisms (biological fouling)
- Pre-processing energy overhead
- Generation: 275,700 × 0.65 = ~179,200 kWh/day
- Consumption unchanged: 67,700 kWh/day
- Net: ~179,200 - 67,700 = +111,500 kWh/day — STILL POSITIVE
The Dewatering Factor
The biggest unknown is the energy cost of removing saltwater from ocean plastic.
What helps:
- Waste heat from the reactor can be used for drying (energy loop)
- Centrifugal dewatering is mechanically efficient
- Pre-sorting removes much of the marine growth before processing
- Salt crystals form on dried plastic (may need washing)
- Salt can corrode equipment and contaminate syngas
- Water in the reactor absorbs enormous energy to vaporize (2,260 kJ/kg latent heat)
- 250 kg water × 2,260 kJ/kg = 565,000 kJ = 157 kWh per tonne of wet feedstock
- At 100 TPD: 15,700 kWh/day additional consumption
- This is already accounted for in the "dewatering" line item of the scenarios above
The Verdict
The energy loop almost certainly closes at scale (50+ TPD), even with ocean feedstock penalties. The math works because:
1. Plastic has energy content comparable to crude oil (30-40 MJ/kg) 2. Plasma gasification extracts ~81% of that energy as syngas 3. Ocean plastic is PE/PP dominant (highest energy content) 4. Economies of scale reduce torch consumption by 45%+ from prototype to full scale 5. Even with a 35% "ocean penalty," the numbers are strongly positive
At prototype scale (1-5 TPD): The loop may not fully close. Diesel backup recommended. But the purpose of the prototype is to TEST this, not to prove it — the math says it should work, the prototype confirms it.
What We Still Don't Know
- [ ] Actual syngas yield from wet, salt-contaminated mixed polymer + nylon net feedstock
- [ ] Energy penalty from specific salt contamination levels
- [ ] Optimal dewatering method and energy cost for ocean plastic specifically
- [ ] Thermal losses in marine environment (wind, waves, salt spray on equipment)
- [ ] Electrode degradation rate in salt-air environment
- [ ] Whether marine growth (barnacles, algae) in the feedstock helps or hurts energy balance
- [ ] Real-world combined efficiency of shredding tangled fishing nets