Two things have to be true for the grown wall to work: seawater electrolysis has to put limestone on steel at a useful rate, and a porous wall has to stop waves. Both are measured. This page holds the numbers the calculators use, each with where it came from.
measured lab or field instrument independent not a proponent paper peer-reviewed published claim asserted, weak or broken cite derived this site
Hilbertz mineral accretion (1979), later “Biorock”. The steel is the cathode.
| Measured rate | kg / time | Also reported | What was running |
|---|---|---|---|
| measured Hilbertz 1979, Port Aransas lab | 88.3 g in 42 h = 2.10 g/h | ~0.046 kg/kWh. Paper’s “1.9 kg per kW” is not kWh | ~46 W on galvanized mesh. Mostly brucite in that test |
| independent EUDP 5052-0010, North Sea | ~7.2 kg/yr = 20 g/day | ~0.4 cm/yr; 1.6–2.0 g/cm³; puncture ≈ C20/25 concrete; €1–12/kg | 50 kg rebar, 0.2 A, 1.2–2.5 V. 215 kWh/yr system draw — 0.2 A × 2.5 V × 8760 h is 4.4 kWh, the rest is supply overhead. So their 0.033 kg/kWh is a power-supply number, not chemistry |
| field Marina Hemingway, Cuba (Amat 1994, in Goreau 2012) | 0.4–0.5 kg/kWh at 6 V = 73% of Faraday | Jamaica battery test 1.07 kg/kWh at 1.5 V (43% of Faraday) | Site rectifiers, stray-current losses included. This is the site default |
| claim Goreau 2012 Table 1 | 0.62 kg/kWh at 6 V, 100% Faraday | “not more than 1–2 cm/yr” for strength; 60–80 MPa compressive (Graz) | Ceiling, not a field result |
| peer-reviewed Sharker 2023, Electrochimica Acta | ≤150 µA/cm² = 1.5 A/m² of steel for compact CaCO3; higher j → brucite. Deposit keeps growing above ~0.55 A/m² | ||
Kriebel 1992 on the grown face. Water forced through the holes loses head; that energy is gone. At 20% open half the wave height gets through (Kt 0.5) and the wall takes 0.75× a solid wall’s force. Square holes are not his vertical slots.
| Number | Value used | Where it comes from |
|---|---|---|
| Kt at 20% open | 0.48 | peer-reviewed Kriebel 1992 head-loss K = Cd(1−P) + (1/(CcP) − 1)², slot flume P 0.10–0.50; shallow-water T factor derived below |
| Wave load on the wall | 0.75 × solid wall | peer-reviewed Kriebel eq. 17, (1 − Kt)(1 + P)/(1 − P) at Kt 0.5, P 0.2 |
| Jarlan chamber Kr | floor 0.3 · optimum B/L 0.1–0.3, 20–40% open | peer-reviewed Medina 2010, Suh 2001, Fugazza & Natale 1992 — detail on Sandbar |
| Faraday yield | 3.73 g CaCO₃ / Ah · 0.62 kg/kWh at 6 V | derived M/(2F); matches Goreau 2012 Table 1 |
| Field efficiency | 73% (choice) | field Cuba 0.4–0.5 kg/kWh at 6 V, table above |
| Deposit density | 1,800 kg/m³ (choice) | field EUDP Table 4: 1.6–2.0 g/cm³; 50% brucite, 44% aragonite, 6% calcite at their current |
| Growth current | 1.5 A/m² steel | peer-reviewed Sharker 2023 compact-deposit ceiling; EUDP: higher current → brucite, porous, weak |
| Power after growth | 0.08 A/m² (choice) | manual DNV-RP-B401 Table 8-2 mean design current, bare steel <30 m: 0.07 tropical – 0.12 arctic; 0.02 buried. The 0.55 A/m² option is Sharker 2023’s deposit floor, 5–8× higher |
| Growth rate | 2.0 cm/yr per side | derived 1.5 A/m² × 73% × 3.73 g/Ah × 8760 h ÷ 1,800 kg/m³. Goreau 2012: “not more than 1–2 cm per year” for strength |
| Mineral strength | 0 MPa tensile (choice) | field Hilbertz/Goreau 60–80 MPa compressive (Graz, Maldives); Hilbertz 1979 Fig. 28 ≈ 26–37 MPa; EUDP low-voltage puncture ≈ C20/25, high-voltage ⅓ of that. Tensile and bond unpublished, so 0 is the default. C20/25 reference: fctm 2.2, fctk,0.05 1.5, design ≈ 1.0 MPa (EN 1992-1-1 Table 3.1) |
| Steel allowable | 100 MPa · AISC 360 F11 | peer-reviewed Fy 250 / 2.5. Dowswell, Eng. J. 53(4): yield if Lbd/t² ≤ 0.08E/Fy; inelastic Mn = [1.52 − 0.274 (Lbd/t²) Fy/E] My; elastic Fcr = 1.9E/(Lbd/t²). Lb = pitch |
| Prices | $0.60/lb steel · +30% slit+weld · $800 anchor · $0.12/kWh | input SMU HR coil 2026-09-01; IndexBox mesh premium 15–40%; Helical Technology 2023; EIA 2025 industrial 8.6¢ / commercial 13.4¢. Sources on Home |
peer-reviewed Head loss per plane K = Cd(1 − P) + (1/(CcP) − 1)², Cc = 0.6 + 0.4P³. Planes in series add K if staggered. Kriebel’s flume: slots, P 0.10–0.50, deep water, H/L 1/40–1/15.
derived T = K H k (sinh 2kh + 2kh) / (12π sinh² kh); T Kt² + Kt − 1 = 0; Kr = 1 − Kt. Deep water this is Kriebel’s T = K H/(3L). Check: P = 0.14, H/L = 1/20 → Kt = 0.50 (his 0.09–0.17 band). Force / solid wall = (1 − Kt)(1 + P)/(1 − P) (eq. 17).
derived Grid: pitch p = (t + 2s)/(1 − √0.2) so the finished face is 20% open. Steel/m² = (2t/p − t²/p²)·w·7850. Wet steel/m² face = 4(t + w)/p. Mineral/m² = (0.8 − steel fraction)(w + 2s)·ρ. kg/kWh = η · 3.73 g/Ah ÷ V. Grow years = mineral ÷ (1.5 A/m² × wet steel × η × 3.73 g/Ah × 8760).
derived Anchors: waterline pressure q = ρg Kr H (1 + P)/(1 − P). Steel moment per m of wall M = φ σ t w²/(6p), φ from AISC F11 with Lb = p. Optional limestone: + ft (1 − √P) D²/6, D = w + 2s, an unreinforced slab between the holes. Span S = √(8M/q). Anchors = ⌈1609/S⌉ × ⌈Hwall/S⌉, each carrying q S².
derived Build $ = steel t × 2,205 lb/t × $/lb × (1 + slit-weld) + kWh × $/kWh + anchors × $. Keep-alive $/yr = chosen A/m² × wet steel × V × 8760 × $/kWh. The search runs t 0.5–8 mm, w 10–400 mm, s 2–100 mm and keeps the cheapest that meets min hole and max grow years.
Limits: regular waves; square holes use the slot contraction coefficient; shallow water is theory, not flume; no breaking on the wall; no overtopping. Day-one strips are too open for the K formula — it applies to the grown face. Anchor grid is conservative: a wall with its toe in the seabed needs fewer rows.