Substrate Stock Coverage

Definition

Substrate Stock Coverage (SSC) is the projected number of days the on-hand inventory of growing substrate will last at the current consumption rate. It is a runway figure: on-hand quantity divided by the trailing-window daily burn rate. Substrate is the facility's highest-volume cultivation consumable — every repotting, propagation, and bench refresh draws it down — so its coverage is the governing constraint on whether cultivation can proceed without an inventory stockout.

Why it matters

A substrate stockout halts propagation and repotting facility-wide; because resupply has a lead time, the danger is not running out today but failing to reorder in time. SSC converts a raw inventory number into the decision-relevant question — how many days of runway remain — and compares it against the supplier lead time. CHLORA recomputes coverage every six hours, auto-raises a procurement ticket as the runway approaches lead time, and surfaces SSC on the Operations Dashboard as a supply-resilience indicator.

Formula

SSC is on-hand inventory divided by the smoothed daily consumption rate:

SSC = Q_onhand / R_daily        [days]

where:
  Q_onhand = current substrate inventory (weighed bins + bagged)
  R_daily  = 14-day trailing mean daily consumption,
             demand-weighted toward the last 3 days (EWMA α=0.3)

Lead-time guard:
  L_supply = current supplier lead time (days)
  if SSC < L_supply + 7  →  auto-raise PROCUREMENT ticket
     (7-day safety buffer above lead time).

Projection note:
  if a planned propagation surge is scheduled, R_daily is
  uplifted by the forecast draw so SSC reflects committed demand,
  not just historical burn.

Recomputed every 6 h; inventory reconciled against weigh-bin
load cells (± 1.5 kg) at each cycle.

Inputs

Units & Scale

SSC is reported in days on hand to whole-day precision. It is a derived runway, not additive across stores; per-store coverage is reported separately where substrate is held in multiple locations, and the facility figure reflects pooled stock only if cross-transfer is feasible. The burn rate is an EWMA-smoothed 14-day mean to avoid a single heavy repotting day collapsing the runway. A DEMAND_SURGE note is attached when forecast draw uplifts R_daily above the historical mean.

Sampling & Source

• Recomputed every 6 hours by CHLORA from weighed inventory and the consumption ledger.
• On-hand quantity reconciled against PhytoSense Mesh weigh-bin load cells (± 1.5 kg).
• Burn rate is a 14-day EWMA (α = 0.3), uplifted by scheduled propagation surges.
• Stale handling: load-cell dropout → last weighed value held and marked STALE; runway below lead time + 7 d → procurement ticket auto-raised.

Thresholds

Recent Trend

Substrate coverage in days on hand, last 14 six-hourly recomputes:

Interpretation Guidance

Related Metrics

Related SOPs

• SOP Library — inventory, procurement, and rationing procedures.
• Expedite-supply & rationing on WARN/CRIT runway — see the SOP Library.
• Inventory weigh-in monitoring & reorder alerts — Monitoring Systems.