Composting & Digester Controls — health check

A one-page checklist for composting and anaerobic digestion (AD) sites. Print it, walk the plant, and mark what you find. It pairs with the full guide on keeping control systems reliable in composting and AD plants. Nothing here asks you to defeat a safety function; if an interlock is nuisance-tripping, note it and find the cause, do not bypass it.

Gas safety comes before the clipboard. H2S kills fast and deadens your sense of smell around 100 ppm (olfactory fatigue; IDLH roughly 100 ppm), so your nose quits right as it turns lethal. Methane is explosive in air from about 5 percent (LEL) to 15 percent (UEL). Digesters, gas holders, sumps, wet wells, and pump vaults are permit-required confined spaces — test the atmosphere before entry, wear a bump-tested personal 4-gas monitor (H2S, LEL, O2, CO), know your wind and escape direction, and never enter a gas structure solo. Before touching anything by hand, prove it is at a zero-energy state. Lock out and tag out (LOTO) and verify de-energization before you check a blower damper or linkage, a mixer, or a pump by hand — a remote start or a spring-loaded actuator does not care that you are standing in it.

Enclosures and the corrosive environment ☐ Control panels sealed, gasketed, and doors latched tight ☐ Positive pressure / clean-air purge on panels in process air, and it is actually flowing ☐ Unused gland holes and cable entries sealed ☐ Panel heater keeping interior above the dew point; no condensation inside ☐ Enclosure cooler / heat exchanger working on the hot side ☐ No visible tarnish (black/gray) on terminals, relays, or connector pins ☐ Corrosion-inhibitor sachets present and not spent

Sensors and field devices ☐ Pile temperature probes reading plausibly; checked against a handheld reference ☐ Oxygen and moisture sensors calibrated and logged for drift ☐ Gas analyzers (digester, biofilter) within calibration