compost Kitchen SYSTEM Kitchen “Compost Wall” — build plan

 

1) Layout (left → right on the exterior wall)

• Prep sink (small basin) → scrap screen → Compost Port

• Main sink (deep basin) → strainer → grease control → greywater manifold

• Dishwasher air gap and supply stubs above counter (code love)

• In-wall compost drum hatch (upper) + service hatch (lower)

• Exterior half-drum cabinet with weatherproof door

The Compost Drum straddles the wall: front half indoors so you can feed it; rear half outdoors so you can empty/muck with zero mess.

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2) Compost system (sealed, sensorized half-in/half-out drum)

• Drum: 60–80 gal insulated, gasketed, tumbler on stainless shaft.

• Drive: slow gearmotor (1–3 RPM) with torque limit; rotation only when hatches latched.

• Seals: EPDM gaskets on both indoor and outdoor doors; compression latches.

• Sensors: drum temperature (goal 55–65 °C), humidity, fill level (ultrasonic/weight), door interlocks, motor torque (jam detect).

• Airflow: constant negative pressure micro-pull through drum → carbon filter → exterior. (No smells inside.)

• Leachate sump: tiny floor pan & drain to a sealed bottle (use in non-edible beds or dump to sanitary).

Feed rates: kitchen scraps only (no big bones, no large fat loads); brown material in caddy (shredded cardboard/leaves) to balance C:N ≈ 25–30:1.

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3) Compost Port (at the prep sink)

A sealed chute with tiny water-assist that only opens when everything is lined up.

• Top door: swing-down, soft-close; magnetic reed switch.

• Pre-screen: removable 2–3 mm scrap screen (no silverware down the chute).

• Auger throat: slow stainless auger (optional) meters scraps into drum.

• Mist ring: very low flow spray (adjustable at panel) pulses 0.1–0.3 L to slick scraps through—NOT a disposal.

• Interlocks:

  • Drum door locked & drum indexed? → port unlocks.

  • Port open? → auger allowed; drum rotates only after port closes.

  • If sensor sees drum absent/misaligned, port stays locked.

You get “no-splash toss-in” convenience, but it’s sealed and smart—no aerosols, no critters.

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4) Water, drains, and code-friendly routing

Supplies

• ½″ cold line → ASSE-listed backflow preventer → pressure regulator → solenoid to mist ring (air-gap visible point).

• Dishwasher and faucets per normal.

Drains

• Prep sink: basket strainer → manual scrap caddy; liquids to greywater trap.

• Main sink: strainer → under-sink grease trap (small hydromechanical) → greywater trap.

• Compost Port: sealed chute; no direct drain (just the mist pulses). Any rinse flows into the drum; leachate captured by the drum sump bottle.

Greywater manifold

• From both sinks after strainers/grease control → 3-way valve:

  • Mode A (preferred): greywater → subsurface landscape drip (legal only where code allows; kitchen sinks are blackwater in many jurisdictions).

  • Mode B: greywater → sanitary.

Many US codes classify kitchen sink as blackwater because of grease/food. To stay compliant, design the manifold so you can flip to sanitary until a permitted greywater system is approved.

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5) Exterior compartment (service heaven)

• Half-drum cabinet: insulated, weather-gasketed, lockable; outdoor access to remove compost.

• Quick-connect for a wheel bin or farm tote (2″ camlock).

• Hose bib & floor drain in the cabinet for occasional wash-downs (to sanitary).

• Carbon filter box + optional UVC in duct (interlocked).

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6) Controls & safety

• Panel above counter (splash-rated):

  • Buttons: Feed (opens port), Mist Level, Tumble, Empty, Service.

  • Status LEDs: Port Closed, Drum Locked, Temp OK, Filter OK, Leachate Full.

• App: temp curve, fill %, door state, filter timer, maintenance prompts.

• Interlocks:

  • Port won’t open unless drum is latched & indexed.

  • Drum won’t tumble with port open.

  • Mist won’t fire unless port closed.

  • Door open? Fan to high; auger disabled.

• Electrical: GFCI, drip loops, IP-rated enclosures, e-stop inside cabinet.

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7) HOLO-cooling tie-in (nice touch)

• Use the house’s negative-pressure exhaust micro-loop at the drum & compost port to keep any whiff moving out.

• Tie outlet to your HOLOcooling plenum return with a carbon/UVC box so odors never re-enter condition air.

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8) Maintenance (quick/clean)

• Daily: feed scraps; toss a handful of browns; glance at panel.

• Weekly: wipe port screen; check carbon filter; empty leachate bottle if present.

• Monthly: swap carbon filter; check torque and latch seals.

• Batch harvest: when temp falls and fill% says mature, roll ⅓ drum to the outdoor side and dump into your transport bin—cleanly.

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9) Materials (kitchen-safe, lifetime)

• Wetted plastics: HDPE/PP/ABS; Metals: 316 stainless; Seals: EPDM/Viton.

• Doors: powder-coated aluminum frames, laminated panels.

• Grease trap: stainless hydromechanical, accessible for clean-out.

• Pipes: Schedule 40 PVC for drains; PEX for supply; all unions where service likely.

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10) Bill of materials (rough)

• Drum, shaft, bearings, motor, latches: $1.2k–$2.2k

• Port assembly (chute, auger, mist, interlocks): $450–$900

• Carbon filter + fan + duct/UVC (opt): $180–$450

• Grease trap (under-sink): $180–$400

• Backflow, regulator, valves, traps, unions: $300–$650

• Controls (ESP32/Pi, sensors, HMI): $250–$600
  Total parts: ~$2.6k–$5.2k plus cabinetry & labor

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11) Code & health notes (so inspectors smile)

• Show backflow preventer and visible air gap for the mist line in your drawings.

• Provide a greywater Plan B (sanitary tie-in) since kitchen greywater is restricted in many places.

• Keep grease trap accessible; log clean-outs.

• Compost for ornamental/non-edible beds unless you can document temps/time (55–65 °C sustained) and follow local regs.

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12) What I can hand you next

• a 1-page install schematic (plan + section) you can give to your GC/plumber,

• a controls I/O table and interlock state-machine (so your electrician knows the logic), and

• a maintenance card to tape inside the exterior cabinet.