Slag Burner — The Two Real Setups

Straight answer: no official machine is called a "Slag Burner" — and "Slag" itself is the old name of the material now called Residue. What you are looking for exists though: two documented ways to burn Residue automatically, the Burner Belt and the lava-trapped Filter.

What Burning Actually Does

Residue comes off your Shakers and "must then be burned, typically with Lava or a Flamethrower, to produce Burnt Residue" — the input the Kinetic Press turns into guaranteed Gold and Seeds.

Burning is lossy by design: "When Residue combines with Fire each pixel has a chance to either turn into Burnt Residue or be consumed with no output." The current wiki puts the rate at approximately 4 Residue → 1 Burnt Residue.

One helpful property: with enough Residue input, a pile ignited once can keep burning continuously without reigniting.

Official Burning Machines and Costs

The Burner Belt is the closest thing to an official "slag burner" — a belt that ignites what rides it. Its detailed mechanics (size, speed, heat use) have no wiki article yet (unverified).

The Lava Auto-Burner (Official Technique)

The wiki documents a fully passive setup on both the Lava and Filter pages: "Lava can be trapped inside Filters and will ignite pixels that pass over it... This can be extremely useful for automating your factory, for things like Residue and Flower auto-burners."

The result once built: "If the Filter is completely full with Lava and Residue is moved over it, the Residue touching the Conveyor Belt will ignite and turn into Burnt Residue." No fuel, no power, no re-igniting.

How to Build It, Step by Step

• Step 1: Set a Filter to only allow Cinder, and place a solid block below it so nothing can exit.
• Step 2: Fill the Filter completely with Cinders.
• Step 3: Ignite the Cinders — they melt into Lava that stays trapped inside the Filter.
• Step 4: Run your Residue line over the full Filter; everything touching it ignites into Burnt Residue.

Every step above comes from the official Lava and Filter wiki pages. The same recipe circulated in the community as early as February 2025 (demo era), phrased then as an "automatic flame thrower for slag."

Which Setup Should You Use?

The lava-trapped Filter costs only a Filter, some Cinder, and one ignition — and runs forever. The Burner Belt and Pyro Dispenser need a Thermal Buffer heat supply but are proper researched machines.

No official source compares their efficiency for Residue burning (unverified — needs in-game testing). What is certain is the input math: whatever burns, expect roughly a quarter of your Residue back as Burnt Residue.