Beyond These Stars By-Products Guide: Soot, Slag, Sludge and Other Waste

When a building’s By-Product storage fills up, the building stops working, even if it still has room for the resource you actually want. There’s no button to throw By-Products away, so every one of them needs somewhere to go: a building that uses it, or storage that buys you time. Plan where each By-Product will end up before you build the thing that makes it.

The tables below list every By-Product, every building that makes it, and every building that uses it. All times are for one task at normal game speed with a full crew.

Why buildings stop when By-Products pile up

A building only starts a task when every output has room for the full amount that task makes. An Ore Smelter making Iron needs space for 3 Iron and 1 Soot before it begins. If its Soot store is full, it won’t start, however empty its Iron store is. The resources a task uses are taken out the moment it starts, so nothing is wasted while a building waits.

That gives each building a countdown you can work out from the tables. An Ore Smelter holds 40 Soot and makes 1 per Iron task, so it can smelt nonstop for about 13 minutes before Soot alone stops it. Switch it to Gold, which makes 2 Soot per task, and that drops to under 7 minutes. A Sawmill fills fastest: 20 Wood Waste at 2 per task stops it after about 3 minutes.

Two other things stop production that are easy to mistake for a waste problem:

• Empty work slots. Most buildings make no progress at all unless every work slot has a Peep assigned and at least one of them is at the building. A three-slot Ore Smelter with two workers does nothing.
• No Power. Power doesn’t get carried around. It flows between neighbouring buildings that make or use it, so check the wires on the Info Card.

You can’t destroy By-Products

There’s no way to delete By-Products, so don’t plan around getting rid of them.

• Demolishing a building returns its construction materials and drops whatever it was storing on the ground as a Resource Cache. The waste is still there.
• Overflow also becomes a Resource Cache. If a building’s storage limit drops below what it’s holding, for example because a new neighbour reduces its storage, the extra spills onto the ground next to it.
• Piles stop deliveries. While a Resource Cache holding a resource sits anywhere in your settlement, buildings stop delivering that resource themselves and wait for collectors to fetch it. A forgotten pile of Soot can leave your smelters full until a Peep picks it up, so give a Storage Shed a worker and switch that By-Product on to clear it.

Older guides mention a By-Product Yard. You can’t build one in the current version of the game, so use the storage buildings below instead.

Where each By-Product comes from

Each row is one building and what it was making when it produced the By-Product. By-Product per task is how much it makes each time it finishes, and By-Product storage is how much it can hold before it stops. Divide storage by the amount per task to see how many tasks it can run with nothing collecting its waste.

What uses each By-Product

Every By-Product has at least one use. Uses and Makes show one full task, including any other resources the task needs, and Unlock shows what you have to do before the building becomes available. “Research with” means you unlock it at a Research Facility by supplying that resource.

Match your users to your producers by rate. One Metal Smelter burns 3 Soot every 18 seconds, which is about the Soot of three Ore Smelters working nonstop. One Battery Plant recharges the Used Batteries of one Battery Generator exactly: 10 Used Batteries come out every 60 seconds, and the plant turns 5 back into Batteries every 30 seconds.

Watch out for users that make a By-Product of their own. The Burner Generator gets rid of Wood Waste but makes 2 Soot per task, and the Metal Smelter clears Soot while making Slag. Follow each chain to the end before you rely on it.

Storage buys you time

Storage holds By-Products until a user catches up, but it fills too. Use it for the gaps while you build the next link in the chain.

• Storage Shed unlocks when you reach 30 Peeps. It holds 80 items with one worker. You can store up to 10 resource types, and each one you switch on starts with 20 spaces that you can raise or lower in steps of 20. The Bigger On The Inside perk raises the total to 100.
• Warehouse unlocks after the Cement Factory once you’ve produced 50 Cement. It holds 360 items across three tiles and needs three workers.

Storage buildings collect goods with their own workers, so a Storage Shed with an empty work slot never picks anything up. Producers can still carry their own output out, but every trip takes a Peep away from the building.

The Fetch/Deliver Behaviour settings on a producer’s Info Card control when it carries output away. The default, When full, waits until the store is full or a task is blocked. Contains a load sends a Peep out as soon as there’s a full load, which keeps By-Products moving before they become a problem.

The Bigger Dumpsters perk says it gives every building 10 extra By-Product storage. In the current version (1.0.1) it doesn’t change storage at all, so spend the points elsewhere.

Power plants and their By-Products

Generators only run when connected buildings have room in their own Power storage. This is the Run When Needed setting, and every generator type starts on it. A building counts as needing Power while it’s switched on and not paused, even if it’s idle. An Ore Smelter waiting for ore still pulls Power until its 15-Power store is full, so your Fuel Generators keep making Sludge to fill it. Pause buildings you aren’t using to stop that.

Open Power Settings from the Work tab of any generator’s Info Card to change this per generator type:

• Power Priority sets which generators run first. Put the generator whose By-Product you can’t use at the bottom, so it only runs when the others can’t keep up.
• Run Continuously keeps a generator running whether or not Power is needed. Power with nowhere to go is wasted, but the By-Product keeps coming. Turn this on for a Burner Generator when you want to burn Wood Waste faster or need its Soot for a Cleaner or Metal Smelter.

The Cleaner turns Soot into clean tiles

The Cleaner unlocks after you’ve produced 50 Soot and uses 4 Soot and 3 Water per task to clean Polluted tiles within 6 tiles of it. It can do the same job with 2 Chemicals and 2 Water, but Soot is the one you’ll want to get rid of. Each cleaning Peep scrubs the tile it stands on and every neighbouring tile at the same time. It can also clean Toxic tiles using 8 Chemicals per task.

The Cleaner only works when a tile in range has Medium pollution or worse. With nothing to clean, it stops using Soot, so pair it with a Metal Smelter or Biofuel Refinery that always takes Soot. Put it right next to your Ore Smelters. They make the Soot and the pollution it cleans up, and a smelter touching a Cleaner works 20% faster, at the cost of 25% more pollution that the Cleaner is there to scrub anyway.

Chains that clear each By-Product

• Wood Waste: a Compost Heap (after you build a Landscaper) turns it into Compost for Dirt tiles. The Burner Generator works earlier but swaps Wood Waste for Soot.
• Soot: Metal Smelters use the most. Add a Cleaner beside your polluters and a Biofuel Refinery for small amounts.
• Slag: a Slag Reclaimer turns it back into Iron Ore and Sand but needs 1 Goo per task. The Fuel Plant turns Slag and Water into Fuel and makes Goo.
• Goo: the Chemical Factory is the main user, at 5 Goo per task. The Slag Reclaimer takes 1.
• Sludge: a Sludge Dehydrator turns it into Water. A Blast Mine uses 8 per task on a Crystal tile.
• Organic Waste: the Compost Heap and Biofuel Refinery both take it. Mixing 2 Wood Waste and 2 Organic Waste in one Compost Heap task gives the most Compost.
• Used Battery: the Battery Plant recharges them.

Get every By-Product turned into something else at least once and you’ll earn the Recycler achievement.