Lime

Lime is an element in Oxygen Not Included obtained primarily as a processed product rather than a raw natural resource. It represents powdered calcium compounds (in-universe analogous to lime/limescale) and is used as an industrial input in mid-to-late game refining. Lime does not function as a building material for construction despite in-world flavor text suggesting it is useful for construction; it has no placeable building recipes.

Lime is produced mainly by crushing organic shells and fossils in a Rock Crusher. Valid Rock Crusher recipes include: 5 kg Egg Shell → 5 kg Lime; Pokeshell Molt items produce lime (a small Pokeshell Molt yields 5 kg Lime while a regular Pokeshell Molt yields 10 kg Lime); and Fossils crush into 5 kg Lime + 95 kg Sedimentary Rock per 100 kg Fossil. Because of these recipes, critters and critter byproducts are a convenient source: Pacu eggs are especially productive because Pacu reproduce rapidly and their eggs have large mass, Shine Bug eggs reproduce quickly but have low egg mass, and Pokeshell Molts represent one of the highest-yield critter sources for Lime. A rare Printing Pod care package can also deliver 150 kg Lime, which is the single most desirable instant source, though care package offers are uncommon and the pod will only begin offering Lime after the player has produced some through normal processes.

Lime’s primary mechanical use is as an input for the Metal Refinery to produce Steel. The Metal Refinery consumes 10 kg Lime + 70 kg Iron + 20 kg Refined Carbon → 100 kg Steel. This recipe is the canonical industrial application for Lime and is required for Steel production chains that use the Metal Refinery. Lime does not have direct uses in other recipes or as a construction material.

Practical notes and strategies:

• Farming critters that lay heavy eggs or that molt (Pacu, Pokeshell, etc.) is an efficient way to sustain Lime production long-term. Prioritize critters with high egg mass or frequent molting to maximize yield per cycle.
• Collecting and crushing Fossils is viable if you have access to sedimentary biomes or fossils in the map; note that crushing Fossils yields mostly Sedimentary Rock with only a small Lime fraction.
• If you see a Printing Pod care package offering 150 kg Lime, it is often worth taking for a large one-time supply, especially early in Steel production setup.
• Because Lime is consumed in the Metal Refinery recipe for Steel, ensure steady sources of Iron and Refined Carbon alongside Lime; shortages of any one input will stall Steel production.
• Although the game’s flavor text suggests construction uses, Lime cannot be assigned as a material for buildings; plan your raw material logistics accordingly and do not reserve Lime expecting to build structures with it.