# How Lime Is Made Lime is limestone that a kiln heats until it releases carbon dioxide. Each processing step uses more energy and gives a more specific, more valuable product. ```mermaid graph LR A[Limestone rock<br/>CaCO3, ≥96% pure] -->|crush| B[Aggregate /<br/>pulverised limestone] A -->|kiln, >1,800°F| C[Quicklime<br/>CaO] C -->|add water| D[Hydrated lime<br/>Ca OH 2] C -->|add more water| E[Lime slurry] B --> U1[Construction fill,<br/>agriculture] C --> U2[Steel mills] D --> U3[Water treatment,<br/>flue gas] E --> U4[Texas road<br/>subgrade] ``` ## Purity is the first filter - Too much silica or magnesium makes lime fail industrial specs. - Steel mills cannot use low-purity lime. It contaminates the melt. - Water utilities cannot use high-magnesium lime. The byproducts can break their permits. - The Texas Department of Transportation (TxDOT) specifies lime by reactivity, not only chemistry. - So two quarries close together do not always compete for the same buyer. ## Energy is the main variable cost - The kiln must stay above 1,800°F continuously. - USLM's old Texas kilns use ~4.8 GJ per metric ton of quicklime. - Fuel can be natural gas, coal or petroleum coke. USLM switches by price. - Q1 2026: fuel, energy and freight were 25% of revenue.^[Colubeat Investment Desk, 28 May 2026, https://colubeatid.substack.com/p/united-states-lime-and-minerals-inc] - See [[USLM Energy and the Vertical Kiln]]. ## Slurry is the special product - Slurry is lime suspended in water. It settles, so it needs agitation and fast use. - It has no spot price and no benchmark. - Its delivery radius is only ~50–75 miles. See [[Transport-Cost Moat]]. > [!note] Carbon > Calcining releases CO2 from the rock itself, not only from fuel. A carbon price would hit lime hard. The source does not discuss this. See [[USLM Open Questions]]. ---- tags: #boat #investing links: [[United States Lime and Minerals MOC]] [[USLM End Markets]] [[Commodities]]