Lime

Image kindly provided by Youtube video: https://youtu.be/9LDG9cnGlDo "Limestone Cycle - limestone, quicklime and slaked lime" (Chemistry for All - The Fuse School)

Basics

Lime is an extremely versatile basic material. Limestone, often composed largely of calcium carbonate (CaCO3), can be burned in a kiln. Heated to 900-1000C for several hours, it vents off carbon dioxide (CO2). What remains is mostly calcium oxide (CaO), also known as “quicklime” or “burnt lime”, a highly caustic material that is very “thirsty” for water. When combined with water – hydrated or “slaked” - the quicklime becomes calcium hydroxide or Ca(OH)2, often simply referred to as "lime". This material quickly reabsorbs CO2 and once again becomes calcium carbonate.

Historical uses for hydrated lime:

• mortar for construction
• agriculture: to neutralize acidic soils to crop production
• "whitewash" - to protect wood (such as fences) or fruit tries from fungal infections
• as a disinfectant: water treatment, dairy, as an antiseptic for livestock

Historical uses for quicklime:

• main industrial uses today: as a steel fluxing agent and in flue gas desulphurization. Other: production of fiberglass, pulp and paper, aluminium, uranium, copper and gold.

Product ecology

• as a stabilizer in compressed earth bricks
• to be mixed with hemp, forming "hempcrete"
• to fire the kiln, one could use the pyrolysis off-gases from biochar production
• use waste heat to heat greenhouses, other facilities

Links:

• Low-Tech Magazine: "Burning the Bones of the Earth: Lime Kilns" http://www.lowtechmagazine.com/2013/09/lime-kilns.html
• http://en.wikipedia.org/wiki/Lime_%28material%29
• Practical Action: "Lime - an introduction" - http://practicalaction.org/lime-an-introduction-1
• Practical Action: "Lime - Kiln Designs" - http://practicalaction.org/lime-kiln-designs
• Practical Action: "A Small Lime Kiln for Batch and Continuous Firing" - http://practicalaction.org/a-small-lime-kiln-for-batch-and-continuous-firing