- [[Bones]] are a source of [[calcium]] [[phosphate]], and so boiling and crushing bones and putting them into the [[land]] can be used to revitalize [[soil]]. Treating the bonemeal with sulphuric acid makes the calcium phosphate even more available to growing plants. [[Potassium]] can be had from a [[potash]] made of [[wood]] [[ash]], though it can also be found in minerals within [[rocks]].
- Excess [[food]] [[production]] and [[preservation]] is needed to give large [[groups]] of people [[time]] to [[think]].
- [[Enzymes]] are only active at particular [[temperature]], [[pH]], and [[salinity]] ranges.
	- A simple method to preserve [[food]] is to [[dry]] it.
		- When [[grain]] is harvested, it needs to be dried before it is stored.
			- High [[sugar]] content changes [[water]] activity by drawing water out of microbial [[cells]].
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				- [[Sugar]] can be extracted from sugar beets by moving [[water]] through the [[beet]], taking that water, and drying it to expose the crystals from the beet.
			- High [[salt]] content changes [[water]] activity by drawing water out of cells and inhibiting microbial [[growth]].
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				- 180g [[salt]]/liter [[water]] will act as a [[brine]] for [[meat]].
			- [[Acid]] is used to preserve food through things like [[vinegar]].
			- Kimchi, sauerkraut, and miso all use [[salt]] to draw out [[water]], and then salt-resistant [[bacteria]] to [[grow]] and produce [[acid]].