Sustainability of ethanol

[Shivan]

I was playing around with a spreadsheet to see if it could be sustainable to have corn be grown to make corn mash and then ethanol. Then burn the ethanol to desalinate water. But it seems like it's net water negative.

I haven't been able to model the natural rainfall on the farms tho. But from my practical setup it seems like the additional natural rain is not enough to make up for the short fall.

The game is pretty realistic is modeling the poor return on energy from bio fuels.

Does anyone know if the numbers given for average water production from rainfall on the wiki are accurate?

[Deadweight]

So you need 54 units of ethanol to desalinate 312 units of water?
to get 54 ethanol, you need double that in corn mash, so 108. it takes 12 corn to make 9 corn mash along with 3 water.

So we're looking at:
1 boiler, 4 desalinators (meh, needed by everything).
12 fermentation tanks (48 workers) requiring 3 air separators (probably. 18 more workers).
12 mills, (60 workers) and 36 water.

so ignoring fertility, an irrigated farm makes (roughly) 16.5 corn/month and uses 40 water.
144 corn/16.5 gives you almost 9 required farms meaning 349 water + 36 water required for the mills too. A deficit of 73 units, an entire desalinator.

Farm replenishment is accurate AFAIK, it would have to rain about 1/3 of the year to make up the defecit, making it really not worth it given the worker cost unless you were desperate.

A greenhouse would give you a requirement of 7 farms and 315 water, making it slightly more efficient.

Have you considered fuelgas? you need 72 units to fuel that water instead of 54 but...
that's 168 potatoes/month or 79 wheat/month.

168 potatoes is also almost 9 farms, but only uses 324 water and doesn't need more for the mill. Wheat works out as just over 8 farms and 256 water. Net positive. Just.

But the benefits are instead of needing 2 stages of processing and like 120+ workers (ignoring farms and desal) it's 1. 12 digesters for potatoes is 48 workers, 11 for wheat.

[SpeedDaemon]

IMO, ethanol just takes too many farms to use as a primary source for anything but disinfectant, where it's a required ingredient.

If you think long-term sustainability:
- The most efficient way to get water is to run a fast-breeder reactor, and directly use the steam to run up to 64 desalinators per reactor (net 4224 water/mo).
- The most efficient way to fuel vehicles and cargo ships (post Update 2), is to use an FBR again to generate H2 directly from water. (Your petrochem industry then uses diesel to make rubber, excess diesel->naphtha for plastic, fuel gas all gets turned into H2, which can be used anywhere fuel gas was otherwise required)