The biggest issue is actually food - most of the seeds grown today are engineered to depend upon fossil-fuel based chemical fertilizers, and cannot actually survive on their own without both the chemical fertilizers and a large helping of herbicides/pesticides/fungicides (many of which are also produced by the chemical industry). Break that dependency and you have to undo the Green Revolution that multiplied agricultural output by 10x. Do that and instead of the world's current food production being able to support a population of 9B if they were all willing to eat a vegetarian diet, you'd be looking at 900M, i.e. about 85% of people on earth would have to die.

I suspect that if you took away all the demand for oil from powering cars, though, there'd be plenty left at reasonable prices for growing food and maybe even flying planes. So you do need some fossil fuel production, but get rid of its use in automobiles, heating, and electricity and the remaining reserves can be allocated much more efficiently.

Oil is not used in the production of fertilizers.

Here's a quote I found in [1]

"The macronutrients required by plants are N (Nitrogen), K (Potassium) and P (Phosphorus). Oil is hydrocarbon, made from H (Hydrogen) and C (Carbon). There are no plant nutrients in oil.

Nitrogen fertilizer (N) is made from ammonia, which in turn is manufactured from natural gas, not oil"

[1] http://peakoildebunked.blogspot.com/2005/08/28-isnt-fertiliz...

> We don't use its chemical properties in any special way,

We do, 99% of plastics is made using fossil fuels. Big players are trying to shift to sustainable alternatives though, for example LEGO: https://www.lego.com/en-us/aboutus/news-room/2018/march/pfp

It is pretty useful as a base for all kinds of chemicals. All plastics for example are made from oil.

> We don't use its chemical properties in any special way, it just happens to be among the most efficient in terms of calories per kg.

As far as I am aware a lot of oil is used as raw material in chemical industry, not only as energy source.

are sure? how many plastics including textiles would have to be replaced if we did not have the chemical properties of oil to create them? Any idea? I bet you are wearing at least one item of clothing with a textiel created with oil chemicals..such as nylon or others

There are processes that create crude oil given energy and some basic resources.