Comment by philipkglass

The Soviet Union ran such a program:

https://www.nytimes.com/1973/11/10/archives/soviet-plant-to-...

https://www.cia.gov/readingroom/docs/CIA-RDP91T01115R0001000...

The term to search for is "single cell protein."

There are newer approaches to making single cell protein from carbon dioxide and renewable energy instead of fossil oil, like Solein:

https://www.solein.com/

There are a few problems with turning oil into single cell protein:

- Microorganisms have small cells that reproduce quickly, which means a lot of nucleic acids in the dry mass, which is trouble for animals (including humans) that can't tolerate a very high purine level in the diet.

- The abundant cell walls of microorganisms also can cause illness when they're a high proportion of dietary intake.

- Feeding single cell protein directly to people has to overcome traditions of cuisine, even in cases where it doesn't actually make people sick. Indirect usage of SCP (e.g. feeding it to salmon, and then having people eat salmon) can overcome that hurdle, but then the cost per human-edible calorie goes up too.