Plants are not a particularly efficient source of protein. They tend to be better at producing carbohydrates. As a result, vegetarian diets often focus on a few high-nitrogen plants like beans, soy and peanuts.
I tend to explore food systems that are familiar, but let's take a minimalist approach and see where it leads. Instead of deriving protein from plant sources directly, what if we use microorganisms to produce amino acids in bioreactors using plant starch as input? This is like that sci-fi staple 'vat meat', but with neither texture nor flavor. Still, amino acids can be stored for years (possibly decades) if powdered and sealed.
As with all my posts, this article is based largely on internet research. I am not a process biologist. I've included sources where possible, but these results should be considered preliminary at best.
Short results: vat-grown amino acids can be yours for 4-6m³ per person.
That includes vats, supporting equipment, hydroponic space and waste treatment.
You will still need to provide bulk calories and other nutrients.
More after the break.