Which foods or food components can be generated without the help of complex life. This is: by chemical reactions or by bacteria or fungi? The motivation is to produce many food components for Mars colonizers from the elements/molecules that are easily accessible there. Plants and animals are quite needy and water, oxygen, CO2 and methane will be available with or without them.

Example: protein from methane (https://www.feednavigator.com/Article/2019/08/26/Partnership-brings-methane-generated-feed-protein-to-Texas)