What does the bean in Guo Moruo's anti-seven-step poem mean?

The meaning of "tofu" in Guo Moruo's "Anti-Seven-Step Poem" refers to: the tofu stalk of soybean is the stem left after soybean threshing, which can be used as firewood after drying.

Anti-seven-step poem

Boil beans, burn beans, beans will turn to ash when cooked.

Mature is precious at the dinner table, and ashes are fertile in the field.

If you don't live for the same root, why give up on yourself?

translate

The beans are cooked in the pot and the beanstalk is burned at the bottom of the pot. By the time the beans are ripe, the beanstalk has turned to ashes. Cooked beans turned into delicious food on the table, and bean skins turned into ashes and fertilizer in the field. How can they be willing to sacrifice themselves if they are not born from the same root?