I've learned that after subordinate conjunctions a subject can be omitted when the subject matches the one in the main clause. I recognize “than” as a subordinate conjunction, but in the subordinate clause in the sentence below it is ‘land and water’ that is omitted. Not ‘they’. Why is that possible? “Plant-based meats have been gaining popularity. One U.S. company is using mushroom root to make its products. They use less land and water than is needed to raise animal meat and produce, which in turn lowers greenhouse gas emissions.”