Manufacturing for Our Future Act of 2021 This bill requires the Department of Energy (DOE) to establish a clean energy manufacturing grant program. Under the program, DOE must award grants to manufacturers for (1) projects to reequip, expand, or establish a facility for the manufacture of clean energy systems (e.g., renewable energy technology); (2) projects to retrofit or convert a facility to enable it to manufacture zero- or low-emission energy-intensive industrial products; and (3) engineering design studies for such retrofit or conversion projects. A zero- or low-emission energy-intensive industrial product means a product the production of which results in significantly less greenhouse gas emissions relative to the production of similar products. The products must also fall in manufacturing categories that are energy-intensive or difficult-to-decarbonize.