DAR ES SALAAM, Oct. 12 -- Africa is becoming increasingly important to the global transition towards cleaner energy, with countries across the continent holding minerals needed for batteries, electric vehicles, renewable-energy systems and other technologies.

But for Tanzania, the emerging green-minerals economy raises a critical question: Will the country become a supplier of minerals for industries abroad, or will it develop the capacity to manufacture products from those minerals at home?

The United Nations has warned that African countries have historically exported raw and semi-processed commodities while capturing a relatively small share of the wealth generated further along global value chains. It says the current increase in de...