Those are grain silos, apparently:

> Satellite images comparing the area before and after the explosion show the complete destruction of Beirut's port. The grain silos that were next to the site of the explosion are still partially upright, although it's believed that up to 85 percent of the country's grain stocks have been lost. (Lebanon imports 80 percent of its food supply, and Beirut normally handles 60 percent of the country's total imports.)

https://arstechnica.com/science/2020/08/what-we-know-about-t...