I’ve done it on a balcony before. You need to be careful about it but it’s possible. I took a plastic bin and drilled holes in the sides/ bottom for air circulation. Then put it up on 2 bricks on top of another bin lid to make sure anything that leaks doesn’t do so on my neighbors. Then you have to make sure to turn it often to prevent it from stinking or getting too hot. And that’s it! It’s not enough for a large garden, but it was enough to restock my large balcony planter every year and made great tomatoes and herbs!