The audience of this is all shoppers, this can be ages of 12+. This is to persuade people to reduce the amount of plastic bags that they used. They say the negatives about the plastic bags and how bad they are for the environment. The format of this is just clear and bold so that they send their point across and so that people from a large age range is able to understand this.
The persuasive technique they are using is listing the main negatives of what happens when we use plastic bags. The writer exerts power into sentences by making them sound nearly dramatic and at this scale, it gets into peoples minds that this is a thing we must change.