In the following sentence:

> Зачем богатые и уважаемые корпорации продолжают использовать материал, который уже загрязнил окружающую среду до такой степени, что каждый житель планеты употребляет вместе с едой и питьем 5 граммов микропластика **— целую кредитную карточку —** в неделю?

Source: https://www.facebook.com/GlobalSearchKG/posts/4677654905608160

I didn't understand what целую кредитную карточку means. Based on the Google translate, it seems that the phrase is used to emphasize the severity of the use of microplastics, meaning that the amount of microplastics each person consumes in a week is equivalent to the amount of microplastics used in a credit card. 

But I also don't understand why the accusative is used in the phrase and also how the two dashes work in these sentences. Is it fine to use the accusative without any prepositions such as за, в or на, and can I replace the dashes with just a comma?