as much carbon dioxide as comes out of cars that burn these fuels

[October wind]

Adapted from an article on National Geographic

Simply put, because plants absorb carbon dioxide as they grow, crops grown for biofuels should absorb as much carbon dioxide as comes out of cars that burn these fuels.

The underlined part is grammatically confusing to me. Could you explain why “comes out of” comes after “as”?

 

[teechar]

Adapted from an article on National Geographic website.

or

Adapted from an article on in National Geographic magazine.

Simply put, because plants absorb carbon dioxide as they grow, crops grown for biofuels should absorb as much carbon dioxide as comes out of cars that burn these fuels.

The underlined part is grammatically confusing to me. Could you explain why “comes out of” comes after “as”?

It's grammatical and is short for: "... as much carbon dioxide as the amount that comes out of cars ..."

 

[October wind]

Thank you very much, teechar. I wonder why “the amount that” can be omitted in the sentence. Is it because it’s understandable without it? Or, is there any grammatical rules of omission I should follow? I think I understand what the writer is trying to say, but I don’t know why he had to omit the part.

 

[tedmc]

Thank you very much, teechar. I wonder why “the amount that” can be omitted in the sentence. Is it because it’s understandable without it? Or, is there any grammatical rules of omission I should follow? I think I understand what the writer is trying to say, but I don’t know why he had to omit the part.

Simply put, because plants absorb carbon dioxide as they grow, crops grown for biofuels should absorb as much carbon dioxide as the amount that comes out of cars that burn these fuels.

It's the amount of carbon dioxide that is being compared. Things that are mentioned in the first part of a sentence are often omitted when they are understood, for brevity and to avoid repetition.

 

[October wind]

I see. I really appreciate your clear explanation.