We don't know how this closure will affect green cars exactly, but we do know that the offices that handles air pollution rules and the update to the renewable fuel volume standards for 2014 are mostly closed. The EPA said in a statement on the shutdown (PDF) that most of the EPA workers still on the job are "providing for homeland and national security" or in some other way involved in law enforcement or emergency response to an environmental catastrophe. We don't think fuel economy testing fits in that designation. The shutdown will also likely push back the EPA's recently issued new rules for coal plants.
We tried to get a comment from the EPA, but emails sent to our contacts at the EPA immediately bounced back with some version of the following message: "I am out of the office for the duration of the government shutdown. I will not be checking messages, but will return your message upon my return to the office." Like everyone else, we wonder when that might be.