Milk & water jugs

HDPE is high-density polyethylene, a thermoplastic made from petroleum. Its production uses fossil fuels and ends with plastic milk and water jugs, among many other common items.

Although they are technically recyclable, recycling rates for these plastic jugs is a meager 10% in the U.S. If they do end up getting recycled, they tend to be made into things other than new jugs. So, your next gallon requires a fresh load of fossil fuels.