Emission Systems & Sub-Systems
WARNING: This page is about a different car, the 2002 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
Since bi-fuel vehicles can operate on gasoline, they have the same emissions equipment as gasoline fueled vehicles. See EVAPORATIVE EMISSION SYSTEMS in THEORY & OPERATION - EEC-V - GASOLINE & NGV article.