Techniques for converting plastic bags to a recyclable form are described. In some implementations, a device includes an outer container having an outer lid, an inner container situated within the outer container having an opening, and one or more heating elements. The inner container has an inner lid configured to cover the inner container's opening, and the outer lid of the outer container is configured to close over the inner lid. In response to a user input to the device, a conversion cycle is initiated in which electric power is supplied to one or more heating elements so that the one or more heating elements raise the inner container's internal temperature to a target temperature and maintain the inner container's internal temperature at a minimum of the target temperature for a predetermined conversion time sufficient to convert one or more plastic bags within the inner container to a recyclable plastic block.