A casket and burial system for human remains includes a casket fabricated from plastics and polymer composites, such as glass-fiber reinforced plastic. The casket includes a base member, a cover member fitting atop the base, and top and bottom closure panels having one or more ports for use in replacing the ambient atmosphere within the sealed casket with a selected gas or fluid such as nitrogen, or to inject a plastic foam into the free space remaining in the casket. The casket is preferably interred in a vertical attitude as that arrangement allows up to four caskets to fit within a standard grave plot.