Promession involves five steps:
1. The body is frozen by immersion in liquid nitrogen, which makes it brittle.
2. The frozen remains are shattered by vibration.
3. The remains are then subjected to a vacuum so that the ice sublimes and the powder becomes dry, and weighs 50% to 70% less than the original body.
4. Any metals (e.g., tooth amalgam, artificial hips, etc.) are removed, either with a magnetic process or sieving.
5. The dry powder is placed in a biodegradable casket which is interred in the top layers of soil, where aerobic bacteria decompose the remains into humus, or compost, in as soon as 12 months.