Green burial and human composting

Both practices rest on a single observation: the standard modern funeral is designed, deliberately or not, to slow decomposition, and reversing that design is mostly a matter of returning oxygen and microbial contact.

Depth is the variable

A grave at conventional depth places the body below the biologically active horizon. Soil oxygen falls with depth, the root zone and its fauna are absent, and temperature is buffered near the annual mean. Under those conditions decomposition switches from aerobic mineralisation to anaerobic hydrolysis, and body fat undergoes saponification — free fatty acids released by lipolysis react with calcium and magnesium ions to form adipocere, a firm, waxy, poorly degradable mass that can persist for decades and preserves rather than consumes the remains. A sealed casket and an impermeable vault push the process further in that direction; embalming with formaldehyde suppresses the microbial community outright. Green burial reverses each of these: a shallower grave inside the aerobic zone, no vault, and a shroud or coffin that decays on a comparable timescale to the body.

Composting is a heat-balance problem

Natural organic reduction places the body in a vessel with a bulking mixture of wood chips, straw and alfalfa. The mixture is not decorative. It supplies structure so air can move, and it corrects stoichiometry: a body is nitrogen-rich, and the microbial community needs a carbon-to-nitrogen ratio of roughly 25–30 to 1 with moisture near 50–60 % by mass. Given that, mesophilic organisms hydrolyse proteins and lipids and release metabolic heat faster than an insulated mass can shed it. The pile self-heats into the thermophilic range, and the actinomycetes and thermophilic bacteria that take over there are what breaks down the more resistant material. Aeration is a genuine trade-off, since the same airflow that supplies oxygen also carries heat away.

Bone does not compost. Its collagen is degraded, but the hydroxyapatite mineral remains, and the resulting fragments are mechanically reduced afterwards — exactly as with cremated remains.

What the temperature argument actually proves

Pathogen reduction here is a time–temperature claim borrowed from sludge and manure composting, where the recognised process condition is holding the material at 55 °C for a defined period — three days in a vessel under the US EPA Part 503 criteria for further reduction of pathogens, and the same 55 °C for 72 hours in Washington State’s rules for natural organic reduction. That exposure reliably inactivates enteric bacteria, viruses and helminth ova.

It does not cover everything, and the honest version of this page says so. Prions are not inactivated at composting temperatures; jurisdictions permitting natural organic reduction exclude bodies with prion disease for that reason, alongside certain other communicable diseases. Pharmaceutical and chemotherapy residues, radiopharmaceuticals and antimicrobial-resistance genes are not addressed by a thermal criterion, and the fate of most of them in a human compost matrix is not well characterised. Dental amalgam is a mercury source and must be removed. Heavy metals are conserved throughout. Whether the finished material meets agricultural quality standards is therefore a soil-contaminant question, decided by testing, not by the temperature record.