Definitions Cremation is the process whereby human remains are reduced through mechanical, thermal, or other means of dissolution.1 The literal translation of the Latin root cremare is “to burn by fire.”2 Cremation uses flame and heat to reduce remains to bone fragments which are then pulverized in a cremator to the consistency of ashes.
This definition is often stretched to include alkaline hydrolysis, often called hydro, water, flameless, or bio cremation, a newer and more limitedly available process that reduces human remains through a water-based dissolution process that uses alkaline chemicals, heat, agitation, and pressure.
Cremation Cremation results in toxic emissions including persistent pollutants such as volatile organic compounds (VOCs), particulate matter (PM), sulfur dioxide (SO2), nitrogen oxides (NOx), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/DFs), co-planar polychlorinated biphenyls (co-PCBs), and heavy metals.3,4,5
Many of these toxins can bioaccumulate in humans, including mercury.3,6 Cremation causes release of mercury (often from dental amalgams, but also from general bioaccumulation in the body) into the environment both in areas close to the source and into the atmosphere.3,5,7 Cremation also requires a significant amount of fuel, and results in millions of tons of carbon dioxide (CO2) emissions each year.8
There are concerns for crematory workers as well, who may be exposed to nuclear medicine treatments (chemotherapeutics/radiation), orthopedic (implants) and pacemaker explosions, and nanoparticles.9,10,11
Emission concentrations of harmful air pollutants from cremators can be affected by several factors, including fuel type, cremator type, flue gas post-treatment system, filters, dust collectors, and operational maintenance.4,12
Environmental regulations requiring scrubbing and filtering systems help to burn and neutralize pollutants like the mercury emissions, particulate matter, and nitrous oxide, however, these filters fail to neutralize the carbon dioxide generated during cremation.8
Other ways to reduce cremation-related emissions include clean energy conversion of fuel types, control over content of hazardous components in burial objects, and combustion optimization.4
Alkaline Hydrolysis Alkaline hydrolysis may be a slightly less environmentally impactful method of cremation compared to traditional, flame-based cremation. Alkaline hydrolysis requires water use, but has a smaller carbon footprint, using less fuel for heat, and releasing no emissions from the body itself. Additionally, the organic liquid produced during this type of cremation can be used for fertilizer.8
What eco-friendly options do I have if I already have cremated remains? If you already have cremated remains and would like to honor your loved one and utilize those remains in a way that positively impacts the environment, the following are some available options.
Scattering Grounds Some cemeteries, natural burial grounds, and conservation areas allow burying or scattering of cremation ashes. Burial in a cemetery protects the land from being re-used for other purposes in perpetuity and funds raised support organizations working to restore and protect natural habitats. Scattering remains in a location meaningful to the deceased is also an option, though discretion and sensitivity to landowners is recommended. There are numerous biodegradable urns made of sustainable materials available that will help to reduce the carbon footprint.
Coral Reef Development Some companies provide families with a legacy opportunity to honor their loved ones by contributing to the artificial development and restoration of coral reefs in oceans worldwide. Cremated remains are added to specially formulated concrete which is cast into reef bases. Families can take part in the release of reefs into the sea, where the reefs help to establish new habitats for fish and other sea life. This approach is similar to a carbon offset.
Tree Planting Urns are available that allow cremated remains to be mixed with an organic medium that purports to support plant growth. Some urn companies provide parks and green spaces for planting the trees that result. Note that cremated remains on their own are not capable of further decomposing without enzyme reduction, and cannot support plant life on their own, as calcium phosphate and sodium, the final elements that make up cremated bone, in concentration, are not conducive to healthy plant life. It is also important to be aware that burial on lands that are not designated as cemeteries or protected with conservation easements cannot promise repose in perpetuity.
Sources 1 Cremation Process - Cremation Association of North America (CANA). https://www.cremationassociation.org/page/CremationProcess. 2 Merriam-Webster Dictionary 3 Tibau, A. V. & Grube, B. D. Mercury Contamination from Dental Amalgam. J. Health Pollut. 9, (2019). 4 Xue, Y. et al. Emission characteristics of harmful air pollutants from cremators in Beijing, China. PLOS ONE 13, e0194226 (2018). 5 Takeda, N., Takaoka, M., Oshita, K. & Eguchi, S. PCDD/DF and co-planar PCB emissions from crematories in Japan. Chemosphere 98, 91–98 (2014). 6 Kimáková, T., Nasser, B., Issa, M. & Uher, I. Mercury cycling in the terrestrial, aquatic and atmospheric environment of the Slovak Republic – an overview. Ann. Agric. Environ. Med. 26, 273–279 (2019). 7 Nieschmidt, A. K. & Kim, N. D. Effects of Mercury Release from Amalgam Dental Restorations During Cremation on Soil Mercury Levels of Three New Zealand Crematoria. Bull. Environ. Contam. Toxicol. 58, 744–751 (1997). 8 @NatGeoUK. The environmental toll of cremating the dead. National Geographichttps://www.nationalgeographic.co.uk/environment-and-conservation/2019/11/environmental-toll-cremating-dead (2019). 9 da Cruz, N. J. T. et al. Environmental impacts caused by cemeteries and crematoria, new funeral technologies, and preferences of the Northeastern and Southern Brazilian population as for the funeral process. Environ. Sci. Pollut. Res. 24, 24121–24134 (2017). 10 Yu, N. Y., Rule, W. G., Sio, T. T., Ashman, J. B. & Nelson, K. L. Radiation Contamination Following Cremation of a Deceased Patient Treated With a Radiopharmaceutical. JAMA 321, 803–804 (2019). 11 Kato, N., Mastui, Y., Takaoka, M. & Yoneda, M. Measurement of nanoparticle exposure in crematoriums and estimation of respiratory deposition of the nanoparticles by number and size distribution. J. Occup. Health 59, 572–580 (2017). 12 Mari, M. & Domingo, J. L. Toxic emissions from crematories: A review. Environ. Int. 36, 131–137 (2010).