Alkaline hydrolysis ('water cremation') regulation in Scotland

A Scottish Government consultation on the regulation of alkaline hydrolysis (‘water cremation’) as a method of body disposal in Scotland.

What is alkaline hydrolysis?

8. Alkaline hydrolysis is a method of disposal of human remains using hot water with the addition of potassium hydroxide, or sodium hydroxide, or a mix of both. The body is wrapped in a silk or woollen shroud, or other biodegradable material, before being placed into a pressurised chamber and heated to up to 150 °C. The Cremation Association of North America report that the body rapidly reduces to bones, any medical implants and sterile DNA-free liquid. The report by The Health Council of the Netherlands sets out the alkaline hydrolysis process:

“Alkaline hydrolysis is a chemical process in which the body of a deceased individual is first placed in a steel pressure vessel. Once the vessel has been closed, water and potassium hydroxide are added. The vessel is then pressurised and the water is heated. The maximum temperature varies from about 100 to 150 degrees Celsius, depending on the type of system being used, and the pressure. The combined action of heat, water, and potassium hydroxide, causes the body’s organic substances to dissolve in the liquid. This fully automated process takes two to ten hours, depending on the temperature and on the weight of the body to be processed. In addition to heating the liquid, a complete cycle involves various cooling and rinsing steps.

There are three types of residual material:

  • The bones. These are dried and ground into a white powder, which consists largely of calcium. As with cremation ashes, this powder can be given to the next of kin.
  • Any prostheses, fillings, and medical devices. These can be collected and disposed of.
  • The liquid used during hydrolysis. This effluent, which has a volume of approximately 1,500 litres, consists of water, potassium hydroxide, and the dissolved organic substances (sugars, amino acids, salts, and fatty acids). The effluent has a high pH, and contains no DNA or RNA. The pH is reduced to less than 10 by adding sulphuric acid.” (page 18)

9. After the process is complete and the bones and any implants removed, the remaining liquid is cooled before being moved to a treatment tank. The liquid produced as a result of alkaline hydrolysis is slightly alkaline (around 9 – 10.5 on the pH scale). It includes compounds such as sugars, amino acids and fatty acids, nitrogen, phosphorus, and potassium hydroxide. It contains no genetic material (RNA or DNA). Addition of acid may be required to make the liquid less alkaline (reduce the pH) before disposal.

10. The bones left at the end are soft and porous and are ground into a powder, also referred to as “ash”. This secondary process is the same as is used during cremation, although the ash is a lighter colour. The “ashes” can then be returned directly to the family of the deceased, collected by the funeral director on behalf of the family, or otherwise disposed of in a way agreed with the alkaline hydrolysis provider. Medical implants, such as pacemakers or metal implants can be recovered and recycled, as happens with cremation.

11. Once the bones and any implants are removed, the remaining liquid (which is made up of a variety of organic and inorganic materials) would need to be disposed of by the operator. One option is for the liquid to be disposed of by being released to drain as happens following the embalming process (subject to consent from Scottish Water). Supporters of alkaline hydrolysis have suggested that the liquid can also be considered for alternative, sustainable disposal options including use in a green space or a garden of remembrance (subject to consents from relevant authorities). (Question 2)

12. The Netherlands report gives some alternative examples of how the remaining liquid might be dealt with. These are methods which may become available in Scotland, subject to the outcomes of the consultation and further development of the next steps.

“there may be alternatives to discharging the effluent into the sewer system. For example, the effluent can be treated locally, immediately after completion of the alkaline hydrolysis process. When using a purification method that preserves nutrients (such as anaerobic purification), the locally purified effluent can be used to fertilise fields, commercial forests, or places of remembrance, for example. Depending on the wishes of the next of kin and the facilities available at the funeral company, some of the processed effluent could be given to the next of kin. Another option would be to use the effluent directly (i.e. without first treating it) as a fertiliser. A third processing method is to transport the effluent by road tanker to a sludge digester, where it would be used to produce biogas.” (page 18)

13. Any organisation proposing to offer alkaline hydrolysis will need to detail in their planning application to the local authority how they intend to dispose of the liquid and demonstrate that they have obtained the relevant consents from Scottish Water or SEPA.

Funeral services

14. Opting for alkaline hydrolysis does not necessarily alter the type of funeral service which may be arranged. A full funeral service, post-funeral gathering (such as a wake) or any other cultural or religious ceremonies would still be possible and subject to the wishes of the deceased and their next of kin.

15. Although a traditional coffin may be used for the funeral service, a coffin is not used during the process itself. Instead, as noted above, the body will be wrapped in a biodegradable material, such as a silk or wool shroud. The person making the funeral arrangements would be able to discuss the options for what would happen to a coffin used as part of the service with the funeral director or provider.



Back to top