Alkaline hydrolysis ('water cremation') regulation in Scotland

Sustainability considerations

53. There have been some studies conducted to examine the environmental impact of alkaline hydrolysis compared with burial or cremation. However, it is important to note that the evidence base in this area is limited and that the following is not a comprehensive review of the evidence.

54. The report from the Health Council of the Netherlands found that available research suggested that alkaline hydrolysis compared favourably to both burial and cremation on three markers of sustainability:

• reduced use of finite resources;
• fewer harmful emissions; and
• reduced use of available space.

55. Crematoriums are currently regulated under the Pollution Prevention and Control (Scotland) Regulations 2012 and so any emissions produced must be made in compliance with a permit which is granted and regulated by the Scottish Environment Protection Agency (SEPA).

56. Scottish Water has previously discussed with SEPA the liquid produced by alkaline hydrolysis and how it should be disposed of. We understand that SEPA’s preference is that the liquid should discharge to a public sewer where a connection is feasible. However, SEPA are also of the view that the liquid may be suitable for putting directly into the water environment (rivers, etc.) following treatment and controls via their usual licencing regime. SEPA considered that the liquid from alkaline hydrolysis may be suitable for discharge via an infiltration system and biosolids containing its residues would be suitable for direct spreading to land.

57. Scottish Water has also noted the amount of liquid produced by alkaline hydrolysis. Based on information available, the volume of liquid from a single cycle of alkaline hydrolysis is around 2000 litres.

58. The associated strength of the liquid – as determined by Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) – is very high. In the water industry the standard figure for expressing the average BOD load for one person in one day is 60g. On this basis the load of the liquid from one cycle of the alkaline hydrolysis process is estimated to be around 1250 times that amount (75 kg). In broad terms, these measurements mean that the liquid has a high organic content.

59. As noted above, any prospective provider would need to detail how they intend to deal with this liquid.

60. The 2016 Act and any regulations made under it do not in themselves have an environmental impact. However the proposals will enable a new method of disposal to become available in Scotland. We therefore intend to develop a Strategic Environmental Assessment (SEA) at the same time as we develop the regulations. (Question 15)