Shibui
Imperial Masterpiece
I think there is some misunderstanding of the term 'sterile' in this thread.
Air, water and most other substances all contain many spores and micro-organisms and as @Wires_Guy_wires pointed out even effectively sterile media is quickly contaminated when exposed to air or water so very little materials we have access to is sterile and the more sterile the substance the more likely pathogens can invade and build up numbers.
For plant purposes we just need to get rid of the worst pathogens that might affect the plants, seeds or cuttings we are trying to grow. Pasteurization gets rid of enough pathogens to be an effective solution. The results are not 'sterile' just 'sanitized'. The dry and wet cycles mentioned are another way to reduce the numbers of pests and diseases and make the media safer for use. It won't sterilize the media but will make it safer for the plants you intend to grow.
Air, water and most other substances all contain many spores and micro-organisms and as @Wires_Guy_wires pointed out even effectively sterile media is quickly contaminated when exposed to air or water so very little materials we have access to is sterile and the more sterile the substance the more likely pathogens can invade and build up numbers.
For plant purposes we just need to get rid of the worst pathogens that might affect the plants, seeds or cuttings we are trying to grow. Pasteurization gets rid of enough pathogens to be an effective solution. The results are not 'sterile' just 'sanitized'. The dry and wet cycles mentioned are another way to reduce the numbers of pests and diseases and make the media safer for use. It won't sterilize the media but will make it safer for the plants you intend to grow.