ISO 15985 is actually the equivalent of ASTM D5511 on international (ISO) level. This is a test method which OWS co-developed many years ago and a test we run on a daily basis. It can be used for two purposes:
Verifying the biodegradation behavior under anaerobic digestion conditions
Verifying the biodegradation behavior under (accelerated) landfill conditions
I expect the customer is looking to obtain data on landfill biodegradation, correct? In that case, testing needs to be run at 37°C.