I can't tell you whether the below is accurate, but this was why they said it is novel. ‘Tephra is cheap, not limiting, and all the required tech already exist

I can't tell you whether the below is accurate, but this was why they said it is novel. ‘Tephra is cheap, not limiting, and all the required tech already exists. Bentonites – altered tephra – are already regularly mined, so we don’t need to develop new approaches,’ Longman says, adding that tephra would only require sieving in preparation for use. This, he added, ‘is unlike other ocean fertilisation approaches, which use processed iron oxide liquids.’