Diatomaceous earth is used for all except-

The walls of diatoms are embedded with silica and thus the walls are indestructible. Thus, diatoms have left behind a large amount of cell wall deposits in their habitat; this accumulation over billions of years is referred to as ‘diatomaceous earth’. Being gritty this soil is used in polishing, making soundproof room, filtration of oils and syrups. 

‘Diatomaceous earth’ has no relation with biogas production.