Question

What is the typical depth and function of the concrete tank (digester) in a biogas plant?

Options

• Above ground; mixing of cattle dung and water to form slurry

• 2–4 ft underground; direct combustion of spent slurry

• 25–30 ft underground; aerobic oxidation of cellulosic waste

• 10–15 ft underground; anaerobic breakdown of organic material by methanogens

Answer 1

The digester is a concrete tank positioned 10–15 ft underground. It provides a sealed anaerobic environment where methanogens break down organic material to produce biogas.