Compressed biogas from cattle dung: how the process works
The Gujarat programme includes planned compressed-biogas plants; this explainer separates a foundation stone from an operating plant.
Compressed biogas is produced by breaking down organic material such as cattle dung in an oxygen-free digester, cleaning the resulting biogas and compressing the upgraded gas for use as fuel.
From dung to biogas
Cattle dung and suitable organic material can be mixed with water and fed into an anaerobic digester. Microorganisms break down the material without oxygen and produce biogas containing methane, carbon dioxide and other impurities.
The gas must be cleaned and upgraded before compression. The leftover digestate can be processed for use as an organic fertiliser, subject to quality and safety standards.
Why a dairy cooperative may build a plant
A dairy ecosystem can generate a concentrated stream of cattle dung and organic residues. A plant can turn part of that waste into fuel if collection, transport, gas upgrading and offtake arrangements work.
The PMO itinerary for 30 October listed planned foundation stones for two Banas Dairy plants at Tharad and Radhanpur, with stated capacities of 75 tonnes and 100 tonnes of cattle dung per day. Those were planned facilities, not proof that the plants were already operating.
What determines performance
Output depends on feedstock quality, moisture, temperature, digester design, gas losses, upgrading efficiency and a reliable buyer. Feedstock capacity is not the same as the volume of compressed gas produced.
Environmental benefits also depend on methane leakage, transport distances and what would otherwise happen to the waste. Judge a project on measured operating data, not only its announced capacity.
Editorial disclosure
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Frequently asked questions
Does a foundation stone mean a biogas plant is operational?
No. Construction, commissioning and commercial operation are later stages.
What is the main gas in compressed biogas?
Methane-rich biogas that has been cleaned and upgraded before compression.