Press Mud

December 4, 2023

Pressmud, a residual byproduct in the sugar industry often known as filter cake or press cake, has been acknowledged as a valuable resource for green energy production.
- It is the agricultural waste obtained when cane juice is repeatedly filtered before being sent for extraction of sugar.
It can help Indian sugar mills generate extra revenue by utilising it as a feedstock for biogas production through anaerobic digestion and subsequent purification to create compressed biogas (CBG).
Usually, the yield of pressmud falls within the range of 3-4 per cent weight by weight with the input sugarcane processed in a unit.
Advantages
- eliminates the complexities associated with the feedstock supply chain
- the feedstock is sourced from one or two producers or sugar mills, as opposed to agricultural residue, which involves multiple producers / farmers within a narrow window of 45 days per year.
- pressmud’s quality is not a concern, unlike municipal solid waste, where the presence of inorganic material can damage anaerobic digesters, leading to lower gas output.
- it eliminates pretreatment costs as it lacks the organic polymer lignin, unlike agriresidue.
- in terms of conversion efficiency, approximately 25 tonnes of pressmud are needed to produce a tonne of CBG.
  - In comparison, cattle dung requires 50 tonnes for the same gas output.
- Challenges
  - Pressmud faces competition for use as fertiliser and in bio-composting.
  - The need for CBG plants to store feedstock for the entire year, given that sugar mills operate for a specific period.
  - Storing pressmud proves challenging as it undergoes gradual decomposition, resulting in the breakdown of organic compounds.
    - This increases long-term storage cost and production costs.