Compressed Biogas from Sugarcane By product ‘Pressmud’: Transforming Waste into Sustainable Fuel

December 1, 2023

GS Paper III Environment and Ecology Geography

Context: Pressmud, a residual byproduct in the sugar industry commonly referred to as filter cake or press cake, has been recognized as a valuable resource for the production of green energy.

Compressed Biogas from Sugarcane Byproduct

Feedstock for Compressed Biogas: Pressmud presents an opportunity for Indian sugar mills to generate additional revenue by using it as a feedstock for biogas production through anaerobic digestion and purification to produce compressed biogas (CBG).
Surge in press mud prices: Earlier, viewed as a disposal concern for sugar mills, owners now acknowledge its potential for generating revenue.
- This recognition has led to a surge in pressmud prices over the past two years, escalating from Rs 100 per tonne to the current range of Rs 500-600 per tonne.

What is Compressed Biogas (CBG)?

Production: Compressed Biogas is produced naturally through a process of anaerobic decomposition from waste / bio-mass sources like agriculture residue, cattle dung, sugarcane press mud, municipal solid waste, sewage treatment plant waste, etc.
After purification, it is compressed and called Compressed Biogas, which has high methane content.
Energy potential: Compressed Biogas is exactly similar to the commercially available natural gas in its composition and energy potential.
Alternative, renewable automotive fuel: It has a similar calorific value to CNG. Thus it can be used as an alternative, renewable automotive fuel.

Yield: The yield of press-mud falls within the range of 3-4 percent weight by weight with the input sugarcane processed in a unit.
Energy potential: India’s sugar production for the fiscal year 2022-23 amounted to 32.74 million tonnes, along with approximately 11.4 million tonnes of pressmud.
- This quantity has the potential to generate 460,000 tonnes of Compressed Biogas valued at Rs 2,484 crore.

Advantages Of Using Press Mud As A Feedstock For Compressed Biogas?

Simplifying the feedstock supply chain: It avoids the complexities associated with agricultural residue, where biomass harvesting machinery is needed for harvesting and aggregation.
Simplified Procurement: The feedstock is obtained from one or two producers or sugar mills, unlike agricultural residue, which involves multiple producers/farmers within a narrow 45-day window each year.
Feedstock Quality: Pressmud has less inorganic material compared to Municipal solid Waste which can harm anaerobic digesters, leading to reduced gas output.

Sugar sector in India

Regional Production: Uttar Pradesh and Maharashtra, the primary sugarcane-growing states, contribute to approximately 65 per cent of the total sugarcane cultivation area.
Key sugarcane-producing states: Uttar Pradesh (225.2 million tonnes), Maharashtra (123.9 million tonnes), Karnataka (62.5 million tonnes), Tamil Nadu (16.9 million tonnes) and Bihar (12.1 million tonnes).
Status of ownership of sugar mills: Among the 531 operational sugar mills in India, 330 were privately owned, 190 were cooperative and 11 were public during the year 2022-23.
Export share: India stands as the second-largest sugar exporter worldwide.

By Product of Sugar Industry:

The four main byproducts of the sugarcane industry are cane tops, bagasse, filter muds and molasses.

No Pretreatment cost: Due to lack of the organic polymer lignin in Pressmud compared to other Agri-residues.
Higher conversion efficiency: It has higher conversion efficiency than agri residue.
Approximately 25 tonnes of pressmud are required to produce a tonne of Compressed Biogas, while cattle dung requires 50 tonnes for the same gas output.
Moreover, it is more economical than other feedstocks like agricultural residue (Rs 1.5-2/kg) and cattle dung (Rs 1-2/kg).

What challenges are associated with pressmud?

Competition for usage: Pressmud encounters competition for its utilization as a fertilizer and in bio-composting, competing with spent wash and being employed as fuel in brick kilns.
Absence of long-term agreements: The challenges are exacerbated by the absence of long-term agreements with sugar mills and the intermediaries involved in procurement.
Concerns with storage: The necessity for Compressed Biogas plants to store feedstock throughout the entire year presents a challenge considering that sugar mills operate for a specific period.
Storing pressmud presents challenges due to its gradual decomposition, leading to the breakdown of organic compounds.
This complicates the feasibility of long-term storage and contributes to increased production costs.

What steps are required to unlock the potential of pressmud?

Enacting bioenergy policies: States should enact bioenergy policies to streamline project approval processes.
- This can offer a unified solution and a range of monetary and non-monetary incentives.
- Uttar Pradesh and Bihar have already taken steps in this direction.
Regulation of pressmud prices: The government should establish a mechanism to regulate pressmud prices, keeping them below a specified threshold.
- Sugar mills need to be encouraged for committing to extended agreements (10-15 years) with CBG plants with an annual rate increase of 5-10 per cent.
Technology for pressmud storage: It needs conducting comprehensive research to develop technology for pressmud storage which prevents methane emissions into the environment and minimizes gas loss from the feedstock.
Capacity building: Focus should be given to conduct regular training sessions to educate operators on the operation of CBG plants, the proper handling of scientific equipment, and the feedstock characterization.