The challenge with fibrous biomass
India has enormous CBG potential from paddy straw, wheat straw, sugarcane trash, Napier grass, maize stalk, cotton stalk and mustard residue. Feeding merely shredded biomass into a digester often gives sub-optimal digestion, because the lignocellulosic structure restricts microbial access. The typical problems are:
- Long, tough, entangled fibres
- Non-uniform particle size
- Difficult mixing and handling
- Floating / scum layers in digesters
- Inconsistent feeding
- Higher load on downstream equipment
The complete pretreatment chain
- Baled / loose biomass
- Bale shredder
- Hammer mill
- Twin-screw shearing
- Slurry preparation
- Hydrolysis
- Anaerobic digestion
1. Bale shredding
Opens compact round or square bales, separates entangled fibres and turns long straw into manageable shredded material.
2. Hammer milling
Reduces irregular shredded straw to a more consistent coarse material for the shearing stage.
3. Twin-screw shearing
Intensive shearing, compression, mixing and fibre opening, with moisture added as the process requires, gives a uniform, process-friendly feedstock.
Benefits of twin-screw shearing
- Better fibre opening and fibrillation
- More homogeneous feed preparation and particle structure
- Improved biomass–water interaction and slurry preparation
- Increased accessible surface area for hydrolysis
- Fewer oversized and entangled fibres, so smoother feeding
- Can be integrated into continuous CBG preprocessing lines
Pretreatment benefits depend on feedstock characteristics, moisture, machine settings and the complete digester process. We recommend plant-specific validation and trials with your own raw material before freezing the design.
Napier grass: farm to CBG
- Napier harvester
- Twin-screw shearing
- Feeder
- Pretreatment tank
- Digester
- Upgrading
- Compression
- CBG
Learn more: Paddy straw CBG plant · Napier grass CBG plant · Full CBG process
Frequently asked questions
Lignocellulosic biomass like paddy straw and Napier grass has tough, long fibres that limit microbial access and can cause floating layers, poor mixing and inconsistent feeding in digesters. Pretreatment opens and homogenises the fibre so it can be mixed into slurry, hydrolysed and digested more effectively.
Inside the machine, biomass undergoes intensive shearing, compression, mixing and fibre opening. The aim is not just to cut the material but to fibrillate and disrupt its structure, increasing accessible surface area and improving interaction between biomass, water and the digestion system.
Research shows that pretreatment can improve anaerobic digestion of agricultural residues by increasing accessible surface area. The actual improvement in methane yield, hydrolysis rate and retention time depends on the feedstock and digester process, so it should be validated for each biomass and plant.
Paddy straw (parali), wheat straw, Napier grass, maize stalk, sugarcane trash, cotton stalk, mustard residue and other crop residues.