Most of India’s crop-residue problems are logistics problems: the straw is in a field, the plant is somewhere else, and nobody has worked out who pays for the truck. Bagasse is the exception. It is the fibre left after cane is crushed, and it is already piled inside the factory gate. So when a lab paper says bagasse can be “liquefied” into a polyol for foam, or “hydrolysed” into sugars, the question that matters is not whether the material can be collected. It is whether the product can beat what the mill already does with it, which is burn it.

This piece reads the published record on both routes, mostly from abstracts and search summaries, because the full texts were not available to this blog (Xie et al. 2015 and the lime and hydrothermal study have since been read in full; see the correction before the sources). The finding is that the chemistry is well shown and the economics are unwritten.

What the material is

Bagasse is three polymers. Cellulose is the prize for sugar; hemicellulose gives a different sugar, xylose, and breaks down first; lignin holds the structure together and is the main reason enzymes struggle. The papers seen agree that lignin drives the difficulty, which is why every hydrolysis route starts with a pretreatment. The proportions above are from one sample. Cane varieties differ, and the 115-variety study found the sugar you can get out varied by a factor of two.

Four things called liquefaction or hydrolysis

The two words cover different processes with different products, and papers sometimes blur them.

Hydrolysis: pretreatment decides the yield

Untreated bagasse releases little sugar. The choice of pretreatment, then the enzyme dose and solids loading, sets how much comes out. The table gives what the studies reported, in the unit each used. The units differ, so the rows cannot be ranked against each other. One study of ten deep eutectic solvents put an ionic liquid at the top for sugar yield but found the deep eutectic solvent was more compatible with the enzymes and easier to recycle. A cheaper protic ionic liquid reached about three-quarters of the glucose of the standard one, and was reported as 40 times cheaper.

Two cautions run through the hydrolysis papers. First, harsher acid is not better. In one study cutting hemicellulose by almost 80% with 4% acid released about as much xylose as 0.5% acid, while inhibitors, the furfural and acetic acid that stop yeast, rose about fivefold. Detoxifying the liquid raised fermentation efficiency by 12.7% for a hydrothermal hydrolysate but made no significant difference for an acid one. Second, the sugar can go to different places. One group made xylitol from the xylose at 100% selectivity from a sugar yield of 82%; another, working with an acid, reported about 75 mol% levulinic acid and 85 mol% furfural from pretreated bagasse, and a model biorefinery of about 190 kg levulinic acid per tonne of dry bagasse. Furfural and levulinic acid compete for the same sugars, and one paper says high yields of both are hard to get together.

Liquefaction: a polyol for foam

The route that turns bagasse into something a foam maker can use is solvent liquefaction. Xie and colleagues, in 2015, cooked bagasse flour in a polyhydric alcohol with phosphoric acid in a microwave reactor. Almost 75% was liquefied within 9 minutes at 150°C, with one part bagasse to four of solvent, and the polyols had hydroxyl values of 426–505 mg KOH/g. Higher temperature and less solvent gave a lower hydroxyl number, the measure of how many reaction sites the polyol has, and foams made from the hotter batches performed better on physical and mechanical tests.

A kinetics study in PEG 400 and glycerol with sulfuric acid at 140 to 180°C found that hemicellulose liquefies first, then lignin, then cellulose, and that ash in the residue rose over time, which the authors read as dissolved material re-condensing. So there is a trade-off in the cook: long enough to liquefy the cellulose, short enough that the lignin does not re-form into solids.

The foams are where the evidence gets thin. A study that replaced part of a commercial PEG polyol with bagasse polyol found that density and compressive strength rose with bio-content, but that above 30% replacement the surface became uneven and the pores irregular. Thermal conductivity fell from 0.035 to 0.029, which is better insulation. A different study that used a hydrothermal bio-oil from bagasse with glycerol saw thermal stability fall in one stage and rise in another. A study across several biomass sources found foam strength was lower than the control, with better results from sources rich in hydroxyl groups. Xie and colleagues do report foam numbers for bagasse polyol itself: foam density of 0.032–0.043 g/cm³ for polyols made at 150°C and 0.031–0.037 g/cm³ at 125°C, and compressive strength of 0.19–0.34 MPa at 125°C, rising to 0.32–0.48 MPa at 150°C as the bagasse-to-solvent ratio fell from 1/2 to 1/4. These are small-batch lab foams from a polyol made entirely from liquefied bagasse in a bi-component alcohol, not a blend with commercial polyol. The other strength figure I found is for cassava, not sugarcane, where replacing 20% to 100% of the polyol cut compressive strength from 0.171 to 0.057 MPa. That is a different feedstock and is no proof for sugarcane, but it shows the direction.

Three 2026 papers add to this. One used a bagasse polyol, made by microwave liquefaction in PEG 400 and glycerol with phosphoric acid, as a plasticiser in a sugarcane-based geopolymer, and the best mix reached 10.4 MPa at 28 days, more than 40% above the baseline: a use that is not foam. A second found that treating bagasse with nanobubble water sped up liquefaction, with cellulose down 2–3% and lignin down 1–4% in the treated fibre. A third fractionated hydrothermal bio-oil by multi-step solvent extraction at 280 to 340°C. The 2015 microwave paper also reported hydroxyl values of 426 to 505 mg KOH per g for its polyols. None of these is a cost, life-cycle or pilot study.

Bio-crude by hydrothermal liquefaction is a separate result. Sugarcane bagasse gave around 36 wt% in the studies seen. The higher figures in the literature, 61.8% and about 95%, are for sorghum bagasse and for a mixture with soybean oil, respectively, and should not be quoted for sugarcane. Lignin from bagasse has also been used to replace up to 30% of the phenol in resin for plywood that met interior-grade standards.

Where the data stop

1. No cost or life-cycle study. No techno-economic or life-cycle study of a bagasse polyol, foam or sugar route turned up, and a re-check on 12 October 2026 found none among 2026 papers. A 2018 life-cycle paper compares bagasse valorisation routes but its content could not be seen.
2. No mass balance for the leftovers. Even in the best case about a quarter of the bagasse is not liquefied. What the residue is, what it can be used for, and how much re-condensed lignin and ash ends up in the polyol are not in the abstracts seen.
3. Few bagasse foam numbers to rely on. One lab study (Xie et al. 2015) gives density and compressive strength for bagasse-polyol foam, but no thermal values or independent replication were found, and the one strength drop found for a blended foam is for cassava.
4. No price for the enzymes or the solids. Hydrolysis papers work at about 5% solids, and none of the sources priced enzymes, inhibitor removal or solvent recycling.
5. No Indian work found. Searches for the National Sugar Institute, ICAR and the IITs turned up no bagasse polyol or liquefaction project. Praj and ICT Mumbai have 2G ethanol work, in which bagasse is one of several residues.

The Indian setting: the competitor is the boiler

This blog has covered the other claimants on bagasse. India has about 527 sugar mills, of which about 456 were crushing in mid-February 2026, and one source puts total wet bagasse at about 80 million tonnes a year at about half moisture, from about 240 million tonnes of cane. That is a secondary estimate, and the blog has been unable to reconcile it with the 5 to 24 million tonnes quoted for paper. Most of it is burned for the mill’s own steam and power: bagasse cogeneration capacity was 9,806 MW at the end of 2024 according to MNRE data reported in the trade press, and the ministry’s July 2026 table put combined bagasse and other biomass cogeneration at about 11,748 MW. Those are different dates and scopes and are not additive.

That is the point. A mill that sells bagasse for a polyol plant loses fuel and has to replace it or lose export power. Whether the polyol price covers that has not been published. India’s 2G ethanol effort shows how much the feedstock side matters: six of twelve plants were sanctioned under the viability-gap scheme, two are operating, and the flagship Panipat plant has been blamed on rice-straw logistics. Bagasse removes that particular obstacle and replaces it with another, which is a boiler that already works.

What would fix this

• The Department of Food and Public Distribution should require sugar mills to report bagasse generated and where it goes: own boiler, power export, paper, other. Without it, no one can say how much is free to divert.
• The Department of Science and Technology should fund an independent bagasse-polyol pilot with a published mass balance: bagasse in, liquid out, residue, catalyst and solvent losses, and the foam’s measured strength and conductivity at a stated replacement ratio.
• The National Sugar Institute, Kanpur, should publish composition and sugar yield by variety and region, since the 115-variety study found a twofold spread and that decides which mills could supply any process.
• The Bureau of Indian Standards should set how bio-based polyol content in polyurethane foam is measured and declared, so a 30% bagasse polyol claim means one thing across makers.
• The Ministry of New and Renewable Energy should report bagasse cogeneration separately from other biomass in its state table, so the power that a diverted tonne would cost is visible.

These are proposals from this blog, not recommendations any agency has adopted.

Corrected 25 October 2026. The dilute-acid row in the hydrolysis table was mislabelled: Timung et al. (Journal of Energy 2016, abstract) report 452.27 mg/g for bagasse after acid alone and 282.85 mg/g after acid then enzymes; 487.50 mg/g is the citronella acid-only figure, not bagasse. And bagasse-polyol foam numbers do exist: Xie et al. (Materials 2015, full text) report foam density 0.031–0.043 g/cm³ and compressive strength 0.19–0.48 MPa depending on liquefaction temperature and solvent ratio, so the earlier claim that none were recoverable has been amended.

Sources and caveats

About this article: Researched, written and edited by Umashankar Triplicane Dwarakanathan, with AI research assistance; every figure is meant to trace to the primary source cited. See the Editorial Policy for how sourcing, AI use and corrections work.