Worms to the Rescue: Transform Sugar Mill Waste to Gold

​Let us count it. In 2025 to 2026, sugar mills of Pakistan produced around 7.7 million tonnes of sugar as per the Pakistan Sugar Mills Association (PSMA). Government and USDA estimates suggest that the cane produce is approximately 83 to 85 MT, with approximately 10% of the cane being used for gur and seed. So, there is about 75 million tonnes available for the mills. Based on the study conducted in Pakistan and the area, it is concluded that approximately 3 to 4 tonnes of pressmud are generated from 100 tonnes of cane in a mill. When calculated, this works out to be approximately 2.3 to 3.1 million tonnes of wet pressmud per season. This is a best estimate, and not an official cane count, and this count will fluctuate based on the quality of cane that he has in his mill and the number of machines he has. However, it's quite clear. Each year, our sugar industry generates a huge pile of organic matter.

​Then walk to the other side of the fence (the farmer's field). There are lots of exhausted soils around. Agronomists state that the organic matter content is less than 1 percent for large areas of our cultivated soils. It is a very low content for healthy soils. In the meantime, fertilizer is becoming even more expensive. The ministry's price review published in the press indicated that in July 2026, a 50-kilogram bag of DAP cost Rs 16,055, some 23 percent higher than a year ago, while it was found that some 50 percent of DAP was being imported. The price of urea has remained more or less at Rs 4,650 per bag. The cost of N2 to farmers is approximately Rs 200 per kilogram since 1 bag of urea is equivalent to approximately 23 kilograms of N2. The farmer is the first to feel the dollar move, or when a ship is late.

​Hence, the question arises, “Why?” A pile of organic waste is placed on one side of the fence. On the opposite side, there is starving soil, and an empty pocket. Can one industry provide a helping hand to another industry with its waste?

​I don't think so, but there should be an understanding of what pressmud can do. It will not be a substitute for either urea or DAP. What is the sum of this amount? Assuming that pressmud contains approximately 30 percent dry matter with approximately 1.8 percent nitrogen, which is borne out by some published trials, then all the pressmud in the country contains about 12,000 to 17,000 tonnes of nitrogen. That is equivalent to approximately 27,000 to 36,000 tonnes of urea, which is a very small portion of the amount of urea used by our farmers in a year. Therefore, pressmud can't be used as an alternative to fertilizer. It's something else that's its real strength. Not only does it provide organic matter, retain soil moisture, and provide a food source for microbes, but it also provides a bit of additional nutrients. It can be used in conjunction with a balanced fertilizer to provide a little extra oomph to each fertilizer bag. At the mill, it's a product out of a dumping issue.

​But fresh pressmud should not be used. It still contains some sugars, wax, salts, and heat. When it is stacked, it ferments and has an odor. When applied fresh on a field, it can burn the young roots, tie up soil nitrogen for a period of time, and affect seedlings. The occurrence of traces of metals in some samples can also be due to the mill. Raw pressmud is a raw material that can be used. The challenge is to make it safe.

​The red wiggler, Eisenia fetida, is where this comes in handy. It is a small worm that can be reddish in color and is found in rotting leaves and manure. It feeds on organic waste that it finely chews up, processes using bacteria and fungi, and outputs as dark, crumbly manure, loved by plants. Such worms are already introduced by the farmers in many countries where they use kitchen wastes and dung to make good compost. Worms are not machines, however! They should be provided with a moist bed, a moderate temperature, a neutral pH, low levels of salt, and soft feed. If one of these doesn't go right, they die.
​Pakistani research has established the fact that these worms can be used with our own farm wastes with great success. In one local study, cattle dung was converted to mature compost in approximately 12 weeks at approximately 25°C and had a carbon-to-nitrogen ratio of approximately 11:1, which is a good indication of maturity. In another, a half-and-half mixture of bagasse and cattle dung resulted in the minimum mortality of the worms, and the mixture started to become granular after 90 to 100 days. Similarly, the mixture of pressmud and boiler ash with distillery wastewater is being tried in Habib Sugar Mills, Nawabshah, implying that our industry is already moving in this direction.

​Pressmud itself is the subject of research studies, showing how it can be conducted properly. Indian researchers conducted this study to find out the growth and breeding performance of these worms when they were fed with cow dung up to a 50:50 ratio in the pressmud, and they found good growth and breeding performance in 13 weeks. Growth and breeding declined with an increasing percentage of pressmud. Other works indicated that worms were not responsive to the pressmud alone, and the wastes should be composted for a short period of 2 weeks or so to leach out the toxic chemicals and heat from the wastes prior to the addition of worms to the compost. A subsequent reactor study which went down this route achieved a carbon-to-nitrogen ratio of 9 to 11 and germination indices of more than 100 percent, indicating a ripe product. The results of all of these studies are the same: mix, rest, cool, and then add the worms.

​This was an experience I learned first-hand in my own research. As part of my Master's zoology research project at the University of Education, Lahore, I experimented with Eisenia fetida and pressmud. Three different garden soil mixtures were made using 50 g, 25 g, and 12.5 g of pressmud, each of which was replicated, and to each was added 190 adult worms. We watched them from 15 to 22 April 2026. All the worms in each unit were dead after 7 days. The more pressmud they took, the quicker they died, and the less they took, the slower they died, but it didn't help, and not at all when they took the least.

​However, it's not a failure; I don't see it as a failure. It's the first truthful chapter of the tale, as far as I can see. It shows that this crop of worms cannot take fresh pressmud directly into the soil, and thus confirms the findings of the previous investigations into the salts, ammonia, organic acids, and heat in the fresh pressmud. It also provides the detailed procedure that has to be followed: pre-composting of the pressmud, mixing of the pressmud with cow dung/bagasse, and making a small-scale bed to test worm survival before making a large-scale bed. May 2026 plant tests, continued with wheat and spinach, resulted in a mixed response with the soil being on the alkaline side (pH of about 8.0 to 8.8). This is what one would expect of an immature material. It also reminds me of one more thing: a seed's success in a pot is a good beginning; the litmus test is a successful harvest in the farmers' field, and that takes more than one year.

​Other sugar-producing countries have followed suit. In Brazil, the use of filter cake is mostly direct, in the planting furrow and often together with phosphate fertilizer. One field test in São Paulo gave the best results with 1 to 2 tonnes/ha of this product and 100–200 kg of P2O5 for an optimum response in ratoon cane. This shows that pressmud without worms (which is given at the correct dose) is effective. As for Pakistan, the wise course is to do all that can be done to try the various alternatives and experiment with them in our own mills, our own climate, and our own soils.

​Then what would a sensible Pakistani plan be? I would take it easy and work up to it. Before a mill starts to use pressmud as a feed, the mill should first have a measurement of its own pressmud: how many tonnes it produces, how wet it is, its pH and salt content, and its carbon, nitrogen, phosphorus, potassium, and metal content. The pressmud will then be pre-composted for a couple of weeks (with regular turning) until it cools. It should then be mixed with cow dung or bagasse in a couple of different proportions, and a small worm survival test should be conducted on each of the mixes. The optimum combination can then be transferred to pilot beds to be monitored weekly for moisture, temperature, and worm populations. When batch sampling reaches maturity, it is to be tested for maturity, salt, pH, germs, and metals in the compost. It should not be made available to farmers until then, and the initial sales should be through demonstration plots along with the normal farms so that the farmer can view the difference.

​In money matters, it's quite straightforward in theory. There is no profit in the selling price; there are costs involved in collecting and transporting (even if you use your own vehicle), composting, mixing, feeding worms, drying, bagging, and testing. The break-even sum is a mere sum: fixed costs of the mill for a year divided by the selling price per tonne minus the running cost per tonne. The answer will be the number of tonnes that the mill must sell each year to break even. Each individual mill will complete the actual values in each mill's pilot. Another consideration is that the pressmud produced in the wet state will not necessarily yield a tonne of compost since there will be water loss and some of the material will be screened out.
​It can be beneficial for the environment, too. With the treatment of pressmud under cover and with a proper record, there will be fewer heaps of smelly pressmud and less of the dirty pressmud will be discharged into canals and groundwater. But there has to be as much attention paid in the other direction. Even poor pile management can leak, and immature or contaminated compost can just transfer the problem from mill to farm. It's management that makes all the difference.
​Everyone has a role to play if this is going to be successful. Sugar mills should measure and record their pressmud, stop open runoff, pay for at least one supervised pilot, and openly discuss the results – good and bad. Researchers need to take some ideas from my work, redo the worm tests with the pressmud that is pre-composted and blended, use a trusted feed as a control – such as cow dung – and track the composting all the way to the field – measuring yield, soil carbon, and cost. Adequate quality control parameters for maturity, germs, and heavy metals in organic fertilizer should be determined, and batch labels should be requested to inform the buyer of the quality of the product. As for farmers, it should be remembered that vermicompost is a soil conditioner and should not be used in isolation; it should be a part of a balanced fertilizer regime, and while buying, farmers should ask for test results.

​Pressmud is, of course, nothing like gold, and every farmer is well aware of this. However, gold isn't simply a metal. It's also what we refer to as something that makes a loss valuable. A stinking, abandoned heap can turn into dark, crumbly, fertile soil, and that's valuable to a country where its farms are depleted and its fertilizer costs continue to rise. My initial worms did not survive, but they did help me with direction as to where the road begins. Worms are now available for work. It is now our responsibility to ensure that they're given the right start.

(The writer is researcher in the field of Zoology and Fisheries.)