Sugarcane fields are burned before harvest primarily to strip away the dense mass of leaves, tops, and dry straw that surrounds the sugar-rich stalks, making the crop far easier and safer to cut. Pre-harvest burning removes roughly 80 percent of this leafy material, which would otherwise slow down both hand-cutters and machines considerably. The practice also kills venomous snakes, scorpions, and stinging insects that shelter in the canopy, reducing the risk of serious injury to field workers. What began as a practical solution to an extremely labor-intensive crop has persisted for decades, but its environmental and health costs are driving a global shift toward unburned, or “green,” harvesting.
How Burning Makes the Harvest Possible
A mature sugarcane field is an imposing tangle. The stalks themselves can reach three to five meters tall, and they are wrapped in layers of green leaves, dead leaves, and fibrous tops collectively called “trash.” This material can account for a substantial fraction of the plant’s total above-ground mass. For a worker swinging a machete, wading through all that foliage to reach the stalk is exhausting, slow, and dangerous. Burning the field the night before or morning of harvest flash-clears most of that trash, leaving bare stalks standing in an open field that can be cut at several times the rate of an unburned one.
The speed advantage matters economically. Once sugarcane is cut, the sugar inside the stalk begins to degrade within hours. Mills need a steady, high-volume flow of freshly cut cane to keep processing lines running efficiently. Anything that slows cutting or loading in the field creates a bottleneck that can reduce the sugar recovery from an entire day’s harvest. Burning solved this throughput problem so effectively that it became standard practice across most major producing countries, from Brazil and India to Australia and the southern United States.
Worker Safety in the Field
The safety argument for burning is not abstract. Sugarcane fields in tropical and subtropical regions harbor real hazards. Venomous snakes, scorpions, and aggressive bee colonies nest in the dense leaf litter and canopy. Workers cutting cane by hand are in constant close contact with the base of the plant, exactly where these animals tend to shelter. Pre-harvest fires flush or kill these creatures, and the open sight lines in a burned field let workers spot any that remain. The practice also reduces lacerations and puncture wounds from machetes catching on tangled leaves rather than cleanly striking the stalk.
In Brazil, which produces more sugarcane than any other country, these considerations shaped harvesting culture for generations. One study on Brazilian sugarcane biomass noted that burning kills bees, snakes, and scorpions, decreases accidents with knives and machetes, and increases the harvesting capacity for both hand labor and machines.1SciELO – Scientific Electronic Library Online / Scientia Agricola. Energy potential of sugar cane biomass in Brazil For smallholder farms that still rely on manual cutting, these are not minor perks. They can be the difference between a manageable harvest season and one marked by hospitalizations.
Pest and Borer Control
Beyond the creatures that threaten workers directly, burning also suppresses agricultural pests that damage the crop itself. Sugarcane stem borers, moth larvae that tunnel into the stalk and reduce sugar yield, are among the most economically damaging pests in cane-growing regions. Fire can kill a meaningful share of borer populations that are present in the field at harvest time. In Colombia’s Cauca River Valley, the widespread adoption of pre-harvest burning in the 1970s, originally introduced to facilitate mechanical harvesting, likely afforded a degree of stem borer control as a side benefit.2BioOne Complete (Florida Entomologist). Sugarcane Stem Borers of the Colombian Cauca River Valley: Current Pest Status, Biology, and Control
This pest-control effect is real but not a magic bullet. Borers that have already tunneled deep inside the stalk often survive the fire, and the heat is brief enough that soil-dwelling pupae can escape lethal temperatures. So burning reduces pest pressure rather than eliminating it, and modern integrated pest management programs use biological controls alongside or instead of fire.
The Air Pollution Problem
For all its practical advantages, burning a sugarcane field is essentially an open biomass fire, and it produces the same toxic cocktail as any large vegetation burn. Smoke from pre-harvest fires contains fine particulate matter, carbon monoxide, nitrogen oxides, methane, and a range of volatile organic compounds. Emissions data from the state of São Paulo, Brazil, one of the world’s densest sugarcane regions, estimated average annual releases of about 1,130 gigagrams of carbon monoxide, 45 gigagrams of fine particulate matter (PM2.5), and 120 gigagrams of coarser particulate matter (PM10) from pre-harvest burning alone.3Atmospheric Environment. Pre-harvest sugarcane burning emission inventories based on remote sensing data in the state of São Paulo, Brazil These are not trivial numbers. PM2.5, the fraction small enough to penetrate deep into the lungs, is the component most closely linked to respiratory disease and cardiovascular harm.
The pollution does not stay in the field. Smoke plumes from sugarcane burns drift over surrounding towns and cities, particularly during the dry-season harvest months when atmospheric conditions tend to trap pollutants near the ground. Communities downwind of cane fields experience sharp, seasonal spikes in air quality degradation that coincide precisely with the burning calendar.
Health Effects on Surrounding Communities
A 2025 scoping review of the health literature on sugarcane-burning air pollution found consistent evidence of harm, particularly to vulnerable populations. Five studies in the review identified effects on infant and child health, including greater risk of respiratory hospitalization, reduced birth weight, shorter gestational periods, and fetal death among people exposed to smoke from sugarcane fires.4PubMed Central. The Adverse Health Effects of Air Pollution from Sugarcane Burning: A Scoping Review of Observational and Experimental Evidence The review also noted respiratory effects in adults, especially among the elderly and those with pre-existing conditions like asthma.
These findings are a major reason governments have moved to restrict or ban pre-harvest burning. São Paulo state enacted legislation phasing out the practice, and similar regulations exist in parts of Australia, Louisiana, and elsewhere. The political dynamic is familiar: the people who benefit from burning (farmers and field workers) are often not the same people who bear its health costs (residents of nearby towns), which makes the issue contentious in every region where it arises.
What Burning Does to the Soil
The damage from pre-harvest fires extends below the surface. When a field is burned repeatedly over years, the soil loses organic matter that would otherwise be replenished by decomposing leaves and straw. A study comparing burned and unburned sugarcane fields in Brazil found that total organic carbon in unburned fields was about 54 percent higher than in burned fields, and microbial biomass carbon, a sensitive indicator of overall soil biological health, was roughly 102 percent higher in unburned fields.5Agriculture, Ecosystems & Environment. Effects of sugarcane harvesting with burning on the chemical and microbiological properties of the soil Native forest soils scored even higher on both measures, but the gap between burned and unburned cane fields alone was striking.
Organic matter is not just an academic metric. It is what gives soil its ability to hold water, retain nutrients, and support the microbial communities that make those nutrients available to plants. A soil depleted of organic matter becomes harder, less absorbent, and more dependent on synthetic fertilizer to maintain yields. Over decades of continuous burning, fields can enter a cycle where the soil’s declining health demands ever-greater chemical inputs to sustain production.
Erosion and Water Loss
Removing the leaf litter through burning also strips the soil’s natural armor against rain. In tropical regions where sugarcane is grown, intense downpours are common, and bare soil erodes far more quickly than soil protected by a layer of crop residue. Research on green-cane cultivation found that sugarcane trash left on the soil surface dissipates the energy of falling raindrops, slows water runoff, and acts as a filter that traps soil particles before they wash away.6Revista Brasileira de Ciência do Solo. Soil, water and nutrient losses by interrill erosion from green cane cultivation When burning removes that cover, the soil is freely exposed to rain impact and runoff, accelerating erosion and the loss of nutrients dissolved in the runoff water.
In irrigated regions, keeping trash on the field also contributes to conserving soil moisture, which could translate into reduced irrigation needs. A study in Mauritius noted that the trash blanket left by mechanized green harvesting conserves moisture, though precise water savings are still being quantified.7Sugar Tech. The Practice of Green Cane Trash Blanketing in the Irrigated Zone of Mauritius: Effects on Soil Moisture and Water Use Efficiency of Sugarcane In a warming climate where water scarcity is an escalating concern for agriculture, even modest moisture retention can be economically meaningful.
The Shift Toward Green Harvesting
Green harvesting, cutting the cane without burning first, has been gaining ground for decades, driven by environmental regulation, public health pressure, and the development of mechanical harvesters capable of handling unburned fields. Modern cane harvesters use rotating blades and powerful fans to cut the stalks and separate most of the leafy trash in one pass. The trash is either scattered back onto the field as a mulch blanket or collected for other uses.
The transition is not painless, though. Mechanical harvesters are heavy, and their repeated passes through wet tropical soils cause compaction that restricts root growth and can reduce yields. Research on this problem found that controlling traffic patterns, restricting the harvester’s wheels to fixed lanes rather than allowing them to wander across the field, increased root biomass by roughly 18 percent and boosted sugarcane yields by anywhere from about 8 to nearly 19 metric tons per hectare, depending on row spacing and harvest cycle.8Soil & Tillage Research. Soil compaction, root system and productivity of sugarcane under different row spacing and controlled traffic at harvest In other words, the compaction problem is manageable with good field planning, but it requires investment in GPS guidance systems and changes to how fields are laid out.
There is also a cost barrier. Mechanical harvesters are expensive capital equipment, and smallholder farmers in many cane-growing regions cannot afford them. For these growers, hand-cutting unburned cane is possible but significantly slower and more labor-intensive, which brings the safety and throughput issues full circle. The transition away from burning tends to happen fastest on large, well-capitalized plantations and slowest on small farms, creating a patchwork of practices within the same region.
Turning Trash Into Energy
One of the strongest economic arguments against burning is that it destroys a resource with real commercial value. The leaves, tops, and straw that fire eliminates are lignocellulosic biomass, essentially plant fiber rich in carbohydrates. When left intact, this material can be collected and used as fuel for electricity generation or as feedstock for producing cellulosic ethanol, sometimes called second-generation ethanol.
Sugarcane bagasse, the fibrous pulp left after stalks are crushed at the mill, already powers most sugar mills through cogeneration. But the field trash, the material that burning destroys, represents an additional energy source that the industry has historically wasted. Research has established that sugarcane straw and bagasse are rich in carbohydrates, renewable, and do not compete with food or feed demands, making them attractive feedstocks for bioethanol production.9PubMed Central. Bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification, and ethanol fermentation Both trash and bagasse can also be burned in boilers to generate electricity that is exported to the grid, turning a sugar mill into a combined food-and-energy producer.10Applied Energy. Biorefineries for the production of first and second generation ethanol and electricity from sugarcane
This reframing changes the economics. If the trash blanket has monetary value as biomass feedstock, burning it is not just an environmental cost but a direct financial loss. Mills and plantations that can collect and process this material have an incentive to stop burning that goes beyond regulatory compliance. The biorefinery model, in which a single facility produces sugar, first-generation ethanol from juice, second-generation ethanol from fiber, and surplus electricity from combustion of residuals, is already operational in parts of Brazil and is expanding.
Nutrient Cycling and Fertilizer Use
When sugarcane leaves decompose on the soil surface instead of being burned away, they return nutrients, particularly potassium, nitrogen, and phosphorus, back to the soil over time. This natural recycling can offset a portion of the synthetic fertilizer that farmers would otherwise need to apply. Research in southern China’s red-soil sugarcane region has explored how returning leaf straw to the field interacts with fertilizer reduction, finding that the soil bacterial communities, which drive nutrient cycling, respond significantly to the combination of straw return and reduced chemical inputs.11PubMed Central. Interactions between Sugarcane Leaf Return and Fertilizer Reduction in Soil Bacterial Network in Southern China Red Soil The bacterial networks were closely tied to soil organic matter content and available nitrogen, both of which increase when straw is retained rather than burned.
The fertilizer savings are not dramatic enough on their own to justify the transition for most farmers, but they add up when combined with reduced erosion, better moisture retention, and the potential sale of biomass. The cumulative case for keeping trash on the field, or collecting it for energy, is stronger than any single benefit taken alone.
Why Burning Persists Despite the Downsides
Given everything above, you might wonder why anyone still burns at all. The answer is mostly structural. In regions where labor is cheap and machines are expensive, hand-cutting remains the dominant harvest method, and hand-cutting unburned cane is genuinely punishing work. The historical entrenchment of burning as standard practice means that supply chains, mill schedules, and labor contracts are all built around burned cane. Converting to green harvest requires not just new equipment but new logistics: different transport schedules because unburned cane is bulkier, different mill intake procedures to handle incoming trash, and sometimes different varieties of sugarcane bred to shed their leaves more easily.
There is also the timing problem. Once burned, a field must be harvested almost immediately because the exposed stalks deteriorate quickly. Green-harvested cane, by contrast, is somewhat more forgiving in timing but brings more extraneous material to the mill, which can reduce processing efficiency if the mill is not equipped to handle it. Each system imposes its own constraints, and switching between them is not as simple as buying a harvester and skipping the match.
Climate and terrain add further complications. Mechanical harvesters work best on flat or gently rolling land. In hilly regions, common in parts of Central America, Southeast Asia, and the Caribbean, machines cannot operate safely, and manual cutting with prior burning remains the most viable option. Until affordable, slope-capable harvesting technology matures, burning will likely continue in these geographies regardless of regulatory intent.
The Greenhouse Gas Dimension
Pre-harvest burning contributes directly to greenhouse gas emissions. Beyond CO₂ released when the biomass combusts, the fires produce methane and nitrogen oxides, both of which have warming potential that exceeds CO₂ on a per-molecule basis over shorter time horizons. The São Paulo emissions inventory estimated annual methane releases from pre-harvest burning at about 16 gigagrams per year and nitrogen oxides at about 26 gigagrams per year, alongside large quantities of non-methane hydrocarbons that contribute to ground-level ozone formation.3Atmospheric Environment. Pre-harvest sugarcane burning emission inventories based on remote sensing data in the state of São Paulo, Brazil
There is a nuance here that often gets lost in the conversation. The COâ‚‚ from burning sugarcane trash is biogenic, meaning it was absorbed from the atmosphere by the plant during the growing season and would eventually be released anyway through decomposition. So the net COâ‚‚ contribution is roughly neutral over time. The real atmospheric concern is the non-COâ‚‚ gases and the particulates, which would not be produced if the material decomposed slowly on the field. When the trash is instead used as fuel in a controlled boiler at the mill, the combustion is more complete and the emissions per unit of energy are substantially lower than in an open field fire, making bioenergy use a cleaner alternative even when the material is ultimately burned.
How Different Countries Are Handling the Transition
Brazil has been the most aggressive in legislating the end of pre-harvest burning, partly because its flat São Paulo plateau is well suited to mechanical harvesting and partly because the air quality impacts on densely populated areas created political urgency. São Paulo state’s phaseout law set deadlines that have already passed for flat land, and the green-harvested share of Brazil’s total cane crop has risen dramatically over the past two decades.
Australia took a different path, using voluntary industry codes and market incentives. Australian mills began paying premiums for green cane and adjusting their intake systems to handle the additional leaf material. The approach worked in part because Australian cane farms are relatively large and mechanized, lowering the barrier to adoption.
India, the world’s second-largest producer, faces the steepest challenge. Its cane sector is dominated by millions of smallholder farmers with fragmented plots, limited capital, and hilly terrain in many growing regions. Burning remains widespread, and the air quality consequences are compounded by the overlap of the sugarcane burning season with other agricultural burning (particularly rice stubble) across northern India. Policy interventions there have focused more on subsidizing mechanical alternatives and providing financial support for cooperative equipment purchases than on outright bans, which would be difficult to enforce across such a dispersed farming base.
In the United States, sugarcane burning in Florida and Louisiana continues under regulated conditions, with burn permits, weather-window restrictions, and smoke-management plans intended to minimize community exposure. The regulatory framework acknowledges that burning still happens but tries to control when and how, rather than whether. Environmental and community groups continue to push for stricter limits, and the tension between agricultural tradition and residential air quality remains unresolved in several parishes and counties near cane fields.