Why burn sugar cane?

The purpose, according to Hawaiian Commercial & Sugar Co., is to remove the unproductive leafy "trash" that makes up 20 percent to 25 percent of the cane plant just before harvesting.

It not only costs more to process and haul the leafy material to the Puunene factory, but if the trash is not removed, less sugar would be recovered from the cane stalk, the company says.

Each field is harvested once every two years, which means about half the 36,000-acre plantation is burned each year, typically from March to November, with the aim of providing a steady flow of cane to the factory.

This averages out to roughly 400 acres per week. The number of acres burned at one time is usually about 70, but can vary depending on field conditions and location, weather and requirements of the factory, HC&S says.

The burns follow roughly 18 months of growth and an additional six months of ripening when the cane plant is denied water and depleted of nutrients that promote growth. This process stresses the plant and forces it to store sucrose rather than grow.

Company officials assess weather conditions and other factors before every burn. The plantation maintains 44 weather monitoring stations and uses a consultant to analyze computerized meteorological modeling to help predict the best times to harvest.

Once the decision is made to proceed with a burn, water trucks wet down the perimeter of the field and backfires are lit to help prevent a jump fire. It’s all over in about 20 to 30 minutes.

Company officials point out that pre-harvest burning is practiced everywhere sugar cane is grown in the United States, including some 850,000 acres in Florida, Texas and Louisi­ana, as well as in most sugar cane-growing areas of the world.

However, green harvesting is a growing phenom­­­­enon. In Australia, for ex­am­­ple, much of the sugar crop is harvested mechanically.

For years critics have complained loudly that cane burning causes respiratory conditions, migraines and other health problems.

The company counters studies by the state Department of Health, the National Institute for Occupational Safety and Health and the University of Hawaii that have found no evidence that sugar cane burning causes any kind of health problems.

"We do recognize that smoke — of any kind — can aggravate an existing respiratory condition. That’s why HC&S makes every effort to alert neighbors, especially those with health problems, whenever a harvest is scheduled nearby," the company’s website says.

HC&S says the emissions from burning sugar cane are similar to those from burning any other organic matter, such as wood. "Even the tubing used for our drip irrigation system is made of polyethylene, composed of carbon and hydrogen, and, if burned, would be similar to burning wood or a candle, emitting carbon dioxide and water."

Critics also worry about HC&S’ practice of spraying glyphosate, the active ingredient in Roundup, on the sugar cane before harvesting. They claim the chemical gets into the smoke, creating toxic fumes that drift into neighborhoods.

Rick Volner, plantation manager, said gly­­pho­sate is used to ripen the sugar cane plant and only a small amount — less than what’s allowed by the label — is applied "many weeks" before the cane is harvested.

"By the time the field is burned prior to harvest, glyphosate residues are minimal to nonexistent and do not approach levels which could cause health effects," he said.

Ripeners containing glyphosates are used extensively in the sugar cane industry and have been approved by the EPA for this purpose, he said.