(Reuters) – Almost 100 sugar and ethanol mills in Brazil’s main sugar cane state Sao Paulo have agreed to stop the practice of burning cane fields by 2017, the Sugar Cane Industry Union (Unica) said on Monday.

These mills crush more than 50 percent of the cane output in Sao Paulo, Brazil’s No. 1 cane producing state that accounts for around 63 percent of the national crop.

In June, Unica had signed an agreement with the state government in which mills were to ban cane burning in the state by 2017, well before 2031 target mandated by a state law.

This pact’s success still depends on mills’ signing on. The protocol is not mandatory but is seen as a move toward protecting the sector from environmental objections.

“The number of mills is surprising and shows how the sector has complied with the demands to end the cane burning,” Unica’s president, Marcos Jank, said in a news conference.

“It puts an end to the environmental incoherence,” Jank added, referring to the environmental impact of burning and the clean benefits of renewable cane-based ethanol fuel.

In September, Unica said it expected 70 to 80 mills to sign the document by year’s end. There are 96 mills already subscribed to it, a number expected to rise in coming months.

The cane burning ban already is ahead of the curve in Sao Paulo state, where more than 40 percent of the harvest is mechanized, with only 30 percent mandated by law, Jank said.

Cane burning facilitates manual harvesting, but causes clouds of smoke and endangers public health in nearby communities, especially when humidity is low. Mechanized harvesting does not require burning.

The end of burning fields has economic advantages too. Extra plant matter can be burned in cogeneration electric power plants and one day may be used to produce cellulosic ethanol. Mechanized harvesting frequently is cheaper than the manual cutting because cane cutters enjoy strong labor rights.

Less than 2.2 million hectares of cane are expected to be burned in Sao Paulo this year, down from the 2.5 million hectares last season, despite an increase of more than 10 percent in the planted area to cane in this period.

The protocol determines that flat areas ban cane burning by 2014 and hilly areas, by 2017. But Jank said the practice should be stopped before that.

“I’m convinced that in 10 years there will not be burning of cane in Sao Paulo, and other states will follow,” he said.

There are around 200,000 cane cutters in the state nowadays, and the industry is now trying to prepare at least part of this group to take new duties in the mills.

The forecast expansion of the ethanol industry in the coming years should absorb 70,000 of these workers, Unica said.

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Sugar Cane Burning in Brazil

Not only is it wasteful, with up to 30% of the energy content of the crop being lost, it is also environmentally malign. The burning process of course releases a significant quantity of carbon dioxide into the atmosphere, hence negating some of the carbon benefits of sugarcane-derived ethanol compared with petrol…

Burning the sugarcane crop prior to harvesting is a traditional practice, which is adopted in order to facilitative manual cutting of the cane. Without the practice of burning, the crop is too dense and the leaves are too aggressive to allow a reasonably rapid rate of cutting.

Not surprisingly, the practice is also controversial. Not only is it wasteful, with up to 30% of the energy content of the crop being lost, it is also environmentally malign. The burning process of course releases a significant quantity of carbon dioxide into the atmosphere, hence negating some of the carbon benefits of sugarcane-derived ethanol compared with petrol. Burning also causes local air quality problems, with black soot released into the atmosphere and subsequently falling as a gentle ‘rain’ upon the surrounding towns and countryside.

The State of Sao Paulo has in place an ‘Agroenvironmental Protocol’ under which there will be a phased reduction in burning of the sugarcane prior to harvesting. In land suitable for mechanisation, it is anticipated that all burning will be eliminated by 2014. This ruling applies to land with fields above a critical threshold size, and having slopes of less than 12 degrees…

These fires and the resultant smoke and steam plume can be seen from miles around in the countryside regions of Sao Paulo. Burning is restricted already, for example it is not allowed within a specified proximity to roads, urban areas, railways, preservation areas, etc.