Sugar cane harvesting

In the area of sugar cane harvesting, the objectives are to improve the equipment and procedures for recovering the cane trash, whilst also studying side effects such as decrease in the use of herbicides. A second objective is to make realistic assessments of the cane recovery potential, fuel quality and the associated cost. 

CURRENT PRACTICES IN SUGAR CANE HARVESTING AND IN SUGAR MILL ENERGY MANAGEMENT... 

The sugar cane harvesting period, with few exceptions, is five to six months, which is also the seasonal period for the sugar mill. Normal practice, with a few exceptions (e g. in Cuba), is to set the fields on fire prior to harvesting, and then harvest the sugar cane stalks manually or automatically. This practice leads to the release of a huge amount of fumes and other contaminants detrimental to the local air quality. Also, the fires release unbumed hydrocarbons which contribute to the greenhouse effect. 

Unbumed sugar cane harvesting 100% in S3o Paulo State and 50% in the rest of the country. The State of S3o Paulo, in accordance with environmental laws, will harvest almost all its cane unbumed. Approximately 55% of Brazil s sugar cane area can be mechanized, and therefore harvested unbumed. 

Table I Availability of Dry Biomass Residues from Sugar Cane Harvesting... 

Yield is 861 dry ethanol (density 0.79 kg/1) per tonne sugar cane harvested at a water content of 72.5 %, or 247 kg ethanol per tonne dry sugar cane (Macedo et al. 2004 as cited by JRC 2007). 

Just like the sensitivity of sugar cane to the hurricane, the sensitive varieties of citrus show a certain degree of permanent productivity reduction which is seen at a maximum at harvest. 

The harvested sugar cane is transported to the sugar mill and, during the milling process, sugar is extracted for use or for further processing by fermentation to yield alcohol. As a side product, bagasse, at a moisture content of about 50%, is recovered for use as a fuel. 

The potential of sugar canc residues is approximately 14% of the mass of stalks. This means that for each tonne of sugar cane stalks, there is 140 kg of dry residues. This potential is only slightly lower than the bagasse yield itself and therefore the biomass potential can, theoretically, be almost doubled by using green harvesting. 

Paraquat is used as a broad-spectrum herbicide on weeds and grasses in agricultural and nonagricultural areas. It is used as a desiccant on tomatoes, cotton, beans, soybeans, potatoes, sunflowers, and sugar cane to aid in harvesting and to induce resin soaking on pine trees. 

For both the cases of methanol production and the use of vehicle-mounted gasifiers, additional investments will be associated with facilities and equipment for harvesting and transport of the biomass to the conversion sites. In the case of ethanol production from currently produced sugar cane juice or molasses, the conversion facilities would be constructed adjacent to sugar mills that already are receiving the biomass raw material. Thus, additional investments for harvesting and transport equipment would not be required. 

The composition of molasses varies from year to year, since it depends on many factors, such as variety of sugar cane or beet, soil type, climatic conditions (rainfall, sunshine), time of harvesting, process conditions, etc. 

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