Sugar Cane: The Process in pictures

Small-scale, family-owned alcohol plant based on sugar cane, near to Palmital Brazil.

Photography and words by: Dr Peter Wells

Sugar cane, ready to harvest is well over 2m high, and densely packed. Only the top 35% or so of growth is green. Harvesting runs from May to December. Yields are typically 80t/ha and from this 80 litres of alcohol per tonne

Cane croppers coming home. A large proportion of the crop is still manually harvested, and this crop is always burned before cropping with energy and environmental consequences. Note the red dust.

Rail is not used in the harvesting of sugar cane, or much at all in Brazil. The VW Beetle, however, remains a common sight in rural areas

This is mechanical harvesting with an un-burnt crop. The machine throws out the green leafy content, and chops up the cane itself. 2% wastage is compensated for by energy efficiency and better loading of trucks.

Mechanical harvesting requires a team: one harvester, at least two tractors with loading trailers, and a waiting truck with double trailers to take the cane to the alcohol plant.

This is mechanical harvesting of burnt sugar cane. As the alcohol plant only pays for the sugar content, it is often seen as preferable to burn off the leaves. Also on rough ground it helps the machines work over the land.

A double load of burnt, mechanically-harvested cane is loaded onto trucks with two, three or sometimes four trailers. About 20km is the viable range to transport the cane before it is uneconomic

Note the specialist equipment that enables tipping into the truck trailer. Each mechanical 'team' displaces about 80 manual workers, but of course this is more skilled (and expensive) labour.

A field after burning and mechanical cropping. The crop re-grows on the same site, and can remain in situ for 8-10 years. Major pests are controlled with new varieties of cane, and in some cases biological controls.

Burnt, manually harvested cane (note the long lengths) is brought into the alcohol plant by truck.

The truck tips its load of cane into a large 'feeder' machine that controls the flow of cane into the primary cutters and crushers.

Washing the cane is vital to protect the downstream machinery. The water used is warm. The feed into the crushing mills is controlled manually at this point. Too rapid a feed will block the process.

The other side of the washing process shows the cane falling into a feeder conveyor belt from which it is carried into the production process.

Mostly this plant uses electric power generated on-site. However the primary crushing mills are steam powered (also generated on-site) because of the highly variable loads at this stage.

By the end of the crushing process most of the liquid has been extracted and the cane has lost most of its fibrous quality, becoming a more amorphous mass.

Solid waste cane is taken up by this conveyor belt with some fed into the on-site furnace to produce steam, and about 40% un-used at this stage, which is sent out as cattle feed.

This is the deposition of the waste dry cane. In fact it blows around all over the site covering everything (including the photographer and his camera!) with dust.

The owner, contemplating his bank of furnaces. This is a vital part of the economics and energy balance for sugar cane as waste solid matter is burnt to provide steam for the process, and to make electricity.

The in-house generator is able to make up to 1.5MW electricity, and can be used to supply back to the grid.

Starting the generator requires this monster....a Scania truck engine with a CAT generator attached, able to create 450W

A view of the old furnace chimney, no longer in use. This plant dates back to 1944. The tradition of alcohol production from cane goes back much further!

Liquid from the crushed cane is carried by pipe towards the fermentation and distillation stages seen in the background.

The pipelines carrying liquid sugar cane to the fermentation and distillation stage.

Fermentation is carried out in a series of large vessels run on a batch system. Each cycle takes 8 hours from filling to being ready for the distillation stage. Each vessel is 300,000m3.

First, yeast is prepared in the vessel. A special variety is used for best results. Note, however, that in this case the vessel is actually open to the elements.

The sugar cane juice is added to the yeast mix, and is aerated at the same time to help the process along.

More sugar cane juice is added...

The full vessel is then allowed to ferment, these bubbles are carbon dioxide being given off from the fermentation process.

Fermentation is nearly over here, but the bubbles have an abstract beauty.

The distillation process is fairly simple, the alcohol content is progressively increased and the water content reduced.

An overview of the rear of the distillery plant, showing the furnace with chimneys

Finished alcohol is stored on-site in these large containers before being taken by truck to the distribution system.

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