Hovv Carre Sugar is Made
Sugar cane is a sub-tropical and tropical crop that prefers lots of sun and lots of water -
provided that its roots are not waterloqged.lt typically takes about l2 months to reach maturity
although the time varies widely arounb tne woriO from as short as six months in Louisian ato Z4
months in some places. Where it differs from many crops is that it regrows from the roots so the p,ant
lasts many cycles [or 'ratoons', a word derived from the Spanish to sprout] before it is worn out.
Sugar cane is haryested by chopping down the stems but leaving the roos so that it regrows
in time for the next crop. Harvest times tend to be during the dry season and the length of the harvest
ranges fuom as little as 2 thmonths up to I I months. The cane is taken to the factory: often bytruck or
railwagon but sometimes on a cart pulled bya bullock ora donkel
The first stage of processing is the extraction of the canejuice. ln many factories the cane is
crushed in a series of large roller mills: similar to a mangle [wringerJ which was used to squeeze the
water out of clean washing a century ago. The sueetjuice comes gushing out and the cane ftber is
cartied away for use in the boilers. ln other factories a difr.rser is used as is described for beet sugar
manufacture. Either way thejuice is pretty dtrfy: the soil from the fields, some small fibers and the
green ocracts from the plant are all mixed in with the sugar.
The factory can clean up thejuice quite easily with slaked lime {a relative of chalkf which
settles out a klt of the dirt so that it can be sent back to the fields. Once this is done, thejuice is
thickened up into syrup by boiling offthe water using steam in a process called evaporation.
sometimes the syrup is cleaned up again but more often itjust goes on to the crystal-making step
wjthout any more cleaning. The evaporation is undertaken in order to improve the energy efficiency
of the faAory.
The syrup is placed into a very large pan for boiling, the last stage. ln the pan even more water
is boiled off until conditions are right for sugar cryrstals to grow. You may have done something like
this at school but probably not with sugar becauie it is difficult to get the cryatals to grow weillln the
factory the workeE usually have to throw in some sugar dust to initiate cnntal formation. Once the
crlrtals have grown the resulting mixture of crystals and mother liquor is spun in centrifuges to
separate the two, ratherlike washing is spin dried. The crlrstals are then given a final dry with hot air
before being stored ready for dispatch.
The final raw sugar forms a sticlqy brown mountain in the store and looks rather like the soft
brown sugar found in domestic kitchens. lt could be used,ike that but usually it gets ditytnstorage
and has a distinctive taste which most people don't want. That is why it is refined when it gets to tne
country where it will be used. Additionally, because one cannot get all the sugar out of thajuice, there
is a svveet byproduct rnade: molasses. This is usually turned into a cattle food-or is sent to a distittery
where alcohol is made.
So what happened to allthat fiber from crushing the sugar cane? lt is called "bagasse' in the
industry. The factory needs electricityand steam to run, both of which are generated using this fiber.
The bagasse is burnt in large furnaces where a lot of heat is given out which can bE used in
turn to boil water and make high pressure steam. The steam is then used to drive a turbine in order to
ryake eharicity and create low pressure steam for the sugar making process. This is the same process
that makes most of our electricity but there are several important differences.
When a large power station produces electricity it burns a fossil fuel [once used, a fuelthat
cannot be replacedJ which contaminates the atmosphere and the station has to dump a lot of low
grade heat. All this contributes to global warming. ln the cane sugar factory the bagasse fuel is
renewable and the gases it produces. essentially COZ, are more than used up bythe new cane