Sugarcane, or sugar cane, or simply cane, are several species of tall perennial true grasses of the genus Saccharum, tribe Andropogoneae, native to the warm temperate to tropical regions of South Asia, Southeast Asia, and New Guinea, and used for sugar production. It has stout, jointed, fibrous stalks that are rich in the sugar sucrose, which accumulates in the stalk internodes. The plant is two to six metres (six to twenty feet) tall. All sugar cane species can interbreed and the major commercial cultivars are complex hybrids. Sugarcane belongs to the grass family Poaceae, an economically important seed plant family that includes maize, wheat, rice, and sorghum, and many forage crops.
Sucrose, extracted and purified in specialized mill factories, is used as raw material in the food industry or is fermented to produce ethanol. Sugarcane is the world's largest crop by production quantity, with 1.9 billion tonnes produced in 2016, and Brazil accounting for 41% of the world total. In 2012, the Food and Agriculture Organization estimated it was cultivated on about 26 million hectares (64 million acres), in more than 90 countries.
The global demand for sugar is the primary driver of sugarcane agriculture. Cane accounts for 79% of sugar produced; most of the rest is made from sugar beets. Sugarcane predominantly grows in the tropical and subtropical regions (sugar beets grow in colder temperate regions). Other than sugar, products derived from sugarcane include falernum, molasses, rum, cachaça (a traditional spirit from Brazil), bagasse, and ethanol. In some regions, people use sugarcane reeds to make pens, mats, screens, and thatch. The young, unexpanded inflorescence of Saccharum edule (duruka or tebu telor) is eaten raw, steamed, or toasted, and prepared in various ways in Southeast Asia, including Fiji and certain island communities of Indonesia.
Sugarcane was an ancient crop of the Austronesian and Papuan people. It was introduced to Polynesia, Island Melanesia, and Madagascar in prehistoric times via Austronesian sailors. It was also introduced to southern China and India by Austronesian traders at around 1200 to 1000 BC.
The Persians, followed by the Greeks, encountered the famous "reeds that produce honey without bees" in India between the 6th and 4th centuries BC. They adopted and then spread sugarcane agriculture. Merchants began to trade in sugar from India, which was considered a luxury and an expensive spice. In the 18th century AD, sugarcane plantations began in Caribbean, South American, Indian Ocean and Pacific island nations and the need for laborers became a major driver of large human migrations, both the voluntary in indentured servants. and the involuntary migrations, in the form of slave labor.
Sugarcane is a tropical, perennial grass that forms lateral shoots at the base to produce multiple stems, typically three to four m (10 to 13 ft) high and about 5 cm (2 in) in diameter. The stems grow into cane stalk, which when mature constitutes around 75% of the entire plant. A mature stalk is typically composed of 11-16% fiber, 12-16% soluble sugars, 2-3% nonsugars, and 63-73% water. A sugarcane crop is sensitive to the climate, soil type, irrigation, fertilizers, insects, disease control, varieties, and the harvest period. The average yield of cane stalk is 60-70 tonnes per hectare (24-28 long ton/acre; 27-31 short ton/acre) per year. However, this figure can vary between 30 and 180 tonnes per hectare depending on knowledge and crop management approach used in sugarcane cultivation. Sugarcane is a cash crop, but it is also used as livestock fodder.
There are two centers of domestication for sugarcane: one for Saccharum officinarum by Papuans in New Guinea and another for Saccharum sinense by Austronesians in Taiwan and southern China. Papuans and Austronesians originally primarily used sugarcane as food for domesticated pigs. The spread of both S. officinarum and S. sinense is closely linked to the migrations of the Austronesian peoples. Saccharum barberi was only cultivated in India after the introduction of S. officinarum.
Saccharum officinarum was first domesticated in New Guinea and the islands east of the Wallace Line by Papuans, where it is the modern center of diversity. Beginning at around 6,000 BP they were selectively bred from the native Saccharum robustum. From New Guinea it spread westwards to Island Southeast Asia after contact with Austronesians, where it hybridized with Saccharum spontaneum.
The second domestication center is mainland southern China and Taiwan where S. sinense was a primary cultigen of the Austronesian peoples. Words for sugarcane exist in the Proto-Austronesian languages in Taiwan, reconstructed as *t?buS or **CebuS, which became *tebuh in Proto-Malayo-Polynesian. It was one of the original major crops of the Austronesian peoples from at least 5,500 BP. Introduction of the sweeter S. officinarum may have gradually replaced it throughout its cultivated range in Island Southeast Asia.
From Island Southeast Asia, S. officinarum was spread eastward into Polynesia and Micronesia by Austronesian voyagers as a canoe plant by around 3,500 BP. It was also spread westward and northward by around 3,000 BP to China and India by Austronesian traders, where it further hybridized with Saccharum sinense and Saccharum barberi. From there it spread further into western Eurasia and the Mediterranean.
The earliest known production of crystalline sugar began in northern India. The exact date of the first cane sugar production is unclear. The earliest evidence of sugar production comes from ancient Sanskrit and Pali texts. Around the 8th century, Muslim and Arab traders introduced sugar from medieval India to the other parts of the Abbasid Caliphate in the Mediterranean, Mesopotamia, Egypt, North Africa, and Andalusia. By the 10th century, sources state that every village in Mesopotamia grew sugarcane. It was among the early crops brought to the Americas by the Spanish, mainly Andalusians, from their fields in the Canary Islands, and the Portuguese from their fields in the Madeira Islands.
Christopher Columbus first brought sugarcane to the Caribbean during his second voyage to the Americas; initially to the island of Hispaniola (modern day Haiti and the Dominican Republic). In colonial times, sugar formed one side of the triangle trade of New World raw materials, along with European manufactured goods, and African slaves. Sugar (often in the form of molasses) was shipped from the Caribbean to Europe or New England, where it was used to make rum. The profits from the sale of sugar were then used to purchase manufactured goods, which were then shipped to West Africa, where they were bartered for slaves. The slaves were then brought back to the Caribbean to be sold to sugar planters. The profits from the sale of the slaves were then used to buy more sugar, which was shipped to Europe.
France found its sugarcane islands so valuable that it effectively traded its portion of Canada, famously dubbed "a few acres of snow", to Britain for their return of Guadeloupe, Martinique and St. Lucia at the end of the Seven Years' War. The Dutch similarly kept Suriname, a sugar colony in South America, instead of seeking the return of the New Netherlands (New York).
Boiling houses in the 17th through 19th centuries converted sugarcane juice into raw sugar. These houses were attached to sugar plantations in the Western colonies. Slaves often ran the boiling process under very poor conditions. Rectangular boxes of brick or stone served as furnaces, with an opening at the bottom to stoke the fire and remove ashes. At the top of each furnace were up to seven copper kettles or boilers, each one smaller and hotter than the previous one. The cane juice began in the largest kettle. The juice was then heated and lime added to remove impurities. The juice was skimmed and then channeled to successively smaller kettles. The last kettle, the "teache", was where the cane juice became syrup. The next step was a cooling trough, where the sugar crystals hardened around a sticky core of molasses. This raw sugar was then shoveled from the cooling trough into hogsheads (wooden barrels), and from there into the curing house.
In the British Empire, slaves were liberated after 1833 and many would no longer work on sugarcane plantations when they had a choice. British owners of sugarcane plantations therefore needed new workers, and they found cheap labour in China, Portugal and India. The people were subject to indenture, a long-established form of contract which bound them to forced labour for a fixed term; apart from the fixed term of servitude, this resembled slavery. The first ships carrying indentured labourers from India left in 1836. The migrations to serve sugarcane plantations led to a significant number of ethnic Indians, southeast Asians and Chinese settling in various parts of the world. In some islands and countries, the South Asian migrants now constitute between 10 and 50 percent of the population. Sugarcane plantations and Asian ethnic groups continue to thrive in countries such as Fiji, South Africa, Burma, Sri Lanka, Malaysia, Indonesia, Philippines, British Guiana, Jamaica, Trinidad, Martinique, French Guiana, Guadeloupe, Grenada, St. Lucia, St. Vincent, St. Kitts, St. Croix, Suriname, Nevis, and Mauritius.
Between 1863 and 1900, traders and plantation owners from the British colony of Queensland (now a state of Australia) brought between 55,000 and 62,500 people from the South Pacific Islands to work on sugarcane plantations. It is estimated that one-third of these workers were coerced or kidnapped into slavery (known as blackbirding). Many others were paid very low wages. Between 1904 and 1908, most of the 10,000 remaining workers were deported in an effort to keep Australia racially homogeneous and protect white workers from cheap foreign labour.
Cuban sugar derived from sugarcane was exported to the USSR, where it received price supports and was ensured a guaranteed market. The 1991 dissolution of the Soviet state forced the closure of most of Cuba's sugar industry.
About 70% of the sugar produced globally comes from S. officinarum and hybrids using this species.
Sugarcane cultivation requires a tropical or subtropical climate, with a minimum of 60 cm (24 in) of annual moisture. It is one of the most efficient photosynthesizers in the plant kingdom. It is a C4 plant, able to convert up to 1% of incident solar energy into biomass. In prime growing regions, such as Mauritius, Dominican Republic, Puerto Rico, Peru, Brazil, Bolivia, Colombia, Guyana, Ecuador, Cuba, El Salvador, Jamaica, Bangladesh, India, Pakistan, Indonesia, Philippines, Malaysia, Australia and Hawaii, sugarcane crops can produce over 15 kg/m2 of cane. Once a major crop of the southeastern region of the United States, sugarcane cultivation has declined there in recent decades, and is now primarily confined to Florida, Louisiana, and southeast Texas.
Sugarcane is cultivated in the tropics and subtropics in areas with a plentiful supply of water for a continuous period of more than six to seven months each year, either from natural rainfall or through irrigation. The crop does not tolerate severe frosts. Therefore, most of the world's sugarcane is grown between 22°N and 22°S, and some up to 33°N and 33°S. When sugarcane crop is found outside this range, such as the Natal region of South Africa, it is normally due to anomalous climatic conditions in the region, such as warm ocean currents that sweep down the coast. In terms of altitude, sugarcane crop is found up to 1,600 metres or 5,200 feet close to the equator in countries such as Colombia, Ecuador, and Peru.
Sugarcane can be grown on many soils ranging from highly fertile well-drained Mollisols, through heavy cracking Vertisols, infertile acid Oxisols, peaty Histosols, to rocky Andisols. Both plentiful sunshine and water supplies increase cane production. This has made desert countries with good irrigation facilities such as Egypt some of the highest-yielding sugarcane-cultivating regions.
Although some sugarcanes produce seeds, modern stem cutting has become the most common reproduction method. Each cutting must contain at least one bud, and the cuttings are sometimes hand-planted. In more technologically advanced countries like the United States and Australia, billet planting is common. Billets (stalks or stalk sections) harvested by a mechanical harvester are planted by a machine that opens and recloses the ground. Once planted, a stand can be harvested several times; after each harvest, the cane sends up new stalks, called ratoons. Successive harvests give decreasing yields, eventually justifying replanting. Two to 10 harvests are usually made depending on the type of culture. In a country with a mechanical agriculture looking for a high production of large fields, like in North America, sugar canes are replanted after two or three harvests to avoid a lowering in yields. In countries with a more traditional type of agriculture with smaller fields and hand harvesting, like in the French island la Réunion, sugar cane is often harvested up to 10 years before replanting.
Sugarcane is harvested by hand and mechanically. Hand harvesting accounts for more than half of production, and is dominant in the developing world. In hand harvesting, the field is first set on fire. The fire burns dry leaves, and chases away or kills any lurking venomous snakes, without harming the stalks and roots. Harvesters then cut the cane just above ground-level using cane knives or machetes. A skilled harvester can cut 500 kg (1,100 lb) of sugarcane per hour.
Mechanical harvesting uses a combine, or sugarcane harvester. The Austoft 7000 series, the original modern harvester design, has now been copied by other companies, including Cameco / John Deere. The machine cuts the cane at the base of the stalk, strips the leaves, chops the cane into consistent lengths and deposits it into a transporter following alongside. The harvester then blows the trash back onto the field. Such machines can harvest 100 long tons (100 t) each hour; however, harvested cane must be rapidly processed. Once cut, sugarcane begins to lose its sugar content, and damage to the cane during mechanical harvesting accelerates this decline. This decline is offset because a modern chopper harvester can complete the harvest faster and more efficiently than hand cutting and loading. Austoft also developed a series of hydraulic high-lift infield transporters to work alongside their harvesters to allow even more rapid transfer of cane to, for example, the nearest railway siding. This mechanical harvesting doesn't require the field to be set on fire; the remains left in the field by the machine consist of the top of the sugar cane and the dead leaves, which act as mulch for the next round of planting.
The cane beetle (also known as cane grub) can substantially reduce crop yield by eating roots; it can be controlled with imidacloprid (Confidor) or chlorpyrifos (Lorsban). Other important pests are the larvae of some butterfly/moth species, including the turnip moth, the sugarcane borer (Diatraea saccharalis), the African sugarcane borer (Eldana saccharina), the Mexican rice borer (Eoreuma loftini), the African armyworm (Spodoptera exempta), leaf-cutting ants, termites, spittlebugs (especially Mahanarva fimbriolata and Deois flavopicta), and the beetle Migdolus fryanus. The planthopper insect Eumetopina flavipes acts as a virus vector, which causes the sugarcane disease ramu stunt.
Numerous pathogens infect sugarcane, such as sugarcane grassy shoot disease caused by Phytoplasma, whiptail disease or sugarcane smut, pokkah boeng caused by Fusarium moniliforme, Xanthomonas axonopodis bacteria causes Gumming Disease, and red rot disease caused by Colletotrichum falcatum. Viral diseases affecting sugarcane include sugarcane mosaic virus, maize streak virus, and sugarcane yellow leaf virus.
Some sugarcane varieties are capable of fixing atmospheric nitrogen in association with the bacterium Gluconacetobacter diazotrophicus. Unlike legumes and other nitrogen-fixing plants that form root nodules in the soil in association with bacteria, G. diazotrophicus lives within the intercellular spaces of the sugarcane's stem. Coating seeds with the bacteria is a newly developed technology that can enable every crop species to fix nitrogen for its own use.
At least 20,000 people are estimated to have died of chronic kidney disease (CKD) in Central America in the past two decades - most of them sugar cane workers along the Pacific coast. This may be due to working long hours in the heat without adequate fluid intake.
Traditionally, sugarcane processing requires two stages. Mills extract raw sugar from freshly harvested cane and "mill-white" sugar is sometimes produced immediately after the first stage at sugar-extraction mills, intended for local consumption. Sugar crystals appear naturally white in color during the crystallization process. Sulfur dioxide is added to inhibit the formation of color-inducing molecules as well as to stabilize the sugar juices during evaporation. Refineries, often located nearer to consumers in North America, Europe, and Japan, then produce refined white sugar, which is 99 percent sucrose. These two stages are slowly merging. Increasing affluence in the sugar-producing tropics increased demand for refined sugar products, driving a trend toward combined milling and refining.
Sugarcane processing produces cane sugar (sucrose) from sugarcane. Other products of the processing include bagasse, molasses, and filtercake.
The primary use of bagasse and bagasse residue is as a fuel source for the boilers in the generation of process steam in sugar plants. Dried filtercake is used as an animal feed supplement, fertilizer, and source of sugarcane wax.
Molasses is produced in two forms: Blackstrap, which has a characteristic strong flavor, and a purer molasses syrup. Blackstrap molasses is sold as a food and dietary supplement. It is also a common ingredient in animal feed, is used to produce ethanol and rum, and in the manufacturing of citric acid. Purer molasses syrups are sold as molasses, and may also be blended with maple syrup, invert sugars, or corn syrup. Both forms of molasses are used in baking.
Sugar refining further purifies the raw sugar. It is first mixed with heavy syrup and then centrifuged in a process called "affination". Its purpose is to wash away the sugar crystals' outer coating, which is less pure than the crystal interior. The remaining sugar is then dissolved to make a syrup, about 60 percent solids by weight.
The sugar solution is clarified by the addition of phosphoric acid and calcium hydroxide, which combine to precipitate calcium phosphate. The calcium phosphate particles entrap some impurities and absorb others, and then float to the top of the tank, where they can be skimmed off. An alternative to this "phosphatation" technique is "carbonatation", which is similar, but uses carbon dioxide and calcium hydroxide to produce a calcium carbonate precipitate.
After filtering any remaining solids, the clarified syrup is decolorized by filtration through activated carbon. Bone char or coal-based activated carbon is traditionally used in this role. Some remaining color-forming impurities are adsorbed by the carbon. The purified syrup is then concentrated to supersaturation and repeatedly crystallized in a vacuum, to produce white refined sugar. As in a sugar mill, the sugar crystals are separated from the molasses by centrifuging. Additional sugar is recovered by blending the remaining syrup with the washings from affination and again crystallizing to produce brown sugar. When no more sugar can be economically recovered, the final molasses still contains 20–30 percent sucrose and 15–25 percent glucose and fructose.
To produce granulated sugar, in which individual grains do not clump, sugar must be dried, first by heating in a rotary dryer, and then by blowing cool air through it for several days.
Ribbon cane is a subtropical type that was once widely grown in the southern United States, as far north as coastal North Carolina. The juice was extracted with horse or mule-powered crushers; the juice was boiled, like maple syrup, in a flat pan, and then used in the syrup form as a food sweetener. It is not currently a commercial crop, but a few growers find ready sales for their product.
Particulate matter, combustion products, and volatile organic compounds are the primary pollutants emitted during the sugarcane processing. Combustion products include nitrogen oxides (NOX), carbon monoxide (CO), CO2, and sulfur oxides (SOX). Potential emission sources include the sugar granulators, sugar conveying and packaging equipment, bulk loadout operations, boilers, granular carbon and char regeneration kilns, regenerated adsorbent transport systems, kilns and handling equipment (at some facilities), carbonation tanks, multi-effect evaporator stations, and vacuum boiling pans. Modern pollution prevention technologies are capable of addressing all of these potential pollutants.
|Sugarcane production |
(in millions of tonnes)
Global production of sugarcane in 2017 was 1.84 billion tonnes, with Brazil producing 41% of the world total, India producing 17% of the total, and China and Thailand producing about 6% each. (Production statistics for the top twenty producers are shown in the table alongside).
Ethanol is generally available as a byproduct of sugar production. It can be used as a biofuel alternative to gasoline, and is widely used in cars in Brazil. It is an alternative to gasoline, and may become the primary product of sugarcane processing, rather than sugar.
In Brazil, gasoline is required to contain at least 22 percent bioethanol. This bioethanol is sourced from Brazil's large sugarcane crop.
The production of ethanol from sugar cane is more energy efficient than from corn or sugar beets or palm/vegetable oils, particularly if cane bagasse is used to produce heat and power for the process. Furthermore, if biofuels are used for crop production and transport, the fossil energy input needed for each ethanol energy unit can be very low. EIA estimates that with an integrated sugar cane to ethanol technology, the well-to-wheels CO2 emissions can be 90 percent lower than conventional gasoline.
A textbook on renewable energy describes the energy transformation:
Presently, 75 tons of raw sugar cane are produced annually per hectare in Brazil. The cane delivered to the processing plant is called burned and cropped (b&c), and represents 77% of the mass of the raw cane. The reason for this reduction is that the stalks are separated from the leaves (which are burned and whose ashes are left in the field as fertilizer), and from the roots that remain in the ground to sprout for the next crop. Average cane production is, therefore, 58 tons of b&c per hectare per year.
Each ton of b&c yields 740 kg of juice (135 kg of sucrose and 605 kg of water) and 260 kg of moist bagasse (130 kg of dry bagasse). Since the lower heating value of sucrose is 16.5 MJ/kg, and that of the bagasse is 19.2 MJ/kg, the total heating value of a ton of b&c is 4.7 GJ of which 2.2 GJ come from the sucrose and 2.5 from the bagasse.
Per hectare per year, the biomass produced corresponds to 0.27 TJ. This is equivalent to 0.86 W per square meter. Assuming an average insolation of 225 W per square meter, the photosynthetic efficiency of sugar cane is 0.38%.
The 135 kg of sucrose found in 1 ton of b&c are transformed into 70 litres of ethanol with a combustion energy of 1.7 GJ. The practical sucrose-ethanol conversion efficiency is, therefore, 76% (compare with the theoretical 97%).
One hectare of sugar cane yields 4,000 litres of ethanol per year (without any additional energy input, because the bagasse produced exceeds the amount needed to distill the final product). This, however, does not include the energy used in tilling, transportation, and so on. Thus, the solar energy-to-ethanol conversion efficiency is 0.13%.
Sugarcane is a major crop in many countries. It is one of the plants with the highest bioconversion efficiency. Sugarcane crop is able to efficiently fix solar energy, yielding some 55 tonnes of dry matter per hectare of land annually. After harvest, the crop produces sugar juice and bagasse, the fibrous dry matter. This dry matter is biomass with potential as fuel for energy production. Bagasse can also be used as an alternative source of pulp for paper production.
Sugarcane bagasse is a potentially abundant source of energy for large producers of sugarcane, such as Brazil, India and China. According to one report, with use of latest technologies, bagasse produced annually in Brazil has the potential of meeting 20 percent of Brazil's energy consumption by 2020.
A number of countries, in particular those devoid of any fossil fuel, have implemented energy conservation and efficiency measures to minimize energy used in cane processing and furthermore export any excess electricity to the grid. Bagasse is usually burned to produce steam, which in turn creates electricity. Current technologies, such as those in use in Mauritius, produce over 100 kWh of electricity per tonne of bagasse. With a total world harvest of over 1 billion tonnes of sugar cane per year, the global energy potential from bagasse is over 100,000 GWh. Using Mauritius as a reference, an annual potential of 10,000 GWh of additional electricity could be produced throughout Africa. Electrical generation from bagasse could become quite important, particularly to the rural populations of sugarcane producing nations.
Recent cogeneration technology plants are being designed to produce from 200 to over 300 kWh of electricity per tonne of bagasse. As sugarcane is a seasonal crop, shortly after harvest the supply of bagasse would peak, requiring power generation plants to strategically manage the storage of bagasse.
A greener alternative to burning bagasse for the production of electricity is to convert bagasse into biogas. Technologies are being developed to use enzymes to transform bagasse into advanced biofuel and biogas.
In most countries where sugarcane is cultivated, there are several foods and popular dishes derived directly from it, such as:
Many parts of the sugarcane are commonly used as animal feeds where the plants are cultivated. The leaves make a good forage for ruminants.
A video of sugarcane juice extraction