Sugarcane - Bioenergy Crop Plants - page 524

21.7 Sugarcane Improvement Tools: Marker-Assisted Breeding and Transgenics .................... 536
21.7.1 Genetic Maps and Molecular Markers ................................................................. 536
21.7.2 Transgenics ........................................................................................................... 537
21.8 Sugarcane Functional Genomics and Bioinformatics ........................................................ 538
21.9 Conventional Bioethanol Production ................................................................................. 542
21.9.1 Extraction, Juice Treatment, Concentration, and Sterilization ............................ 543
21.9.2 Fermentation ......................................................................................................... 543
21.9.3 Distillation and Dehydration ................................................................................544
21.9.4 Simulations for Increasing Efficiency of Hydrated Bioethanol Production ......... 544
21.9.4.1 Ordinary Distillation ...........................................................................544
21.9.4.2 Multiple Effect Distillation .................................................................. 545
21.9.5 Simulations for Increasing Efficiency of Anhydrous Ethanol Production ........... 545
21.9.5.1 Azeotropic Distillation ......................................................................... 546
21.9.5.2 Extractive Distillation ........................................................................... 546
21.9.6 Simulations for Increasing Efficiency of Extraction Processes ............................ 546
21.10 Cellulosic Ethanol Production ............................................................................................ 547
21.11 Future Prospects: Research and Development for Productivity and Sustainability ........... 549
References ...................................................................................................................................... 552
21.1 IntroductIon
Sugarcane is a tropical grass of the Poacea family and Saccharum genus and comprises several spe-
cies although plants presently cultivated are mostly hybrids derived from S . officinarum , S. spon-
taneum , S. robustum , S. sinnensis , and S. barberi (Figueiredo 2008). Sugarcane is originated from
Asia; the exact center of origin is unknown, but evidence points to Polynesia, New Guinea, India,
China, Fiji Islands, and Tahiti. There are reports that S. officinarum was known in 6000 BC in India
(Daniels et al. 1975). Sugarcane was already cultivated in the Middle East before the Christian era.
Later the Arabs introduced the plant in Europe and from there it spread to America and parts of
Africa in the early fifteenth century with the start of colonization (Figueiredo 2008).
Sugarcane is highly efficient in biomass accumulation. Its C 4 carbon metabolism allows for
increased photosynthesis at high temperatures and efficient carbon assimilation, which leads to
the highest yields produced among grasses. In fact, the “C 4 ” combination of biochemical and
morphological specializations was discovered in sugarcane (Kortschak et al. 1965; Hatch and
Slack 1966). Nowadays, sugarcane is grown in more than 100 countries (FAOSTAT 2009), mostly
between the parallels 35°N and 35°S, covering an area of about 22 million ha and with a yield of
approximately 1.6 billion tons of cane (Table 21.1), which represents 0.45% of the world's agri-
cultural area and 1.6% of the arable area, with Brazil, India, and China topping the list. Data of
2007 show that these countries account for almost 63% of the world's cane production; the cor-
responding figure for Brazil alone is 33% (Table 21.1). In the last 20 years, sugarcane production
grew approximately 57% worldwide. In Brazil, the sugarcane production will reach 664 million
tons in 2010/2011.
Among the world's four most productive crops—rice, wheat, maize, and sugarcane — sugarcane
produces the greatest crop tonnage and provides the fourth highest quantity of plant calories in the
human diet (Ross-Ibarra et al. 2007) even though each of the major cereals occupy a severalfold
larger fraction of the world's arable land. The stalks of most commercial varieties contain 10-16%
fibers and 84-90% juice. The latter contains 75-82% water and 18-25% soluble solids of which the
greater part (15-24% of the sugarcane juice) is sucrose; 1-2.5% are nonsugars such as amino acids,
fatty acids, waxes, and mineral components (Stupiello 1987). Therefore, 1 t of sugarcane yields
approximately 130-170 kg of sucrose.
Sugarcane is nowadays a source of food, feed, biofuels, and bioelectricity. Soon, biopolymers
will also be added to the product list. Sugarcane ethanol is produced through the fermentation of