Bio-ethanol is obtained from the conversion of carbon based feedstock. The feedstock used for Bioethanol production can be grouped as following
- Sugary Crops- Sugarcane, sugar beet, rotten fruits and molasses.
- Starchy Crops- sorghum, grain sorghum, switch grass, poplar, barley, hemp,
- potatoes, sweet potatoes, cassava, sunflower, stover, grain, wheat.
- Cellulosic Crops- wood, paper, straw and cotton.
- Other biomass-whey or skim milk, grass, agricultural residues.
Sugarcane or Sugar cane (Saccharum) is a genus of 6 to 37 species of tall grasses belonging to family Poaceae, native to temperate and tropical regions of the Old World. The stalk is stout, jointed, fibrous that are rich in sugar and measure 2 to 6 meters tall. All of the sugarcane species interbreed and the major commercial cultivars are complex hybrids
Cultivation and uses:
About 200 countries grow the crop sugarcane to produce 1,324 million tons. Uses of sugar cane include the production of sugar, molasses, rum, and ethanol for fuel. Sugarcane cultivation requires a tropical or subtropical climate, with a minimum of 600 mm (24 in) of annual moisture. It is one of the most efficient photosynthesizers in the plant kingdom able to convert up to 2 percent of incident solar energy into biomass. Sugarcane is propagated from cuttings, rather than from seeds; although certain types still produce seeds, modern methods of stem cuttings have become the most common method of reproduction. Each cutting must contain at least one bud, and the cuttings are usually planted by hand. Once planted, a stand of cane can be harvested several times; after each harvest, the cane sends up new stalks, called ratoons. Usually, each successive harvest gives a smaller yield, and eventually the declining yields justify replanting. Depending on agricultural practice, two to ten harvests may be possible between plantings.
Maize (Zea mays ssp. mays), also known as corn, is native to Mesoamerica. However, it is popularly called corn in the United States, Canada, New Zealand, and Australia. Corn is a shortened form of “Indian corn”, i.e. the Indian grain. It is called mealies in Southern Africa. Some maize varieties grow 7 m (23 ft) tall at certain locations; commercial maize has been bred for a height of 2.5 m (8 ft). Sweetcorn is usually shorter than field-corn varieties. Stem has the resemblance of bamboo canes and the joints (nodes) are about 20–30 cm (8–12 in) apart. Maize has a very distinct growth form, the lower leaves being like broad flags, 50–100 cm long and 5–10 cm wide (2–4 ft by 2–4 in); the stems are erect, conventionally 2–3 m (7–10 ft) in height, with many nodes, casting off flag-leaves at every node. Under these leaves and close to the stem grow the ears.
Cultivation and uses
Maize (Zea mays) is widely cultivated throughout the world and a greater weight of maize is produced each year than any other grain. While the United States produces almost half of the world’s harvest, other top producing countries are as widespread as China, Brazil, France, Indonesia, and South Africa. The primary use of maize is as a feed for livestock, forage, silage or grain. The grain also has many industrial uses, including transformation into plastics and fabrics. Maize is hydrolyzed and enzymatically treated to produce syrups, particularly high fructose corn syrup, a sweetener; it can be fermented and distilled to produce grain alcohol. Grain alcohol from maize is traditionally the source of bourbon whiskey. Maize is alternatively used as a biomass fuel, such as ethanol
3. Sugar Beet:
Sugar beet (Beta vulgaris L.), a member of the family Chenopodiaceae, is a plant whose root contains a high concentration of sucrose. It is grown commercially for sugar. The sugar beet is directly related to the beetroot, chard and fodder beet, all descended by cultivation from the sea beet. The European Union, the United States, and Russia are the world’s three largest sugar beet producers, although only Europe and Ukraine are significant exporters of sugar from beet. Beet sugar accounts for 30% of the world’s sugar production.
Sugar beet is a hardy biennial plant that can be grown commercially in a wide variety of temperate climates. During its first growing season, it produces a large (1–2 kg) storage root whose dry mass is 15–20% sucrose by weight. In commercial beet production, the root is harvested after the first growing season, when the root is at its maximum size. In most temperate climates, beets are planted in the spring and harvested in the autumn. In warmer climates, sugar beets are a winter crop, being planted in the autumn and harvested in the spring. Beets are planted from a small seed; 1 kg of beet seed comprises 100,000 seeds and will plant over a hectare of ground (1 lb will plant about an acre). Unrefined sugary syrup can be produced directly from sugar beet. This sugar beet syrup is widely used for the production of Sugar and Ethanol. Commercially, if the syrup has a Dextrose Equivalency above 30 DE, the product has to be hydrolyzed and converted to a high fructose syrup, much like High Fructose Corn Syrup, or iso-glucose syrup in the EU.
Sorghum is a genus of about 30 species of grasses raised for grain, native to tropical and subtropical regions of Eastern Africa, with one species native to Mexico. The plant is cultivated in Southern Europe, Central America and Southern Asia. Other names include Durra, Egyptian millet, Feterita, Guinea Corn, Jowar, Juwar, kaffir corn, Milo, Shallu and Sudan Grass.
Cultivation and Uses:
Sorghum requires an average temperature of at least 25°C to produce maximum grain yields in a given year. Maximum photosynthesis is achieved at daytime temperatures of at least 30°C. Night time temperatures below 13°C for more than a few days can severely impact the plant’s potential grain production. Sorghum cannot be planted until soil temperatures have reached 17°C. The long growing season, usually 90–120 days, causes yields to be severely decreased if plants are not in the ground early enough. Grain Sorghum is usually planted with a commercial corn seeder at a depth of 2–5 cm, depending on the density of the soil (shallower in heavier soil). The goal in planting, when working with fertile soil, is 50,000 to 300,000 plants per hectare. Therefore, with an average emergence rate of 75%, sorghum should be planted at a rate of 2–12 kg of seed per hectare. It has been found that yields can be boosted by 10-15% when optimum use of moisture and sunlight are obtained by planting in 25 cm rows instead of the conventional 1 m rows. Sorghum in general is a very competitive crop and does well in competition with weeds in narrow rows. Sorghum is the “fifth most important cereal crop grown in the world”. It is used for food, fodder, and the production of alcoholic beverages. It is drought tolerant and heat tolerant and is especially important in arid regions. In India, Sorghum is increasingly being used in recent times as a substitute for sugarcane in the production of ethanol.
Wheat (Triticum spp.) is a grass that is cultivated worldwide. Globally, it is the most important human food grain and ranks second in total production as a cereal crop behind maize; the third being rice
Wheat is widely cultivated as a cash crop because it produces a good yield per unit area, grows well in a temperate climate even with a moderately short growing season and yields versatile, high-quality flour that is widely used in baking. Wheat grain is a staple food used to make flour for leavened, flat and steamed breads; cookies, cakes, pasta, noodles and couscous and for fermentation to make beer, alcohol, biofuel. The husk of the grain, separated when milling white flour, is bran. Wheat is planted to a limited extent as a forage crop for livestock and the straw can be used as fodder for livestock or as a construction material for roofing thatch.
Potato (Solanum tuberosum) is a perennial plant belonging to the family Solanaceae, commonly grown for its starchy tuber. Potatoes are the world’s most widely grown tuber crop and the fourth largest crop in terms of fresh produce (after rice, wheat, and maize), but this ranking is inflated due to the high water content of fresh potatoes relative to that of other crops.
Cultivation and uses:
Potatoes grow best in cool climates with good rainfall or irrigation such as in Western Europe. But they are also widely grown in the subtropical lowlands of the Indo-Gangetic plains of India (as a winter crop) and in the highlands of southwest China (for example, Sichuan and Yunnan province) and in equatorial highlands of Java. Potatoes are generally grown from the eyes of another potato. Potatoes are rich in carbohydrate content and include protein, minerals (particularly potassium) and vitamins. Freshly harvested potatoes retain more vitamin C than stored potatoes.Potatoes also provides starch, flour, alcohol, dextrin, and livestock fodder.
7. Sweet potato:
Sweet potato (Ipomoea batatas) is a crop plant whose large, starchy, sweet-tasting tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. The sweet potato is only distantly related to the potato (Solanum tuberosum). The sweet potatoes are sometimes called “yams”. The plant is a herbaceous perennial vine, bearing alternate heart-shaped or palmately lobed leaves and medium-sized sympetalous flowers. The edible tuberous root is long and tapered, with a smooth skin whose color ranges between red, purple, brown and white. Its flesh ranges between white, yellow, orange, and purple.
Sweet potatoes are cultivated throughout tropical and warm temperate regions wherever there is sufficient water to support their growth. The plant does not tolerate frost. It grows best at an average temperature of 24 °C (75 °F). Depending on the cultivar and conditions, tuberous roots mature in 2 to 9 months. Sweet potatoes rarely flower when the daylight is longer than 11 hours, as is normal outside of the tropics. They are mostly propagated by stem or root cuttings or by adventitious roots called “slips” that grow out from the tuberous roots during storage. True seeds are used for breeding only. Although the leaves and shoots are also edible, the starchy tuberous roots are by far the most important product. In some tropical areas, they are a staple food-crop. Besides starch, they are rich in dietary fiber, vitamin A, vitamin C, and vitamin B6. All cultivars are more-or-less sweet-flavored.Industrial uses include the production of starch and industrial alcohol. All parts of the plant are used for animal feed. In South America the juice of red sweet potatoes is combined with lime juice to make a dye for cloth. By varying the proportions of the juices every shade from pink to purple to black can be obtained.
Switchgrass (Panicum virgatum) also called Tall Panic Grass, is a warm-season plant and is one of the dominant species of the central North America. Other common names for this grass include Wobsqua grass, lowland switchgrass, blackbent, tall prairie grass, wild redtop, and thatch grass. This hardy, perennial grass begins growth in late spring. It can grow up to 1.8-2.2 m in height but is typically shorter than Big Bluestem Grass (Andropogon gerardii) or Indian grass (Sorghastrum nutans). The leaves are 30-90 cm long with a prominent midrib. Due to its hardiness and rapid growth, switchgrass is often considered a good candidate for farming as feedstock or for ethanol production. Switchgrass has the potential to produce the biomass required for production of up to 400 liters of ethanol per metric tonne. A high yield like this makes it a very attractive crop to grow as the value by far exceeds any other crop.
Wood is derived from woody plants, notably trees and also shrubs. Wood from the latter is only produced in small sizes, reducing the diversity of uses. It is the secondary xylem of a woody plant, but this is an approximation only: in the wider sense, wood may refer to other materials and tissues with comparable properties. Wood is a heterogeneous, hygroscopic, cellular and anisotropic material. Wood is composed of fibers of cellulose (40%–50%) and hemicellulose (15%–25%) held together by lignin (15%–30%). Of all the types of wood, Poplar and Willow are most commonly used for Ethanol Production.
Cassava or manioc (Manihot esculenta) is a woody shrub of the Euphorbiaceae that is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrate. The boiled cassava could be diluted to produce a drink called caxiri. Caxiri was often left to ferment for several days and even months. Alternatively chewing and fermentation of cassava gruel produced cauim, a mild alcoholic beverage, which is consumed in vast quantities. Another mild alcoholic beverage pajuaru was made by soaking stacked cassava pancakes in water for three days. This produces a starchy, brown, moldy lump that is then diluted.
Hemp is a common name for Cannabis and the name most used when this annual plant is grown for non-drug purposes. When grown for industrial purposes hemp is often called industrial hemp. Biofuels such as biodiesel and alcohol fuel can be made from the oils in hemp seeds and stalks and the fermentation of the plant as a whole respectively.
Kenaf (Hibiscus cannabinus) is a species of Hibiscus, probably native to southern Asia, though its exact natural origin is unknown. Other names include Bimli, Ambary, Ambari Hemp, Deccan Hemp, and Bimlipatum Jute. The name also applies to the fiber obtained from this plant. Kenaf is one of the allied fibers of jute and shows similar characteristics. The main uses of kenaf fiber are the manufacture of rope, twine, coarse cloth (similar to that made from jute) and paper. Because it is very fast-growing compared to most trees, kenaf is a promising alternative to wood pulp for paper making that could free valuable timber for other uses. Kenaf seeds yield a vegetable oil that, while considered inedible, is used for industrial purposes and as oil-lamp fuel.Emerging uses of kenaf fiber include engineered wood, insulation, and clothing-grade cloth, ethanol production.
Miscanthus is a genus of about 15 species of perennial grasses native to subtropical and tropical regions of Africa and southern Asia, with one species (M. sinensis) extending north into temperate eastern Asia. It can grow to heights of 3.5 m over 5 to 6 years. Its dry weight annual yield can reach 25t/ha (10t/acre). It is sometimes called “Elephant Grass”. The rapid growth, low mineral content and high biomass yield of Miscanthus make it a favorite choice as a biofuel. After harvest, it can be burned to produce heat and power turbines. The resulting CO2 emissions are equal to the amount of CO2 that the plant used up from the atmosphere during its growing phase, and thus the process is greenhouse gas-neutral. When mixed in a 50%-50% mixture with coal, it can be used in some current coal-burning power plants without modifications.
Paper is a fat, thick material produced by the amalgamation of plant fibers, which are subsequently held together without extra binder, largely by oxygen bonds and to a large degree by fiber entanglement. The fibers used are usually natural and composed of cellulose. The most common source of these kinds of fibers is wood pulp from pulpwood trees, largely softwoods such as spruce. However, other vegetable fiber materials including cotton, hemp, linen, and rice may be used. The high cellulose content makes it one of the most favorite raw materials for ethanol production.
Stover consists of the leaves and stalks of corn (maize), sorghum or soybean plants that are left in a field after harvest. It can be directly grazed by cattle or dried for use as fodder (forage). It is similar to straw, the residue left after any cereal grain or grass has been harvested at maturity for its seed. Stover has attracted some attention as a potential alternative fuel source and as biomass for fermentations.
Straw is an agricultural byproduct, the dry stalk of a cereal plant, after the nutrient grain or seed has been removed. Straw makes up about half of the yield of a cereal crop such as barley, oats, rice, rye or wheat. The use of straw as a carbon-neutral energy source is increasing rapidly, especially for biobutanol.
17. Olive Wood & Sunflower Stalk:
Olive wood and sunflower stalks are two of the most abundant, renewable lignocellulosic residues occurring in Mediterranean countries. To date, these crop residues have no specific use but being burnt for domestic use (olive wood) or ground and scattered in the fields. As an alternative, these residues could potentially serve as a low cost feedstock for the production of fuel ethanol.
Following are some of the merits of using Cellulosic Crops for the production of ethanol:
- Low-maintenance crops – Production of a perennial cellulosic biomass crop such as switch grass requires lower inputs of energy, fertilizer, pesticide, and herbicide.
- Recycling of nutrients – Since crops like switchgrass are deep-rooted perennials (i.e., they are not replanted and cultivated every year), their extensive root systems increase nutrient capture, improve soil quality, sequester carbon, and reduce erosion.
- Converting cellulose to ethanol increases the net energy balance of ethanol compared to converting corn to ethanol.
- Cellulosic crops also have significantly lower carbon emissions. While corn-based ethanol reduces carbon emissions by about 20 percent below gasoline, cellulosic ethanol is predicted to be carbon-neutral, or possibly even net-carbon-negative. Cellulosic ethanol use can reduce greenhouse gas emissions.
- Ethanol made from these crops will become cost-competitive, won’t compete with food for cropland, and will have a sizeable positive energy balance.
- Perennial energy crops provide a better environment for more-diverse wildlife habitation.
- Finally, cellulosic biomass differs from corn kernels in that it contains substantial amounts of non-fermentable, energy-rich components that can be used to provide energy for the conversion process as well as to produce electricity.