Bagasse

Bagasse (pronounced /bəˈɡæs/ bə-gas) is the fibrous residue remaining after sugarcane or sorghum stalks are crushed to extract their juice.^[1] It is currently used as a biofuel and as a renewable resource in the manufacture of pulp and paper products and building materials.

Agave bagasse is a similar material which consists of the tissue of the blue agave after extraction of the sap.

Contents 1 Production, storage and composition 2 Use 2.1 Fuel 2.2 Paper 2.3 Other products 3 Health impact 4 References

[edit] Production, storage and composition

For each 10 tonnes of sugarcane crushed, a sugar factory produces nearly 3 tonnes of wet bagasse. Since bagasse is a by-product of the cane sugar industry, the quantity of production in each country is in line with the quantity of sugarcane produced.

The high moisture content of bagasse, typically 40 to 50%, is detrimental to its use as a fuel. Generally, bagasse is stored prior to further processing. For electricity production, it is stored under moist conditions and the mild exothermic reaction which results from the degradation of residual sugars dries the bagasse pile slightly. For paper and pulp production, it is normally stored wet in order to assist in removal of the short pith fibres which impede the papermaking process as well as to remove any remaining sugar.

A typical chemical analysis of bagasse might be (on a washed and dried basis):
Cellulose 45–55%
Hemicellulose 20–25%
Lignin 18–24%
Ash 1–4%
Waxes <1%

Bagasse is an extremely inhomogeneous material comprising around 30-40% of "pith" fibre which is derived from the core of the plant and is mainly parenchyma material, and "bast", "rind" or "stem" fibre which comprises the balance and is largely derived from sclerenchyma material. These properties make bagasse particularly problematic for paper manufacture and have been the subject of a large body of literature.

[edit] Use

Many research efforts have explored using bagasse as a renewable power generation source and for the production of bio-based materials.

[edit] Fuel

Bagasse is often used as a primary fuel source for sugar mills; when burned in quantity, it produces sufficient heat energy to supply all the needs of a typical sugar mill, with energy to spare. To this end, a secondary use for this waste product is in cogeneration, the use of a fuel source to provide both heat energy, used in the mill, and electricity, which is typically sold on to the consumer electricity grid.

The resulting CO₂ emissions are equal to the amount of CO₂ that the sugarcane plant absorbed from the atmosphere during its growing phase, which makes the process of cogeneration greenhouse gas-neutral. Florida Crystals Corporation, one of America's largest sugar companies, owns and operates the largest biomass power plant in North America. The 140 MW facility uses bagasse and urban wood waste as fuel to generate enough energy to power its large milling and refining operations as well as supply enough renewable electricity for nearly 60,000 homes. The facility reduces dependence on oil by more than one million barrels per year.^{[citation needed]}

Ethanol produced from the sugar in sugarcane is a popular fuel in Brazil. The cellulose-rich bagasse is now being tested for production of commercial quantities of cellulosic ethanol. Verenium Corporation is building a cellulosic ethanol plant based on cellulosic by-products like bagasse in Jennings, Louisiana. They are using a biotech approach to improve ethanol production above and beyond the midwest corn-based ethanol production method. This will allow regional cellulosic ethanol production, getting around the problem of ethanol transportation. The Verenium approach will deliver ethanol and E85 fuel to markets in California and the Northeast.

[edit] Paper

Around 5–10% of paper production worldwide is produced from agricultural crops, valuing agricultural paper production at between $5 and $10 billion.^[2] One of the most notable of these is bagasse. Paper production is the second largest revenue stream from bagasse, after electricity cogeneration. Using agricultural crops rather than wood has the advantage of reducing deforestation. It is thought that bagasse has the added advantage over other forms of papermaking feedstock in that it requires fewer greenhouse gases to collect, compared to harvesting of wood chips, as the fibre has already been transported to the factory for extracting the sugar. However, there has not been a full life cycle analysis to support this claim. Due to the ease with which bagasse can be chemically pulped, bagasse requires less bleaching chemicals than wood pulp to achieve a bright, white sheet of paper. The fibers vary in length depending on the country and cane variety but are typically about 1.3 to 1.7 mm long. Bagasse fibers are well suited for tissue, corrugating medium, newsprint, and writing paper.^[3][4]

Bagasse pulp and paper mills tend to be smaller than wood-based mills, although many world-scale factories exist.

Most chemical bagasse pulp mills concentrate the spent reaction chemicals and combust them to power the paper mills and to recover the reaction chemicals.

[edit] Other products

Bagasse is used to make insulated disposable food containers, replacing materials such as styrofoam, which are increasingly regarded as environmentally unacceptable (see Polystyrene#Environmental impact).

Sugarcane bagasse has recently been used as the primary ingredient in 'Soex' brand Herbal Shisha. The shisha is sold as 100% tobacco, nicotine and tar free. The health effects of smoking sugarcane bagasse have not been studied.

Bagasse is also made into cattle feed whereby it is mixed with molasses. The resulting byproduct has been marketed in Australia as "cow candy".

Efforts were made in late 1998 to use bagasse as a sorbent material to clean up oil spills. Dr. Gary Breitenbeck, a soil microbiology and environmental researcher in the agronomy department of the LSU Agricultural Center, used milled bagasse to soak up spilled oil and created an environment that sustains the bacteria that digest the goo using ammonia. "Breitenbeck's process puts the bagasse, along with ammonia and air, in a reactor and pumps up the pressure to 1,000 pounds per square inch. The high pressure drives the ammonia into the fibers and produces nitrogen compounds the microbes use to convert the hydrocarbons into humic material."^[5]

[edit] Health impact

Historically, bagasse factories have had harsh working environments due to the process of milling the pulp. Factory workers have reported bleeding hands and arms. Workers must wear masks to prevent breathing in pulp fibres.

Workplace exposure to dusts from the processing of bagasse can cause the chronic lung condition pulmonary fibrosis, more specifically referred to as "bagassosis".^[6]

[edit] References