BioMass

The Problem

Many areas of the world, including the United States, are experiencing energy crises. With more and more electricity being consumed everyday, scientists and engineers are searching for an alternative fuel source. They would like to use a fuel source that is renewable and environmentally friendly. Brazil in particular, has been facing a tremendous energy crisis. The government has implemented a number of measures aimed at cutting electricity consumption, including shutting off a portion of streetlights, turning off air conditioners in government buildings, and penalizing citizens and businesses who do not cut their consumption by at least 20% (see related articles). They have also begun to explore an alternative energy source: biomass (or bagasse). Biomass is organic matter found in wood products, dried vegetation, crop residues, aquatic plants, and sugar cane. The biomass obtained from processing sugar cane is called bagasse. Because Brazil has a large sugar cane industry, there is an abundance of available bagasse. However, the cost of building a plant that converts bagasse into electricity requires a substantial monetary investment. Is bagasse a feasible energy source for Brazil? When will the value of the electricity produced by the plant offset the cost to construct the plant?

Areas of Application

Research and data collection
Mathematical modeling
Reading/interpreting tables
Creating graphs
Linear regression & line of best fit
Cost analysis
Algebra, percents, and ratios

Explanation of Alignment with Standards

Background Information

The following table includes data for a Biomass plant as a co-generation facility at a major sugar/alcohol producer:

FUEL METRICS

Cane Yield	65 tonnes/hectare
Bagasse Yield	28% by weight
Bagasse Water Content	48% water
Bagasse HHV	10,2265 kj/kg high heat value
Fuel at Site (bagasse)	850,000 tonnes/year
Fuel Imported (bagasse)	270,000 tonnes/year

PLANT OUTPUT METRICS

Gross Electric Capacity	80MW
Annual Output	580,000 MWhr
Annual Exported Power	520,000 MWhr
Co-generation Steam	400 tonnes/hr
Supplemental Steam Generated	250 tonnes/hr

When bagasse is burned, several products are produced: ashes � returned to the sugar cane field as fertilizer, steam � converted to energy, methane gas � contained and sent to a power plant

There are many difficulties that must be overcome before biomass can be used to produce energy. For example, biomass plants are capital intensive because extra equipment is required to handle the fuel and process it. This extra capitalization requires that only large generating plants will be economically feasible. Minimum economic plant size requires finding and harvesting very large geographic areas of potential biomass fuel. The fuel will most likely be gathered and concentrated for another economic purpose. To take advantage of this economic symbiosis, the Biomass energy plant must be adaptable to co-generation sites and capable of providing other resources (heat, steam, process gases) beside straight electrical generation.

Another problem is that fuel sources can contain substantial amounts of water and the energy density of the fuel is low and the fuel material itself may be widely distributed. The quality of the fuel will change during its growing season. In particular, the content of water, sugar, starch, and cellulose will vary and proper controls must be in-place in the combustion system to maintain efficiency.

Materials Included

Articles about the Brazilian energy Crisis (BioMass Articles.doc)
List of Problems & Questions to Consider
Suggested approaches and solutions

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Last modified: Jun 25, 2010, 14:49 UTC