They can also use wastewaters, recycle fertilizers, and have lower overall greenhouse gas emissions than conventional biofuels or animal feeds. The high biomass yields of microalgae cultures allows efficient use of land and water resources. Microalgae have both potentially high yields (tons biomass/acre-year) and can be used for biofuels or high value animal feeds. The Orlando Utilities Commission (OUC) operates an approximately 900-MWe coal fired-power plant at Stanton Energy Center (SEC), which was the site for this project to develop an integrated process for microalgae utilization of flue gas CO 2 for the production of biofuels and animal feeds. Direct application of municipal wastewater to a dry-land Energy Plantation has been analyzed, also. In a second project, the PEF model has been expanded and generalized by analyzing possible model improvements in the areas of materials transportation, water and nutrients balances, other types of wetlands biological systems, and improvements in wood-fired combustion systems. In the initial study, a general technoeconomic model was used to investigate possible interactions between more » the various subsystems. Effluents and by-products from one system part can be beneficially used by other parts, leading to increased energy conversion and resource recovery at lower costs. Products of a PEF are electricity from the power plant (produced via combustion of woody biomass), synthetic natural gas from digestion of the wetlands biomass, and reclaimed wastewater. = ,Ī Photosynthesis Energy Factory (PEF) is an integrated bioconversion system consisting of a dry-land Energy Plantation, a wood-fired power plant, and a wetlands biological wastewater treatment system, such as an algae pond.
A major possible extension of the PEF concept is to include the possibility for irrigation. The following sites are recommended for more detailed evaluation as potential more » demonstration sites: Pensacola, Florida Jamestown, New York Knoxville, Tennessee Martinsville, Virginia, and Greenwood, South Carolina. Analysis of the Energy Plantation subsystem at 15 sites revealed that plantations of 24,000 to 36,000 acres produce biomass at the lowest cost per ton.
This system does not recycle CO/sub 2/ from the flue gas. Using only conventional or near-term technology, the most cost-effective algae pond for a PEF is the carbon-limited secondary treatment system. The cost of electricity was as low as 35 mills per kilowatt-hour for a typical municipally-owned PEF consisting of a 65-MWe power plant, a 144-acre algae pond, and a 33,000-acre Energy Plantation. The algae pond also produces fertilizer, which reduces the cost of the biomass produced on the Energy Plantation, and some gas. Designed to produce algae up to the limit of the amount of carbon in municipal wastewater, the algae pond provides a positive cash credit, resulting mainly from the wastewater treatment credit, which may be used to reduce the cost of the Photosynthesis Energy Factory (PEF)-generated electricity. This quantitative assessment of the potential of a combined dry-land Energy Plantation, wood-fired power plant, and algae wastewater treatment system demonstrates the cost-effectiveness of recycling certain by-products and effluents from one subsystem to another.
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