A pilot project begun at NRG Energy’s 1,700-MW Big Cajun II power plant will evaluate local conditions for growing switchgrass and high-biomass sorghum and determine if they could replace a portion of the plant’s combusted coal to reduce its carbon intensity. The project could lead to commercial-scale projects that would substitute biomass for some of the coal burned at NRG’s other carbon-intensive plants, the company said last week.
The pilot project entails sowing improved seed varieties and using growing techniques provided by Ceres, a developer and marketer of high-yield energy grasses. NRG said it is planting 20 acres of land at the power plant site. Switchgrass and high-biomass sorghum were chosen specifically because they suit Louisiana’s soil and climate. They will be managed by a local grower.
“Biomass from locally grown energy grasses has the potential to be an important part of NRG’s multi-pronged approach to reduce our carbon intensity and can also be a source of economic development in rural communities,” said David Crane, NRG’s president and CEO. “In addition to nuclear, wind and solar, energy from biomass has the potential to help support an energy future that addresses global climate change in an environmentally and economically sustainable manner.”
The Big Cajun II test site will deliver data on yield (tons per acre) and other performance factors under local environmental conditions—a first step toward expanding the use of biomass fuels at NRG’s other existing coal facilities. A follow-on phase, expected to be conducted in 2010, will actually use the biomass in fuel blends for electrical generation.
“Due to their low inputs, high yields and photosynthetic efficiency, energy grasses have the potential to provide scalable renewable baseload power to the grid at a scale not possible before. By working together with a leading company like NRG, we can determine the best ways to produce and deliver biomass as a source for biopower and create a model for the bioenergy industry and rural communities,” said Richard Hamilton, president and CEO of Ceres.
The U.S. Department of Energy has identified switchgrass as an ideal dedicated energy crop. As a perennial, once established, switchgrass requires little or no tilling and minimal nitrogen fertilizer and other crop inputs. It can grow over nine feet high and has deep roots that can sequester carbon in the root biomass instead of releasing it into the atmosphere. Similarly, fast-growing high-biomass (nongrain) sorghum hybrids can reach 20 feet tall, while requiring much less water than conventional crops.
Harvested into bales like hay, energy grasses can be dried by the sun and then shredded into fine particles before being fed into the combustion chamber of a power plant, NRG said. “Since the carbon emitted from the grasses was previously absorbed from the atmosphere during the growing season, combusting the above-ground biomass is nearly carbon neutral,” the company said in a statement. “When the extensive root systems of perennial grasses are considered, power from biomass may even be considered carbon negative. Preliminary studies funded by the USDA demonstrated that each acre of switchgrass could sequester up to five tons of CO2-equivalent below ground each year.”
Source: NRG Energy