In a multifaceted experiment, NRG Energy set out in 2009 to not only cofire dedicated biomass in its Big Cajun II boilers in Louisiana, but also grow the biomass on-site. Unfortunately, the test crops yielded discouraging results and the power company has shelved its biomass cofiring project for the 1,495-megawatt generating station.
“It was a combination of things that led us to basically shelving the effort for right now,” says David Knox, NRG spokesman.
For the crop trial, a 20-acre plot was seeded with warm-weather and cold-weather switchgrass and sorghum. The warm-weather variant didn’t grow at all and the cold-weather crops produced just 60 percent of NRG’s expectations, according to Knox. “It wasn’t what we had expected and in today’s environment, we decided, let’s move on.” NRG, as well as seed supplier Ceres Inc., is evaluating what factors led to the disappointing yields.
Equally important are two assumptions Knox says were made at the onset of the project that proved incorrect: the fact that a mandatory carbon tax was expected but not implemented; and gas prices then were $15 per million Btu and expected to remain high, but today are $4 per million Btu. Still, while the trial didn’t yield the anticipated results, NRG set out to determine whether the crops could grow successfully in Louisiana’s climate and did just that, he adds.
“It’s not the right time,” he says. “We’re still very interested in any effort that would allow us to reduce our carbon profile and our carbon intensity, and biomass is definitely a part of that.”
Moving on, NRG will work on compliance with the Maximum Achievable Control Technology rules, tweaking backend controls instead of incorporating biomass into the mix. The MACT rules set emission limits for a range of boilers and process heaters. Knox says NRG currently has no plans to replant or plant other types of biomass crops for similar testing and possible use at Big Cajun II.
“[The test] did exactly what we wanted,” he says. “We wanted to test the crops, and the focus right now is to take care of some other things while we’re evaluating the potential for biomass to be an economically viable way to reduce carbon intensity.”