Technology Research Area:

Biomass Direct Generation

What is biomass direct generation, and what does it have to do with TVA's mission?

Renewable energy sources such as biomass — the name energy experts use for any organic material used as an energy source — have the potential to greatly reduce overall greenhouse gas emissions and could help reduce global warming. Biomass could also reduce other pollutants released into the air during conventional power generation. TVA is committed to using more renewable energy sources for generating power.

Direct power generation with biomass means burning biomass by itself to produce electrical power. Biomass may also be mixed with coal to produce power.

What is TVA doing about it?

TVA is investigating the use of biomass for the direct generation of electricity by converting a coal-fired plant to 100 percent biomass generation.

What are the possibilities for biomass direct generation?

Direct firing of biomass for power generation is a technology that is ready for commercial use. Stoker and fluidized-bed boilers are the two technologies that are usually used for direct biomass power generation.

Alternatives to direct generation include

• modification of existing pulverized coal boiler systems to burn biomass
• replacement of existing systems at the end of their useful life with new systems built for biomass
• building entirely new plants dedicated to burning biomass
• addition of gasification to existing boiler systems, allowing transformation of biomass into syngas for more efficient production of power.

Many of these technologies are already in commercial use; some, such as gasification, are not yet well established on the larger scale required by electric utilities.

There are other possible drawbacks. Biomass could become expensive if supply does not keep up with increased demand. Biomass has a lower heating value than coal, and generation efficiency will drop as its use increases. Alkali in biomass could degrade equipment used to control emission of pollutants at fossil plants.

But rewards could be great. When biomass fuel is grown sustainably, there is no net increase in carbon emissions, a great advantage in the battle against global warming. Biomass is less expensive than other renewable energy sources and increased use of biomass as fuel could benefit the local economy.

The more biomass is used as fuel, the less certain kinds of biomass, such as wood waste, will have to go to landfill. Because decomposition in landfills produces carbon dioxide and methane, biomass generation could reduce these sources greenhouse gases as well.