Direct Combustion in Biomass Power Plants


Giant King Grass is suitable as a fuel for direct combustion (burning) in 100% biomass electricity-generating power plants. Today, biomass power plants are fueled by agricultural and forestry waste such as corn stover, wheat straw, rice husks and wood waste. The price of agricultural waste has increased dramatically in China and India due to market demand, and in many areas, growing Giant King Grass as a dedicated energy crop is less expensive and more reliable than using waste. Agricultural waste is seasonal, because it is only available after the food crop such as corn is harvested. The corn stover must be gathered over long distances because the yield is quite low, then dried, baled, stored and utilized as fuel until the next agricultural waste crop is available. Reliability, consistency and cost of biomass fuel are the major issues facing biomass power plants today. A dedicated Giant King Grass plantation co-located with a power plant is a cost effective and reliable solution to producing clean electricity.

Direct Combustion-Overview

DP CleanTech 30MW Biomass Electric Power Plant Suitable for Giant King Grass

DP CleanTech 30MW Biomass Electric
Power Plant Suitable for Giant King Grass

Giant King Grass has been analyzed by DP CleanTech which has built and operates dozens of biomass power plants in China and Europe. They conclude that Giant King Grass has energy content, physical properties and ash properties very similar to corn stover that they use routinely as a fuel. Other potential customers have analyzed Giant King Grass and have come to the same conclusion. VIASPACE Green Energy is pursuing several opportunities for co-located Giant King Grass plantations and biomass power plants. The fast-growing nature and proven, dependable energy characteristics of Giant King Grass allows power plants to run 24 hours a day, seven days a week without interruption or variable output due to availability or inconsistent performance of the fuel.

Direct combustion (or "direct-fired") systems burn biomass in boilers to produce high pressure steam. The steam turns a turbine connected to a generator-the same kind of steam-electric generator used in fossil fuel power plants. As the turbine rotates, the generator turns, and electricity is produced. This is the simplest and oldest way to generate electricity from biomass. To increase the energy-producing efficiency of direct combustion, power plants also operate cogeneration facilities, which capture waste heat and "secondary" steam and use it to heat buildings and provide steam and heat for industrial processes such as ethanol production or drying of chemical and wood products.


Schematic of Direct Combustion Process

Schematic of Direct Combustion Process. Biomass is delivered and burned in the
boiler which heats water into steam that powers a steam turbine and generator.

Agricultural waste and Giant King Grass have different properties than coal and require a different boiler technology. Biomass power plants are usually 10 to 30 MW in size which is much smaller than coal power plants at 500 to 2000 MW. Most of the world's biomass power plants use direct combustion to produce renewable and low carbon electricity. Existing coal power plants can be readily modified to replace up to 20% of their coal with biomass pellets, but their boiler technology cannot accommodate 100% biomass.




Corn Stover bales at DP CleanTech power plant. Baling is only necessary if the fuel needs to be transported over long distances and stored or stored for several months. The bales are broken up before entering the boiler.

Corn stover bales at DP CleanTech power plant.
Baling is only necessary if the fuel needs to be
transported over long distances and stored
or stored for several months. The bales are broken
up before entering the boiler.

In a warm area, Giant King Grass that is co-located with the biomass power plant can utilize year round just-in-time harvesting to eliminate the need for bailing and long-term storage of the fuel. This is a major logistical advantage that lowers costs. Direct combustion power plants have a much lower capital investment than solar power, and equipment is widely available. By using high yielding Giant King Grass, the cost of electricity is much cheaper than solar electricity. Furthermore, biomass can produce low carbon electricity 24 hours a day which is needed for "base power" applications.