OWOE - Other Renewables Energy - What is biomass and how is it used for energy?
Figure 1 - Biomass Sources (Eric Delmonaco)
Figure 1 - Biomass Sources (Eric Delmonaco)
Video - US Dept of Energy - Energy 101: Biofuels
Figure 2 - Biomass to Energy Conversion Technologies (NREL)
What is biomass and how is it used for energy?
Topic updated: 2015-09-01
Biomass is defined as biological material derived from living, or recently living, organisms. It most often refers to plants or plant-based materials, which can be utilized in a wide variety of forms, as illustrated in Figure 1. As an energy source, biomass can either be used directly via combustion to produce heat, or indirectly after converting it to various forms of biofuel. Historically, biomass energy has been associated with burning wood, peat, dung, etc. for generating heat. There was a time when biomass in the form of wood was the primary fuel for heating and cooking around the world. Currently, the term is used to capture a variety of fuels and techniques to convert them to energy. The primary of these techniques are:
Direct burning: This is the traditional application for cooking and heat. Although this is not a significant source of energy in the United States, it is still a common practice in developing countries.
Electric generation: Biomass is burned in a boiler to heat water as is done with fossil fuels.
Gassification: Biomass is heated to release biogas, which is primarily methane and carbon dioxide. The biogas is then burned, which converts the methane to carbon dioxide and water, and the heat is used to boil water as in a typical gas-fired steam electrical generation plant.
Anaerobic Digestion: Similar to gasification in which biomass is fermented to convert the organic materials into biogas. Typically, enzymes or catalysts are used to enhance conversion.
Conversion to Biofuels: Biomass, primarily in the form of vegetable oil, is converted to liquid fuel, most commonly ethanol and biodiesel, for use in transportation.
Conversion to hydrogen: Biomass is converted to biogas, which can then be processed to strip out the hydrogen for use in hydrogen fuel cells to generate electricity, e.g., for use in an electric car
The video shows how biomass is converted to fuel, and Figure 2 illustrates the two different paths and associated technologies that biomass plants use to convert plant materials into either power or liquid fuel.
Total biomass electrical power generation in the United States at the end of 2014 was approximately 7 GW which was approximately 1.5% of the total US electrical supply. Currently, the New Hope Power Partnership is the largest biomass power plant in the US. The 140 MW facility uses sugar cane fiber (bagasse) and recycled urban wood as fuel to generate power for its milling and refining operations with the remainder, enough to supply electricity for approximately 60,000 homes, provided to the grid.
Total biofuel generated from biomass during 2014 was approximately 1.2 billion gallons of biodiesel and 14 billion gallons of ethanol, or approximately 5% of the total US transportation fuel consumption.