What is Biomass Energy?- Definition, and Types

What is biomass energy?

Biomass energy is energy generated or produced by living or once-living organisms. Biomass is organic, meaning it is made of material that comes from living organisms, such as plants and animals. The most common biomass materials used for energy are plants, wood, and waste. These are called biomass feedstocks.

People have used biomass energy—energy from living things since the earliest “cavemen” first made wood fires for cooking or keeping warm.

Biomass energy can also be a non-renewable energy source. Biomass contains energy first derived from the sun: Plants absorb the sun’s energy through photosynthesis, and convert carbon dioxide and water into nutrients (carbohydrates).

The energy from these organisms can be transformed into usable energy through direct and indirect means. Biomass can be burned to create heat (direct), converted into electricity (direct), or processed into biofuel (indirect).

What is Biomass?

Biomass is a plant or animal material used as fuel to produce electricity or heat. Examples are wood, energy crops, and waste from forests, yards, or farms. Since biomass technically can be used as a fuel directly (e.g. wood logs), some people use the terms biomass and biofuel interchangeably.

Biomass is renewable organic material that comes from plants and animals. Biomass contains stored chemical energy from the sun. Plants produce biomass through photosynthesis. Biomass can be burned directly for heat or converted to renewable liquid and gaseous fuels through various processes.

Biomass continues to be an important fuel in many countries, especially for cooking and heating in developing countries. The use of biomass fuels for transportation and electricity generation is increasing in many developed countries to avoid carbon dioxide emissions from fossil fuel use.

Types of Biomass

We use four types of biomass today wood and agricultural products, solid waste, landfill gas and biogas, and alcohol fuels (like Ethanol or Biodiesel). Most biomass used today is homegrown energy. Wood, logs, chips, bark, and sawdust, account for about 44 percent of biomass energy.

Biomass energy is energy generated or produced by living or once-living organisms.

1. Wood And Agricultural Products

Most biomass used today is homegrown energy. Wood, logs, chips, bark, and sawdust, account for about 44 percent of biomass energy. But any organic matter can produce biomass energy. Other biomass sources can include agricultural waste products like fruit pits and corncobs.

Wood and wood waste are used to generate electricity. Much of the electricity is used by the industries making the waste; it is not distributed by utilities, it is a process called cogeneration.

Paper mills and sawmills use much of their waste products to generate steam and electricity for their use. However, since they use so much energy, they need to buy additional electricity from utilities.

2. Solid Waste

Burning trash turns waste into a usable form of energy. One ton (2,000 pounds) of garbage contains about as much heat energy as 500 pounds of coal. Garbage is not all biomass; perhaps half of its energy content comes from plastics, which are made from petroleum and natural gas.

Power plants that burn garbage for energy are called waste-to-energy plants. These plants generate electricity much as coal-­red plants do, except that combustible garbage not coal is the fuel used to ­re their boilers.

3. Landfill Gas And Biogas

Bacteria and fungi are not picky eaters. They eat dead plants and animals, causing them to rot or decay. A fungus on a rotting log is converting cellulose to sugars to feed itself. Although this process is slowed in a land­ll, a substance called methane gas is still produced as the waste decays. New regulations require land­lls to collect methane gas for safety and environmental reasons.

Methane gas is colorless and odorless, but it is not harmless. The gas can cause ­res or explosions if it seeps into nearby homes and is ignited. Land­lls can collect methane gas, purify it, and use it as fuel. Methane can also be produced using energy from agricultural and human wastes.

Biogas digesters are airtight containers or pits lined with steel or bricks. Waste put into the containers is fermented without oxygen to produce a methane-rich gas. This gas can be used to produce electricity, or for cooking and lighting.

4. Ethanol

Ethanol is an alcohol fuel (ethyl alcohol) made by fermenting the sugars and starches found in plants and then distilling them. Any organic material containing cellulose, starch, or sugar can be made into ethanol. The majority of the ethanol produced in the United States comes from corn.

New technologies are producing ethanol from cellulose in woody ­bers from trees, grasses, and crop residues. Today nearly all of the gasoline sold in the U.S. contains around 10 percent ethanol and is known as E10. In 2011, the U.S.

Environmental Protection Agency (EPA) approved the introduction of E15 (15 percent ethanol, 85 percent gasoline) for use in passenger vehicles from the model year 2001 and newer. Fuel containing 85 percent ethanol and 15 percent gasoline (E85) quali­es as an alternative fuel.

5. Biodiesel

Biodiesel is a fuel made by chemically reacting alcohol with vegetable oils, animal fats, or greases, such as recycled restaurant grease. Most biodiesel today is made from soybean oil. Biodiesel is most often blended with petroleum diesel in ratios of two percent (B2), ­ve percent (B5), or 20 percent (B20). It can also be used as a neat (pure) biodiesel (B100).

Biodiesel fuels are compatible with and can be used in unmodi­ed diesel engines with the existing fueling infrastructure. It is one of the fastest-growing transportation fuels in the U.S. Biodiesel contains virtually no sulfur, so it can reduce sulfur levels in the nation’s diesel fuel supply, even compared with today’s low-sulfur fuels.

While removing sulfur from petroleum-based diesel results in poor lubrication, biodiesel is a superior lubricant and can reduce the friction of diesel fuel in blends of only one or two percent. This is an important characteristic because the Environmental Protection Agency now requires that sulfur levels in diesel fuel be 97 percent lower than they were prior to 2006.

Converting biomass to energy

Biomass is converted to energy through various processes, including

  • Direct combustion (burning) to produce heat
  • Thermochemical conversion to produce solid, gaseous, and liquid fuels
  • Chemical conversion to produce liquid fuels
  • Biological conversion to produce liquid and gaseous fuels

Direct combustion is the most common method for converting biomass to useful energy. All biomass can be burned directly for heating buildings and water, for industrial process heat, and for generating electricity in steam turbines.

Thermochemical conversion of biomass includes pyrolysis and gasification. Both are thermal decomposition processes in which biomass feedstock materials are heated in closed, pressurized vessels called gasifiers at high temperatures. They mainly differ in the process temperatures and the amount of oxygen present during the conversion process.

  • Pyrolysis entails heating organic materials to 800–900oF (400–500 oC) in the near complete absence of free oxygen. Biomass pyrolysis produces fuels such as charcoal, bio-oil, renewable diesel, methane, and hydrogen.
  • Hydrotreating is used to process bio-oil (produced by fast pyrolysis) with hydrogen under elevated temperatures and pressures in the presence of a catalyst to produce renewable diesel, renewable gasoline, and renewable jet fuel.
  • Gasification entails heating organic materials to 1,400–1700oF (800–900oC) with injections of controlled amounts of free oxygen and/or steam into the vessel to produce a carbon monoxide and hydrogen-rich gas called synthesis gas or syngas. Syngas can be used as fuel for diesel engines, heating, and for generating electricity in gas turbines. It can also be treated to separate the hydrogen from the gas, and the hydrogen can be burned or used in fuel cells. The syngas can be further processed to produce liquid fuels using the Fischer–Tropsch process.

A chemical conversion process known as transesterification is used for converting vegetable oils, animal fats, and greases into fatty acid methyl esters (FAME), which are used to produce biodiesel.

Biological conversion includes fermentation to convert biomass into ethanol and anaerobic digestion to produce renewable natural gas. Ethanol is used as a vehicle fuel. Renewable natural gas—also called biogas or biomethane is produced in anaerobic digesters at sewage treatment plants and at dairy and livestock operations. It also forms in and may be captured from solid waste landfills. Properly treated renewable natural gas has the same uses as fossil fuel natural gas.

Researchers are working on ways to improve these methods and to develop other ways to convert and use more biomass for energy.

How much biomass is used for energy?

In 2019, biomass provided nearly 5 quadrillion British thermal units (Btu), equal to about 5% of total primary energy use in the United States. Of that 5%, about 46% was from wood and wood-derived biomass, 45% was from biofuels (mainly ethanol), and 9% was from the biomass in municipal wastes.

The amounts, in trillion British thermal units (TBtu), and percentage shares of total U.S. biomass energy use by the consuming sector in 2019 were

  • industrial—2,451 TBtu—49%
  • transportation—1,410 TBtu—28%
  • residential—529 TBtu—11%
  • electric power—448 TBtu—9%
  • commercial—146 TBtu—3%

The industrial and transportation sectors account for the largest amounts, in terms of energy content, and the largest percentage shares of total annual U.S. biomass consumption. The wood products and paper industries use biomass in combined heat and power plants to process heat and generate electricity for their own use. Liquid biofuels (ethanol and biomass-based diesel) account for most of the transportation sector’s biomass consumption.

The residential and commercial sectors use firewood and wood pellets for heating. The commercial sector also consumes, and in some cases, sells renewable natural gas produced at municipal sewage treatment facilities and at waste landfills.

The electric power sector uses wood and biomass-derived wastes to generate electricity for sale to the other sectors.

Advantages of Biomass Energy

Some of the advantages of biomass energy are:

  • Biomass is always and widely available as a renewable source of energy. The organic materials used to produce biomass are infinite since our society consistently produces waste such as garbage, wood, and manure.
  • It is carbon neutral. As a natural part of photosynthesis, biomass fuels only release the same amount of carbon into the atmosphere as was absorbed by plants in the course of their life cycle.
  • It reduces the overreliance on fossil fuels. Not only is there is a limited supply of fossil fuels, but fossil fuels come with environmental baggage, including the release of large amounts of carbon dioxide into the atmosphere and the pollutants that result from removal, transportation, and production.
  • Is less expensive than fossil fuels. While fossil fuel production requires a heavy outlay of capital, such as oil drills, gas pipelines, and fuel collection, biomass technology is much cheaper. Manufacturers and producers can generate higher profits from a lower output.
  • Biomass production adds a revenue source for manufacturers. Producers of waste can add value by channeling their garbage to create a more profitable use in the form of biomass energy.
  • Less garbage in landfills. By burning solid waste, the amount of garbage dumped in landfills is reduced by 60 to 90 percent, reducing the cost of landfill disposal and the amount of land required for landfill.

Disadvantages of Biomass energy

While the disadvantages of biomass energy are plenty, there are also some shortcomings, including:

  • Biomass energy is not as efficient as fossil fuels. Some biofuels, like Ethanol, are relatively inefficient as compared to gasoline. In fact, it has to be fortified with fossil fuels to increase its efficiency.
  • It is not entirely clean. While biomass is carbon neutral, the use of animal and human waste escalates the number of methane gases, which are also damaging to the environment. Additionally, the pollution created from burning wood and other natural materials can be considered just as bad as that resulting from burning coal and other types of energy resources.
  • Can lead to deforestation. Since wood is one of the most used sources of biomass energy, vast amounts of wood and other waste products have to be burned to produce the desired amount of power. While currently there is enough wood waste already, there is a risk of deforestation in the future.
  • Biomass plants require a lot of space. While it’s difficult to find a plant that is in a convenient place in an urban area companies can create biomass energy at a fraction of the space of a large facility.

What are the main advantages and disadvantages of biomass?

Advantages of Biomass EnergyDisadvantages of Biomass Energy
It is RenewableIt’s Not Completely Clean
Carbon NeutralityHigh Costs in Comparison to Other Alternatives
Less Dependency on Fossil FuelsPossible Deforestation
It Is VersatileSpace
AvailabilityIt Requires Water
Low Cost in Comparison to Fossil FuelsIt Has Inefficiencies
It Reduces WasteIt’s Under the Development