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Describe the effects of the use of biomass in power generation on the environment.

Biomass Energy

The United States Energy Information Agency (EIA) describes biomass as “renewable organic material that comes from plants and animals.” Until the mid-1800s, biomass was the largest source of energy in the United States. Even today, biomass is an important source of energy, especially for cooking and heating in developing countries.

Biomass obtains its energy from the sun through photosynthesis.

Leaf photosynthesis: CO2 is absorbed from air, water is absorbed from soil, glucose is used, and O2 is released to air. — **Photosynthesis is the process plants use to make glucose from CO₂, water, and light energy.**

Although many people think mainly of wood as biomass, the EIA considers several other sources to also be biomass:

an informational graphic that visually represents different types of biomass, including ‘garbage’, ‘crops’, ‘alcohol fuels’, ‘landfill gas’, and ‘wood’. — **Biomass is more than just wood.**

The energy in biomass can be released in several ways including direct combustion, thermochemical combustion, chemical conversion, and biological conversion.

Each method has some benefits and drawbacks, of course. Regardless of these challenges, biomass can be used as a renewable energy source far into the future. Explore the tabs below to learn more about each type of biomass production. After reading through the tabs, would you drive a french fry truck? Why or why not?

Direct
Thermochemical
Chemical
Biological

Direct Combustion

a close-up view of a fire burning on a bed of small, cylindrical wood pellets. — **Burning wood for heat is direct combustion.**

What is it?

Organic materials such as wood, crop residues, or animal waste are burned to generate heat. This heat is used to produce steam, which drives turbines to generate electricity.

Benefits:

✅ Simple

✅ Well-established process

Drawbacks:

❌ can lead to air pollution and release of greenhouse gases

❌ can lead to deforestation, reducing a carbon sink, climate moderator, and habitat for many species

❌ growing plants for energy requires a lot of space and would compete with food for agricultural land

Thermochemical Combustion

an industrial building, likely a factory or power plant, with a tall chimney emitting a plume of smoke against a clear blue sky. — **Thermochemical combustion is more efficient than direct combustion.**

What is it?

By controlling the amount of oxygen in a super-heated chamber, fuels such as charcoal, bio-oil, renewable diesel, methane and hydrogen can be produced through pyrolysis. Gasification of biomass can produce syngas, a mixture of carbon monoxide and hydrogen. Syngas can be used directly as a fuel, or the hydrogen can be separated from the carbon monoxide to be used in hydrogen fuel cells.

Benefits:

✅ Higher energy efficiency

Drawbacks:

❌ requires advanced technology

❌ process must be carefully controlled

❌ can lead to deforestation, reducing a carbon sink, climate moderator, and habitat for many species

❌ growing plants for energy requires a lot of space and would compete with food for agricultural land

Chemical Combustion

a clear glass flask containing a golden liquid, likely oil, placed in front of two ears of corn. — **Chemical combustion can produce fuels from fats, oils, and grease.**

What is it?

Produces biodiesel through the process of transesterification, which utilizes catalysts or chemicals to break down organic materials into simpler compounds that can be used as fuels or chemicals. In this process, animal fat, vegetable oils, and greases are turned into fatty acid methyl esters which are then used to produce biodiesel.

In college, my brother-in-law used to go to fast food restaurants and pick up their extra cooking oil. Then, he'd convert it to gas for his truck. We called his truck the "french fry truck" because it smelled like french fries, but he didn't mind because his gas was free!

Benefits:

✅ potential to produce a wide range of products

Drawbacks:

❌ requires complex processing steps

❌ may involve the use of toxic chemicals

❌ can lead to deforestation, reducing a carbon sink, climate moderator, and habitat for many species

❌ growing plants for energy requires a lot of space and would compete with food for agricultural land

Biological Combustion

a close-up view of a vehicle’s fueling process. — **Ethanol from biological conversion can be added to vehicle fuel.**

What is it?

Biological conversion of biomass involves fermentation and/or anaerobic digestion to produce either renewable natural gas (also called biogas or biomethane) or ethanol. Ethanol is used as an additive in vehicle fuel. Biogas, which also forms in landfills and during the anaerobic digestion process at sewage treatment plants, can be treated and used for the same uses as conventional fossil fuel natural gas.

Benefits:

✅ environmentally friendly

✅ efficiently converts a variety of biomass

Drawbacks:

❌ sensitive to changes in temperature and pH

❌ requires careful monitoring

❌ can lead to deforestation, reducing a carbon sink, climate moderator, and habitat for many species

❌ growing plants for energy requires a lot of space and would compete with food for agricultural land

Essential Knowledge

Burning of biomass produces heat for energy at a relatively low cost, but it also produces carbon dioxide, carbon monoxide, nitrogen oxides, particulates, and volatile organic compounds. The overharvesting of trees for fuel also causes deforestation.

Ethanol can be used as a substitute for gasoline. Burning ethanol does not introduce additional carbon into the atmosphere via combustion, but the energy return on energy investment for ethanol is low.

Waste-to-Energy Plants

Waste produced in society can be burned to produce either electricity or steam for industrial processes. Many countries depend on plants such as this to both provide electricity and dispose of waste. The burning process can reduce the volume of the waste by up to 90%!

As of 2016, Japan led the countries of the world by burning 72% of its solid waste. As a comparison, the United States only burned 13% of its solid waste.

a bar graph displaying the percentage of total municipal solid waste that is burned with energy recovery in selected countries. Japan leads with 72%, followed by Scandinavia at 53%, and Switzerland at 47%. The graph highlights the significant variation in waste management practices across different nations. — **Japan leads the world in biomass energy production.**

Burning waste creates significant amounts of air pollution along with toxic ash. As such, copious amounts of pollution control equipment are needed to avoid widespread contamination of surrounding areas with heavy metals such as lead and mercury. Additionally, the waste ash that is produced must be disposed of carefully to avoid polluting local land and water.

We continue to work to make this process more environmentally safe and to protect the health of humans who live nearby.

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