How Does Biomass Produce Energy?

Biomass is defined as biomaterials from living or recently living organisms, including trees, timber waste, wood chips, corn, rice hulls, peanut shells, sugar cane, grass clippings, leaves, manure, agricultural wastes, and municipal solid waste. Such biomaterials are renewable, as they can be reproduced nearly in perpetuity, as long as there are sufficient materials to grow them, such as sunlight, water, and soil. Biomass energy is electricity and other energy forms that are produced from biomass as a feedstock. Biomass can be used for energy because it is originally produced through the energy from the sun through the process of photosynthesis, and this transformed solar energy can then be harnessed for our own energy purposes, such as electricity generation.

Biomass energy production methods

All biomass energy production methods ultimately rely on the process of photosynthesis in plants, where plants capture sunlight, carbon dioxide from the air, and water and use them to produce carbohydrates. These plant-based carbohydrates are the materials that are used to produce biomass energy.

In general, the two methods for producing biomass energy are by burning the biomass directly and through the gasification of biomass.

1. Direct burning of biomass materials. The biomass materials are burned and the heat that is produced is used to heat water into steam. The steam is then sent through a steam turbine, which generates electricity.
2. Gasification. Wet biomass, such as manure or food waste, undergoes fermentation in a special tank, producing methane. Dry biomass, such as agricultural waste, is subjected to high temperatures in the absence of oxygen, producing synthesis gas (syngas). The gas produced through either process is then burned to produce electricity in a gas engine or a gas turbine.
3. Fuel Cells. If the syngas is pure, it can be utilized in fuel cells for electricity production. This is not yet a commercially-available technology.

Some advantages and disadvantages of biomass energy

As with any other energy source, biomass energy has advantages and disadvantages for its use.

Advantages of Biomass Energy

• Biomass energy can provide a viable solution for what to do with excessive organic waste, such as lumber waste and agricultural waste.
• Because biomass energy production produces both electricity and heat, gas turbines and steam turbines have an approximate 50% efficiency rate, compared to a traditional gas engine with an efficiency of 30-35%[sc:1][sc:comma][sc:2].
• The long-term energy savings of biomass energy typically outweigh the expenses that are associated with biogas plant construction and upkeep.
• Biomass energy can be a net carbon neutral energy source if the biomass crops are replanted after harvesting, thus absorbing the amount of CO₂ emissions during their lifecycle that were generated from the burning of biomass.

Disadvantages of Biomass Energy

• Biomass may be needed for soil enrichment and compost instead of burning it for energy production purposes.
• Net greenhouse gases can be produced when biomass feedstocks are burned and they are not sufficiently replanted.
• Biomass can: be harvested at unsustainable rates, cause damage to ecosystems, cause air pollution, and require large amounts of water for growth.

For more information, check out our article on Biomass Energy Advantages and Disadvantages.

References

[sc:1] http://goo.gl/X5qaDc
[sc:2] http://goo.gl/5TF9WJ