Electricity from Twigs and Trash: Biomass
Electricity consumption from renewable energy sources is 7% of the US consumption total, and 22% of the world's consumption total without the US.
Within the US, biomass makes up 54% of that renewable total. Hydroelectricity makes up 36%. Together, they account for 90% of the renewable energy sources in the US.
Let's we'll talk about biomass as an energy source for producing electricity:
- what it is
- what biomass is used
- how we get the energy out of it
As always, the explanation will be kid-friendly.
What Is Biomass?
The scientists say it's "organic nonfossil material of biological origin constituting a renewable energy source."
What they wanted to say is it's living stuff that dies and can be burnt (such as wood) or that decomposes and gives off gases (such as methane) that can be burnt.
Ever gone camping and had a camp fire or cooked with charcoal? You used biomass fuel.
As a fuel for generating electricity, it includes:
- products you may associate with recycling (such as paper and boxes).
- products with fibers from plants (eg, clothing).
- products made from trees (such as rubber automobile tires).
Separately, biomass is used as a transportation fuel (ethanol from corn) for powering vehicles.
In short, biomass is based on trees and plants that have not had the hundreds of millions of years to decompose and turn into oil and natural gas.
What Biomass Is Used?
Let's take a look at these three areas:
- Wood and wood waste
- Municipal solid waste
- Landfill gas
Wood and Wood Waste
Wood is a substantial renewable resource that can be used as a fuel to generate electric power and useful thermal output. Wood for use as fuel comes from a wide variety of sources.
The top 3 sources are:
- the nation's forestland (or timberland) is the primary, and in most cases original, resource base for fuel wood.
- private land clearing and tree farming, and urban tree and landscape residues.
- waste wood (including manufacturing and wood processing wastes, and construction and demolition debris
Municipal Solid Waste
Municipal solid waste is total waste excluding industrial waste, agricultural waste, and sewage sludge.
The municipal solid waste industry has four components: recycling, composting, land filling, and waste-to-energy via incineration.
As defined by the US Environmental Protection Agency, municipal solid waste includes durable goods, non-durable goods, containers and packaging, food wastes, yard wastes, and miscellaneous inorganic wastes from residential, commercial, institutional, and industrial sources.
Examples from these categories include: appliances, newspapers, clothing, food scrapes, boxes, disposable tableware, office and classroom paper, wood pallets, rubber tires, and cafeteria wastes.
Waste-to-energy combustion and landfill gas are byproducts of municipal solid waste. We'll talk about landfill gas next and skip waste-to-energy combustion entirely.
Municipal solid waste contains significant portions of organic materials that produce a variety of gaseous products when dumped, compacted, and covered in landfills. Anaerobic bacteria thrives in the oxygen-free environment, resulting in the decomposition of the organic materials and the production of primarily carbon dioxide and methane.
Carbon dioxide is likely to sink deeper into the ground below because it is soluble in water. Methane, on the other hand, which is less soluble in water and lighter than air, is likely to migrate out of the landfill. Landfill gas energy facilities capture the methane (the principal component of natural gas) and burn it for energy.
So far, very simple. Let's quickly review:
Biomass as a fuel for generating electricity comes from wood and wood waste, municipal solid waste, and methane bubbling up from landfills.
How Do We Get The Electricity?
First, the fuel is delivered to the power plant.
The heat released from burning the wood, municipal solid waste, or landfill methane is used to produce steam, which turns a steam turbine to generate electricity.
With municipal solid waste, it's unloaded from collection trucks and shredded or processed to ease handling. Then, recyclable materials are separated out. The rest is the fuel.
Is It That Simple?
Yes. It's simply finding a fuel we can deliver cost-effectively to a power plant. We already have the power plants ready to use steam to generate electricity.
What's The Catch?
Generating electricity from biomass can affect land resources in different ways. Biomass power plants, much like fossil fuel power plants, require large areas of land for equipment and fuel storage. If these biomass plants burn a waste source such as construction wood waste or agricultural waste, they can provide a benefit by freeing areas of land that might otherwise have been used for landfills or waste piles. Biomass grown for fuel purposes requires large areas of land and, over time, can deplete the soil of nutrients. Fuel crops must be managed so that they stabilize the soil, reduce erosion, provide wildlife habitat, and serve recreational purposes.
Back To The Big Picture
Currently, electricity consumed from biomass fuel sources makes up 54% of the US renewable energy consumption. Hydropower makes up 36%, and all other sources make up 10%.
Renewable energy makes up 7% of the US electricity consumed. We just need to grow that percentage to match the rest of the world's 22%.