Last Updated: Jul 10, 2021
When we talk about renewable energies, most of us probably think about the sun, the wind, or the steady and energy that can be harnessed by the movement of water. Biomass renewable fuels, however, are another type of potentially carbon-neutral renewable energy for homeowners and our society in general. Through photosynthesis, plants capture energy from the sun and turn that energy into biomass before producing seeds, dying, and allowing future generations of plants to grow back. This cyclical process offers a renewable strategy for energy and electricity production that we will explore below.
Biomass energy is the oldest form of renewable energy used on earth. Think of our prehistoric ancestors cooking their recently killed wooly mammoth over a fire made from the fallen branches of a pine tree. This example, in essence, was taking organic material to generate energy for human uses. The word "biomass" might sound fancy, but it only refers to organic matter. Biomass relies on any natural material derived from plants or animals such as wood, grass clippings, crop residues, and even cow dung.
On a worldwide scale, at least three billion people cook the majority of their meals with firewood. Many more people use dried cow dung and other sources of biomass harvested from local farms for their cooking and heating needs. In more developed countries, the use of biomass is more industrial in scale. Wood pellet stoves, for example, rely on compressed sawdust and other leftover material from the timber and lumber industries.
The Energy Information Administration (EIA) explains how plants absorb and transform energy from the sun to stored biomass energy through a process called photosynthesis. Biomass produces heat through the discharge of chemical energy when it is burned. It can be burned directly or after being converted into biogas or liquid biofuels.
Some common examples of biomass for energy use include:
As mentioned above, biomass energy is a renewable source of energy. Plants will regrow. As long as the sun keeps shining, the process of photosynthesis will continue to deliver more organic material that can be burned or converted into fuel for human use. Fossil fuels, on the other hand, are widely considered to be sources of "ancient sunlight." Oil, natural gas, and coal were initially formed from organic matter suppressed deep within the earth. This organic material transformed over millions of years from exposure to extreme heat and pressure. Fossil fuels will eventually replenish, though the million-year timeline isn't of much use to our human societies. Plant matter for biomass energy, however, can grow and be harvested annually.
Renewable biomass fuels are mostly carbon neutral. Plants, as they grow, capture carbon dioxide from the air and store it in their biomass. When burned, the carbon dioxide is again released, though efficient burning techniques are beneficial as they can lead to less carbon returning to the atmosphere.
Another benefit of renewable biomass fuels is that sources of organic waste material abound in our society. Unfortunately, millions of homeowners across the country continue to rake up their autumn leaves and place them in plastic bags. When this organic material ends up in a landfill, it contributes to an enormous amount of methane emissions, one of the most potent greenhouse gasses. These leaves, along with tree branches and other sources of yard waste, could be sent to a biomass electricity plant.
Crop residues from grains, legumes, and tree crops represent an enormous source of potential biomass fuels. One recent study found that agricultural residue produces an estimated 1 billion barrels of diesel equivalent or eight quads in the US electricity sector. To give you a better idea of how much energy could be produced from burning or transforming crop residues, the EIA estimates the total amount of energy produced in the United States was equal to 95.7 quads in 2018. In theory, crop residues from around the world could produce enough electricity for millions of households.
In many places around the world, small farmers burn their crop residues in the fields. This practice wastes a potential source of renewable energy. It also leads to urban air pollution through contaminating air quality with soot particles, nitrogen oxides, sulfur dioxide, carbon dioxide, carbon monoxide, and polycyclic aromatic hydrocarbons. Burning that residue in carefully controlled biomass electricity plants can turn that plant matter into renewable energy while also regulating how emissions affect regional air quality.
Biomass energy, however, also has its drawbacks. When forests are clear cut to produce material for electricity production at biomass energy plants, the overall environmental impact is negative. The total biomass in old-growth forests stores an enormous amount of carbon. While trees will grow again, it would take hundreds of years for an old-growth forest to reach a state of maturity once again. The loss of topsoil, biodiversity, wildlife habitat, and the adverse effects on groundwater aquifers are other negative aspects associated with using forests for biomass energy.
Also, there are ethical considerations associated with using plants for biomass. Corn and sugar cane are two of the most commonly used plants for biomass energy and biodiesel production. A 2011 study found that "land area for corn ethanol was 13.9 million acres, 17% of the total 83.98 million total corn acres." Growing food crops for energy production can come under scrutiny when 9.3 percent of the world's population is "severely food insecure," including 2.7 million households in the United States.
As stated by Project Drawdown, using high energy input and groundwater depleting crops like corn and sorghum, or, worse, depleting native forests, is not a solution. Rather, biomass can be sustainable using appropriate feedstock from waste in mills and agriculture or responsibly grown perennial crops.
Many households across the country might be benefitting from biomass energy every time they turn on their lights. The EIA reports that "biomass and waste fuels generated 71.4 billion kilowatt-hours of electricity in 2016 or 2% of total generation in the United States."
If your local municipal electricity provider doesn't rely on biomass energy as part of their portfolio, biomass energy can still be an option for your home. Here are a few other options for using sustainable sources of biomass energy on a household scale:
Wood stoves are an excellent way to supplement the heat for your home. They are relatively inexpensive and will help you cut back on your winter heating cost. This guide on how to best burn firewood can allow homeowners to harvest their fuel from trees planted in their backyard.
The wastes from our kitchen and yards will naturally produce methane as they break down and decompose. Instead of merely releasing that methane into the atmosphere, household biogas digester systems allow homeowners to capture that gas and utilize it for your household cooking needs.
Biomass energy might not be a panacea for our energy needs, but this ancient energy solution can and should be a part of our transition to a more sustainable future.
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.