S. Howes

Biomass 101: What You Need to Know

An aerial image of a biomass plant.

The use of biomass by modern humans  for energy is older than their emergence as a species, with evidence of the use of fire dating back a million years to modern humanity’s ancestors, homo erectus. Renewable resources like wood and other once-living combustible substances were first used to generate fire for cooking food and keeping warm by ancient humans and their ancestors. As one of the most common examples of biomass, wood continues to be used today as an energy source in many developing countries, as it’s the most readily available energy resource.

However, the use of wood as biomass for energy has also led to shortages of timber, as was the case in the late 1600s in Great Britain. The scarcity of wood is what precipitated the expanded use of coal for energy and arguably helped start the industrial revolution. In the United States, the use of biomass peaked in 1870, when wood  accounted for 70 percent of the country’s energy usage. While coal, and later petroleum, largely replaced wood as an energy source, such examples of biomass are now looked at favorably as renewable sources of energy, which have driven production of biofuels like ethanol and biodiesel in recent decades.

What is Biomass?

Examples of biomass extend beyond just wood. In fact, biomass is any renewable organic material that comes from flora or fauna. Though its use as an energy source had waned in developed countries as fossil fuels replaced them, biomass use has increased markedly as countries worldwide seek to reduce carbon dioxide emissions. In fact, as of 2021, biomass accounted for about 5 percent of all energy use in the United States and is expected to grow.

Most examples of biomass used in the world today come from waste. Produced via the process of photosynthesis, plant-based biomass contains untapped chemical energy derived from the sun. It’s easily burnable for heat, though it can also be processed into renewable liquid or gaseous fuels. Waste from dead animals or their droppings can also be converted into energy. Animal waste has been used as fuel for thousands of years, with bacteria within manure producing methane gas.

3 Examples of Biomass

Biomass feedstocks include dedicated crops, the harvested material from agricultural or woody waste, and other waste material.  Many examples of biomass used by industry in the modern world come from waste or renewable resources which  also provides a sustainable option for energy production.

Harvesting Energy from Dedicated Crops

Dedicated Crops  are crops that aren’t meant for human consumption and many examples of biomass that are grown and harvested for this purpose use land unsuitable for the growing of conventional crops. Examples of biomass crops include water based plants and plants that are woody or herbaceous  . Many species of these plants also improve a farm’s productivity, enhance the quality of soil and water, provide habitat for wildlife and diversify a farmer’s sources of income.

For herbaceous biomass crops, it takes a couple years to produce a full crop for harvest, after which they can be harvested annually. These plants are also perennial grasses, meaning they’ll provide at least two full harvests before fields may require replanting.

Herbaceous plants used for biomass include: 

  • Bamboo
  • Switchgrass
  • Kochia
  • Tail Fescue
  • Miscanthus
  • Wheatgrass
  • Sweet Sorghum

When it comes to woody crops, these quick-growing hardwood trees take up to eight years before they can be harvested.

Woody plants used for biomass include:

  • black walnut
  • eastern cottonwood
  • green ash
  • hybrid poplar
  • hybrid willow
  • silver maple
  • sweetgum
  • sycamore

Just like their land-based cousins, aquatic plants use photosynthesis and nutrients in water to provide biomass that can then be turned into energy. Fundamental elements within the plant like carbohydrates, lipids and proteins can be transformed into various biofuels, including biodiesel, biobutanol, bio-gasoline, biogas, methane, ethanol and even jet fuel.

Aquatic plants used for biomass include:

  • cyanobacteria
  • macroalgae, also known as seaweed
  • microalgae

Algae grow in diverse environments, which can be sourced from lakes or reservoirs, water from underground or seawater. Like land-based plants, certain types of algae can  be cultivated as well. Depending on the variety, algae can grow in brackish, fresh, or saline water. Algae can even be utilized within treatment plants that handle wastewater from agricultural, aquacultural, industrial or municipal sources, along with wastewater generated from drilling for petroleum or natural gas.

Examples of Biomass from Agricultural & Woody Waste 

Though biomass can be grown directly, it can also be made from agricultural, forestry or timber waste. These examples of biomass from waste leverage discarded material from feed, fiber, food or forestry harvests. This includes diverse types of plant material that’s readily available. When sold to a biorefinery, this can provide additional income for farmers beyond what they receive for the actual crops.

Examples of biomass from agricultural waste include: 

  • barley straw
  • corn stalks, leaves, husks and cobs
  • oat straw
  • rice straw
  • sorghum stubble
  • wheat straw

Similarly, biomass from forestry and lumber operations can be sources of waste timber after logging. Woody debris are collected for bioenergy, leaving behind sufficient biological material to ensure habitats for plants and animals remain intact, as well as to ensure plant growth that helps prevent floods or landslides is kept in place. Harvesting excessive growth in forests also reduces the risk of fire and pests, contributing to forest restoration, and the vitality of the natural ecosystems. This can be done without creating a negative effect on the ecology of forested areas, thus promoting healthy forests and woodlands.

Examples of biomass from forestry harvests or lumber operations include: 

  • dead and diseased trees left over from timber harvests
  • sawdust from mills
  • tree bark, branches, leaves, limbs, needles and tops
  • unmerchantable tree components
  • whole trees harvested for biomass

As waste from paper, lumber or other wood processing involves collecting byproducts and waste at the point of production, these sources offer an inexpensive and convenient source of biomass for biofuel production.

Biomass from Other Waste Material

Other waste materials can be used for biomass as well. Types of material used for biomass production include commercial, institutional, industrial, municipal and residential waste. Using mixed waste from residential and commercial garbage also reduces the amount of material going into landfills, and often helps solve problems relating to waste disposal.

Examples of biomass from mixed refuse include:  

  • food
  • leather
  • manure
  • paper and paperboard
  • plastics
  • rubber
  • textiles
  • treated sewage
  • yard trimmings

In addition, biomass can be made from wet waste that includes food waste, manure slurries from stockyards and other livestock operations, organic industrial waste, and solid biological waste. Like waste coming from the agricultural, forestry or wood processing industries, these examples of biomass feedstocks can generate revenue for the communities from which they’re sourced, which can help boost rural economies.

Examples of Biomass Processing Equipment 

Biomass equipment must be able to handle a variety of materials and processes. Examples of biomass feedstocks this equipment must be able to handle includes agricultural waste, grass, treated sludge from sewage, wood and yard waste. Biomass processing systems also need to carry out certain operations like vibratory screening, separation by density, metering or drying. These processes must also handle these processes efficiently, so that processing material results in little wastage and isn’t too time-consuming. A biomass processing system should also include an efficient conveying system that won’t be disrupted easily and thus interrupt production.

Examples of biomass equipment might include customizable vibratory conveyors. It may also combine processes to save production costs and time. For example, combining a pile activator and two vibratory feeders improves flow control, which helps avoid issues like off-center loading or bridging.  

Screw conveyors can also be used to effectively transport and treat biomass material. In many applications, the biomass needs to be transported from one piece of processing equipment to another. Screw conveyors have been used as a form of transport for many of these materials due to their robust nature, high processing rates, and their ability to handle a multitude of different materials. In some processes, the material will be heat treated during this conveyance stage in order to dry, sterilize, or preheat the biomass prior to the next processing stage. Thermal screw conveyors have been used in many of these applications due to their effective indirect heat transfer rates. The indirect heat transfer allows a heating media such as hot water, steam, or hot oil to warm the product to the proper temperature without directly contacting the product and causing contamination. Separating material by density might include the use of water, as is the case when separating wood mulch from stones, metal or glass. However, this also creates a challenge, as it generates wastewater that can negatively affect the environment. Since water separation can be hazardous to the environment, and potentially lead to environmental lawsuits against a company, biomass processors may instead wish to utilize a more efficient process.

Consideration should be taken when using water to separate materials by density.s. These technologies create environmental emissions and wastewater that challenge the sustainability of the process. For this reason, separating material by density is often done with an air classifier, sometimes referred to as an air finisher. An air classifier or air finisher separates heavier from lighter materials instead using air, which is a more efficient way to separate the materials.

Biomass processing equipment must be able to process a wide variety of materials that differ in composition, density, dimensions and size. This is a challenge for makers of biomass processing equipment, with blinding, bridging, jamming and trapping becoming an issue in many biomass separation systems. When this happens, production halts and often results in considerable downtime as maintenance personnel try to correct the issue. For this reason, it’s important that processors utilize state-of-the-art equipment with a good track record for biomass processing when seeking to separate and classify such materials.