What is Biomass?

What is Biomass?
Biomass Crop on Left, Corn on Right

So what is Biomass and how green is it?

Biomass is any organic matter, plants, animals, trees, seaweed, animal waste, humans, are all biomass. Life on earth is organic or carbon based, and anything that is alive or is dead and was once alive, could be classified as biomass.

Biomass is probably our oldest source of energy after the sun. Since humans harnessed the heat and light of fire, to cook their food, and heat and light their homes, we have been using biomass. 

Traditional fuels such as coal and gas, are carbon based and are actually biomass. The only difference is the source of the biomass fuel, how efficient it is as a fuel, how pollutant it is as a fuel, and ultimately is it carbon neutral?

There are other considerations to bear in mind such as the secondary impact on the environment of the production, transportation and management of the biomass fuel, whether it is wood pellets, methane, or a log burner.

The main arguments for Biomass fuels are that they are renewable and are carbon neutral. This view does not take into account the secondary considerations mentioned above, but in simple terms means that the amount of carbon produced by the burning of the biomass fuel, is offset by the savings of using the biomass fuel in the first place.

The argument regarding the renewability of the fuels is based on the fact that we can replace the trees burnt as biomass fuel with an equal number/volume of trees, so this means that there is an unlimited ever renewable supply of wood-based biomass fuel.

This does not take into account the length of the carbon cycle which we will be shortening when we replace trees with younger and younger variants. It also does not take into account the finite resource of the land itself, either the amount of land you need to replace the trees with smaller and younger versions, or the impact of heavy-duty forestry management on our environment.

What are Biomass Fuels?

Biomass fuels are organic materials produced in a renewable manner. The major classifications of Biomass fuels are:

  • Plant/Tree Based Biomass Fuels
  • Animal Based Biomass Fuels
  • Chemical Process Based Biomass Fuels

Plant/Tree Based Biomass Fuels

Wood wastes of all types make excellent biomass fuels and can be used in a wide variety of biomass technologies. Combustion of woody fuels to generate steam or electricity is a proven technology and is the most common biomass-to-energy process.

Different types of woody fuels can typically be mixed together as a common fuel, although differing moisture content and chemical makeup can affect the overall conversion rate or efficiency of a biomass project. There are at least six different types of plant-based Biomass fuels currently available. They differ on availability, cost and environmental impact of their production, transportation and use.

Some are direct, literally the tree itself, others are the by-products of the use of trees and forestry management processes, such as sawdust, debris, wood chip, pulp, mill residues etc

Others include the by-products of crop production such as orchard prunings, and others still include dedicated biomass crops, planted specifically for use as a Biomass fuel, such as corn, oilseed etc.

Forestry Residues

Forestry residues have been the focus of many recent biomass studies and feasibility assessments due to increasing forest management and wildfire prevention activities. 

The USDA Forest Service and the Bureau of Land Management have been tasked with reducing the hazardous fuel loading within the forests and the urban-wildland interface.

Forestry residues are typically disposed of by on-site (in-forest) stacking and burning. This results in substantial air emissions that affect not only the forest lands and nearby populations, but the overall regional air quality as well. 

Open burning can also cause water quality and erosion concerns. The Forest Service and other public and private land management entities would like to have viable alternatives for disposing of their forestry residues in a more environmentally benign manner. 

An ideal situation, from the perspective of forest managers, would be the creation of a market for the forestry residues. The market they envision would generate revenues for the forest managers, which in turn would allow much needed expansion of the forest management programs.

Mill Residues

Mill residues are a much more economically attractive fuel than forestry residues, since the in-forest collection and chipping are already included as part of the commercial mill operations. 

Biomass facilities collocated with and integral to the mill operation have the advantage of eliminating transportation altogether and thus truly achieve a no-cost fuel. Mill residues have long been used to generate steam and electricity.

Agricultural Residues

Agricultural residues can provide a substantial amount of biomass fuel. Similar to the way mill residues provide a significant portion of the overall biomass consumption in the Pacific Northwest, agricultural residues from sugar cane harvesting and processing provide a significant portion of the total biomass consumption in other parts of the world. One significant issue with agricultural residues though is the seasonal variation of the supply.

Large residue volumes follow harvests, but residues throughout the rest of the year are minimal. Biomass facilities that depend significantly on agricultural residues must either be able to adjust output to follow the seasonal variation, or have the capacity to stockpile a significant amount of fuel.

Urban Wood and Yard Wastes

Urban wood and yard wastes are similar in nature to agricultural residues in many regards. A biomass facility will rarely need to purchase urban wood and yard wastes, and most likely can charge a tipping fee to accept the fuel. 

Many landfills are already sorting waste material by isolating wood waste. This waste could be diverted to a biomass project, and although the volume currently accepted at the landfills would not be enough on its own to fuel a biomass project, it could be an important supplemental fuel and could provide more value to the community in which the landfill resides through a biomass project than it currently does as daily landfill cover.

Dedicated Biomass Crops

Dedicated biomass crops are grown specifically to fuel a biomass project. The most prevalent example of dedicated biomass crops are corn varieties grown for ethanol production. Fast-growing poplar trees have also been farm-raised for a biomass fuel, but this has not proven to be economically sustainable. Another dedicated crop example is soybean oils used in the production of biodiesel.

Animal Based Biomass Fuels

Animal wastes include manures, renderings, and other wastes from livestock finishing operations. Although animal wastes contain energy, the primary motivation for biomass processing of animal wastes is mitigation of a disposal issue rather than generation of energy. 

This is especially true for animal manures. Animal manures are typically disposed of through land application to farmlands. Tightening regulations on nutrient management, surface and groundwater contamination, and odour control are beginning to force new manure management and disposal practices. 

Biomass technologies present attractive options for mitigating many of the environmental challenges of manure wastes. The most common biomass technologies for animal manures are combustion, anaerobic digestion, and composting. 

Moisture content of the manure and the amount of contaminants, such as bedding, determine which technology is most appropriate.

The dairy industry in particular is well suited to biomass-to-energy opportunities because of the large volume of manure that a milking cow produces, and because dairy operations have automated and frequent manure collection processes. 

Dry Animal Manure

Dry animal manure is produced by feedlots and livestock corrals, where the manure is collected and removed only once or twice a year. Manure that is scraped or flushed on a more frequent schedule can also be separated, stacked, and allowed to dry. 

Dry manure is typically defined as having a moisture content less than 30 percent. Dry manure can be composted or can fuel a biomass-to-energy combustion project.

Animal manure does have value to farmers as fertilizer, and a biomass-to-energy project would need to compete for the manure. However, the total volume of manure produced in many livestock operations exceeds the amount of fertilizer required for the farmlands, and Nutrient Management Plans are beginning to limit the over-fertilization of farmlands. 

Therefore, although there are competitive uses for the manure and low-cost disposal options at this time, manure disposal is going to become more costly over time, and the demand for alternative disposal options, including biomass-to-energy, will only increase.

Wet Animal Manure (Dairy Manure Slurry)

Wet animal manure is typically associated with larger and more modern dairy operations that house their milking cows in free-stall barns and use a flush system for manure collection. 

The combination of free-stall barns and manure flushing collects all of the milking cow manure with every milking cycle, two or three times a day. The manure is significantly diluted through the addition of the flush water, but after separation of some of the flush water, the slurry is an excellent fuel.

Landfill Gas and Biogas

Bacteria and fungi are not picky eaters. They eat dead plants and animals, causing them to rot or decay. A fungus on a rotting log is converting cellulose to sugars to feed itself. 

Although this process is slowed in a landfill, a substance called methane gas is still produced as the waste decays. New regulations require landfills to collect methane gas for safety and environmental reasons. 

Methane gas is colourless and odourless, but it is not harmless. The gas can cause fires or explosions if it seeps into nearby homes and is ignited.

Landfills can collect the methane gas, purify it, and use it as fuel. Methane can also be produced using energy from agricultural and human wastes. Biogas digesters are airtight containers or pits lined with steel or bricks. 

Waste put into the containers is fermented without oxygen to produce a methane-rich gas. This gas can be used to produce electricity, or for cooking and lighting.

Chemical Recovery Biomass Fuels

Chemical recovery fuels are responsible for over 60 percent of the total biomass energy consumption of the United States, and therefore must be mentioned in any analysis of biomass. By and large, the chemical recovery facilities are owned by pulp and paper facilities and are an integral part of the facility operation.

Ethanol is an alcohol fuel (ethyl alcohol) made by fermenting the sugars and starches found in plants and then distilling them. 

Any organic material containing cellulose, starch, or sugar can be made into ethanol. The majority of the ethanol produced in the United States comes from corn. New technologies are producing ethanol from cellulose in woody fibres from trees, grasses, and crop residues.

Biodiesel is a fuel made by chemically reacting alcohol with vegetable oils, animal fats, or greases, such as recycled restaurant grease. Most biodiesel today is made from soybean oil.

Biodiesel fuels are compatible with and can be used in unmodified diesel engines with the existing fuelling infrastructure. It is one of the fastest growing transportation fuels in the United States.

Is Biomass Energy ‘Green’?

The man problem with a biomass fuel is that compared to traditional fuels such as coal, it is pretty inefficient. Regardless of its source, it has a higher moisture content, and this means that more is needed to generate the same amount of energy as a smaller amount of a traditional fossil fuel, and it is heavier, so there is a greater transportation cost based on volume and weight. 

This can be offset by building the biomass sites close to their fuel source, but this itself has an impact on the financial viability of the end to end operation

The idea is that if trees harvested as biomass are replanted as fast as the wood is burned, new trees take up the carbon produced by the combustion, the carbon cycle theoretically remains in balance, and no extra carbon is added to the atmospheric balance sheet. So, biomass is then considered “carbon neutral.” 

Since nothing offsets the CO2 that fossil fuel burning produces, replacing fossil fuels with biomass theoretically results in reduced carbon emissions.

By 2030, biomass could account for 60 percent of total final global renewable energy use, according to the International Renewable Energy Agency.

Biomass will be around for a long time, and yes, it is more sustainable than fossil fuels. Is it Green? You decide. 

Written by Simon
I am a published writer, journalist and photo-journalist. I have an MA in Creative Writing and Journalism from the University of Wales and my journalism has been published in a number of UK national newspapers including 'the Observer'. Having read Rachel Carson's 'Silent Spring' as a teenager, I have life long interest in environmental and political issues. This website is an exploration of this in all its forms and guises.