Below, we explain what biomass, biofuel, bioenergy, and biogas are.
We provide definitions, and discuss how they’re made, what they’re used for, the different types (with examples), plus other relevant information.
This guide complements our much shorter separate comparison guide where we outline the similarities and differences between biomass, biofuel, bioenergy and biogas.
What Is Biomass? (Definition)
Biomass is organic material
Some reports indicate that it primarily comes from plants, and to a lesser extent algae
Other reports indicate that some biomass also comes from some animal sources too
It’s commonly referred to as being renewable (as opposed to being non renewable like fossil fuels)
Where Does Biomass Come From?
There might be three main sources of biomass:
1. From edible food crops and plants
2. From non edible organic material like non edible crops, as well as residues and waste
3. From algae (and microalgae)
Different Types Of Biomass, & Examples
Traditional biomass has been used since the beginning of human time – using organic matter like wood to provide heat energy.
But in modern times, one report from wikipedia.org indicates that:
‘There are five general categories of biomass: industrial waste and co-products, food waste, agricultural residues, energy crops, and virgin lumber’
However, this is just one way to categorise the different types of biomass.
Another way to categorise the different types of biomass, with examples, include but aren’t limited to:
Edible Food Crops
According to wikipedia.org, the following might be the main food crops harvested for energy:
‘… sugar-producing crops (e.g. sugarcane), starch-producing crops (e.g. corn) and oil-producing crops (e.g. rapeseed)’
Another example of edible food crops can be soybeans
The crop/plant material itself can be utilized, but vegetable oils and fats can also be extracted from crops and plants, and then used
Non Edible Organic Material (Wood, Plants/Grasses, Residues & Waste)
– Wood residues & wood waste
Might come from leftover wood and residue from forestries
Might also come from wood processing waste in the form of offcuts, wood chips, sawdust, and so on
– Grassy crops, and woody plants
– Agricultural residues and waste
Such as crop residue waste, and food processing waste
Animal manure may also be used
Animal fats may also sometimes be used
– Municipal and industrial waste
Human waste (such as sewage)
Waste from factories and mills (such as pulp and paper mills)
And, organic materials from municipal waste like cotton, wool, yard trimmings and garden waste, food wastes, and so on
Algae (& Microalgae)
Algae is used specifically for biofuel
Algae is considered the ‘third generation’ of biofuel
It follows first generation edible crops, and second generation non edible organic materials like residues and waste
Which Types Of Biomass Are Used The Most?
The type of biomass that is used can depend on what the biomass is being used for i.e. whether it’s being used for heat, electricity, biofuels, or something else.
It can also depend on the country in question – different countries might use different biomass materials more frequently, or in greater quantities
A few examples of common types of biomass used in the US might include …
For Primary Energy Use – In The US
Aside from biofuels, primary energy use in the US came in large part from wood and wood derived biomass
eia.gov indicates that:
[In 2017, of the 5% of the US’ total primary energy use that biomass fuels made up:]
47% was from biofuels (mainly ethanol)
44% was from wood and wood-derived biomass
10% was from the biomass in municipal waste
Biofuels – In The US
For biomass for biofuels specifically, plant starches and sugars (like corn starch) might be commonly used in the US
Most ethanol is made from plant starches and sugars—particularly corn starch in the United States
[Biodiesel is made by] combining alcohol with vegetable oil, animal fat, or recycled cooking grease
What Is Biomass Used For?
Biomass is versatile with a range of uses, and, a range of products are derived from biomass.
The key uses for converted biomass might be:
– Fuel (biofuel)
In some countries, biomass fuels may not make up a large % of the country’s primary energy use.
For example, in the US, eia.gov indicates that:
‘Biomass fuels provided about 5% of total primary energy use in the United States in 2017’
– Biomass used to make commodities and ‘bioproducts’
Biomass can partially or fully replace fossil fuel feedstock in different ‘bioproducts’
energy.gov explains that:
‘[Biomass can serve as a] renewable alternative to fossil fuels in the manufacturing of bioproducts such as plastics, lubricants, industrial chemicals, and many other products currently derived from petroleum or natural gas’
We’ve written in a separate guide specifically about bioplastics here
– Cooking and heating in developing regions of the world
Some developing regions may not have the access to electricity grids that some developed countries do
For centuries, these regions have burnt biomass like wood for heating and cooking
– By-Products From Different Processes Involving Biomass
Some of the different by-products include but aren’t limited to:
Digestate, which can be used as a soil amendment. It comes from the anaerobic digestion of biomass in a digester
And, biochar is another byproduct. It is made of carbon and ashes, and remains after the pyrolysis of biomass in an anaerobic or oxygen deprived environment
– *A Note About Biomass & Energy Generation
Energy from biomass comes from the chemical energy stored in plants (in the form of glucose or sugar), which has been converted from energy from the sun via the process of photosynthesis
Direct Use Of Biomass vs Conversion Of Biomass
Biomass can be used in two main ways – directly, or converted into different products …
1. Direct Use Of Biomass (Direct Combustion)
This is where biomass is burnt/combusted without processing or refinement
Biomass might be combusted directly for electricity, or heat, as examples
2. Conversion Of Biomass Into Different Products
Biomass can be processed and refined to make biofuels.
Biomass can also be processed or refined to make ‘bio’ products, in the form of solids, gases or liquid fuels.
There’s three main types of conversion:
Thermal Conversion (also called thermochemical conversion)
Biological Conversion (also called biochemical conversion)
eia.gov explains each of these conversion processes in more detail in their report
What Are Biofuels? (Definition)
Biofuels are fuels derived from biomass sources
The biomass is converted into a liquid ‘biofuel’
What Are Biofuels Used For?
Biofuels are primarily used as a substitute fuel for petroleum in transportation
Biofuels can be used in road based transport such as cars and trucks, but also for air travel like airplanes and jets, in addition to water transport like ships
In addition to transportation fuels, biofuels may also be used for heating, and also electricity
How Are Biofuels Made?
Different biofuels have their own conversion processes to convert biomass into a finished/refined biofuel product
Biofuels might generally go through a two step conversion process to produce the finished biofuel product:
This involves breaking down the biomass material
It can involve high temperature deconstruction, and also low temperature deconstruction
Upgrading takes the broken down building blocks from deconstruction of the biomass material, and upgrades it into a finished biofuel product
Either biological or chemical processing might take place
energy.gov explains both of these conversion process steps in greater detail
Another report indicates that conversion of biomass to biofuel can be achieved thermally, chemically, and biochemically.
Mixing Biofuels With Fossil Fuels
Only some vehicle engines are designed to be able to use biofuels in their pure form.
This is why for engines that aren’t designed for this, biofuels might be mixed with fossil fuels.
Different Types Of Biofuels, & Examples Of Biofuels
Types Of Biofuels
Two of the main types of biofuels, which are both first generation biofuels, are:
An alcohol made by fermentation
It can be used in vehicle engines where it is blended in different %’s with gasoline
There’s also different types of ethanol, such as corn ethanol vs cellulosic ethanol
eia.gov indicates that (paraphrased) ethanol accounts for the largest share of US biofuel production (85%) and consumption (82%)
One of the potential benefits of ethanol might be that it has a higher octane rating than gasoline
It is made by combining alcohol with vegetable oil, animal fat, or recycled cooking grease
It can be used in car engines where it is usually blended with petroleum diesel in different %’s
It’s intended as a cleaner-burning replacement for petroleum-based diesel fuel in vehicles with diesel engines
eia.gov indicates that (paraphrased) it makes up a much smaller share of US biofuel production and consumption compared to ethanol
Next Generation Biofuels
There’s also development being done on the next generation of biofuels known as ‘Renewable hydrocarbon ‘drop in’ fuels’
These biofuels are made from different biomass (waste, algae, etc), and are hydrocarbon biofuels
This means they are the ‘functional equivalent’ of fossil fuel based fuels (i.e. petroleum based fuels), such as gasoline, diesel fuel and jet fuel
This also means they can be used as a petroleum substitute fuel without the requirement to blend them
eia.gov indicates that (paraphrased) renewable diesel (also called green diesel) is one example of a drop in fuel, and has a small but growing production and consumption in the US already
eia.gov lists other renewable drop in fuels that are (paraphrased) at various stages of development and commercialisation in their report
wikipedia.org also discusses ‘green diesel’ and how it’s produced via hydrocracking in their report
First Generation vs Second Generation vs Third Generation Biofuels
The difference between first, second, and third generation biofuels, apart from when they were developed, is what they are each derived from.
Derived from food crops such as sugar and wheat (or plants such as sugarcane and corn starch)
Vegetable oil might form a key part of first generation biofuels
Derived from non edible biomass such as wood, organic waste, food crop waste, and other types of waste and residues.
Derived specifically from algae (and microalgae), which have an energy rich oil
Specific microalgae species are used to make these fuels (where their oil is separated and used for the oil)
These are currently considered as the most advanced form of biofuel
Fourth Generation Biofuels
wikipedia.org describes the fourth generation of biofuels as including:
‘… electrofuels and solar fuels [and, …] biofuels that are produced by bioengineered organisms i.e. algae and cyanobacteria’
These biofuels might still be in the development stage though.
More About Biofuels
We’ve provided more information about biofuels, biodiesel and ethanol in this guide, including a comparison.
What Is Bioenergy, Or Biopower? (Definition)
Bioenergy is energy derived from biomass
Different reports define bioenergy in two main ways:
1. As all products that are derived from biomass
Such as transportation fuels (biofuels), heat, electricity, and ‘bio’ commodities/products
2. Or, specifically biomass energy used to generate heat or electricity
This is as opposed to biomass used to produce biofuels or other bio-products
In this context/description, some reports also refer to bioenergy as ‘biopower’ too
When using the phrase in this context, ‘bioenergy’ is one of a number ways to generate energy, along with other energy generation methods using other energy sources, such as fossil fuels, other renewable energy sources like solar and wind
What Is Bioenergy Used For?
Bioenergy (the energy stored in biomass), is generally used for:
– Heat generation
– Electricity generation
How Is Bioenergy Made?
How Bioenergy Is Made
There is energy in the solid organic matter used for bioenergy, and this energy is:
‘… stored sunlight in the form of chemical energy’ (wikipedia.org)
This chemical energy usually comes from photosynthesis.
This organic matter, referred to as biomass, is converted into heat or electricity via different processes.
energy.gov indicates that (paraphrased) the main three ways to release the energy stored in biomass to produce biopower are:
– Burning via direct combustion
– Bacterial decay (also called bacterial decomposition or anaerobic digestion)
– Conversion to gas or liquid fuel.
energy.gov explains each of the three electricity generation processes in their report
But, as a paraphrased summary of some of their most important points:
– Direct combustion
Biomass can be burnt in a boiler to create steam, which turns turbine blades, which drives a generator, which produces electricity
Biomass can also substitute a portion of coal in an existing power plant furnace (via co-firing)
– Conversion of biomass to biogas (via anaerobic digestion)
Biomass is converted to renewable natural gas (biomethane), and it can then be purified and used to generate electricity
– Conversion of biomass to syngas (conversion to gas)
energy.gov outlines the steps in making syngas (a gas comprised mostly of carbon monoxide and hydrogen) via gasification
Once biomass is converted to syngas, syngas can be burned in a conventional boiler to produce electricity
Syngas can also ‘be used to replace natural gas in a combined-cycle gas turbine’
– Conversion of biomass to bio-oil (conversion to liquid fuel)
Once biomass is converted to crude bio-oil via pyrolysis, it ‘… is then substituted for fuel oil or diesel in furnaces, turbines, and engines for electricity production’
Most Common Way To Produce Electricity From Biomass
Most electricity generated from biomass is produced by direct combustion (i.e. burning biomass directly) (energy.gov)
Different Types Of Bioenergy, & Examples Of Bioenergy
There aren’t necessarily different types of bioenergy
There is however different biomass sources can be used as energy to produce heat or electricity
There’s also different processes to convert biomass into electricity e.g. burning biomass directly vs turning it into a gas or oil first
Bioenergy might be categorised based on these different variables
What Is Biogas? (Definition)
Biogas is gas derived from different types of biomass i.e. organic waste
The biogas that comes from decomposing organic waste contains two main gases – methane, and also some carbon dioxide
There’s also trace amounts of other gases in biogas
What Is Biogas Used For?
After biogas is captured, it can be used to produce heat and electricity
It can also be used as a vehicle fuel
eesi.org indicates that:
[Biogas can be] used in engines, microturbines, and fuel cells.
Biogas can also be upgraded into biomethane, also called renewable natural gas or RNG, and injected into natural gas pipelines or used as a vehicle fuel.
In their report, eesi.org also outlines (paraphrased) the potential uses for raw biogas, renewable natural gas/biomethane, and RNG converted to CNG or LNG (i.e. RNG converted into CNG or LNG can be used as a vehicle fuel)
How Is Biogas Made?
Biogas is produced in nature, landfills, and some livestock manure management systems
However, controlled and contained biogas is generated using an anaerobic digestor
Organic materials and organic waste undergo anaerobic digestion whereby bacteria break down the organic waste without the presence of oxygen
Biogas is captured from the break down of organic waste
Another product is also produced from anaerobic digestion in the form of digestate, which is liquids and solids that can be used as a soil amendment
Different Types Of Biogas, & Examples Of Biogas
Biogas can take the following forms:
– Raw biogas
– Renewable natural gas (RNG) (or biomethane)
A biogas that has been refined to remove carbon dioxide, water vapor, and other trace gases
More About Biogas
In this guide, we’ve provided more information about raw biogas, biomethane and the conversion of biogas, as well a providing a comparison of these gases.