Biomass, Biofuel, Bioenergy & Biogas Explained: Definitions, Uses, Types, Examples, & More

In the guide below, we explain what biomass, biofuel, and bioenergy 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 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, residues and waste

3. From algae (and microalgae)

 

Different Types Of Biomass, & Examples

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

wikipedia.org indicates that ‘The main food crops harvested for energy are sugar-producing crops (e.g. sugarcane), starch-producing crops (e.g. corn) and oil-producing crops (e.g. rapeseed)’

Another example 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

Such as:

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)

Used specifically for biofuel

Algae is considered the ‘third generation’ of biofuel, after first generation edible crops, and second generation non edible organic materials like residues and waste

 

Which Types Of Biomass Are Used The Most?

It depends on what the biomass is being used to produce i.e. whether it’s heat or electricity, biofuels, or something else.

It also depends on the country in question (as different countries might use different biomass materials)

As a few examples …

 

Primary Energy Use

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

From energy.gov

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.

A few of the key uses for biomass can include:

– Biomass used for energy generation i.e. bioenergy

Specifically for electricity and also heat

 

To look at one example of how much of a country’s energy mix bioenergy makes up, eia.gov indicated that ‘Biomass fuels provided about 5% of total primary energy use in the United States in 2017’

 

– Biomass used for biofuels

Such as ethanol and biodiesel

 

-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

Developing regions may not have the access to electricity grids that some developed countries do, and therefore may burn biomass like wood for heating and cooking

 

– By Products From Different Processes Involving Biomass

Some of the different byproducts 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 directly, or converted into different products:

1. Direct Use Of Biomass (Direct Combustion)

This is where biomass is burnt without processing or refinement

 

2. Conversion Of Biomass Into Different Products

This is where biomass is 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)

Chemical Conversion

Biological Conversion (also called biochemical conversion)

 

eia.gov explains each of these conversion processes in more detail

 

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, and water transport like ships

In addition to transportation fuels, biofuels can can also be 

 

How Are Biofuels Made?

Different biofuels have their own conversion processes to convert biomass into a finished/refined biofuel product

Biofuels generally go through a two step conversion process to produce the finished biofuel product:

1. Deconstruction

This is the breaking down of the biomass material

It can involve high temperature deconstruction, and also low temperature deconstruction

 

2. Upgrading

Upgrading takes the broken down building blocks from deconstruction of the biomass material, and upgrades it into a finished biofuel product

Processing can be biological or chemical during this step

 

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.

 

Different Types Of Biofuels, & Examples Of Biofuels

Types Of Biofuels

Two of the main types of biofuels, which are both first generation biofuels, are:

– Ethanol 

An alcohol made by fermentation that can be used in different blend %’s with gasoline

There’s also different types of ethanol, such as corn ethanol vs cellulosic ethanol

eia.gov indicates that ethanol accounts for the largest share of US biofuel production (85%) and consumption (82%)

One of the potential benefits of ethanol is that it has a higher octane rating than gasoline

 

– Biodiesel

Usually blended with petroleum diesel in different %’s

It is made by combining alcohol with vegetable oil, animal fat, or recycled cooking grease

It’s intended as a cleaner-burning replacement for petroleum-based diesel fuel in vehicles with diesel engines

eia.gov indicates 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 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 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.

 

First Generation

Derived from food crops such as sugar and wheat (or plants such as sugarcane and corn starch)

 

Second Generation

Derived from non non edible biomass such as wood, organic waste, food crop waste, and other types of waste and residues.

 

Third Generation

Derived specifically from algae (and microalgae)

 

Fourth Generation Biofuels

wikipedia 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

 

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, nuclear energy, and so on

 

What Is Bioenergy Used For?

Bioenergy – that is, the energy stored in biomass – is generally used for:

– Heat generation

– Electricity generation

 

How Is Bioenergy Made?

How Bioenergy Is Made

Biomass is converted into heat or electricity via different processes.

energy.gov indicates that 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 the 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 are necessarily different types of bioenergy

There is however different biomass sources can be used as energy sources 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 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.

 

 

Sources

1. https://en.wikipedia.org/wiki/Biomass

2. https://en.wikipedia.org/wiki/Biofuel

3. https://www.energy.gov/eere/bioenergy/bioenergy-basics

4. https://www.eia.gov/energyexplained/biofuels/

5. https://www.eia.gov/energyexplained/biomass/

6. https://www.energy.gov/eere/bioenergy/biopower-basics

7. https://www.energy.gov/eere/bioenergy/bioproduct-basics

8. https://www.energy.gov/eere/bioenergy/biofuel-basics

9. https://www.eesi.org/papers/view/fact-sheet-biogasconverting-waste-to-energy

10. https://bettermeetsreality.com/biomass-energy-pros-cons-now-future/

11. https://education.nationalgeographic.org/resource/biomass-energy

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