Biomass energy: what is it and how does it work?
By Aimee Tweedale Thursday 26 November 2020
‘Biomass’ is a fancy word for something very simple: stuff that’s found in nature. People have used biomass energy ever since the very first cave-dwelling person thought to make a fire out of wood!
Today, biomass power plants use everything from animal waste to wood pellets to create electricity. There are lots of advantages to biomass energy, which is a renewable energy source. But there’s also some debate about whether it’s the greenest type of energy around. Here at OVO, we chose to remove biomass from our fuel mix in 2017, in favour of cleaner energy sources: wind, solar, hydro and tidal energy.
Ready to learn more? Read on to find out everything you need to know about biomass and biofuels.
What is biomass energy?
Biomass is made up of living things (or things that were once living). This can include any plant or animal material, such as sugarcane or corn crops, wood chips, or even dung.
All these types of biomass contain energy, because they’re organic materials. So, whether they started life as plants or animals, they’ve all absorbed chemical energy naturally from the sun.
When they’re used as biomass, these materials are called ‘feedstocks’.
How does biomass energy work? Biomass energy production explained
Biomass feedstocks can be used to create 3 types of energy:
Biofuels, such as biodiesel
Some biomass plants are multi-taskers, creating both heat and electricity. These are known as CHP (Combined Heat and Power) plants.
So, how do biomass plants create heat? Simple: by burning feedstocks, just like our ancestors have done for thousands of years.
Read on to find out how biomass energy production turns wood into electricity or diesel.
How can biomass generate electricity?
Biomass can generate electricity in a number of ways – but the most common is ‘direct combustion’. This means burning the agricultural waste or wood to heat water. This produces steam, which spins turbines.
In some biomass plants, the extra steam can also be used in on-site manufacturing processes, or for heating. This makes the whole process even more energy efficient. Smart, right?
There are many other ways to generate electricity using biomass. Some scientists are even exploring the possibility of using what we’ll politely call ‘human waste’ to power homes!
What are biofuels?
Biofuels are basically fuels that are made out of biomass. These can be solid, liquid, or gas.
Biodiesel and bioethanol are two of the most common types of biofuel.
Biodiesel dates all the way back to the late 1800s, when Rudolf Diesel (of the diesel engine fame) invented an engine powered by vegetable oil. That was before petroleum-based diesel fuel became so widely available.
Bioethanol is an alcohol-based biofuel – but it’s not one you’d want to drink. It’s made by fermenting plants, and can also be used in vehicles. It was also used in the US way back in the 1800s, to light lamps.
When was biomass energy discovered?
Technically, it was discovered back in our cave-dwelling days, when we realised that wood could burn.
And we’ve been at it ever since. In fact, up until the Industrial Revolution, biomass was our main source of energy (until fossil fuels came along).
These days, as the world seeks more renewable energy solutions to fight the climate crisis, the use of biomass is rising again. In fact, it’s currently the biggest source of renewable energy used in the UK1.
But how renewable is it, really? Keep reading to find out more.
How much energy does biomass contain?
Energy is measured in joules. If you’ve got a tomato handy, lift it 1 metre from the ground. No sweat, right? That was the equivalent of 1 joule of energy.
A kilogram of cut grass contains about 4 million joules, also known as megajoules (MJ). That’s slightly more electricity than a kilowatt hour (or kWh).
Air-dried wood, the most commonly used biomass, contains around 15 MJ/kg. But if it’s oven-dried before it’s burned, that’s boosted to around 18 MJ/kg2.
The advantages and disadvantages of biomass energy
Let’s start with the good:
Biomass is always available. Humans and animals will always create waste, and plants will always grow – so there’s no danger we’ll run out of the stuff!
Using waste to create energy means that less of it goes into the landfill. That’s a win for the environment
Burning biomass doesn’t release sulfur or mercury, and it releases less nitrogen than burning coal
It’s cheap – after all, you wouldn’t charge someone for taking out the trash, would you?
You can produce biomass energy in your own home – for example, with a wood-burning stove or a biomass boiler
Bio-oils can also be used in things like plastics and medicines
Biomass has a lot of fans – but it has some downsides, too. These are the main ones:
Crops grown in order to be burnt for energy take up a lot of land. That land could be used for other things like conservation, housing, or growing crops for food
The burning process releases CO2, which contributes to the climate crisis
It also releases carbon monoxide, which adds to air pollution
When trees are cut down specifically to create energy, this is, overall, worse for the environment – more on this below
How can biomass energy be negative to the environment?
Whether you’re burning fossil fuels or biomass, you’re still going to create carbon emissions.
The idea of biomass energy is that living things like plants and animals absorb carbon dioxide from the environment as they grow. So when you burn them, the carbon they release into the atmosphere is the same amount they took out. This supposedly makes the process carbon neutral.
But it’s not such an effective system when trees or crops are cut down specifically to be used for energy.
This is because, even if every tree is replanted, it will take a long time for the forest to grow big enough again to suck all that carbon back out of the atmosphere.
Some biomass plants get around this by using BECCS (Bio-Energy with Carbon Capture and Storage) technology. This is a way of catching all the carbon that’s released during the burning process, and stopping it from being released into our air.
Food vs fuel
Another problem is that growing crops takes up a huge amount of land, water, and resources.
If we’re growing crops to be burnt for energy, what effect would this have on growing crops for food?
This is a fairly big debate in the world of biomass energy, as some people argue that it will have an effect on our ability to provide enough food for humans to eat.
So, is biomass a form of renewable energy?
Yes, according to the EU and the UN. Biomass is a renewable source of energy because you can literally renew it by planting more trees and plants.
However, it might not be as green as once hoped. Some researchers have found that burning biomass creates a ‘carbon debt’, which could take up to 104 years to pay back (or reabsorb)3.
How is the UK using biomass energy?
Here are some of the main biomass players in the UK:
- The Drax Power Station in North Yorkshire – the largest producer of carbon dioxide in the UK – has been converting its coal-fired boilers to use biomass instead. It also uses BECCS technology to make sure that no carbon is released into the atmosphere from its biomass boilers.
- The Blackburn Meadows Cogeneration Plant in South Yorkshire is a great example of a biomass plant harnessing excess heat from combustion to heat nearby businesses.
- The Templeborough Biomass Plant, which opened in August 2017, makes enough energy for 78,000 homes – saving up to 150,000 tonnes of carbon dioxide every year.
How about the rest of the world?
In 2016-2017, 70% of the renewable energy used worldwide was biomass energy4. In fact, biomass currently accounts for about a tenth of the world’s total energy use5.
Biomass energy is being adopted in Asia and Africa, where decentralised biomass plants provide electricity to communities who aren’t connected to a national power grid.
Existing biomass plants in India, Kenya, Mauritius, and Ethiopia are already proving successful, by co-generating power with agricultural waste.
And countries like Brazil are gradually freeing themselves from oil by increasing their blending of biofuels in the transport sector.
5 quick facts about biomass energy
Let’s recap, so you can sound like a biomass expert!
Biomass is made from plants, animals, and organic materials – most commonly, wood chips or pellets
It’s a renewable source of energy, according to the UN and the EU
However, some researchers have said it can have a negative impact, creating a ‘carbon debt’
About 70% of renewable energy used worldwide comes from biomass
BECCS technology is a way of making sure that biomass energy production doesn’t release carbon into the air
OVO’s commitment to renewable energy
At OVO, we offer all our members 100% renewable electricity as standard6.
We removed biomass energy from our fuel mix in 2017. This is because we believe that wind and sunshine are cleaner sources of energy. They don’t require any burning, so they’re truly carbon neutral.
Hit the button below to get a quote, and join OVO on our journey to zero carbon.
Sources and references
6 The renewable electricity we sell is backed by renewable certificates (Renewable Energy Guarantee of Origin certificates (REGOs)). See here for details on REGO certificates and how these work.