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Biomass energy explained

 

What is biomass energy?

Biomass energy is the use of organic material to generate energy. Biomass is just organic matter – think, stuff that’s made in nature – like wood pellets, grass clippings and even dung.

Crops, like sugarcane and corn, can also be used to create biofuels. And because plant matter can be regrown, it’s a renewable source of energy.

 

When was biomass energy discovered?

Technically, it was discovered back in our cave-dwellings days when we realised that wood could burn.

And we’ve been at it ever since. Back in the 13th century, explorer Marco Polo noted the use of processes to create biofuels, after seeing the Chinese using covered sewage tanks to generate biogas.


Diesel power

Meanwhile, in the late 1800s, Rudolf Diesel (of the diesel engine fame) invented a biofuel engine powered by vegetable oil. That was before petroleum-based diesel fuel became so widely available.

Biofuels are now playing an important role in the transport industry, where cars, buses and planes are largely dependent on fossil fuels. Transport produces a huge amount of greenhouse gases, and biofuels hold the potential to reduce this carbon footprint.

 

What are the main forms of biomass?

 

How can biomass generate electricity?

Biomass can generate electricity in a number of ways, but the most common is combustion – burning agricultural waste or woody materials to heat water and produce steam, which spins turbines.

In some biomass plants, excess steam can also be used in on-site manufacturing processes, or for heating, which rises the energy efficiency of biomass electricity generation to approximately 80%. Smart, right?


Science

There’s also snazzy-sounding scientific methods like anaerobic digestion, gasification and pyrolysis. The key thing to remember is that they all speed up the snail-paced breakdown process, so we’re left with biogas or bio-oil, which are used as fuels to generate electricity.

And there’s even ways of generating electricity directly from the stuff you flush down the toilet. We won’t go into the details... but the organic material in sewage contains electrons, which can be stripped by enzymes and then used in an electric circuit.

The good, the bad (and the mucky) of biomass energy

 

  The good

  The bad

  Human and animal waste is always available, as we’re always producing the mucky stuff.   

  Energy crops take up land which we could use for farming, conservation, housing.

  It doesn’t produce sulfur or mercury and releases less nitrogen than coal.

  Releases CO2, which needs to be carefully monitored so it doesn’t exceed limits.

  It’s cheap. You wouldn’t charge a lot for someone taking your rubbish, would you?

  It’s not entirely clean – there’s the smell and methane gas is released.

  Using waste for energy reduces the amount that ends up in a landfill.

  There’s a risk of deforestation with uncontrolled biomass production.

  Anyone could produce biomass energy, reducing the need for centralised power.

  Mass production of biomass needs an extensive, costly irrigation infrastructure.

  Bio-oils can also be used for plastics, medicines and other consumer products.

  With current technology, biomass energy is behind fossil fuels in energy efficiency.

 

How much energy does biomass contain?

In case you’d forgotten, energy is measured in joules. If you’ve got a tomato handy, lift it 1 meter 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 the kilowatt hour used in the energy retail market.

And wood, the most commonly used biomass, contains around 15 MJ/kg. But if it’s dried before it’s burned, that’s boosted to around 18 MJ/kg.
 

Squaring up to fossil fuels

But when you consider coal, with an energy content of around 25 to 30 MJ/kg, and crude oil, with about 42 MJ/kg, it’s clear that biomass isn’t as efficient.

Biofuels, like sunflower oil and castor oil, fair a little better compared to petrol – with sunflower oil having an energy content of 33 MJ per litre, and petrol at around 32 to 35 MJ per litre.


Food vs fuel

But if we’re growing crops for biofuels, what effect will this have on growing crops for food? This is a fairly big debate in the world of biofuels, as some argue that it will have implications on our ability to provide enough food for human consumption.

There’s no debate, however, on how efficient energy crops are when it comes to land use. One crop of castor beans, planted over a hectare, provides 1,413 litres of castor oil, equivalent to 1,400 litres of petrol.

 

How is the UK using biomass energy?

First, let’s take a look at some of the current and upcoming biomass projects 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. Up to now, half the plant is co-fired and burns wood pellets imported from the US and Canada.

The Blackburn Meadows Cogeneration Plant in South Yorkshire is a great example of a biomass plant harnessing excess heat from combustion to provide heating to nearby businesses via a district heating system.

The Templeborough Biomass Plant, which opened in August 2017, provides enough energy for 78,000 homes, saving up to 150,000 tonnes of carbon dioxide every year.

And as the UK moves away from coal dependence, there’s more biomass energy plants on the way:

The Kent Biomass power station, coming online in Summer 2018, will meet the energy demands of up to 50,000 homes.

Tees Renewable Energy Plant, costing £650m and due to be finished in 2020, will be the largest biomass plant in the world. The finished plant will save 1.2 million tonnes of CO2 emissions per year, while producing enough electricity for 600,000 homes.


Rest of the world

Currently, biomass energy represents around 10% of the global energy supply, with 70% of electricity produced from biomass coming from Europe and North America. This is because large, sustainable forests can support a constant supply of wood pellets.

And more recently, 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 transportation sector.

 

Let’s recap, so you can sound like a biomass expert.

  1. Biomass is organic matter and can be burned to generate electricity.

  2. Biomass is sustainable, renewable and is a low-carbon option.

  3. Wood pellets are the most commonly used biomass for electricity production.

  4. They’re typically ‘co-fired’ with a little bit of coal to reduce CO2 emissions.

  5. Biofuels, like sunflower oil, can provide as much energy as petrol.