How is Bio-Energy Produced?

How is bio-energy produced? This is a question that many people ask as bio-energy doesn’t seem to have the same interest as other forms of renewable energy. Bio-energy is another type of renewable energy that can help us to reduce carbon emissions. In the same way as the history of wind energy, we have been producing bio-energy for centuries.

From the moment we found out how to burn wood, we have been using it as a form of fuel. So, in a similar way, bioenergy production reduces greenhouse gases as it replaces fossil fuels. As we improve technology to produce electricity from organic materials more cleanly, we will be able to more widely adopt this renewable energy source in place of fossil fuels6. So how is bio-energy produced and what is it?

What is Bio-Energy?

Bio-energy is carbon neutral energy that we generate from agricultural residues and waste. In the past, we put this waste in a landfill or burnt it. However, when we burn it or allow it to ferment, it releases energy. The raw materials used for bio-energy include plants, wood waste and other forms of waste. This raw material is typically called biomass.

Bio-energy also includes biofuel production which we can hope to use as a replacement for traditional transport fuels3. So, from burning wood and waste to using oil, fats and recycled grease, we can create bio-energy in the form of fuel and electricity.

Rapeseed Field Biofuel Energy Crop
Bio-Energy can be produced from sustainable crops. Shown is a Rapeseed field near Bavenhausen, Germany. Rapeseed crops have a higher oil content than many other vegetables. As a result, they can generate more energy when burnt. A total of 125 thousand hectares of agricultural land produced bioenergy crops In the UK in 2017.7 Wheat and maize made up the largest contributors by hectare. Photo Credit Daniel Schwen CC BY-SA 2.5

How is Bio-Energy Produced?

So bio-energy creates energy from waste materials, but how is bio-energy produced? A bio-energy power plant can vary in size. Therefore, it can range from a small heating system to a huge industrial plant that uses thousands of tonnes of biomass fuel annually.

To release the energy from biomass, we can use several different types of technology. These can range from combustion which is a proven method through to newer technologies. The new technologies can now turn biomass into liquid fuels that we can use in place of other liquid fuels.

So, we can create bio-energy by using the following processes:

Combustion

Combustion is the most common process8.  A biomass power plant will burn agricultural waste and other waste. As it uses heat, it converts the source into energy using combustion or gasification. We can burn the waste to heat water before the steam spins turbines. This process uses excess air to create heat. The first part of the process involves the creation of vapours that can combust from the biomass. These will then burn like flames. The residual material, which is often charcoal is then burnt while a forced-air supply helps to create more heat. The gases then pass through a heat exchanger where they produce steam, hot air or hot water.

Gasification

Biomass gives off gas naturally when it rots. When this occurs in the open, it releases methane which can cause more harm than carbon dioxide. However, if we store the biomass in sealed tanks, they prevent the gases from entering the atmosphere. We can then extract it allowing us to burn it. This leaves us with water and carbon dioxide which is better for the environment.

Gasification is a thermal process whereby it converts plant matter into several gases that are combustible. These gases are hydrogen, carbon monoxide, methane and ethylene. Using direct or indirect heating and a reduction in the supply of oxygen, the biomass creates gases that can then be burnt.

Pyrolysis

This process involves burning biomass and waste food products at high temperatures with oxygen removed2. This causes new molecules to form. This changes the character of the waste and then ensures that a vast amount of energy produced. This thermal decomposition of biomass creates products known as biochar, bio-oil and a range of gases including hydrogen, carbon monoxide and carbon dioxide.

Anaerobic Digestion

This uses an almost natural process. This process uses microorganisms to break down biomass. As a result, it produces gas that consists of methane and carbon dioxide.

Fermentation

The fermentation process is one that breaks down the biomass anaerobically. A series of chemical reactions convert sugars into alcohol. We can then add yeast and bacteria before the ethanol goes through a distilling process, which increases the concentration of alcohol1. This then makes it possible to use in vehicles.

Who Uses Bio-energy?

Bio-energy is a diverse and accessible form of energy. Homeowners can begin generating energy just by creating a compost heap. However, on a grand scale, large energy suppliers are now creating bio-energy power plants. As they search for new sustainable energy sources, they now invest more money in bio-energy technology and research.

When we use biomass to create energy, the raw material is known as feedstock. These are specially grown or consist of waste products. There are dry feedstocks and wet feedstocks. Dry feedstock mainly consists of wood pellets that we then burn. This boils water and creates steam. They then use this steam to drive a turbine and generate electricity.

Wet feedstocks include food waste. These are stored in sealed tanks where they rot and produce methane. The gas can then be burnt in order to generate electricity.

Bio-energy is a source of energy that is extremely flexible. We have the ability to turn it up and down in order to meet demand. Therefore, it is a valid alternative to the likes of wind and solar energy.

How is Bio-energy Produced from Biomass?

What are the main forms?

As we know, biomass consists of waste or a special material that we can grow that is high in energy. However, there are many forms of biomass available for use.

Wood and Agricultural Products

Commonly forms of biomass are chips, bark, sawdust and other forms of wood waste. This makes up the largest percentage of biomass energy. It is also mainly used for electricity generation.

Bio-Diesel

We make this from vegetable oil, animal fat and grease that we recycle. There is hope that biodiesel can replace diesel that we use in cars, trucks and other modes of transport.

Soy Beans Bio Energy Production
Soybeans form part of the raw materials for everything from meat alternatives to oils found in cosmetics. In the US soybeans also make up around 50% of the feedstock for biodiesel. In 2017 US cars, homes and other users of biodiesel consumed nearly 2 billion gallons of biodiesel4. Pictured is a variety of Soybeans in their raw form. Photo Credit: Scott Bauer, Public Domain via WikiCommons.

Solid Waste

Solid waste is made up of waste biomass and non-biomass material. 1 tonne of solid waste has as much energy in the form of heat as 500 pounds of coal.

Bioethanol

Bioethanol is a fuel that comes from plants that have been fermented to produce fuel. We now have the ability to use this in vehicles as the technology is evolving. In fact, even certain high-performance cars have the ability to use this fuel.

Landfill Gas and Biogas

We can now use high-temperature digesters to help sewage and agricultural waste rot quickly. This then releases gas that we can capture and then use as fuel.

Is Bio-energy Sustainable and Good for the Environment?

When we burn biomass, it does release carbon dioxide. However, the amount that it releases is the same amount that it absorbed when it grew. As a result, it does not break the carbon balance.

In contrast to this, when we burn fossil fuels, they release large amounts of carbon dioxide. This results in more carbon dioxide finding its way into the atmosphere. It is this process that causes global warming.

The energy efficiencies of bio-energy are better than that of other combusted sources. However, sustainability and environmental benefits can depend on the feedstocks that we use.

Is Bio-energy really carbon neutral?

There is some debate about the classification “carbon neutral” which makes bio-energy a renewable source worthy of scrutiny. When you consider that waste or crops are used to create biomass, then it certainly provides a feasible alternative to how this waste would have been dealt with otherwise. Of course, it is likely that biomass or bio-energy is not completely neutral but what are we comparing it to? If we compare it to that of fossil fuels, then it is a far better option, even if it is not completely carbon neutral.

How Are We Using Bio-energy Around the World?

The UK

In the UK, we are adopting a new and encouraging approach to bio-energy. There are several plants and biomass projects already up and running.

The Drax Power Station is presently the largest producer of polluting carbon dioxide in the UK. To address it’s environmental harm It has been replacing coal burners with biomass, importing wood pellets from the United States and Canada. The switch to biomass has meant that 20 million tonnes of CO2 have been prevented from entering the atmosphere, making the switch a positive one. Drax shows the way in demonstrating how bio-energy is produced by big producers.

Drax Power Station
Shown Drax Power Station in the UK. Two-thirds of electricity generation at Drax is now possible using renewable energy. Photo Credit: Alan Murray-Rust CC BY-SA 2.0

Providing power for 78,000 homes is the Templeborough Biomass plant. Whilst still a new plant as it has only been open since 2017, it saves around 150,000 tonnes of carbon dioxide annually.

The Blackburn Meadows Cogeneration Plant uses heat from the combustion process. It then feeds this into local businesses using a direct heating system. In Kent, around 50,000 homes now benefit from bio-energy.

Finally, the largest biomass plant is soon to reach completion in the UK. The Tees Renewable Energy Plant will prevent 1.2 million tonnes of CO2 emissions from entering the atmosphere each year. It will also have the ability to power 600,000 homes.

The US

In the US, bio-energy is also largely recognised as a renewable source of energy. In 2018, around 5 quadrillion British thermal units that came from biomass were used. This is a figure that is expected to grow. In 2016, the US produced 36.9 metric tons of bio-oil, which is a significant rise from the 3 million metric tons produced in 2000.

The top five performing states are North Dakota, Iowa, Mississippi, Georgia and North Carolina.

The New Hope Power Partnership which is based in Florida is now one of the largest biomass power plants in the world. It has an installed capacity of 140MW, using sugar cane fibre as well as recycled urban wood. It now has the ability to provide electricity to 60,000 homes.

Rest of the World

Throughout the rest of the world, bio-energy makes up 10% of the global energy supply. However, 70% of the electricity made from biomass comes from Europe and North America. This is down to the fact that we can use large, sustainable forests to supply wood pellets5.

Countries in Asia and Africa now use biomass energy. There are many communities that do not have the ability to connect to a national power grid. Therefore, biomass plants are now providing partial electricity needs in these countries. In Brazil, a commitment has been made to move away from the use of fossil fuel-based oil. The aim is to replace it with biofuels.

Bio-Energy is a Serious Renewable Energy Contender

Bio-energy is a term that many of us have heard. However, many of us wonder “how is bio-energy produced”. Unlike wind energy or solar energy, it is slightly more reliant on manpower. This is especially the case when we consider the ongoing growth of crops or sourcing of waste materials. Despite this, when we can use waste to create energy and even grow energy crops to burn, we have an element of control of the energy we produce.

In some ways, it is similar to that of fossil fuels in the way that we use it to create energy. Bioenergy does still produce emissions. However, it presents significant CO2 reductions when compared to fossil fuels.

Therefore, it does seem as though it is a serious contender when it comes to a renewable energy source that will take its own place as we strive to reduce our reliance on polluting fossil fuels.

Maria Shanina

Further Reading:

Sources & References:

#Description
1Inhibition of ethanol-producing yeast and bacteria by degradation products produced during pre-treatment of biomass. Klinke, H.B., Thomsen, A.B. & Ahring, B.K. Appl Microbiol Biotechnol (2004) 66: 10. https://doi.org/10.1007/s00253-004-1642-2
2Patrick A. Horne, Paul T. Williams, Influence of temperature on the products from the flash pyrolysis of biomass, Fuel, Volume 75, Issue 9, 1996, Pages 1051-1059, ISSN 0016-2361, https://doi.org/10.1016/0016-2361(96)00081-6.
3Biomass for Renewable Energy, Fuels, and Chemicals. By Donald L. Klass. Entech International Inc. 1998 Academic Press.
4Biodiesel and Other Renewable Fuels Overview, U. S. Energy Information Administration / Monthly Energy Review June 2019
5James A. Scott, William Ho, Prasanta K. Dey, Strategic sourcing in the UK bioenergy industry, International Journal of Production Economics, Volume 146, Issue 2, 2013, Pages 478-490, ISSN 0925-5273, https://doi.org/10.1016/j.ijpe.2013.01.027.
6Günther Fischer, Leo Schrattenholzer, Global bioenergy potentials through 2050, Biomass and Bioenergy, Volume 20, Issue 3, 2001, Pages 151-159, ISSN 0961-9534, https://doi.org/10.1016/S0961-9534(00)00074-X.
7Crops Grown For Bioenergy in the UK: 2017. Department for Environment Food & Rural Affairs (UK). 31st January 2019.
8B.M Jenkins, L.L Baxter, T.R Miles, T.R Miles, Combustion properties of biomass, Fuel Processing Technology, Volume 54, Issues 1–3, 1998, Pages 17-46, ISSN 0378-3820, https://doi.org/10.1016/S0378-3820(97)00059-3.

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