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What is biomass and why is it important?

Converting our waste into sustainable energy

Reading time: 5 min

Human beings generate organic material on a daily basis, but what if it could be harnessed to produce energy that was also renewable? That is biomass: an energy source that harnesses different waste to create a renewable fuel, neutral in CO2 emissions and very competitive.

What is biomass and how is it obtained?

Biomass is a heterogeneous energy source as it can appear in diverse forms: agricultural waste (stubble), forestry (cleaning of forests and river basins), agri-food (waste from the livestock industry or industrial oil), and the organic matter generated by human beings in the form of rubbish. 

According to the European Renewable Energy Directive, biomass is also understood by “the biodegradable fraction of products, waste, and residues of biological origin from agricultural, including plant and animal substances, from forestry and related industries, including fisheries and aquaculture, as well as the biodegradable fraction of waste, including industrial and municipal waste of biological origin."

The most used material in the production of energy from biomass is wood, whether it be in the form of pellets, wood chips, briquettes, sawdust, or firewood; thanks to the combustion of these organic materials, we can obtain heat, fuels, and electricity. In countries such as Spain, with a rich natural environment and an extensive agricultural and livestock production, the possibility of having energy obtained from biomass is magnificent news, as it is much more simpler to access the necessary raw materials for its production.

How is energy from biomass harnessed?

Biomass can be harnessed to produce heat, electricity, or fuels. Furthermore, its adaptability allows it to be used both on a small scale (for example, in the boiler of a house or building) and on a large scale (in biofuel plants). 

The methods to produce energy from biomass are grouped in two big groups:

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Thermochemical methods

They are those that transform biomass from heat; they are used in materials with less moisture.

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Biochemical methods

Certain microorganisms are used to degrade organic matter molecules. They are applied to materials with higher moisture content.

Ways of harnessing energy from biomass according to its origin

Given the diversity of organic materials that can be used to produce energy, this also adopts different forms according to the origin. 

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Biofuels production (biodiesel, biojet, etc.)

  • First generation biofuels: They are obtained from agricultural food crops (for example, vegetable oils).
  • Advanced biofuels or of second generation: They come from crop residues, food industries, urban waste, and those obtained from non-food agroforestry crops. They can also be extracted from aquatic plants and algae whose oil content is greater than 50%. Although these latter still haven't been put on sale, studies demonstrate their great potential.
  • In addition, there are routes under development in which genetic modification of certain microorganisms can improve CO2 capture and storage. 

Currently, the most used biofuels are bioethanol and biodiesel, although other very interesting alternatives are emerging, such as hydrobiodiesel (HVO) or biojet (SAF).

  • Bioethanol: As a substitute for gasoline, it is currently obtained from traditional crops such as corn, sugar beet, sugar cane, and certain grains. 
  • Biodiesel: It is derived from fats such as vegetable oils, animal fats, and recycled cooking fats, and can be blended with oil-based diesel.
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Biogas production

Biogas is mainly formed by methane and carbon dioxide that has been obtained from the decomposition of organic matter anaerobically (in other words, without the intervention of oxygen). 

It is obtained from livestock and agro-industrial waste, sludge from water treatment plants, and domestic waste. 

Currently, it is used above all to generate thermal and electrical energy, but in the future it will be possible to inject it into the conventional natural gas network.

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Thermal energy production (heating, pellets, etc.)

Thermal energy is generated from direct combustion systems, in other words, boilers, heaters, ovens, or fireplaces. 

It can be harnessed to generate steam that is used in industry or for air conditioning or to obtain domestic hot water, among other uses.

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Electrical energy production (biomass plants)

It is possible to obtain electrical energy from biomass that is burned in boilers to produce steam; this steam is harnessed in turbines to generate electricity. 

Power outputs of up to 50 MW can be obtained. 

Advantages of biomass

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Sustainable, cost-effective, and accessible

The availability of raw materials is high and their use contributes to the good use and conservation of natural areas.

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It favors the circular economy

It transforms its own waste (for example, through the use of ash as agricultural fertilizer) and minimizes the environmental impact. 

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It drives the creation of jobs

It is an asset to combat energy poverty in those parts of the world where the cost of fossil fuels consumes a large part of their GDP.

It reduces dependence on fossil fuels

In sectors where decarbonization is very complicated, such as heavy vehicle or air transport.

Types of biomass

We can classify biomass into three main groups:

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Natural biomass

It is produced in nature without human intervention.

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Residual biomass

It is organic waste produced by human activity. For example, solid urban waste or that which comes from agricultural, livestock, or industrial activities. This, in turn, can be classified as wet or dry. 

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Biomass produced by energy crops

It is those crops whose purpose is the use of energy and in which a specific species is planted to maximize the production of living matter. 

Repsol and biomass

Biomass is emerging as one of the pillars of the circular economy thanks to the use of what was once considered mere waste, which can now be used as renewable energy resources. For us at Repsol, this is a factor of great importance, as the circular economy is one of our strategic pillars for accelerating the energy transition and achieving the ambitious goal of becoming a company with net zero emissions by 2050. We will therefore invest 200 million euros into the Cartagena industrial complex (Murcia), which will become the first plant in Spain to produce advanced biofuels such as hydrobiodiesel, biojet, and biopropane, amongst others. 

The facilities will be operational by the first quarter of 2023 and will produce 250,000 tons of advanced biofuels per year, which will allow 900,000 tons of CO2 to be reduced each year. In this way, it will be a boost for sustainable mobility and a firm commitment to the use of renewable energies.

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Rewofuel, a new biorefinery concept

In turn, at Repsol we have the Rewofuel project. This project has 11 European partners, which have joined to demonstrate the technical, environmental, and socioeconomic viability of transforming residual soft-wood into biofuels through the process of hydrolysis.