Innovating the energy change: Purification of biogas for biomethane

Author: Ing. Carlos Álvarez, September 13, 2023.

Introduction

The world is facing an unprecedented energy and environmental crisis. The growing demand for energy, and the urgent need to reduce greenhouse gas emissions, has led to the search for cleaner and more sustainable energy sources .

In this context, biogas has emerged as a promising alternative, and its purification to produce biomethane has become a key technological advance in the fight against climate change. In this article, biogas purification and how this innovation is transforming the energy sector is discussed in detail.

What is biogas and why is it important?

Biogas is a mixture of gases produced from the anaerobic decomposition of organic matter, such as agricultural waste, manure, food waste and sewage sludge. This gas mixture usually contains mainly methane (CH ₄ ) and carbon dioxide (CO ₂ ), along with traces of other gases such as hydrogen sulfide (H ₂ S) and nitrogen (N ₂ ).

The importance of biogas lies in its potential as a renewable energy source and its ability to address environmental and energy problems simultaneously. By using organic waste, the amount of waste that is deposited in landfills is reduced, which in turn reduces the release of greenhouse gases. In addition, methane is a much more powerful greenhouse gas than carbon dioxide, so its capture and use are essential to mitigate climate change.

The challenge of biogas purification

Although biogas has great potential as an energy source, its composition is not ideal for all uses. The content of CO ₂ and other pollutants present makes it less efficient and less suitable for injection into the natural gas network or for use in compressed natural gas vehicles. To reduce the carbon footprint, it is necessary to purify it and convert it into biomethane.

Biogas purification is a complex process that involves the elimination of contaminants present in the mixture, mainly CO ₂ and H ₂ S. This process is necessary to increase the methane content and improve its quality as fuel. Additionally, purification may also involve the removal of additional impurities, such as water vapor and volatile organic compounds, which may have a negative impact on its utilization as fuel.

Biogas purification technologies

Below are the most common technologies to produce biomethane.

1. CO ₂ absorption with solvents

This method involves the use of chemical solvents that have an affinity for CO ₂ . When biogas comes into contact with the solvent, CO ₂ is selectively absorbed, enriching it into methane. The most commonly used solvents include monoethanolamine (MEA) and diethanolamine (DEA). However, this process can be energy intensive due to solvent regeneration.

2. Adsorption with activated carbon or zeolites

Adsorption is a process in which CO ₂ adheres to the surface of materials such as activated carbon or zeolites. These materials have a high CO ₂ adsorption capacity and can be used in fixed bed or moving bed systems. The advantage of this method is that it does not require solvent regeneration, which can make it more energy efficient.

3. Selective membranes

Selective membranes are used in the purification process. These membranes allow methane to pass through them while retaining CO ₂ and other pollutants. As the biogas flows through the membrane, gradual enrichment into methane occurs. This method is highly efficient and requires less energy compared to other purification processes.

4. Cryogenic

Cryogenic purification involves cooling the biogas to extremely low temperatures to condense and separate the components. Since CO ₂ and H ₂ S have lower boiling points than methane, they can be easily separated by this process. Although effective, cryogenics is energy intensive and requires expensive equipment.

Benefits of biogas purification

This process offers numerous benefits both from an environmental and economic point of view:

1. Reduction of CO₂ emissions

By reducing the amount of CO₂ released into the atmosphere, you significantly contribute to the mitigation of climate change.

2. Use of organic waste

Through the purification process, organic waste is transformed into a renewable energy source and reducing the need for landfills.

3. Income generation

The production and sale of biomethane generates additional income for biogas producers, making investment in purification technologies profitable in the long term.

4. Diversification of energy sources

Biomethane can be used in a variety of applications, such as heating, electricity generation and as vehicle fuel. This contributes to diversifying energy sources and reducing dependence on fossil fuels.

Examples of success

Several countries and companies have begun to adopt biogas purification as part of their energy strategy. A prominent example is Sweden, where a network of service stations offering biomethane as fuel for cars has been developed. This has driven the transition towards more sustainable mobility and significantly reduced CO₂ emissions in the transport sector.

On the business front, companies such as IKEA and Nestlé have invested in biogas purification facilities in their manufacturing and distribution operations. These companies use the organic waste generated in their processes to produce biomethane and reduce their carbon footprint.

Challenges and considerations

Among the main challenges and important considerations are the following:

1. Initial costs

Investment in purification technologies can be expensive, being an obstacle for small businesses or farmers. However, the long-term benefits often outweigh the initial costs.

2. Energy required

Some purification methods, such as cryogenics, consume significant amounts of energy, which can affect the overall efficiency of the process.

3. Maintenance and operation

Biogas purification facilities require proper maintenance and trained personnel to operate them efficiently and safely.

4. Rules and regulations

Environmental and safety regulations can vary from location to location, influencing the feasibility and implementation of purification systems.

Conclusions

The purification of biogas to produce biomethane is a crucial innovation in the energy and environmental field. This technology makes it possible to make the most of organic waste and reduce CO ₂ emissions, contributing significantly to the fight against climate change.

As challenges are overcome and more efficient technologies are developed, biomethane has the potential to play a critical role in the transition to a more sustainable and cleaner energy mix. It is the responsibility of governments, companies and citizens to encourage the adoption of this technology and promote a greener and more sustainable future for new generations.

Bibliographic references

• MARÍA T. VARNERO, MARGARITA CARÚ, KARINA GALLEGUILLOS AND PATRICIO ACHONDO. Technologies available for the Purification of Biogas used in Electrical Generation; Consulted on September 11, 2023; https://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-07642012000200005
• CHRISTOPH ZIMMERMANN. Biogas purification, Basics, technologies, examples; Consulted on September 12, 2023; https://www.biorrefinerias.cl/wp-content/uploads/2017/12/C-Zimmermann.pdf
• BION. Purification of biogas and biomethane; Consulted on September 13, 2023; https://www.bioconservacion.com/es/purificacion-biogas .
• CONDORCHEN ENVIRO SOLUTIONS. Biogas treatment; Consulted on September 13, 2023; https://condorchem.com/es/blog/tratamiento-del-biogas/