Biomethane: recovering the waste from my home

The use of domestic organic waste for the production of biomethane is presented as a mature and environmentally friendly alternative, which allows users to play a more active and conscious role in the change of energy model.

Interest in the production of biomethane has grown considerably in the last few years, since it is presented as a renewable and sustainable energy source with a multitude of applications and benefits. One of its standout aspects is its organic waste recovery-based production, allowing the waste we generate daily to be transformed into a valuable energy source.

What is biomethane?  

Biomethane is part of biogas, a renewable gas that is generated from the anaerobic digestion (in the absence of oxygen) of biodegradable organic matter, and which is composed mainly of methane (CH₄) and carbon dioxide (CO₂). Once the biogas is obtained, the CO₂ is removed, resulting in biomethane as a product.

The waste used comes from industries such as the food industry, agricultural industry, livestock industry, or forestry industry, from the water treatment process, as well as from the domestic waste generated in homes. This waste is collected and taken to biogas plants to be treated in the fermenter or biodigestor, a hermetically closed tank, where the organic matter goes through a decomposition process in which bacterias and other microorganisms are involved. During this process, called anaerobic digestion, the matter decomposes into molecules, releasing gases that give way to what we know as biogas. Once the biogas is obtained, this is treated by a system called Upgrading, in which the CO₂ is removed, resulting in a product with >95% of CH₄, called biomethane, with the same characteristics and applications as fossil natural gas.

Once the biogas is extracted from the waste by anaerobic digestion, there is an additional stream, called digestate, with approximately 90% moisture, and in which the nutrients present in the waste entering the digestion are retained.

Main benefits  

As it is an energy source that is generated by means of a natural decomposition process, the production of biomethane has significant advantages. 

• 100% renewable. The organic matter used in its production constitutes an inexhaustible recourse and which experiences a new useful life when it is recycled, promoting the circular economy.
• Low-carbon solution. It is a gas that, as it has an organic origin when it undergoes combustion processes, in the same way as fossil natural gas is neutral in CO₂ emissions, which directly contributes to reducing greenhouse gas emissions. That biomethane is neutral in CO₂ emissions means that those emitted in its combustion process have been previously captured from the atmosphere by plants in their photosynthesis process. 
• Waste reduction. It helps to prevent the accumulation of organic waste in landfills and limits the extraction of new resources. 
• Responsible economic development. It allows to decentralize the supply of natural gas and represents a business and employment opportunity for rural areas, as biomethane plants are found in agricultural and livestock areas, where organic waste is generated.
• Energy dependence. Local production of bioemthane can help to promote greater energy autonomy, reducing imports from other countries.  
• Production of biofertilizers. The resulting digestate from the anaerobic digestion process is an ideal raw material for the production of biofertilizers. Moreover, the digestate can be directly used in agriculture as an organic fertilizer, replacing inorganic fertilizers.

Applications in industry and customers

Biomethane, obtained once the upgrading of biogas has been carried out, can be injected into the natural gas network, or directly used as a liquefied natural gas (bio LNG) or compressed natural gas (bio CNG) for use in mobility. It is a very versatile renewable energy source that can be used thermally, electrically, and as a raw material for the production of other renewable biofuels.

The potential of biogas in Spain

In Spain, there is a large availability of organic matter coming from livestock and agriculture, which can be perfectly harnessed to be converted into biomethane. The development and production of these types of projects, so far, has been quite poor, due to the lack of regulation and incentives compared to other countries in our environment, but for some years now, work has been underway on an appropriate regulatory framework that will allow us to take full advantage of it.

At the end of 2023, there were more than 140 biogas plants in Spain, but only 10 biomethane plants, compared to the more than 20,000 biogas plants and 1,300 biomethane plants in Europe. According to SEDIGAS, Spain has the potential to be the third largest producer of biomethane in Europe, being capable of having more than 2,300 biomethane plants.

In this context, the Ministry for Ecological Transition and Demographic Challenge launched the Biogas Roadmap in 2021, within the Integrated National Energy and Climate Plan (PNIEC) 2021-2030. This initiative establishes a series of specific guidelines to expand the generation of this gas and achieve, as a minimum objective (which was revised in 2023), 20 TWh annually of biogas production by 2030. According to SEDIGAS, in Spain there is a production potential of 163 TWh/y.

In order to achieve this goal, the measures included in this proposal are organized into five key areas of action.

1. Regulatory instruments. They are based on administrative simplification and homogenization of procedures, key when facilitating the start-up of new projects related to the production of this renewable gas. 
2. Sectoral instruments. One of the most relevant proposals is the establishment of annual biogas and biomethane penetration targets through the sale or consumption of natural gas. Through quotas or mandatory percentages of the presence of these gases in the supply, their consumption can be prioritized and their expansion made easier. 
3. Financial instruments. Allocating resources and financing to the development of biomethane throughout its production chain is a key point for its development. For example, allocations from the Recovery, Transformation, and Resilience Plan (PRTR) will be available and the possibility of positively modifying its taxation is also being assessed.  
4. Cross-cutting instruments. These measures are focused on enhancing the use of biomethane by public administrations and bringing this fuel closer to citizens. It can be done through the inclusion of the study of these in educational plans or by promoting the involvement of citizens in the recycling of waste.
5. Boosting R&D&I. Promoting the research and carrying out of studies, promoting demonstration projects, and opting for innovation in technologies will allow the development of processes that allow a greater and better use of raw materials.  
   

What can we do at home to favor the production of biomethane?

The correct recycling of waste at home plays a crucial role in the generation of biogas, since a significant part of the matter used for its production comes from domestic use. Firstly, one would have to emphasize the importance of separating the different waste generated daily appropriately, such as food scraps, fruit or vegetable peels, cardboard or plastic packaging, glass bottles, etc.  

Depending on the type of waste, they should be deposited in their corresponding recycling bins to promote their recovery and give them a new useful life. In the case of biomethane, organic waste will be converted into raw material, but adopting responsible recycling habits at home for all waste generated is essential for the preservation of the environment that surrounds us.