{"id":79774,"date":"2026-03-27T10:00:34","date_gmt":"2026-03-27T10:00:34","guid":{"rendered":"https:\/\/biometano.lneg.pt\/?page_id=79774"},"modified":"2026-03-27T10:06:17","modified_gmt":"2026-03-27T10:06:17","slug":"faqs-2","status":"publish","type":"page","link":"https:\/\/biometano.lneg.pt\/?page_id=79774&lang=en","title":{"rendered":"FAQs"},"content":{"rendered":"\t\t
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FAQ<\/span><\/div>

FAQ<\/h2><\/div>
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This document compiles the most frequently asked questions from our users, with the aim of providing quick access to essential information.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

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What is biomethane?<\/h3><\/div><\/div>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Biomethane<\/strong> is a gas that is generally produced from biogas derived from anaerobic digestion, following cleaning and purification (upgrading) to remove carbon dioxide (CO\u2082), hydrogen sulphide (H\u2082S), water vapour, siloxanes and other impurities. At the end of this treatment, biomethane has a methane (CH\u2084) concentration of between 92\u201397%, achieving compositional and thermodynamic characteristics similar to those of natural gas<\/b>. By reducing impurities to residual levels, biomethane meets the regulatory requirements for injection into the natural gas grid and for use in conventional combustion equipment, as well as being suitable for use as a vehicle fuel. Because it is produced from biomass, biomethane is considered a renewable energy source.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

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How does biomethane differ from natural gas? And from biogas?<\/h3><\/div><\/div>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Natural gas<\/b> is a fossil fuel<\/b> composed mainly of methane (CH\u2084, 85\u201398%), with smaller amounts of ethane (C\u2082H\u2086), propane (C\u2083H\u2088), carbon dioxide (CO\u2082), nitrogen (N\u2082), and other light hydrocarbons and inert gases.<\/p>

Biogas<\/b> is a gas of biological origin<\/b> produced by the anaerobic digestion of organic substrates, such as manure, food-waste, wastewater treatment sludges or agricultural residues. Its typical composition includes 50\u201365% methane (CH\u2084) and 35\u201350% carbon dioxide (CO\u2082), as well as small amounts of hydrogen sulfide (H\u2082S), water vapour, siloxanes, ammonia (NH\u2083) and other volatile compounds. Due to its high CO\u2082 content and the presence of corrosive or toxic impurities, biogas does not meet the necessary requirements for direct injection into the natural gas grid, requiring prior purification treatment.<\/p>

Biomethane<\/b> is produced from biogas following cleaning and purification, in a process known as upgrading, which removes CO\u2082 and contaminants to residual levels. With a methane (CH4) content of between 92\u201397%, biomethane has properties similar to those of natural gas and can be injected into the gas grid or used as a renewable fuel. Being derived from biomass, it is a renewable alternative to fossil natural gas.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

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Does the production of biomethane in Anaerobic Digestion plants cause unpleasant odours in the surrounding area?<\/h3><\/div><\/div>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Yes. During the handling of organic substrates (manure, sludge, biodegradable waste) and during the biogas production \u2014 before upgrading \u2014 odour emissions may occur, particularly from sulfur compounds (such as H\u2082S), nitrogen compounds (amines, ammonia) and other volatile organic compounds. However, proper containment systems, air treatment (biofilters, chemical scrubbers, activated carbon filters) and the adoption of good operational practices can significantly reduce, or even eliminate, these odours in practice.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

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Does the use of biomethane in the industry, transport or after injection into the Public Gas Grid (RPG) cause bad odors?<\/h3><\/div><\/div>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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No. Biomethane is odourless following the purification (upgrading) process, during which odorous compounds such as H\u2082S, ammonia, siloxanes and other volatile organic compounds are removed. For distribution in the grid, biomethane is artificially odourised, just like natural gas, solely to enable the rapid detection of any leaks. It is also important to note that, as methane is a gas with a high global warming potential, the operation and use of biomethane follow strict practices to prevent leaks and atmospheric emissions.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

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What are the main feedstocks used in biomethane production?<\/h3><\/div><\/div>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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According to the Biomethane Action Plan (PAB 2024\u20132040), the most relevant raw materials for biomethane production in Portugal stem directly from five identified strategic sub-sectors, on the basis of which the national production potential has been estimated. These sub-sectors provide the waste streams with the greatest availability, stability and technical and economic viability for anaerobic digestion. Namely:<\/p>

  1. Municipal solid waste (MSW)<\/span>: this includes the organic fraction of municipal waste collected separately or treated in organic waste treatment facilities. This is one of the pillars of the first phase of PAB 2024-2040 development, due to the significant production already existing in municipal waste management systems. This sub-sector includes out-of-date packaged food obtained from the food retail sector (hypermarkets, supermarkets, food retailers) and food waste obtained from the HORECA sector (restaurants, hotels, etc.) via direct collection.<\/li>
  2. Wastewater and sludges from wastewater treatment plants (WWTP)<\/span>: these sludges have high organic loads and are already commonly treated by anaerobic digestion, offering significant potential for conversion into biomethane.<\/li>
  3. Agricultural residues and plant by-products<\/span>: these include crop residues, agricultural processing waste and other organic materials from farming activities, considered essential for increasing the availability of organic matter for anaerobic digestion.<\/li>
  4. Livestock waste<\/span>: identified as having one of the greatest growth potentials for the 2026\u20132040 period, the livestock sector provides large volumes of manure and slurry with a high organic load, making it one of the main raw materials for scaling up biomethane production.<\/li>
  5. Agro industrial by-products and effluents<\/span>: these include effluents and organic waste from the agri-food industries (e.g. dairy, animal slaughter, fruit and vegetable processing, beverages, amongst others). These effluents have high organic matter content and are considered strategic in boosting national biomethane production.<\/li><\/ol>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t
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    What are the first steps to licensing a new biomethane production plant?<\/h3><\/div><\/div>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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    The installation of a new biomethane production plant with main Economic Activity Code (CAE) 35210 (gas production) involves four stages<\/span>:<\/p>

    1. Application for Prior Registration with the Directorate-General for Energy and Geology (DGEG) in accordance with Decree-Law No. 62\/2020 and Joint Order of the Portuguese Environmental Agency (APA) and DGEG No. 1\/2026.

      The application for prior registration may be rejected within 30 days in the following cases: