Natural gas is relatively clean energy source, which emits less greenhouse gases (hereinafter – GHG), compared to other fossil fuels, such as hard and brown coal, and therefore it may be the most feasible resource to ensure smooth energy transition towards Europe’s climate neutrality by 2050. Traditional natural gas can be easily transported and used in liquefied (hereinafter – LNG) or compressed form. As for biomethane, in future it also can be used in liquefied (hereinafter – bioLNG) and compressed form, as well as transported by means of the current natural gas infrastructure. It can also significantly enhance regional and national energy security and independence, which has been challenging for the European Union (hereinafter – EU) over at least several decades. Issue on energy independence, security of supply, alternative natural gas sources has been in a hotspot of the Baltic energy policy makers as well. Now, considering Russia’s invasion in Ukraine, since late February 2022, a problem of the EU natural gas dependency on the Russian Federation has escalated again and with force never before experienced. The European natural gas prices also hit records, as the natural gas prices in the Netherlands Title Transfer Facility reached 345 euros per megawatt-hour (hereinafter – EUR/MWh) in March 2022. Therefore, LNG import terminal is the only viable option to reduce national dependency of the so-called pipe gas which in some cases, due to the insufficient interconnections, may be delivered from very limited number of sources. The European policy makers and relevant institutions are currently working towards radical EU natural gas supply diversification, where LNG deliveries coming from outside of Russia will certainly take a central stage. In case of Latvia, the potential benefits of the LNG terminal development in Skulte were evaluated in order to reduce energy independence of the Russian natural gas deliveries in the Baltic region and to introduce new ways and sources of the natural gas flows to the Baltics. LNG terminal in Skulte could ensure significant capital investment cost reduction comparing to other projects proposed for Latvia in different periods, due to already existing natural gas transmission infrastructure and the relative closeness to the Incukalns underground gas storage (hereinafter – UGS). Various aspects, such as technical, political and economic ones, were analysed to assure that Skulte LNG terminal would be a real asset not only to customers of Latvia, but also to those of the whole Baltic region, where in future it would be possible to use biomethane for efficient utilisation of existing and developing natural gas infrastructure.

The integration of biomethane into the natural gas infrastructure is a critical element of energy-sector decarbonization, yet optimal infrastructure development scenarios remain insufficiently compared using unified decision frameworks. This study evaluates three biomethane market integration scenarios—direct connection to the gas system, biomethane injection points (compressed biomethane transported by trucks to the gas system), and off-grid delivery using the multi-criteria decision-making method TOPSIS. Environmental, economic, and technical dimensions are jointly assessed. Results indicate that direct connection to the system provides the most balanced overall performance, achieving the highest integrated score (Ci = 0.70), driven by superior environmental and technical characteristics. Biomethane injection points demonstrate strong economic advantages (Ci = 0.49), particularly where capital investments need to be reduced or there is limited access to the gas system, but show weaker environmental and technical performance. Off-grid solutions perform poorly in integrated assessment (Ci = 0.00), reflecting limited scalability and high logistical complexity, although niche applications may remain viable under specific conditions. Sensitivity analysis confirms the robustness of these rankings across a wide range of weighting assumptions, strengthening the reliability of the findings for policy and infrastructure planning. This study provides one of the first integrated multi-criteria assessments explicitly incorporating virtual pipeline logistics, offering a transferable decision-support framework for sustainable biomethane development in diverse regional contexts.

This study investigates the role of biogas and biomethane in accelerating the decarbonization of district heating systems in Europe. A structured literature review combined with two representative case studies evaluate technological, economic, and environmental performance across different system scales. The Meppel optimization model developed for the Netherlands and the large-scale Backbone energy system modelling framework for Finland are compared to identify methodological synergies and operational insights for integrating bioenergy into heating networks. The results show that biogas-based combined heat and power systems can reduce carbon dioxide emissions by more than 70 percent compared with fossil-based alternatives and significantly improve local energy security, especially when coupled with heat pumps and thermal storage. Large-scale modelling further demonstrates that biomethane and bioenergy resources provide valuable system flexibility, facilitating sector coupling and supporting the balancing of variable renewable electricity production. This study’s main contribution is an integrated comparative assessment at two different scales (local and regional), linking operational data, modelling, and performance results to determine how biogas and biomethane can optimize the energy system in the short and long term for centralized heat supply. The findings confirm that biogas and biomethane are essential, dispatchable renewable resources capable of supporting scalable, low-carbon, and resilient district heating systems across Europe.

The Doctoral Thesis analyses the significance of biomethane as a renewable and widely applicable energy resource in the decarbonisation of Latvia’s energy system. The study evaluates the technical, economic, environmental and policy aspects of biomethane production, infrastructure integration and use. By applying a multi-method approach, an analytical decision-making framework is developed to help identify the most suitable biomethane development scenarios. The results confirm biomethane’s potential to promote energy security, the circular economy and the use of local resources.

Promocijas darbā analizēta biometāna kā atjaunīga un plaši izmantojama energoresursa nozīme Latvijas energosistēmas dekarbonizācijā. Pētījumā izvērtēti biometāna ražošanas, integrācijas infrastruktūrā un izmantošanas tehniskie, ekonomiskie, vides un politikas aspekti. Izmantojot multimetodisku pieeju, izstrādāts analītisks ietvars lēmumu pieņemšanai, kas palīdz noteikt piemērotākos biometāna attīstības scenārijus. Rezultāti apliecina biometāna potenciālu veicināt energoapgādes drošību, aprites ekonomiku un vietējo resursu izmantošanu.

This research presents a conceptual framework for an interdisciplinary approach to national biomethane development, addressing the sector’s complexity, gaps and the need for systemic analysis. Biomethane plays a key role in decarbonizing existing gas infrastructure, supporting a circular economy, and strengthening energy security by reducing reliance on fossil fuels. However, national-level uncertainties require both comprehensive and targeted strategies. The study highlights the value of establishing a centralized data bank gathering information from biogas and biomethane plants, natural gas infrastructure, connection cost estimates, and technical configurations. System dynamics modelling is proposed as a method to simulate the various elements of the biomethane system. Additionally, tools such as life cycle assessment (LCA) and multi-criteria decision analysis (MCDA) are identified to assess environmental, economic and technological impacts, therefore facilitating informed decision making. This creates theoretical integrated approach. TOPSIS is used in practical test scenario to evaluate balanced gaseous energy source. Test scenario results calculations showed biomethane as the most favourable scenario (score 0.68) across multiple sustainability and economic criteria, followed by hydrogen (0.45), which shows strong decarbonization potential but faces maturity and risk challenges, while natural gas (0.35) ranks lowest, reflecting its limited role in long-term sustainable energy transitions and being impacted by low climate performance. By applying interdisciplinary approach, it could help develop an efficient, flexible and sustainable biomethane sector.