Biomethane is one of the most promising renewable gases (hereafter – RG) – a flexible and easily storable fuel, and, when used along with the natural gas in any mixing proportion, no adjustments on equipment designed to use natural gas are required. In regions where natural gas grids already exist, there is a system suitable for distribution of the biomethane as well. Moreover, improving energy efficiency and sustainability of the gas infrastructure, it can be used as total substitute for natural gas. Since it has the same chemical properties as natural gas, with methane content level greater than 96 %, biomethane is suitable both for heat and electricity generation, and the use in transport.Biomethane is injected into the natural gas networks of many Member States of the European Union (hereafter – the EU) on a regular basis for more than a decade, with the Netherlands, Germany, Austria, Sweden and France being among pioneers in this field. In most early cases, permission to inject biomethane into the natural gas grids came as part of a policy to decarbonize the road transport sector and was granted on a case-by-case basis. The intention to legally frame and standardise the EU’s biomethane injection into the natural gas networks came much later and was fulfilled in the second half of the present decade.This paper addresses the biomethane injection into the natural gas grids in some EU countries, highlights a few crucial aspects in this process, including but not limited to trends in standardisation and legal framework, injection conditions and pressure levels, as well as centralised biogas feedstock collection points and the biomethane injection facilities. In a wider context, the paper deals with the role of biomethane in the EU energy transition and further use of the existing natural gas networks.

The European Union sets targets for the extensive use of renewable energy. Meanwhile, the energy production network is changing and transferring from the classic “producer to consumer” scheme to new operation models, where a small consumer with local renewable energy systems becomes a producer–prosumer, an active energy consumer who is also an energy producer. This study evaluated a potential of Latvian households’ participation in the energy market as prosumers. The analysis was based on an informal prospective extrapolation data evaluation method, based on real historical data from the Central Statistical Bureau of Latvia, annual reports of distribution and transmission system operators, assessments, and the conclusions of relevant experts. In addition, the real performance of a photovoltaic (PV) system was evaluated to get information on the whole year’s energy balance, and to compare it with seasonal electricity price fluctuation. The Latvian electricity transmission system is able to accept about 800 MW of additional new renewable energy source (RES) capacity, so there is a great potential for prosumers. The biggest obstacle for a household’s involvement in the energy market is the lack of support mechanisms and relatively high cost of RES technologies. The results show that with the current dynamics of new microgenerator connections, Latvia will achieve the set goals regarding the involvement of prosumers in the achievement of RES goals only in the next century. In order to attract the public to energy production, the concept of energy community needs to be defined in Latvian legislation, a balanced peer trading mechanism needs to be developed for various RES self-consumption groups willing to sell surplus electricity, and tax policy conditions need to be reviewed for electricity transactions outside the NET (payment system), in order to fully ensure the rights of prosumers.

Currently, problems related to the operation and exploitation of safe gas distribution networks are deepening in Latvia and Eastern Europe, as the number of outworn underground gas pipelines is steadily increasing. It should be noted that there is a rather wide choice of technology and materials for gas distribution pipeline reconstruction, while at the same time there is no universal method that equally meets all possible work requirements. Therefore, it is an urgent task to understand the operational algorithm, while choosing optimal reconstruction option, classifying and determining the criteria affecting the choice, and determining the scope of each reconstruction method. For this reason, it is necessary to develop a scientifically based methodology for selecting the optimal method for the reconstruction of outworn gas distribution pipelines. Therefore, there are the following tasks that need to be accomplished: to carry out a complex analysis of reconstruction methods and factors determining the choice of an optimal gas distribution pipeline reconstruction method as well as perform the analysis of current state and development of gas supply network; to develop an algorithm for selecting an optimal gas distribution pipeline reconstruction method based on a multi-criteria approach; to develop a mathematical model for the selection of an optimal reconstruction method and scientifically based complex evaluation procedures taking into account technical and economic criteria; to analyse the interaction of the polyethylene gas pipeline with the steel frame during the post-reconstruction process using U-shaped pipe; to develop recommendations for the optimisation of gas distribution network reconstruction programmes. As a result of these tasks, a scientifically justified methodology for the selection of an optimal method for the reconstruction of the gas distribution pipes has been developed.

Residential energy consumption accounts for more than 40% of the total energy consumed in the world. The residential sector is the biggest consumer of energy in every country, and therefore focusing on the reduction of energy consumption in this sector is very important. The energy consumption characteristics of the residential sector are very complicated and the variables affecting the consumption are wide and interconnected, so more detailed models are needed to assess the impact of adopting efficient and renewable energy technologies suitable for residential applications. The aim of this paper is to review some of the techniques used to model residential energy consumption. They are gathered in two categories: top-down and bottom-up. The top-down approach considers the residential sector as an energy sink and does not take into account the individual end-uses. The bottom-up approach uses the estimated energy consumption of a representative set of individual houses and extrapolates it to regional and national levels. Based on the strengths, shortcomings, and purposes, an analytical review of each technique, is provided along with a review of models reported in the literature.

Despite various benefits that the natural gas mobility can provide, CNG (hereinafter – compressed natural gas) and LNG (hereinafter – liquified natural gas) filling infrastructure both in Latvia and the Baltic States as a whole is still at the stage of active development. As a result, the natural gas fuelled vehicle fleet comprises less than 1 % of all registered road vehicles in the Baltics, but, with regards to transport and climate policies of the European Union (hereinafter – the EU), it has a significant potential for further growth. In order to estimate the perspectives of mobility of natural gas, including bioCNG and liquified biomethane (hereinafter – LBM), CNG has been chosen and analysed as a possible alternative fuel in Latvia with its environmental and economic benefits and payback distance for CNG vehicles compared to petrol and diesel cars. The review of various types of CNG filling stations is also presented, along with information on operating tax rates and currently registered vehicles divided by types of fuel in Latvia. It was established that with the Latvian fuel price reference of the late 2020, exploitation of CNG-powered vehicle was by 24 % cheaper per kilometre in comparison with diesel and by 66 % cheaper in comparison with petrol vehicles. CNG vehicles have smaller operational taxes, since they are based on carbon dioxide (hereinafter – CO) emissions, which are lower for CNG-powered vehicles. Calculation results also indicate that CNG vehicle payback time may fall within the warrant period, if at least 57650 kilometres as an alternative to a petrol vehicle or 71 531 kilometres as an alternative to a diesel vehicle are driven by it.