Stricter requirements from the European Union and the German government regarding the utilization of renewable and sustainable fuels for transportation, power, and heat production are currently in effect. This has led to that heavy transportation companies are looking for a more sustainable alternative to liquefied natural gas, such as liquefied biomethane. The monetary costs for the release of greenhouse gas are also increasing due to the carbon certificates that are being traded are decreasing in numbers each year. Carbon certificates grant companies an allowance of releasing a certain amount of emissions without being fined. Carbon dioxide and biomethane liquefaction can be a good investment for producers of biomethane to find new markets by for example trading in carbon certificates, selling liquid carbon dioxide, and producing liquefied biomethane as an alternative transportation fuel. The sale price of biomethane is heavily dependant on the emission factor for the biomethane and as such, capturing the carbon dioxide from the biomethane plant and off-setting fossil carbon dioxide would increase the sale price of the biomethane. The methods used are theoretical and quantitative, Numerical data was collected to be able to perform the economical and environmental calculations. The investment cost for the liquefaction technologies was scaled down to correspond to a plant with a production capacity of 350 Nm3/h. Also included in this thesis is a review of biomethane production, together with theory for the economical and environmental calculations.  By performing a technical, economical and environmental assessment of the technologies for the liquefaction of carbon dioxide and biomethane. This thesis shows that liquefaction of biomethane is not an economical viable option at the moment for plants equal or below this production capacity, due to a negative net present value, negative return on investment, sensitivity to fluctuating costs, and a high payback time. However, it could help in achieving the sustainability goals set forth by the European Union and the German government. With regards to the liquefaction of carbon dioxide it is deemed a viable investment option with an investment cost of approximately 1 million Euro and a payback time of approximately 3 years. Liquefaction of carbon dioxide could bring an extra income to the biomethane plant. This due to an added revenue in the sales of liquid carbon dioxide and an increase in the sale price of biomethane due to a reduction of the emission factor from 17 gCO2-eq /MJ to -23 gCO2-eq /MJ. The investment could also help achieving the sustainability goals by decreasing the dependence on fossil carbon dioxide for various sectors.

Due to population expiation and the increased awareness of the impact on the environment by wastewater treatment, improved wastewater treatment systems are needed to treat municipal and agricultural wastewater. Treating wastewater with oxygen decreases carbon compounds at the expense of energy to move carbon and oxygen to be in contact with each other. Anaerobic digestion of wastewater can reduce the cost by utilizing microbes to treat high amounts of carbon in wastewater without the need for extensive oxygen requirement. With a proper balance of nutrients, microbes also produce methane, a renewable energy source. It has been suggested that microalgae be utilized to help balance the nitrogen content of wastewater for treatment by microbes. One challenge with the use of algae is the initial breakdown of algae cells. Using a digester with microorganism that can produce methane and decompose algae could enhance production of methane from the digestion of algae. The combination of wastewater, which is high in carbon content relative to nitrogen, with algae, which is high in nitrogen, could provide the balance needed for the microbes to treat wastewater and provide methane. A biomethane potential test was used to compare the ability of two microbe communities, facultative lagoon sediment and anaerobic digester sludge to digest algae. Each microbe community treated dairy, swine, municipal, and petrochemical wastewater augmented with algae and acetate. The ability to degrade augmented wastewater and produce methane was determined by measuring the volume and composition of biogas produced over time. Both treatments were successful in production of methane. Facultative lagoon sediment showed more methane produced per carbon dioxide than anaerobic digester sludge.

This thesis describes the production of biogas and subsequent enrichment methods thus obtained biogas to natural gas quality. The reason is the efficient use of natural resources to address the energy needs of mankind. Should be answered the main question. The method of biogas to biomethane enrichment economically viable ? The answer should be obtained from each successive calculations and economic calculations.

Biomethane (upgraded form of biogas) holds unlocked potential as a substitute to fossil natural gas, in terms of achieving climate reduction targets as well as developing a locally secured fuel supply. Biomethane is fully compatible with the existing natural gas grid infrastructure. Currently, nine countries in European Union are practicing natural gas grid injection. Remaining countries are in various phases of development concerning production and utilisation of biomethane. Successful deployment of a biomethane project requires coordinated action in terms of academic, industrial and economic co-operation. It demands established legal and political framework as well as supportive financial conditions. The thesis aims at researching how the state of development of biomethane generation and utilization gets affected by the support activities within a countries policy framework? To seek a solution, the theoretical framework of “Technological Innovation System (TIS)” is adapted. TIS provide a methodological approach to assess the development of an upcoming technology under the existing policies, regulatory and financial conditions. In the given study, the framework of TIS is adapted to the technology of “biomethane generation and injection into natural gas grid”. This adaptation led to the development of: Detailed overlapping matrix of the main structural components i.e. Actors, Networks and Institutions and their corresponding activities across the value chain. Development of a set of diagnostic questions and performance indicators, enabling an assessment of the dynamics of the technological system, eventually leading to the identification of strengths and weaknesses in the system. The adapted technological system analysis framework is further applied on two countries “Germany and UK” as case studies. With the aid of diagnostic questions, the dynamic system characteristics are evaluated in each country context. Germany reveals a well-functioning biomethane TIS. Considerable knowledge base and experience is available, appropriate policies and financial incentives are in place, dedicated organisations are established to address the technological and industrial issues. Germany currently has a market promoting biomethane utilisation via CHP applications. Further growth can be expected by addressing resource mobilisation to fulfill a larger share of heat demand and application as renewable transport fuel. Biomethane industry is in its nascent stage in the UK. At the time of thesis research two upgrading plants are in operation. Analysis of the system functions within UK, signals a healthy biogas industry, but there is lack of activity within the “biomethane” context. The industry is in the stage of knowledge development. Biomethane production is well communicated within national strategies. The key technical issues being encountered by the industry are the focus of research. A balanced market formation would require increasing the resource mobilisation in terms of availability of skilled manpower as well as providing access to financial capital. The industry is experiencing pilot trials and subsequent dissemination of information of the results of these trials to the stakeholders in the value chain is recommended. Overall, Technological Innovation System (TIS) has been an effective tool to evaluate the national approach towards development and deployment of biomethane as a technology .Moreover TIS assists in systematic identification of the strengths and weaknesses of the system. It provides a methodological approach to statically and dynamically analyse biomethane development strategy within a given region and can also assist in benchmarking the development conditions in more than one region. / European Project Titled "GreenGasGrids"

Bioenergy contributes significantly towards the share of renewable energies, in Europe and worldwide. Besides solid and liquid biofuels, gaseous biofuels, such as biogas or upgraded biogas (biomethane), are an established renewable fuel in Europe. Although many studies consider biomethane technologies, feedstock potentials, or sustainability issues, the literature on the required legislative framework for market introduction is limited. Therefore, this research aims at identifying the market and legislative framework conditions in the three leading biomethane markets in Europe and compare them to the framework conditions of the top six non-European biomethane markets. This study shows the global status and national differences in promoting this renewable energy carrier. For the cross-country comparison, a systematic and iterative literature review is conducted. The results show the top three European biomethane markets (Germany, United Kingdom, Sweden) and the six non-European biomethane markets (Brazil, Canada, China, Japan, South Korea, and the United States of America), pursuing different promotion approaches and framework conditions. Noteworthy cross-national findings are the role of state-level incentives, the tendency to utilise biomethane as vehicular fuel and the focus on residues and waste as feedstock for biomethane production. Presenting a cross-country comparison, this study supports cross-country learning for the promotion of renewable energies like biomethane and gives a pertinent overview of the work.

In recent years, there is a rapid growing interest in the use of biomethane for the transport sector. A new method of combining anaerobic digestion and biomass gasification is proposed.The feasibility study shows that more biomethane can be produced; resulting in an increase in the revenue compared to individual biogas plants. The GoBiGas project,which is initiated by Göteborg Energi, adopted another method based on gasification, water gas shift and methanation to enable biomethane production from forest residue. The aim of the present study is to investigate the economic viability of the new method when compared with the GoBiGas (Gothenburg Biomass Gasification) process. For this study, a model of GoBiGas process was developed in Aspen Plus to perform the technical analysis, in which the overall efficiency and exergy efficiency were calculated at different moisture contents of biomass. For the economic analysis, the annual revenue was also estimated during the study. The results show that the overall efficiency of the new method is higher than the efficiency of the GoBiGas process and there is more production of biomethane from the new process.

More and more people live in cities, cities that both present opportunities, in terms of potential sustainable growth and challenges, for example regarding insufficient infrastructure and waste management. There are several examples on initiatives to make cities reach their sustainability potential; one is to turn municipal organic waste, MOW, and sewage sludge into biogas and use it to produce electricity and/or heat or to upgrade it to biomethane and use it as a fuel in for example public transport or feed it to a gas grid. This study has focused on the potential and feasibility of producing and using biogas/biomethane as well as the remains from the production process, called digestate, in Chisinau, the capital of Moldova. For the most feasible options an indication of the environmental improvement and economic performance was also estimated. The study included biogas produced from municipal organic waste, sewage sludge and methane collected at landfills. For the areas of use, electricity or heat produced from biogas was included as well as using biomethane in public transport or feeding it to the gas grid and to use the digestate as biofertilizer. Since multiple factors needs to be considered in order to adequately assess the potential and feasibility a multi-criteria approach was used for developing a framework based on an early assessment tool for biomethane solutions in the urban context. In summary it is indicated that there are good conditions for biogas production in Chisinau with biogas production from sewage sludge being included in the ongoing rehabilitation of the largest wastewater facility and methane collection from the largest landfill historically being part of the operations and planned (although not confirmed) to soon be part of these again. However, the largest potential is for municipal organic waste where the main impediments relates to financial issues and to some extent legislation that indirectly favour short term landfilling. When investigating the possible use of the digestate as biofertilizer the outlooks are considerably less promising than for the supply side. Despite the fact that the law explicitly allows the use of digestate (both from MOW and sewage sludge) the lack of knowledge within the farmer community result in a low or non-existent customer demand. Regarding the possible use of biogas/biomethane it was concluded that electricity production is the most feasible option and heat generation placing as the second most feasible. Feeding the gas to the grid appears more difficult and the least likely option is for the biogas to be used within public transport. Overall it is in general technically possible to use the gas in terms of infrastructure and there is some demand, especially for electricity and heat. The biggest inhibitory factors are rather institutional since biogas in general is overlooked or not prioritized in the strategies leading to a shortcoming in economical instruments or funds and to some extent in the legislation. This thesis is complemented by an executive summary with the same name, both in English and translated to Romanian.

A exploração energética do biogás é dominada desde tempos remotos, e tem contribuído, mesmo que em pequena escala, para a diversificação das matrizes energéticas de muitos países, a partir da premissa da expansão no uso das energias renováveis. Mais recentemente, a necessidade de aprimoramento da gestão de resíduos e questões como a segurança no suprimento energético e mudanças climáticas impulsionaram o refinamento de técnicas de purificação de biogás, com o objetivo de produzir o biometano, potencial substituto do gás natural de origem fóssil. É de interesse desta pesquisa a purificação de biogás de aterros e sua utilização como combustível veicular e injeção em gasodutos, uma vez que o recente desenvolvimento de projetos no Brasil se dá a espelho do que ocorre em países desenvolvidos, apesar de os setores de saneamento e energia brasileiros apresentarem características distintas. O estágio de desenvolvimento atual da exploração do biometano na Alemanha, Reino Unido e Suécia foi identificado através de revisão de literatura e análise documental. O resultado foi confrontado com o contexto atual, perspectivas atuais e futuras para este recurso no Brasil, considerando em especial, a Política Nacional de Resíduos Sólidos, os planos de desenvolvimento do setor energético nacional, e políticas estaduais do Rio de Janeiro e São Paulo, que tratam especificamente da promoção do uso do biogás. As condicionantes verificadas em nível nacional e regional foram então classificadas enquanto barreiras e oportunidades para a exploração do biometano obtido a partir de gás de aterros. Como resultado, a pesquisa identificou que a implantação de mecanismos de incentivo e a definição dos usos finais selecionados em função da infraestrutura disponível foram indutores do desenvolvimento deste recurso nos países selecionados. A verificação do cenário atual de desenvolvimento do biometano de gás de aterros no Brasil demonstra que, apesar de não apresentar potencial energético significativo e a regulação em vigor limitar suas aplicações, seu desenvolvimento pode ser uma alternativa para, em última análise, contribuir para a melhoria das condições sanitárias vigentes no país. / Biogas as an energy source has been explored since ancient times, and has contributed, if only to a small degree, to diversify the energy mix of many countries, based on the increased use of renewable energy. Recently, the need to improve waste management and issues such as power supply safety and climate change, have driven the development of biogas purification techniques to produce biomethane, a potential substitute for fossil-based natural gas. The focus of this research is the purification of landfill biogas, its use as a fuel for vehicles and injecting it into gas pipelines, since the recent development of projects in Brazil reflect those in developed countries, even though the Brazilian sanitation and energy sectors present distinct characteristics. The current development stage of biomethane investigations in Germany, United Kingdom and Sweden, were analyzed by reviewing literature and examining documents. The result was compared with the actual situation of this resource in Brazil, as well as current and future perspectives based mainly on the National Solid Waste Policy, the development plans for the national energy sector and state policies for Rio de Janeiro and São Paulo that specifically deal with promoting the use of biogas. National and regional constraints were verified and classified in relation to challenges and opportunities for use of biomethane obtained from landfill gas. As a result, the research revealed that the implementation of incentive mechanisms and the definition of selected end uses based on the available infrastructure are drivers for the development of this resource in the selected countries. Analysis of the current scenario of biomethane development from landfill gas in Brazil demonstrates that, even though it does not present a significant energy potential and current regulations limit its applications, its development could be an alternative, at least, to help improve the prevailing sanitary conditions of the country.

Os sistemas de produção e utilização do biogás podem envolver externalidades positivas como o tratamento de resíduos, a produção de biofertilizante e a redução de emissões de gases de efeito estufa. Além disso, possibilitam o desenvolvimento do potencial energético desta fonte renovável, que pode ser aproveitada por meio da geração de energia elétrica ou pela produção de biometano, combustível obtido pela purificação do biogás, e que é similar ao gás natural. Nesse contexto, o objetivo desta dissertação é detalhar estas estratégias e compará-las para o caso brasileiro. Busca-se identificar o uso mais desejável do biogás no contexto do setor energético nacional, considerando as características da fonte e sua relação com a situação atual e as perspectivas dos mercados de eletricidade e gás. Para isso, inicialmente é realizada uma revisão das tecnologias de aproveitamento do biogás e são discutidas as vantagens de se identificar um uso que possa se tornar prioritário, capaz de reunir em si os incentivos para a expansão dessa fonte na matriz energética. Argumenta-se que o desenvolvimento de uma indústria local e de projetos bem-sucedidos, necessários ao fortalecimento do biogás no Brasil, podem ser alcançados por meio da criação de mecanismos de fomento específicos para uma estratégia, que sejam claros e de longo prazo. Em seguida, a evolução desse setor na Alemanha e na Suécia é avaliada, observando-se que políticas de direcionamento da utilização do biogás conduziram o mercado, tendo como consequência sistemas voltados, respectivamente, à geração de energia elétrica e à produção de biometano para uso veicular. Baseada na definição de política energética, a comparação entre a produção de eletricidade e de biometano a partir do biogás no Brasil é apresentada segundo os critérios: segurança no abastecimento, preço da energia, balança entre importações e exportações, infraestrutura, e aspectos ambientais. As conclusões apontam para o biometano como um uso promissor da energia do biogás no país em termos da redução de importações e em projetos de grande escala próximos à infraestrutura de gás natural, mas com barreiras a serem superadas principalmente quanto a competitividade em plantas menores e distantes dos gasodutos. A produção de energia elétrica, por outro lado, tem incentivos e mecanismos de comercialização estabelecidos e pode ser competitiva principalmente se exploradas suas características de energia firme e flexibilidade, mesmo em um contexto de concorrentes renováveis de grande potencial e em crescimento. / Biogas production systems may involve positive externalities such as waste treatment, biofertilizer production and the reduction of greenhouse gases emissions. Besides, they enable the use of its renewable energy potential, which can generate electricity or produce biomethane. Biomethane is obtained from biogas upgrading and it is similar to natural gas. This study details these strategies and compare them for the Brazilian case, with the aim of identifying if there is one optimal solution for biogas utilization within the context of the national energy sector, by analyzing the characteristics of biogas and its correlation with the status and the perspectives of the electricity and gas markets in the country. First, the advantages of selecting one alternative of biogas utilization to be the focus of policy instruments and to guide the development of the biogas sector are discussed. It is argued that the development of a local industry and successful projects, required to expand the biogas sector in Brazil, could benefit from technology-specific incentives, designed as clear and long-term mechanisms. The evolution of biogas systems in Germany and Sweden are investigated, and it is observed that the policies implemented in these countries have guided biogas utilization, respectively, to electricity generation and to biomethane use as vehicle fuel. Then, based on the definition of energy policy, five criteria are selected to evaluate and compare electricity and biomethane production from biogas in Brazil: security of supply, energy price, balance of trade, infrastructure, and environmental aspects. It can be concluded that, although biomethane can have a positive impact reducing natural gas imports especially in large-scale projects close to pipeline infrastructure, it also has many barriers to overcome, including its adaptation to small-scale units and the limitation of infrastructure. Electricity generation is a more established alternative that can be feasible if its capacity to provide baseload and flexibility are properly evaluated, even facing the competition of other renewable technologies with low-cost and large potential in the country.

Anaerobic digestion is a key energy and resource recovery technology. This work investigated potential organic waste resources to co-digest with household food waste (HFW) to stabilise the process and future-proof feedstock availability. This included novel feedstock macroalgae (seaweed) waste (SW). Hydrothermal (autoclave) pretreatment was also investigated to optimise energy recovery from HFW and SW. Preliminary experiments investigated the behaviour of HFW co-digested with either a green waste (GW) or paper waste (PW), using a batch-test laboratory scale and systematic approach with a revised waste mixture preparation method. Following preliminary trials, the co-digestion of HFW/SW was investigated using an air-dried SW mixture. Batch experiments to determine the biomethane potential (BMP) at different ratios of HFW to SW were set up. Co-digesting HFW and SW at ratio 90:10 (d.w.) achieved a BMP similar to HFW alone (252±13 and 251±1 cm3 g-1 VS, respectively), and a peak methane yield for HFW:SW (90:10) at day 12 of 69±3% compared to a peak methane yield for HFW at day 19 of 70±3%. Addition of SW optimised the C/N ratio, increased concentrations of essential micronutrients and produced an overall increase in reaction kinetics. Concentrations of SW ≥25%, associated with high sulphur levels, reduced final methane productivity. Analysis of the macroalgae strains L. digitata, U. lactuca and F. serratus from the SW mixture was carried out to compare mono-digestion and co-digestion with HFW at a 90:10 ratio and the effect of autoclave pretreatment at 136°C. Co-digestion had a positive impact on methane yields for U. lactuca and F. serratus, whilst autoclave pretreatment had no significant impact on the SW strains When results were modelled for a 320 m3 anaerobic digester treating 8m3 feed per day the theoretical energy balance showed that optimal energy production from pretreated HFW at 8.09 GJ/day respectively could be achieved. To verify the suitability of using macroalgae, known to readily uptake polycyclic aromatic hydrocarbons (PAH), toxicity tests were used to determine the impact of phenanthrene sorbed by U. lactuca on the AD process. Despite U. lactuca’s ability to biosorb phenanthrene in under 2 hours, no impact on the AD process was observed. Overall, results of this study demonstrated that co-digestion of HFW and SW, at batch laboratory scale, provide a viable and sustainable waste revalorisation solution. In addition, low temperature autoclave pretreatment increased methane production (p=0.002) from the AD of HFW.