The agricultural sector holds great potential for contributing to European biomethane production, but how to best exploit it is still not clear. This study compares three technical solutions for producing liquefied biomethane from manure in Sweden: centralized biogas production and liquefaction, decentralized biogas production and centralized liquefaction, and decentralized biogas production and liquefaction. Technical and practical aspects of the three configurations are assessed through interviews with professionals, and the economic performance is compared through life cycle cost analysis. Depending on the conditions, the most cost-efficient alternative is either a gas pipeline from decentralized biogas production to a centralized liquefaction, or fully centralized production. The economic benefit of centralization increases with the number of farms involved but decreases with the biogas capacity of the system and the transport distance. The pipeline solution provides simple logistics and operation, although concession for pipe laying can be challenging. Moreover, a partly or fully centralized setup improves the delivery security of the system and reduces downtime. However, decentralized biomethane production can be an option for remote farms where centralization is not possible. For existing biogas plants, small-scale liquefaction or a pipeline to centralized liquefaction can be options for developing more biomethane production.

Sweden aims to increase biogas production from anaerobic digestion (AD) from 2 to 7 TWh/year until 2030. This paper investigates the requirements, challenges and implications of such a development through qualitative and quantitative assessment of three scenarios. Seven key elements—national policies and policy instruments, regional policies and policy instruments, mobilization of feedstock, infrastructure for feedstock and gas, mobilization of actors, new production facilities, and stable and increasing demand—were defined for the scenario construction and were also used to structure the comparative analysis. Quantitatively, increasing the biogas production from 2 to 7 TWh is estimated to require up to 5 times larger digester volume and up to 12 times more AD plants, meanwhile producing 6 – 8 times more biofertilizers. While a centralized production structure would be more efficient, a decentralized structure with small biogas plants would facilitate the logistics of agricultural substrates and biofertilizers. New production capacity could be incentivized through new and increased production subsidies, as well as an increased demand for renewable energy. Regardless of how the goal is to be achieved, it will require collective efforts from both public and private actors to overcome the many challenges on the way.

Koldioxid (CO₂) har en negativ påverkan på klimatet, men har även många praktiska användningsområden. Många industriella processer släpper ut CO₂ i höga koncentrationer som skulle kunna fångas in för att begränsa emissioner och samtidigt skapa värdefulla produkter. Ett exempel på en sådan process är biogasuppgradering – en separationsprocess av förnybara gaser, där metan tas till vara för användning som fordonsbränsle eller energibärare inom industri, medan CO₂ släpps ut i atmosfären. Syftet med detta projekt har varit att kartlägga möjligheter och tekniker för att tillvarata grön CO₂ från biogasproduktion, så kallad carbon capture and utilization (CCU), samt att utreda förutsättningar för att tillämpa dessa i en svensk kontext. Arbetet har vägletts av följande frågeställningar:

• Hur stor är den nuvarande och framtida potentialen för CCU från biogasproduktion?
• Vilka möjliga användningsområden finns det för CO₂ från biogasproduktion?
• Vilka faktorer påverkar valet av användningsområde för CO₂ från biogasproduktion?
• Hur stor är den miljömässiga nyttan av CCU från biogasproduktion?

För att besvara dessa frågeställningar genomfördes potentialberäkningar, multikriterieanalys och livscykelanalys, med utgångspunkt i svensk biogasproduktion. En referensgrupp bestående av representanter för stora svenska företag inom biogasproduktion och teknik för biogasuppgradering användes för att möjliggöra samproduktion och nätverkande mellan forskargruppen och branschen.

Produktionen av CO₂ från biogas uppskattades till 160 000 ton/år 2020, med potential att öka till 540 000 – 840 000 ton/år på medellång sikt och 790 000 – 1 230 000 ton/år på lång sikt, som en följd av en förmodad ökning av biogasproduktionen i Sverige. En stor del av koldioxiden produceras dock vid relativt små uppgraderingsanläggningar, vilket kan begränsa möjligheten att tillämpa CCU på grund av höga investerings- och driftskostnader. Att tillföra vätgas för att omvandla all CO₂ till metan skulle potentiellt kunna öka metanproduktionen från biogas från 2 till 3 TWh/år på kort sikt och från 11 till 17 TWh/år på lång sikt, förutsatt tillräckligt stor tillgång på vätgas.

Andra sätt att använda CO₂ från biogas innefattar bland annat produktion av biomassa eller kemikalier, härdning av betong, pH-reglering av processvatten och användning som köldmedium. Valet av CCU- alternativ kan påverkas av miljömässiga, tekniska, ekonomiska och policyrelaterade aspekter. Ur biogasproducenternas perspektiv är metanisering det som är mest kompatibelt med det befintliga produktionssystemet och affärsmodellen, medan andra lösningar oftast innebär att en annan aktör tar hand om koldioxiden. Vätgas behövs för såväl metanisering som produktion av kemikalier. En annan begränsande faktor är höga renhetskrav på all CO₂ som distribueras och säljs på marknaden. Den geografiska spridningen på anläggningarna kan också vara en utmaning.

Många CCU-alternativ kan förbättra biogasens miljöprestanda genom att ersätta fossilbaserade produkter. Klimatpåverkan blir lägst om koldioxiden metaniseras med förnybar vätgas eller mineraliseras i betong, men även andra former av miljöpåverkan kan minskas genom att tillämpa dessa eller andra CCU-alternativ. Som jämförelse kan permanent lagring av CO₂ i geologiska formationer (carbon capture and storage, CCS) endast minska klimatpåverkan, medan det ökar övriga typer av miljöpåverkan. Samtidigt kan permanent lagring av biogen CO₂ göra det svårare att minska användningen av fossil CO₂ och ställa om till ett mer hållbart samhälle. Behovet av kol i många viktiga processer och produkter talar för att biogen CO₂ bör användas och inte lagras.

Carbon dioxide (CO₂) has a negative impact on the climate, but it also has several practical areas of use. Many industrial processes emit CO₂ in high concentrations, which could be captured to mitigate emissions while also creating valuable products. One example of such a process is biogas upgrading – a process separating renewable gases, where methane is taken care of for use as vehicle fuel or industrial energy carrier, while CO₂ is released into the atmosphere. The aim of this project has been to chart alternatives and technologies for taking care of green CO₂ from biogas upgrading, so-called carbon capture and utilization (CCU), and to investigate the conditions for applying these in a Swedish context. The work has been guided by the following research questions:

• How large is the current and future potential for CCU from biogas production?
• What are the possible areas of use for CO₂ from biogas production?
• What factors influence the choice of areas of use for CO₂ from biogas production?
• How large is the environmental benefit of CCU from biogas production?

To answer these questions, calculations of potentials, a multi-criteria assessment and a life cycle assessment were carried out, based on the Swedish biogas production. A reference group comprising representatives for large Swedish companies within biogas production and biogas upgrading technology was used to enable coproduction and networking between the research group and the business sector.

The production of CO₂ from biogas was estimated to 160,000 ton/year in 2020, with potential to increase to 540,000 – 840,000 ton/year in a few years and 790,000 – 1,230,000 ton/year in a longer perspective, as a consequence of an expected increase in the Swedish biogas production. A large share of the CO₂ is however produced at relatively small upgrading facilities, which could limit the feasibility for CCU due to high costs for investment and operation. Adding hydrogen to transform all the CO₂ into methane could potentially increase the methane production from biogas from 2 to 3 TWh/year in a short-term perspective and from 11 to 17 TWh/year in a long-term perspective, given sufficient access to hydrogen.

Other ways of utilizing CO₂ from biogas include production of biomass or chemicals, concrete curing, pH control of process water and use as a refrigerant. The choice of CCU options can be influenced by environmental, technical, economic and policy-related aspects. From the biogas producers’ perspective, methanation is the option that is the most compatible with the existing production system and business model, while other solutions usually involve another actor taking care of the CO₂. Hydrogen is required for methanation as well as for production of chemicals. Another limiting factor are the high purity requirements on all CO₂ that is distributed and sold on the market. The geographical distribution of the production plants can also be a challenge.

Several CCU options can improve the environmental performance of biogas by replacing fossil-based products. The potential climate impact is the lowest if the CO₂ is methanized with renewable hydrogen or mineralized in concrete, but other forms of environmental impact can also be reduced by applying these or other CCU options. For comparison, permanent storage of CO₂ in geological formations (carbon capture and storage, CCS) only reduces the climate impact, while it increases other forms of environmental impact. Furthermore, permanently storing biogenic CO₂ can make it difficult to reduce the use of fossil CO₂ and transition to a more sustainable society. The need for carbon in many essential processes and products suggests that biogenic CO₂ should be utilized and not stored.

Carbon capture and utilization has been proposed as an essential climate change mitigation strategy, but only a few implemented cases exist. During biomethane production from anaerobic digestion, CO₂ is commonly separated and emitted into the atmosphere, which can be utilized as raw material for various products. This research aims to identify and assess CO₂ utilization alternatives for possible integration with biogas upgrading from anaerobic digestion by developing a soft multi-criteria analysis (MCA). A literature review complemented with stakeholder participation enabled the identification of relevant alternatives and criteria for assessment. Potential alternatives for CO₂ utilization include methane, mineral carbonates, biomass production, fuels, chemicals, pH control, and liquefied CO₂. Results show that although no alternative performs well in all indicators, there is an opportunity for short-term implementation for methane, biomass production, mineral carbonates, liquefied CO₂, and pH control. Moreover, the uncertainty analysis reveals that even though the technologies have a high technological development, more information on critical aspects is still required. The soft MCA provides information to decision-makers, practitioners, and the academic community on learning opportunities of the alternatives and indicators to step from development into implementation. For instance, the method can be used to assess more specific systems with different locations and scales or to direct efforts to ease the implementation of CCU.

This paper compares and analyzes the relations between the biogas development and the national policy frameworks for biogas solutions in eight European countries. The policy frameworks are compared using a biogas policy model, comprising five dimensions: type of policy; administrative area; administrative level; targeted part of the value chain; and continuity and change over time. The studied countries show examples of both increasing and stagnating biogas production, all of which can be associated with changes in national policy frameworks. Many different policy tools?particularly economic instruments?have proven successful for stimulating biogas production, but changing a well-functioning framework risks impeding the development. Therefore, predictability and relevance for targeted actors are key in policymaking. Targeting specific parts of the value chain can however be required to integrate all the benefits of biogas solutions, such as agricultural methane emissions reduction. Moreover, it can be challenging to design policies and policy instruments that are both effective and sustainable over time, without needs for modifications or adjustments. Finally, biogas policies and policy instruments that are effective in one country would not necessarily lead to the same outcome in another country, as they are dependent on the broader context and policy and economic framework.

Looking to reduce climate change impact and particle emissions, the heavy-duty transport sector is moving towards a growth within technology and infrastructure for use of liquefied natural gas (LNG). This opens an opportunity for the biogas market to grow as well, especially in the form of liquefied biomethane (LBM). However, there is a need to investigate the economic conditions and the possible environmental benefits of using LBM rather than LNG or diesel in heavy transports. This study presents a comparison of well-to-wheel scenarios for production, distribution and use of LBM, LNG and diesel, assessing both environmental and economic aspects in a life cycle perspective. The results show that while LNG can increase the climate change impact compared to diesel by up to 10%, LBM can greatly reduce the environmental impact compared to both LNG and diesel. With a German electricity mix, the climate change impact can be reduced by 45 – 70% compared to diesel with LBM from manure, and by 50 – 75% with LBM from food waste. If digestate is used to replace mineral fertilizer, the impact of LBM can even be less than 0. However, the results vary a lot depending on the type of feedstock, the electricity system and whether the calculations are done according to RED or ISO guidelines. Economically, it can be hard for LBM to compete with LNG, due to relatively high production costs, and some form of economic incentives are likely required.

The literature indicates that the life cycle costs of biomethane fueled light vehicles may be 15 to 20% highe rthan for similar petrol and diesel fueled vehicles, while liquid biomethane fueled heavy duty trucks may have similar life cycle costs to diesel. However, such an analysis can be two dimensional and limited in the message it conveys. On one hand the acceptance of diesel fueled trucks and buses will be limited due to the climate emergency and air pollution and after 2030 diesel may not be the competition for biomethane anymore. On the otherhand, biomethane production is part of a larger circular economy, energy, and environmental system. It is verydifficult to divorce the energy vector, biomethane, from the system through which it is produced. In essence biomethane can be considered as one of the products or services of a broad biogas system.

An advantage of biogas is that it can be produced from most wet organic wastes or by-products, includingfor food waste, animal by-products, (such as manure), agricultural residues, sewage sludge, industrial biowaste (such as from slaughterhouses and food and beverage processing industries). Biogas production is an element in the environmental management of such wastes; biogas plants can also deliver digestate, which contains most ofthe nutrients in the feedstock and can be an excellent biofertilizer. In addition, it is possible to utilize the carbon dioxide removed in upgrading biogas to biomethane as a product with added value. The resource of biomethane is very significant in considering the vast amounts of organic wastes landfilled around the world each year, that instead could be used to produce biogas, biofertilizers and food grade CO2 while improving the environment through reduced fugitive methane emissions and improved water quality. Furthermore, the application of biogas systems in bio-industrial contexts (such as paper mills, food production facilities, or other types of biorefineries) has huge potential to decarbonize industry while significantly increasing the resource of biomethane. Due to the multifunctionality of biomethane solutions, broad assessment methods are needed to grasp thewide spectrum of relevant factors when comparing different technologies:

• Biomethane has a competitive performance compared with fossil fuels and other biofuels on a whole lifecycle analysis and is particularly suited to long distance heavy vehicles.

• Biomethane from manure, residues, waste & catch crops is estimated to have low GHG emissions ascompared to other renewable fuels.

• Biomethane may contribute to reduced air pollution in comparison with diesel, petrol, and other biofuels.• Biomethane can contribute to a substantial reduction in acidification compared with fossil fuels.

• Biomethane may contribute to significantly reduced noise levels in comparison with diesel heavy goodsvehicles.

• Well-designed and applied biogas systems may be essential to transform conventional farming to moresustainable farming and to organic farming.

• Common types of biogas solutions provide essential sociotechnical systems services as components ofsystems for waste and (waste) water management.

• Biogas solutions may importantly contribute to improved energy supply/security and flexibility.

Natural gas systems should be a facilitator of the introduction of biomethane for transport, but the sustainability problems associated with natural gas negatively impact the view of biomethane. This is where arguments amongst the renewable sector actors can hinder progress. Biomethane and (power to methane) can utilize the existing gas grid and accelerate progress to decarbonization of the overall energy sector beyond just electricity and also to decarbonize chemical (such as ammonia and methanol) and steel production. This should be advantageous especially when realizing that more energy is procured from the natural gas grid than the electricity gridin the EU and the US; however, suggestions that biomethane is only greenwashing the natural gas industry, and in doing so extending the lifetime of natural gas, greatly impedes this progress.

This report provides exemplars of very good biomethane based transport solutions, with a high technologicalreadiness level for all elements of the chain from production to vehicles. Transport biomethane sits well in the broad circular economy, energy, and environmental system providing services across a range of sectors including reduction in fugitive methane emissions from slurries, treatment of residues, environmental protection, provision of biofertiliser, provision of food grade CO2 and a fuel readily available for long distance heavy haulage. What we do not have is time to postpone the sustainable implementation of such circular economy biomethane systems as the climate emergency will not wait for absolutely perfect zero emission solutions; should they exist.

Focusing on tailpipe emissions, current EU policies do not favor the use of biofuels in transports. This paper analyzes the well-to-wheel climate performance of gas and electric vehicles in Europe, taking into account the share of biomethane in vehicle gas as well as the production systems for biomethane and electricity in different countries. The results show that both gas and electric vehicles can significantly reduce the climate change impact of transports compared to diesel. In an average European electricity system, electricity has around 30% lower climate impact than diesel for a heavy truck, and 65-70% lower for a passenger car or city bus. Average European vehicle gas reduces the climate impact by up to 28% compared to diesel, or 11% compared to fossil natural gas, and in some countries vehicle gas has lower climate impact than electricity. This demonstrates the importance of not limiting analysis and policy to tailpipe emissions.