Society is largely moving into electric mobility to achieve net -zero emissions, with the choice of electrification as the sole viable option for decarbonizing personal road transport. While this perspective has some merits, it overlooks the potential of biomethane produced through anaerobic digestion (AD) as a carbon -negative solution. Biomethane from AD offers not only carbon -neutrality but the possibility of being carbon -negative, with estimates suggesting it could provide 10 % of the world 's primary energy consumption by 2050. AD provides socio-environmental advantages, including improved quality of life and employment opportunities, a particularly relevant topic in developing countries. The technology is mature, cost-effective, and applicable across various sectors and therefore it is imperative that it is considered as an alternative or complementation to electrification of road transport.

I denna studie undersöktes potentialen för etableringen av nya biogassystem inom ett geografiskt område som utgjordes av Region Sörmlands kommuner samt kommunerna Södertälje, Nykvarn, Norrköping och Söderköping. Anledningen till studien är det studerade områdets förhållandevis låga nuvarande biogasproduktion samt den stora potentiella efterfrågan på biogas i området, då SSAB i framtiden kommer behöva biogas till sin fossil-fria stålbearbetning. I studien studerades den tekniska och administrativa potentialen, det vill säga vad som är möjligt att producera under dagens administrativa villkor samt med dagens (och en nära framtids) teknik. Potentialen undersöktes utifrån fyra olika potentialer: rötbar biomassapotential, biogaspotential, koldioxidproduktionspotential och näringscirkulationspotential. Resultatet visar på en biogaspotential mellan 380 och 540 GWh per år vilket skulle motsvara en stor ökning från dagens produktion på mellan 50 och 60 GWh per år. Ytterligare 100 GWh per år skulle kunna produceras av koldioxiden genom biometanisering men då krävs stora mängder vätgas. Angående näringscirkulationspotentialen så kan biogödseln (som samproduceras med biogas i biogasanläggningar) uppfylla cirka tre fjärdedelar av kvävebehovet, nära hela fosforbehovet och fyra gånger kaliumbehovet i det studerade områdets jordbruk. Det studerade området delades upp i fem produktionsområden för att öka upplösningen i studien. Dessa områden valdes för att de skulle kunna utgöra delområden som är stora nog för att etablera biogasanläggning av den storlek som krävs för att förvätska biogasen och samtidigt undvika alltför långa transportsträckor för substrattransporter. Detta svarar upp mot trenden att etablera större och större biogasanläggningar samt ett ökat fokus på förvätskad biogas. Dock kan mindre anläggningar vara nödvändiga för att uppnå vissa delar av potentialen i områden med små, men betydelsefulla, substratmängder. Det produktionsområde med störst potential var Söderköping/Norrköping men det betyder nödvändigtvis inte att det är det mest lovande produktionsområdet att börja mer fokuserade implementeringsstudier i då andra faktorer så som lönsamhet inte undersökts i denna studie. Fortsatta studier bör fokusera på hur lantbruksrelaterade substrat kan användas inom biogasproduktion. Här kan studier fokusera på olika områden, exempelvis hur biogasanläggningar kan drivas stabilt på enbart grönmassa (till exempel vall och mellangrödor) och hur ökad odling för biogasproduktion påverkar mat- och foderproduktion, individuella lantbrukare samt åkermarkens långsiktiga hälsa. Dessutom behövs implementeringsstudier för att realisera potentialen, dessa bör fokusera på att undersöka specifika etableringsmöjligheter utifrån ekonomiska, tekniska, logistiska och administrativa perspektiv.

Föregående kapitel bidrog med grundläggande kunskaper om stora tekniska system. Men den kunskapen som bas kan man närma sig frågan hur några av de system som finns i dag kommit till och utvecklats med tiden. Dessutom ges i detta kapitel en historisk introduktion, som på en övergripande nivå beskriver hur industrisamhället och industriella system utvecklats. Kapitlet avslutas med en utblick mot framtiden.

Stora tekniska system fyller en viktig funktion i många människors vardag och de har också en stor miljömässig betydelse. Det gäller dels systemen själva, dels många delsystem i form av produkter och tjänster vars miljöpåverkan till stor del kan avgöras av de stora systemen. I kapitlet introduceras stora tekniska system. Fokus ligger på systemens framväxt och miljökoppling, viktiga komponenter och aktörer, och hur systemen kan utvecklas och förändras.

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.

Because biogas systems may take many forms, utilizing different feedstock and finding different end uses for the biogas, it is becomes difficult to produce explanations, inferences, and conclusions about biogas systems in general, which is why concepts for specific types of biogas systems are needed. This paper introduces the concept of the Nordic biogas model, an urban waste-based biogas system where biogas is upgraded to biomethane and used as transport fuel and the digestate applied as biofertilizer on farmland. The Nordic biogas model has three functions, namely, renewable transport fuel production, waste management service, and biofertilizer production that all bring secondary and tertiary positive societal effects, such as reduced climate gas emissions and productivity benefits to industry. This has implications for environmental and sustainability assessment of the Nordic biogas model as the multi-functionality must be considered when choosing reference scenarios, system boundary, and indicators to use within assessments. Finally, the paper discusses policy recommendations for supporting the implementation of the Nordic biogas model. Such policy should respect the multi-functionality of the Nordic biogas model by creating coherent policy mixes that neither neglect nor over-compensate for the multi-functionality of the Nordic biogas model.

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.

There are several alternatives for how to phase out diesel in heavy-duty transports, thereby reducing the sector’s climate change impact. This paper assesses the well-to-wheel (WTW) greenhouse gas (GHG) emissions of energy carriers for heavy-duty vehicles, analyzing the effect of the carbon intensity of the electricity used in production. The results show that energy carriers with high electricity dependence are not necessarily better than diesel from a WTW perspective. In particular, fuels produced through electrolysis are not well suited in carbon-intense electricity systems. Conversely, waste-based biofuels have low GHG emissions regardless of the electricity system. Battery-electric buses show a large reduction of GHG emissions compared to diesel buses and many other alternatives, while battery-electric trucks have higher GHG emissions than diesel in carbon intense electricity systems. Thus, electrifying transports or switching to renewable fuels will not suffice if the electricity system is not made renewable first.

Biorefineries are examples of industries striving towards a circular and bio-based economy through valorising natural raw materials to a spectrum of products. This is a resource-efficient process which also decreases overall environmental impact, as the products from a biorefinery can replace fossil-based products such as plastics or fuels. To become even more resource efficient, an optimisation of the by-product use can increase the performance. This study will evaluate different scenarios for the valorisation of stillage coming from a wheat-based biorefinery. The alternatives range from the direct use of the stillage for fodder, fertiliser or incineration to three different biogas production-based scenarios. The biogas scenarios are divided into the production of fuel at a local or distant plant and the alternative of creating heat and power at the local plant. The results show how locally produced biogas for vehicle fuel and fodder usage are the better alternatives regarding greenhouse gas emissions, the finances of the biorefinery, energy balance and nutrient recycling. The results also indicate that biorefineries with several high-value products may receive lower quality by-product flows, and to these, the biogas solutions become more relevant for valorising stillage while improving value and performance for the biorefinery.