Circular Economy, and Carbon Capture in the Energy Sector, an AAU Energy mission

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    The two overarching objectives of the C3 mission are in essence to “close the loops” and to “close the gap”. In the green transition, there is a need for new industrial ecosystems with the primary goal to put less pressure on fossil resources and enable the harvesting of renewable energy. However, new industrial ecosystems increase the appetite for other finite energy resources and non-energy raw materials, of which the majority are hardly recycled - but all critical and irreplaceable in many clean energy technologies. As examples, lithium, cobalt, and graphite for batteries, cobalt, platinum, and titatium in fuel cell applications, and further, finite biomass resources as a carbon source for future biofuels, biochemicals, and bioenergy. On a European level, this brings growing concerns about future supply chains and how to ensuring reliable and sustainable access to critical resources and raw materials as key enablers for the green transition. Another growing concern related to the green transition is the lack of recycling markets for end-of-life energy technologies, such as EV batteries, electronics, wind turbine components such as the blades, plastics, and even residual nutrients recovered in bio-based industries, which all together leads to a massive waste generation. Finally, according to the latest assessment report by IPCC, negative emission technologies (NET’s) are likely to play a significant role to “close the gap” between the fossil and renewable energy technologies to meet the future climate targets and hold global warming below the 2 °C target. Among these are direct air capture of atmospheric CO2 and the combined use of biomass with carbon capture and storage (BECCS) technologies.

    As a response to the actions needed to ensuring a sustainble green transition, through research and industrial collaboration, the C3 mission will extend products’ lifetime and lifecycles by repurposing second-life applications, create material closed-loops by recovering raw materials and achieve neutral or even negative emission impact by turning existing linear economies into circular economies and thus bring benefits for both the environment and the economy, within the context of clean energy technologies.

    Sub-objectives related to the mission include:

    • Reduce the total cost of ownership of batteries by enabling second-life applications  
    • Provide a circular bio-economy, where all fractions of bio-resources are utilized and converted into biofuels, biochemicals, and bioenergy, and fertilizers.
    • Enabling complete closed-loop recycling or repurposing of recovered materials, and ultimately waste elimination in the energy sector
    • Enable a green transition with net-zero or even negative emissions.   


    The mission is in line with EU goals:

    • The European Commission introduced the CE Action Plan (CEAP, March 2020) as the main building block of the European Green Deal. This plan formulates the agenda for sustainable growth whereby CE is the core instrument for reducing the pressure on natural resources, creating sustainable growth and generating jobs. Hence, CE is central to achievement of the European 2050 Green House Gas (GHG) emission goals.
    • In 2015, the European Commission adopted its first circular economy action plan. It included measures to help stimulate Europe's transition towards a circular economy, boost global competitiveness, foster sustainable economic growth and generate new jobs.
    • The European Commission has announced that it will prepare in 2021 an Integrated Nutrient Management Action Plan (INMAP).


    The mission on “Circularity and Carbon Capture” is in line with the IFD mission roadmaps:

    • IM1: “Capture and storage or use of CO2”
      • Further DAC will contribute to carbon neutrality in 2050 by carbon-offsetting sectors that are difficult to decarbonize. DAC is siting-flexible, and DAC facilities can be installed at potential geological storage sites. Direct air capture with storage can in the long term provide a solution for net-negative CO2 emissions from a limitless resource. Globally, direct air capture is expected to capture 10-15 Gt CO2/year.
      • Producing materials and chemicals by biorefinery instead of using fossil sources can reduce CO2 emissions to zero and for some elements even to negative values. Consequently, much of today’s CO2 emissions from fossil-based chemicals and materials can be avoided.
    • IM2: “Green fuels for transport and industry”
      • Direct air capture can contribute to deliver carbon for materials in a fossil-free future where CO2 may be a limited resource due to constraints on land for biomass production.
    • IM3: “Climate- and environment-friendly agriculture and food production”
      • Production of agricultural commodities using a minimal amount of external inputs, closing nutrient loops, and reducing negative discharges to the environment
    • IM4: “Recycling and reduction of plastic waste and textiles”
      • Development and demonstration of close-to-market complementary technologies, involving mechanical sorting and recycling of household waste, combined with chemical recycling of non-mechanically recyclable fractions by turning them into high-quality monomers and chemical feedstock to fully substitute virgin material, and ultimately increasing recycling rates significantly.


    The mission on “Circularity and Carbon Capture” is in line with several of the AAU Engineering Faculty’s nine sustainable focus areas, e.g.:



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    The vision of the C3 mission is a green transition built on a circular foundation with reduce, reuse, and recycling principles. Ultimately, the green transition leads to a future climate neutral economy powered by renewable energy sources, with balanced energy and non-energy resource consumption, and in which new waste2value chains will eliminate societal waste production. 

    In order to achieve the vision of the mission, the following research objectives will be targeted:

    • Capture of CO2 by photosynthesis and storage in biomass (incl. algae) and ecosystems with subsequent biorefining of the produced biomass.
    • Develop point source and direct air CO2 capture, CO2 transportation and storage technologies, and provide the link between emissions control and PtX applications. 
    • Develop circular biorefineries with high potential for providing a carbon-neutral replacement for fossil fuels, chemicals, and materials. Fuels, chemicals, materials as well as food, fibers and energy can be produced from biomass through direct extraction, enzymatic modification, fermentation, chemical catalysis, or chemical modification. Furthermore, microalgae and chemical transformations of feedstocks represent an unexploited potential for CO2 capture from point sources.
    • Develop processes which enables recycling of valuable biomass components e.g. essential nutrients such as phosphorous.
    • Develop algorithms for state-of-health (SOH) estimation of batteries in first-life applications. Accurate estimation of the battery SOH at the end of first-life is necessary in order to know its performance and determine its techno-economic feasibility for the second-life application. Pattern recognition techniques and machine learning will be used to tackle this objective.
    • Develop techniques for sorting batteries at the end of their first-life. As batteries retired from their first-life are coming from various applications and with different SOHs, techniques for battery clustering have to be proposed in order to sort batteries for specific second-life applications
    • Develop algorithms for state-of-health estimation of batteries in second-life applications.
    • Precise knowledge of the battery SOH in second-life application becomes mandatory in order to enhance the reliability of the system, avoid cathastrophic failure, and subsequnetly ensure economic feasibility of the application. Thus, SOH estimation methods beyond SOA should be developed.
    • Developing chemical recycling technologies for end-of-life plastics, textiles, and composites.


    With the above objectives, the following impacts will be targeted:

    • Contribute to a sustainable green transition with least impact on scarce, finite resources.
    • Accelerate the deployment of negative emission technologies for the capture and storage or utilization of CO2 on a gigaton CO2/yr scale.
    • To realize the potential of a plastic circular economy and unlock the CO2 emission saving potential of up to 1.5 Mt CO2(eq.) per year in a Danish context.
    • Benefits associated to circular business models are substantial. Meyer (2011) estimated that resource efficiency improvements across different value chain could provide raw material savings in the region of 17–24 % and costs savings of around 630 million EUR in Europe.
    • Phosphorus is as vital for food production as water. It is estimated that at current rates, we could be exhausting our phosphate rock reserves as soon as in 50-100 years. Phosphorus is a critical raw material in EU as no rock reserves exist within the community. Furthermore, it has been concluded that up to half of the mined phosphate is wasted – if not recovered from bio-waste and WWT sludge.


    The mission are collaborating with the AQUA-COMBINE consortium (as coordinator of the EU project) as well as the FLEXI-GREEN FUEL consortium (as partner in the EU project).

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    Biomass is a scarce resource but it plays a pivotal role in the green transition, e.g. as carbon resource for fuels and chemicals and as a nutrient source for a future circular bio-economy, and to enable net negative emissions. For these reasons we must mature bio-refinery concepts, which realise the highest possible value from the biomass resources. Complete valorizing of bio-resources, including the organic and inorganic fractions, calls for novel integration of thermochemical and biochemical technologies. For energy purposes, thermochemical processes are superior for the complete valorization of the organic fractions, but thermochemical processes lack selectivity towards the production of chemicals and nutrient recovery. Biochemical technologies can be highly selective and can be tailored to extract high values compounds upstream and downstream primary conversion, but typically less versatile for bulk conversion. The combination creates a synergetic interplay that indeed has the potential to fully valorise bioresourses.

    A continued need for carbon-based aviation fuels, makes biomass a major contender for future biofuel production. However, to make biofuels price competitive these must be produced from inexpensive bio-sources. Such bioresources are typically characterized be a high degree of inhomogeneity and a broad mix of organics and inorganics – for which the complete valorization cannot rely on a single process. Therefore, a research topic is to delevop a biorefinery concept to selectively produce avaition fuels with the ultimate goal of ensuring circular usage of all sidestreams.

    Lithium-ion (Li-ion) batteries have drawn much attention from academia and industry due to their superior performance, such as high energy density, long life-span, low maintenance, etc. However, the wide range of application results in large variations in the usage of the batteries. As the usage of the batteries is one of the primary causes of degradation, accurate state-of-health (SOH) estimation can ensure reliable and economically viable operations of the battery by managing its lifespan. Furthermore, the usage variations results in varying SOH conditions after first-life application, which complicates the prediction of second-life application. This stimulates the development of state-of-health estimations and diagnostic tools to extend battery lifetime and lifecycles. Second-life application of batteries is a relatively pristine territory and at the moment cannot be realized without the participations of the OEMs (i.e., EV manufacturers), who are creating a, to-some-extent, monopolistic market. Thus, diagnostic tools for EV batteries, which do not rely of information from OEMs, have to be developed. This is of real importance especially for Denmark who (i) is aiming for approximately 1 million EVs on the roads before 2030 (their batteries will be retired by 2035-2040) and (ii) does not have EV manufacturers. In order to reach these goal (i.e., tools for second-life battery diagnostics), research, development, and demonstration activities are foreseen:

    • Step 1 (year 1 & 2) – funding for pure research activities to investigate and develop the expected methods (DFF, Villum etc.)
    • Step 2 (year 3 to 5) – funding for development and demonstration projects together with Danish partners in order to demonstrate the techno-economic feasibility of the methods and create business models
    • Step 3 (end of year 5) – AAU spin off company to commercialize the battery diagnostic tools.

We take action by

Mission Chair

Thomas Helmer Pedersen - AAU Energy
Thomas Helmer Pedersen
Direct phone: +45 2829 1679

Vice mission Chair

Daniel Stroe - AAU Energy
Daniel Stroe
DIRECT PHONE: +45 9940 3327
E-mail: dis@ENERGY.AAU.DK

Research groups committed to this mission

Batteries - AAU Energy research group

Advanced Biofuels - AAU Energy research group

Bioenergy and Bioproducts - AAU Energy research group

Offshore Process Control and Cybernatics - AAU Energy research group