SkyClean Scale-up is a three-year project maturing the SkyClean pyrolysis technology, documenting CO2e sequestration and environmental effects and developing biochar value chains.

The SkyClean Scale-up project facilitates a pyrolysis-based reduction of greenhouse gas emissions from the Danish agricultural sector of at least 2 million tons of CO2e per year in 2030.

In addition, production of CO2 neutral energy will lead to a reduction in Danish greenhouse gas emissions of at least 1.6 million tons of CO2e per year in 2030 through displacement of fossil fuels.

Hear about the first project results at our project conference in Vejle on 22/11, read more and sign up here.

Project Activities

Mature Technology

The SkyClean Scale-up project focuses on pyrolysis technology and upscaling a plant to industrial size. Most funds go to constructing a 20 MW SkyClean pyrolysis plant in Vrå, Denmark. It’s ten times larger than the largest existing plant. The SkyClean plant in Vrå will process 40,000 tons of biogas residual plant fibers yearly, producing 14,000 tons of biochar and a large amount of green gas. The production of biochar alone corresponds to about 23,000 tons of CO2 removed from the atmosphere. The project also demonstrates clean syngas production for advanced biofuels.

The main partners invovled are Stiesdal SkyClean, Agri Energy Vrå, KK Wind, AEA, Topsoe, DTU KT and DTU Construct.

The construction of the the plant will be completed in the second half of 2023.

Biochar in the Soil

When applying biochar to the soil, the project will document that the CO2 is stored in the biochar in the long term, that applying biochar to the soil does not have any bad sideeffects, and that it has a positive effect on crop growth.

This will be investigated through laboratory-, lysimeter-, small and medium scaled field studies. Some of these are new, and some continues using research fields which have been used for biochar for many years.

The main partners involved are KU Plen, AU Envs, AU Agro, DTU KT and SEGES.

The initial findings from the 2023 studies will be shared at the end of the year.

Biochar Handling

The project aims to produce 10,000 tons of biochar. It will be investigated how to best handle, distribute and apply the biochar in the agricultural sector. This includes identifying the best packaging and storage methods and ensuring safety throughout the supply chain. It will be investigated how to best minimize dust and protect against heat generation or self-ignition. The goal is to create a well-defined biochar product with handling instructions for CE-marking.

The main partners involved are Stiesdal SkyClean, Vestjyllands Andel, SEGES and DTU KT.

The first results from the tests carried out during 2023 will be shared at the end of the year.

The CO2 Emission Challenge

The CO2 emission challenge is a pressing global issue due to its detrimental impact on the earth’s climate system. The burning of fossil fuels for energy production and transportation releases large amounts of CO2, leading to the greenhouse effect and global warming. These emissions contribute to climate change, resulting in adverse consequences such as rising temperatures, altered weather patterns, sea-level rise and ecosystem disruption.

The Pyrolysis Process

In essence, pyrolysis is putting CO2 back in the ground while producing CO2-neutral energy. The figure below shows pyrolysis at the most general level.  1) Plants capture CO2 from the atmosphere through photosynthesis. 2) Either directly or after being processed at e.g. a biogas plant, the biomass is sent to the pyrolysis plant. 3) The biomass is heated in an oxygen free environment, turning approx. half of the material to gas and half to biochar. 4) The biochar can be returned to the field where it was harvested, improving the soil and storing CO2 in the ground. The CO2 neutral gas can be used for various energy purposes somewhat similar to biogas.

Pyrolysis is today an established method for storing CO2 safely and has been proven to be scaleable, as seen in the status on European biochar production below.

Cumulative European Biochar Production Capacity
The biochar production capacity has grown significantly in Europe in the last five years. In 2022, it grew by 52% to 53.000 ton biochar, and for 2023, the production capacity is expected to exceed 90.000 ton. Pyrolysis is, thereby, a proven technology, but it is still early days with a number of different pyrolysis designs competing on the market.

Annual European Biochar Production
As the pyrolysis plants are not all commissioned on January 1st, the actual production is lagging slightly behind the installed capacity. But it is estimated that 33.500 ton biochar was produced in 2022, equivalent to more than 90.000 ton of CO2e stored. In 2023, it is expected that more than 50.000 ton biochar will be produced in Europe, storing more than 150.000 ton of CO2e.

Results & Resources


We will share the first results from the project at the SkyClean Scale-up conference held on November 22nd in Vejle. Read more and sign up here.

If you want to recieve news about the project, sign up here.


A large body of litterature about pyrolysis and biochar exists. The publications below can be a good starting point for getting more informed.

Other Pyrolysis and Biochar Projects

As it is an important topic, there is a large number of related projects. Some of them are listed below.

  • BioAdapt – Biochar as a tool for climate adaptation in crop production on coarse sandy soil
  • Biostore – Biochars for soil carbon storage and sustainable agriculture
  • Grass Biochar – Process energy and biochar from pyrolysis of grass pulp from green biorefineries
  • PowerBio – Increasing biomass potentials for energy and high value products
  • SIMPLY – Supporting implementation of pyrolysis via constructive alignment of climate impact assessment methods, goals, frameworks and incentives
  • SkyClean 2 MW – Industrialising the 2 MW SkyClean plant and advancing bio-oil production
  • STABIL – Reduction of greenhouse gas emissions and increased carbon sequestration from pyrolysis of nutrient rich fibers

    The projects marked with an asterisk are finished, the rest are ongoing. If you know a project which should be on the list, email us.





    Stiesdal SkyClean A/S

    Stiesdal SkyClean A/S is a fully owned subsidiary of Stiesdal A/S, founded by Henrik Stiesdal with the purpose of developing solutions to fight climate change. Stiesdal SkyCleans’s purpose is to develop and commercialize the SkyClean technology.

    Stiesdal A/S’ other technologies include 1) The TetraSpar industrialized floating offshore wind foundation, 2) The GridScale energy storage system with 10 hours – 10 days capacity and 3) The HydroGen electrolyzer unit for low-cost hydrogen production. The company has large corporate companies e.g. Shell as customers and utilizes experience from offshore wind power to ensure safety. Stiesdal A/S has been ISO 9001 certified to better service the customer base.

    Agri Energy Vrå

    Agri Energy Vrå is a local energy company that strives to be a part of the agriculture’s contribution to solve the climate challenges. With a unique technology, they produce energy from local biomass from agriculture. Their biogas plant uses residue biomass from local farmers to produce natural gas to the national gas grid.

    KK Wind Solutions A/S

    Building on more than 40 years of experience in electronic systems for wind, KK Wind Solutions’ capabilities span development of state-of-the-art technologies, LEAN production facilities and an effective, global setup for operation and maintenance.

    Aktive Energi Anlæg A/S (AEA)

    AEA is a general contractor specializing in the design and construction of unique district heating and combined heat and power plants as well as customized energy systems for the industry in Denmark. They operate at the intersection of consulting, optimization, installation and servicing.


    The company specializes in carbon emission reduction technologies. That includes proprietary Solid Oxide Electrolyzer Cell (SOEC) high-temperature electrolysis technology, the production of heterogeneous catalysts and the design of process plants based on catalytic processes. Focus areas include hard-to-abate sectors such as heavy industry (steel and iron, chemicals, cement), long-haul transportation (aviation, shipping, trucking) and clean fuels (bio-diesel and Ultra-Low-Sulfur Diesel (ULSD).

    Vestjyllands Andel A.m.b.a.
    The corporation works with trade, handling and logistics related to the agricultural sector.
    DTU KT

    The CHEC research center focuses on chemical engineering principles applied in combustion, harmful emission control, gasification, pyrolysis, catalysis, continuous production of pharmaceuticals and advanced measuring technology. Their primary expertise covers chemical reaction engineering, transport phenomena and design and development of thermal energy processes for conversion of biomass and waste.

    DTU Construct

    DTU Construct, the department of Civil and Mechanical Engineering, develops and utilises science and technical knowledge for the benefit of society and the sustainable development. They undertake research, education, innovation and scientific advice of the highest quality within building design and processes, building construction and safety, building energy and services, solid mechanics, fluid mechanics, materials technology, manufacturing engineering, engineering design and thermal energy systems.


    From RUC IMT (department of people and technology), researchers from the METRIK (Environment, Energy, Transport – Regulation, Innovation and Climate Policy) and MOSPUS (Mobility, Space, Place and Urban Studies) research groups are involved in the project.

    The research in METRIK aims at generating knowledge about the interaction between societal development and technological development with a focus on problems related to environment, energy, nature and resources. The researchers seek to increase impact of the research in academia and in society through frequent collaboration with external stakeholders from industry, authorities and NGO’s. The research often bridges social sciences and natural sciences and technology for example in studies of implementation of renewable energy, where technological insight into resource flows and technology assessments is linked to social science knowledge about regulation and planning.

    MOSPUS develops theoretically informed and critical research on the themes of space, place, mobility and urban studies. The work is guided by a strong commitment to social justice and to making more sustainable and democratic futures. Efforts to conduct research that reaches beyond the university include participatory knowledge production, ‘future creating’ workshops and advocacy- and policy-oriented outputs.

    SEGES Innovation

    SEGES Innovation is a private, independent, non-profit research and development organization and is the leading agricultural knowledge and innovation center in Denmark.

    Their primary objective is to identify and develop the commercial possibilities of agriculture in order to provide farmers with the best options for running their businesses more profitably while taking the environment and animal welfare into consideration.

    KU - Plen

    KU-PLEN-Soil is the Soil Fertility and Waste Recycling Research Group at the Department of Plant and Environmental Sciences, University of Copenhagen. PLEN-soil has long-term research experience within the turnover of organic matter and nutrients in agricultural soils. A focus of the research is on soil carbon sequestration and recycling of nutrients with organic waste and bio-based fertilizers and the evaluation of the impacts of their use on soil quality and the environment. The group has large expertise in a range of methods from lab to field scale, such as gaseous emission measurements and isotope techniques and soil chemical and microbial measurements.

    AU - AGRO

    The Department of Agroecology (AU-AGRO) is a department under Technical Sciences at Aarhus University. The majority of the 270 employees are physically located in Foulum. Furthermore, AU-AGRO have employees working at the experimental station in Askov. The Department carries out research related to interactions between climate, soil and plants in agro-ecosystems, hereby contributing to sustainable production through research, consulting and teaching. AU-AGRO has unique research facilities at its disposal, including land for field trials, outdoor lysimeter facilities and laboratories. The Department has strong expertise and facilities for GC measurements of greenhouse gases (CO2, N2O, CH4) and has equipment for analyses of soil biological, chemical and physical properties. AU-AGRO participates in several national and international projects with the aim of reducing greenhouse gas emissions from agriculture.


    AU-Ecoscience has competences within ecotoxicity testing on soil fauna delivered by the Department of Ecoscience, AU.

    AU - ENVS

    AU-Environmental Science has strong scientific experience with environmental applied research dealing with environmental and agricultural risk assessment, soil health and biodiversity, both at the community level and at cell-to-cell microbial interaction level. The section of environmental microbiology focuses on soil food webs, environmental risk assessment of microorganisms and chemicals, soil health and general soil biology using NGS and eDNA tools as well as culturing and biochemical assays. AU-ENVS houses several nucleic acid sequencing platforms, quantitative DNA and RNA extraction expertise and bioinformatic capabilities and all necessary equipment for environmental risk assessment in the soil.

    Energy Cluster Denmark

    Energy Cluster Denmark is the result of the recent simplification of the business support system in Denmark and is now the one cluster organization responsible for connecting the Danish actors in the energy ecosystem (industry, knowledge institutions and public authorities). This is primarily done through joint development projects with participation from both potential customers, leading technology companies and university experts, such as SkyClean. Our total project portfolio is currently 3+ billion DKK and 59 projects. We also arrange innovation related events and match Danish and foreign competences for international development projects.

    Food & Bio Cluster (FBC)

    FBC is a non-profit organization operating within the agri-food value chain. FBC has more than 350 members ranging from small start-ups to some of the largest food producing companies in the world. FBC is a team of 38 specialists with skills within e.g. sustainable production and utilization of bioresources, biorefining, business development and financing. FBC is involved in a number of national and international projects centered around innovation, financing and internationalization within the agriculture, bioresources, energy, environmental technology and food sectors.


    Achieving the goal of pyrolysis-based reduction of greenhouse gas emissions from the Danish agricultural sector of at least 2 million tons of CO2e per year in 2030 will require broad involvement. You are welcome to reach out with questions and sign up here to stay up to date with the project.


    Project Communication

    Christian Munk Jensen
    Project Manager
    Energy Cluster Denmark
    +45 5055 2606

    The project has been co-funded by the European Union.