Microalgae for Carbon Dioxide Removal

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Small algae, big impact – This project contributes to reversing climate change through a new negative emission technology: the production of fast-growing microalgae in highly efficient photobioreactors. A 500-liter-reactor will be realised as a pilot for future reactor facilities that each will enable the direct removal of almost 55 tons of atmospheric CO2 yearly. Why net zero is not enoughTo counteract anthropogenic climate change, not only anthropogenic CO2 emissions must be reduced quickly and significantly, but also Negative Emission Technologies (NET) must be used on a large scale [1]. In 2019, Switzerland also committed to a net zero target for 2050, which includes long-term Carbon Dioxide Removal (CDR) from the atmosphere. Net zero means that from 2050 onwards, CO2 may still be emitted, but CO2 at the same time must be removed from the atmosphere by natural and engineered storages at the same scale. According to the IPCC, we need global cumulative net negative emissions of 380 Gt CO2 from 2050 to 2100 to return to 1.5°C after a likely overshoot. NET include numerous approaches such as afforestation of forests, ocean fertilization, replacement of concrete and metals with woods, etc.Small algae, big impact – so far entirely untapped potentialThe growth of plants on land through photosynthesis sequesters CO2 from the atmosphere and stores it long-term if the biomass is removed from the natural cycle. If the goal is to maximize the production rate of biomass with high energy and space efficiency, photosynthesis of microalgae in water is significantly superior to photosynthesis of land plants by a factor of up to 50 under suitable conditions [2]. The biomass consisting of the elements C, H, O, N, P and S binds on average 1.66 kg CO2 per kg microalgae [3]. It is expected that with natural light alone an area-related production rate of up to 287 t/ha/a biomass can be achieved with photobioreactors, where today already up to 155 t/ha/a can be reached. With open ponds a rate of roughly 60 t/ha/a can be achieved [4]. Almost all large and widely cited studies and reviews of NET list biomass production either by plants on land and/or algae in oceans. So far, the production of algae in bioreactors has been entirely missed.Improving an already highly efficient processThe specific costs of producing microalgae with photobioreactors when additionally adding pure CO2 instead of just air as feed to the reactors currently start at about 0.5 US$ to about 0.68 EUR per kg dry biomass, which corresponds to about 0.3 US$ to 0.41 EUR per separated kg CO2 [5]. The demand for technical energy as a differentiation to ambient heat and solar irradiation starts at almost zero, if one accepts relatively low growth rates compared to systems optimized to maximize the production rate.Scaling striking research results into practiceThe project team has now been studying the process of microalgae cultivation in photobioreactors for one and a half years. We have evaluated our process theoretically and conducted numerous practical investigations. Initially with friends from and in Germany, and since mid-2021 mainly here in Switzerland. As part of Reto Tamburini’s master’s thesis on this topic, the algae growth rate of various algae species under different operating conditions is currently being investigated using ten small experimental reactors (12 liters each). From these experiments, valuable information has already been obtained on the production rate and yield of the algae and the nutrients required for this purpose. Furthermore, it will be determined how to design upscaled algae reactors from a geometrical and process-specific point of view.Our plan to contribute to negative emissionsOur goal is that our technology will be used globally for the long-term removal of carbon dioxide, removing significant amounts of CO2 from the atmosphere. To achieve this, we need to increase the size of our prototypes step by step, while gaining new experiences and knowledge about the process. With support of the energylab we would like to leave the laboratory scale and start to design a 500-liter prototype. The design will take about two months, which will be followed by manufacturing and commissioning, before we start producing biomass in October this year, that means, removing CO2 from the atmosphere. After the successful commissioning of the 500-liter prototype, we want to take it to the next level and design a larger prototype with a capacity of 12’500 liter where 25 modules are operated in parallel. Under optimal conditions, 6 g of biomass per liter and day can be produced. A 12’500-liter prototype can therefore produce 75 kg of biomass per day or 27 t per year and thus permanently remove around 55 t of CO2 from the atmosphere per year.[1] IPCC Special Report: Global Warming of 1.5°C, https://www.ipcc.ch/sr15/[2] Khan, S.A. et al., “Prospects of biodiesel production from microalgae in India”, Renewable and Sustainable Energy Reviews[3] Williams, P.J.I.B., Laurens, L.M.L, “Microalgae as biodiesel & biomass feedstocks: Review & analysis of the biochemistry, energetics & economics.”, Energy and Env. Science[4] Stephens, E. et al., “An economic and technical evaluation of microalgae biofuels.”, Nature Biotechnology[5] Norsker, N.H. et al., “Microalgal production – a close look at the economics.”, Biotechnology Advances

Project Idea Metadata

• Project Idea Name: Microalgae for Carbon Dioxide Removal
• Date: 3/10/2022 9:41:18 AM
• Administrators:
  • Reto Tamburini

Project Idea Description

Why net zero is not enough

To counteract anthropogenic climate change, not only anthropogenic CO2 emissions must be reduced quickly and significantly, but also Negative Emission Technologies (NET) must be used on a large scale [1]. In 2019, Switzerland also committed to a net zero target for 2050, which includes long-term Carbon Dioxide Removal (CDR) from the atmosphere. Net zero means that from 2050 onwards, CO2 may still be emitted, but CO2 at the same time must be removed from the atmosphere by natural and engineered storages at the same scale. According to the IPCC, we need global cumulative net negative emissions of 380 Gt CO2 from 2050 to 2100 to return to 1.5°C after a likely overshoot. NET include numerous approaches such as afforestation of forests, ocean fertilization, replacement of concrete and metals with woods, etc.

Small algae, big impact – so far entirely untapped potential

The growth of plants on land through photosynthesis sequesters CO2 from the atmosphere and stores it long-term if the biomass is removed from the natural cycle. If the goal is to maximize the production rate of biomass with high energy and space efficiency, photosynthesis of microalgae in water is significantly superior to photosynthesis of land plants by a factor of up to 50 under suitable conditions [2]. The biomass consisting of the elements C, H, O, N, P and S binds on average 1.66 kg CO2 per kg microalgae [3]. It is expected that with natural light alone an area-related production rate of up to 287 t/ha/a biomass can be achieved with photobioreactors, where today already up to 155 t/ha/a can be reached. With open ponds a rate of roughly 60 t/ha/a can be achieved [4]. Almost all large and widely cited studies and reviews of NET list biomass production either by plants on land and/or algae in oceans. So far, the production of algae in bioreactors has been entirely missed.

Improving an already highly efficient process

The specific costs of producing microalgae with photobioreactors when additionally adding pure CO2 instead of just air as feed to the reactors currently start at about 0.5 US$ to about 0.68 EUR per kg dry biomass, which corresponds to about 0.3 US$ to 0.41 EUR per separated kg CO2 [5]. The demand for technical energy as a differentiation to ambient heat and solar irradiation starts at almost zero, if one accepts relatively low growth rates compared to systems optimized to maximize the production rate.

Scaling striking research results into practice

The project team has now been studying the process of microalgae cultivation in photobioreactors for one and a half years. We have evaluated our process theoretically and conducted numerous practical investigations. Initially with friends from and in Germany, and since mid-2021 mainly here in Switzerland. As part of Reto Tamburini’s master’s thesis on this topic, the algae growth rate of various algae species under different operating conditions is currently being investigated using ten small experimental reactors (12 liters each). From these experiments, valuable information has already been obtained on the production rate and yield of the algae and the nutrients required for this purpose. Furthermore, it will be determined how to design upscaled algae reactors from a geometrical and process-specific point of view.

Our plan to contribute to negative emissions

Our goal is that our technology will be used globally for the long-term removal of carbon dioxide, removing significant amounts of CO2 from the atmosphere. To achieve this, we need to increase the size of our prototypes step by step, while gaining new experiences and knowledge about the process. With support of the energylab we would like to leave the laboratory scale and start to design a 500-liter prototype. The design will take about two months, which will be followed by manufacturing and commissioning, before we start producing biomass in October this year, that means, removing CO2 from the atmosphere. After the successful commissioning of the 500-liter prototype, we want to take it to the next level and design a larger prototype with a capacity of 12’500 liter where 25 modules are operated in parallel. Under optimal conditions, 6 g of biomass per liter and day can be produced. A 12’500-liter prototype can therefore produce 75 kg of biomass per day or 27 t per year and thus permanently remove around 55 t of CO2 from the atmosphere per year.

[1] IPCC Special Report: Global Warming of 1.5°C, https://www.ipcc.ch/sr15/

[2] Khan, S.A. et al., “Prospects of biodiesel production from microalgae in India”, Renewable and Sustainable Energy Reviews

[3] Williams, P.J.I.B., Laurens, L.M.L, “Microalgae as biodiesel & biomass feedstocks: Review & analysis of the biochemistry, energetics & economics.”, Energy and Env. Science

[4] Stephens, E. et al., “An economic and technical evaluation of microalgae biofuels.”, Nature Biotechnology

[5] Norsker, N.H. et al., “Microalgal production – a close look at the economics.”, Biotechnology Advances

Small algae, big impact – This project contributes to reversing climate change through a new negative emission technology: the production of fast-growing microalgae in highly efficient photobioreactors. A 500-liter-reactor will be realised as a pilot for future reactor facilities that each will enable the direct removal of almost 55 tons of atmospheric CO2 yearly.