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Algae and microalgae. Carbon farming and CO2 upcycling

carbon farming e upcycling – the keywords for mitigating climate change and giving life to the circular economy (1,2) – find unparalleled expression on the earth's surface in algae and microalgae.

These primitive life forms not only sequester huge volumes of carbon in the atmosphere, but rapidly convert CO2 into organic matter and thus into food, feed, fertilizer, biofuels.

ABECCS (Algae-based Bioenergy with Carbon Capture and Storage) is one of the applications of the blue bioeconomy more interesting. Produce proteins and energy by devouring carbon dioxide.

1) Mitigate the climate change with negative emission systems. IPPC

'Mitigation of Climate Change', the IPCC 2022 report (The Intergovernmental Panel on Climate Change), confirms what was already noted in 2014. (3) The probability of containing the increase in global temperature within the limit of +2°C is associated with 116 possible scenarios, where:

  • 87% of the hypotheses are based on the adoption of BECCS systems (Bioenergy with carbon capture and storage),
  • 67% of these scenarios postulate that these systems will express at least 2100% of the world's primary energy by 20.

Produce energy with zero emissions (e.g. solar, biomethane), according to IPCC, is not sufficient to mitigate global warming. We also need systems with negative emissions, i.e. systems capable of absorbing more carbon than they emit.

2) Storage of carbon. The limits of terrestrial ecosystems

Trees and plants (e.g. hemp, bamboo) are fundamental tools to combat climate change through carbon storage. (4) A scientific study published in Nature (Terrer et al., 2021) has also highlighted the existence of a variable relationship, even negative, between the development of plant biomass and the storage of CO2 in the soil (SOC, Soil Organic Carbon). (5)

Observation of 108 experimental studies showed that soil carbon storage (SOC) decreases when plant biomass is strongly stimulated by CO2. The reduction of PERFORMANCE of the soils seems to be linked to the greater absorption of nutrients by some plants, perhaps also in relation to the agronomic practices adopted. SOC projections may therefore require revision.

3) Superstar microalgae in carbon storage

Microalgae represent one of the most promising solutions both for producing foods of high nutritional value (6,7) and for contributing to the mitigation of climate change. Also through the creation of carbon storage systems that can overcome the limits of terrestrial ecosystems, due to the following.

3.1) Ratio between bioenergy produced and space used

The production of bioenergy through microalgae requires a surface ten times smaller than that necessary to produce the same amount of energy through terrestrial plants.

3.2) Water consumption and growing conditions

The cultivation of microalgae consumes less water than many terrestrial crops. With two substantial differences:

  • the use of fresh water is not required, even if possible,
  • it is possible to supply nutrients via waste water from other industrial processes.

3.3) Rapidity of growth

Photosynthesis it is used by microalgae to absorb CO2, water, sunlight and produce energy. But unlike many plants, microalgae don't need to develop stems and/or roots.

The energy of microalgae it is therefore mainly dedicated to cell division, which allows it to constantly replicate at a much faster rate than trees.

Therefore too Aquatic microalgae have been identified as fast growing species whose rate of carbon fixation is higher than that of terrestrial plants.

3.4) Prosperity in environments with a high concentration of CO2

Some species of microalgae are able to thrive in environments with a high concentration of CO2 and effectively remove it at a rate 10 to 50 times higher than that of terrestrial plants. One acre (0,4 ha) of algae can remove up to 2,7 tons of CO2 per day.

Chlorella it stands out in its great resistance to difficult environmental conditions, showing excellent growth rates at different concentrations of CO2 (15%), as well as in the presence of nitrogen and sulfur oxides (NOx, SOx), gases responsible for smog. (8)

4) Upcycling of CO2 for the industrial production of algae. The example of Pond Technology

Pond Technologies (Canada) developed a system of upcycling of the CO2 emitted by various industrial plants (e.g. power plants, oil refineries, cement factories, food industries, etc.).

Conventional bioreactors, connected to the infrastructures, transfer the emissions from the chimneys to the tanks where the algae consume the carbon dioxide and release oxygen into the atmosphere, also producing biomass for various destinations.

5) Biofuels with negative emissions from microalgae

ABECCS systems (Algae-based Bioenergy with Carbon Capture and Storage) use marine microalgae to produce energy with negative emissions, i.e. able to meet the needs indicated by the IPPC (see above, paragraph 1).

The advantages of biofuels thus produced, compared to other materials falsely represented as such, are:

  • effectively negative carbon footprint (unlike, for example, palm oil. See note 9),
  • absence of competition with food production, in the input (e.g. fresh water) and the output (as instead, among others, the crops of corn for use biofuel). (10)

6) Integrated systems of agriculture, forestry and seaweed cultivation

Embedded systems of agriculture, forestry and algae cultivation are also promising – from various economic and environmental points of view – for the production of food, feed and bioenergy. In this regard, a study (Beal et al., 2018) on an ABECCS project where a 121-hectare algae plant was combined with a 2.680-hectare eucalyptus forest. (11)

Eucalyptus biomass powers the combined generation of heat and electricity (combined heat and power plants, CHP) with subsequent carbon capture and storage (Carbon capture and storage, CCS). Part of the captured CO2 is used for algae cultivation, the rest is sequestered. Biomass combustion provides CO2, heat and electricity, while promoting algae cultivation.

6.1) Integrated systems, output of protein and energy

The integrated system object of analysis (Beal et al., 2018) produced an amount of protein equal to that of soy, while generating 61,5 TJ of electricity and sequestering 29.600 t/year of CO2. The energy generated was greater than that consumed, the water footprint (fresh water) almost equal to that of soybeans.

The economic results results were equal to those of a soybean monoculture, thanks to the availability of combinations of products that can include the supply of algal biomass - with functions that replace fishmeal, or soybean - with corresponding carbon credits. And an appreciable environmental value for the respect of biodiversity in the forest area.

7) Provisional conclusions

Algae and microalgae represent a concrete solution for the production of biomass with various destinations (food, feed, fertilizers and biostimulants, biofuels) and bioenergy, with a negative carbon footprint.

The integration of microalgae production in agricultural and industrial systems also looks promising for the prospects of upcycling lateral process flows (e.g. co-products) in food ingredients.

Dario Dongo and Giulia Pietrollini


(1) Dario Dongo, Giulia Pietrollini. Carbon farming, green light from the Council for EU certification of carbon credits in agriculture. GIFT (Great Italian Food Trade). 21.12.22

(2) Dario Dongo. Upcycling, the main road to research and innovation. GIFT (Great Italian Food Trade). 1.1.23

(3) IPPC, The Synthesis Report of the Fifth Assessment Report, (2014) AR5 Synthesis Report: Climate Change 2014 — IPCC

(4) Martha Strinati. The power of hemp to sequester carbon at the core of Hemp-30. GIFT (Great Italian Food Trade). 10.1.23

(5) Terrer, C., Phillips, RP, Hungate, BA et al. (2021). A trade-off between plant and soil carbon storage under elevated CO2. https://www.nature.com/articles/s41586-021-03306-8 Nature 591, 599-603. https://doi.org/10.1038/s41586-021-03306-8

(6) Dario Dongo. ProFuture, microalgae to feed the planet. The EU research project. GIFT (Great Italian Food Trade). 18.6.19

(7) Dario Dongo, Andrea Adelmo Della Penna. Algae and microalgae for food use in Europe, the ABC. GIFT (Great Italian Food Trade). 14.11.22

(8) SP Singh, Priyanka Singh (2014). Effect of CO2 concentration on algal growth: A review. Renewable and Sustainable Energy Reviews. Volume 38, 2014, Pages 172-179, ISSN 1364-0321, https://doi.org/10.1016/j.rser.2014.05.043.

(9) Dario Dongo, Giulia Caddeo. Palm oil biodiesel. Antitrust condemns ENI. Equality. 8.2.20

(10) Martha Strinati. Rising prices and food crisis in times of war. Background in the iPES FOOD report. GIFT (Great Italian Food Trade). 10.5.22

(11) Beal, Colin M.; Archibald, Ian; Huntley, Mark E.; Greene, Charles H.; Johnson, Zackary I. (2018). Integrating Algae with Bioenergy Carbon Capture and Storage (ABECCS) Increases Sustainability. Earth's Future. doi: 10.1002/2017EF000704

(12) Dario Dongo. Upcycling, the main road to research and innovation. GIFT (Great Italian Food trade). 1.1.23

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Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.

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Graduated in industrial biotechnology and passionate about sustainable development, she participates in the research projects of Wiise Srl benefit

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