1348 · the Middle Ages
Founding of Charles University
279 ppm
Charles IV founds the first university in central Europe.
Carbon is not waste. We grow from it.
Monitored photosynthesis of microalgae, using controlled technology.
Helena 04 visualisation.
We do not have a carbon problem. We have a problem with its speed.
Carbon was laid down underground over millions of years - peat, coal, oil, gas - and volcanoes, together with weathering, returned it at a rate of roughly a third of a billion tonnes of CO₂ a year.1 We are returning 38 billion. A hundred times faster than the planet stored it, and over a hundred and fifty years instead of hundreds of millions.
Helena is a photobioreactor.
A closed tubular system in which microalgae grow on medium and carbon dioxide - food to them, feedstock to us. Per square metre of footprint it captures orders of magnitude more CO₂ than a forest. At the Metropole Zličín shopping mall in Prague, where the reactor was built, we measured roughly a hundredfold of what a temperate forest captures on the same area. At a CO₂ source the calculation gives up to a thousandfold.2
Each reactor is built for a different purpose and tests a different degree of process scalability. Reactor 04 is at TRL 7.3
There is twice as much CO₂ in the air as the mammoths breathed
During the ice age 180 parts per million, before the Industrial Revolution 278, today 427.4 Stopping CO₂ emissions is necessary. Part of what is already in the air will have to be taken back out.
What existing CCS installations put out is CO₂ that has to be compressed, transported and stored. All three steps are paid for - and above all in energy. At a coal-fired power plant, capture consumes about a quarter of the electricity generated.5
We took the path nature has been using for four billion years and gave it control systems and sensors.
1750 · the start of the industrial era
The Industrial Revolution
278 ppm
Europe is going through the first phase of the Industrial Revolution.
1958 · the start of precise data
Measurement begins
314 ppm
Measurement begins at Mauna Loa.1
2026 · the present
Today
427 ppm
Current measured data.4
2050 · outlook
In the near future
490 ppm
At today’s rate of growth - a scenario, not a forecast.
2026 · the present
How much the world captures
0.17 %
The world has 64 Mt CO₂ a year of capacity in operation - 0.17 % of emissions.6
Data: NOAA - Law Dome (Rubino et al. 2019) and Mauna Loa (NOAA GML). Outlook to 2050: linear extrapolation of the last ten years of measurements, a scenario, not a forecast.
How Helena works
- 01
Air - or CO₂ straight from a source - bubbles through the microalgae culture in the tubes. The algae take carbon from it and grow.
- 02
Light. The reactor uses daylight and the LEDs only make up the difference when there is not enough of it. Not by the clock - by what the culture needs at that moment.
- 03
Control. The reactor maintains aeration, light and temperature on its own and measures what is happening in the culture every minute. Rising pH is the first sign that photosynthesis is running.7
- 04
Harvest. The biomass is either a product (feed, nutraceuticals, biostimulant), or the carbon in it is stabilised by pyrolysis into biochar and stays in solid form - which is no longer use of the carbon but its storage.8
What can we do?
The other routes end with pure CO₂ that has to be compressed, transported and stored. Helena ends with biomass.8
Our solution
Helena - controlled biological fixation
Photobioreactor with microalgae
- CO₂ source
- flue gas and ambient air alike
- Durability
- days to years in the product - hundreds of years after pyrolysis
- What is left
- biomass: feed, nutraceuticals, biostimulant - or biochar
Amine absorption (post-combustion)
Scrubber at the emission source
- CO₂ source
- flue gas from a single source
- Durability
- depends on where the CO₂ is stored afterwards
- What is left
- pure CO₂ and the bill for compression, transport and storage
Direct air capture (DAC)
Sorbents in fan units
- CO₂ source
- ambient air - anywhere (0.04 %)
- Durability
- depends on where the CO₂ is stored afterwards
- What is left
- pure CO₂ and a large energy bill
Geological storage (CCS)
Injection into deep formations
- CO₂ source
- pure CO₂ from a scrubber or from DAC
- Durability
- hundreds to thousands of years, as long as the formation holds and someone monitors it
- What is left
- nothing to sell - and part of the volume goes to enhanced oil recovery
Enhanced weathering
Crushed basic rock on soil
- CO₂ source
- ambient air, via rainwater
- Durability
- thousands of years - the carbon ends up as carbonate
- What is left
- limed soil and carbonates carried off to the ocean
Afforestation and soil carbon
Fixation in the landscape
- CO₂ source
- ambient air
- Durability
- decades - fire, bark beetle or logging return the carbon
- What is left
- timber, biodiversity, retained water, a cooler landscape
Biochar (pyrolysis)
Pyrolysis of biomass
- CO₂ source
- carbon already captured by plants or algae
- Durability
- hundreds of years in soil
- What is left
- biochar as a soil amendment and heat from the process
Microalgae in the ocean (MCFS)
Algae that sink (Puro.earth)
- CO₂ source
- CO₂ dissolved in the surface ocean
- Durability
- 200+ years under the methodology
- What is left
- nothing to sell - the methodology applies only to ocean phytoplankton, not to cultivation
Two tenths of a percent
The world emits over 38 billion tonnes of CO₂ a year. It captures and stores 64 million - just under two tenths of a percent.6 Net-zero scenarios count on roughly five times that volume by 2030.9
That is the space Helena aims at: CO₂ capture that is documentable and continuously measured, and whose output is not waste but feedstock. The carbon in it comes from emissions that would otherwise have ended up in the atmosphere - for the customer these are avoided emissions, an item that can be evidenced in their own reporting.10
Who we build Helena for.
Biomass customers
Producers of feed and nutraceuticals who want Chlorella of defined origin: closed cultivation with no contact with wastewater and documented carbon provenance. We tailor the form of samples and small batches with you.
Cities and buildings
The reactor measures air quality: CO₂, temperature, humidity, light levels, particulate matter, oxygen. Minute-by-minute data for the operator or the city, photosynthesis running behind glass.13 Measurement of your own cultivation is available by arrangement - get in touch.
Nature's way
Helena is a CO₂ capture platform that has chosen nature's way. Among scrubbers, sorbents and mineralisation we are looking for a route where the end product is not waste to be stored but a product, namely controlled and measured photosynthesis.
We test it in three modes - direct air capture, deployment in buildings, and connection straight to a source - and each time we ask the same questions: How much carbon ended up in the biomass? How much electricity did it cost? And above all, what will we do with that biomass? The goal is carbon neutrality reached through a product, not a landfill.
Two things are running in DAC mode today: a CO₂ concentrator on the inlet and smaller bubbles for better gas transfer, both with the Institute of Chemical Process Fundamentals of the Czech Academy of Sciences.14
Air
Buildings
Source
232 days in a shopping mall
Metropole Zličín, 2023. Helena 04, 760 l, 111 360 m³ of air at 650 ppm - and the finding that shaped everything that followed: we are limited by inlet concentration, not by biology.
Completed · 2023
232daysTime in operation
Continuous operation of the reactor in a shopping mall, not in a laboratory.
In preparation
Carbon is delivered into the reactor dissolved. The gas step that slows down every photobioreactor is thereby removed.
In preparation
Raising the inlet concentration of carbon dioxide ahead of the reactor.
In preparation
A source of clean culture for starting up large reactors.
Written about us
- Deník.cz - „Nový český zázrak: Fotobioreaktor Helena" (A new Czech marvel: the Helena photobioreactor) (2023) - https://www.denik.cz/veda-a-technika/fotobioreaktor-helena-pavel-jerabek.html
- Retail News - „Udržitelná Metropole Zličín" (A sustainable Metropole Zličín) (2023) - https://www.retailnews.cz/aktualne/udrzitelna-metropole-zlicin-unikatni-bioreaktor-zelena-energie-a-mnoho-dalsiho/
- Hybrid.cz - „Metropole Zličín má unikátní bioreaktor" (Metropole Zličín has a unique bioreactor) (2023) - https://www.hybrid.cz/metropole-zlicin-ma-unikatni-bioreaktor/
Sources and notes
14
- Geological CO₂ flux from volcanoes and other geological processes: 0.3 to 0.4 Gt a year (Deep Carbon Observatory - volcanic areas alone 0.28 to 0.36 Gt, Werner et al. 2019). Today's emissions from fossil fuels and cement: 38.1 Gt CO₂ for 2025 (Global Carbon Budget 2025). Ratio 38.1 / 0.3 ≈ 127× - we write „a hundred times“, rounded down.↩
- We calculate per footprint, because both a forest and a reactor occupy floor area and the culture in a reactor is stacked upwards. Helena's footprint is 1 m². Measured (Zličín, ambient air, 650 ppm): ~40 kg dry biomass over 232 days ≈ 315 g CO₂ a day ≈ 115 kg CO₂ per m² per year - an estimate from a pilot with an intermittent culture, not reactor performance. Calculated (at a CO₂ source): the ceiling for a large reactor is ~1 t CO₂ a year per 1 m² of footprint. It requires a concentrated input, at 650 ppm that much carbon does not pass through the reactor. Temperate forest: net sink of 3.7 t CO₂e per hectare per year, i.e. 0.37 kg per m² per year - average for 2001 to 2025 (World Resources Institute, Global Forest Review). Afforestation in the temperate zone can reach 2.6 to 27.5 t CO₂/ha/year (Brown et al. 1996 via FAO). Against the 0.37 figure, Zličín works out at ~310× and the ceiling at a source at ~2 700× - in the running text we keep the conservative „roughly a hundredfold“ and „roughly a thousandfold“. This holds with a CO₂ supply and with electricity, which a forest does not need.↩
- TRL 7 = prototype verified in an operational environment. It refers to reactor 04.↩
- Today's value: 427.0 ppm, the Mauna Loa annual average for 2025 (NOAA GML). Pre-industrial value 278 ppm for 1750 (Global Carbon Budget 2025). The 180 ppm value for the Last Glacial Maximum: EPICA Dome C ice cores, Lüthi et al. 2008, Nature 453, 379-382. 427/180 = 2.4× - we write „twice“, because that is the smaller number. The mammoths were not consulted.↩
- Amine absorption: 40 to 90 USD per tonne of CO₂ captured, depending on configuration and scale (review of techno-economic studies - MEA at a coal-fired power plant 40-60 USD/t of CO₂ avoided). Energy penalty: net efficiency drops by 10 to 12 percentage points, electrical output is lower by about a quarter (MIT, Advanced Post-Combustion CO₂ Capture). Direct air capture: in the order of hundreds of USD per tonne, and over 500 USD for the first commercial units. We compare costs because otherwise biological capture looks expensive - until you add in what storage costs.↩
- Global Carbon Budget 2025 - 38.1 Gt CO₂ from fossil fuels and cement for 2025 - including land-use change 42.2 Gt. Global CCS Institute, Global Status of CCS 2025 - 77 facilities in operation with a capacity of 64 Mt/year (as of July 2025), a further 44 Mt/year under construction. 64 / 38 100 = 0.17 %. Capacity is not the same as the amount actually stored, and part of the volume goes to enhanced oil recovery.↩
- Confirmed in consultation with the Czech Academy of Sciences: rising pH indicates intensive growth of the culture.↩
- Biomass on its own is a short carbon cycle: on decomposition the carbon returns to the atmosphere. Durability comes only with pyrolysis into biochar (hundreds of years). That is a separate stage with its own balance - see Case studies.↩
- The Global CCS Institute projects 337 Mt/year in operation by 2030, i.e. five times today's figure.↩
- Avoided emissions = the difference against the same product made from a fossil input. This is neither removal of CO₂ from the atmosphere nor a carbon credit. The quantification will come from an LCA that is being prepared. The same benefit cannot be reported twice - if the CO₂ supplier counts the avoided emissions, the biomass customer does not.↩
- Fermentation gas is almost pure CO₂ - three orders of magnitude more than in air (0.042 %). Algae have their optimum in the single-digit percent range: Chlorella grows best at 5 % CO₂. Above 10 % growth is suppressed (Leflay, Pandhal & Brown 2021, J. CO₂ Util. 52, 101657).↩
- The exact number of breweries in the Czech Republic differs by source - it is in the hundreds. Talks with biogas plants are under way. We will publish names with consent.↩
- CO₂, temperature, humidity, light levels, particulate matter, oxygen. The reactor will not clean a whole building - in its immediate surroundings it improves the air and measures by how much.↩
- Activity 1: concentrator to ≥ 1 500 ppm. Activity 2: bubbles < 1 mm. Technology Incubation project, R&D partner the Institute of Chemical Process Fundamentals of the Czech Academy of Sciences, until 7/2027.↩