# CO2 Enrichment > Part of: [Climate](/climate.md) · Provider: [DutchGreenhouses](/) CO2 enrichment replaces the carbon dioxide a growing crop strips from greenhouse air faster than a closed house can replenish it. Preventing that depletion is the first purpose, because a starved crop wastes the light it receives; lifting concentration above outdoor air adds further growth while the vents stay shut. ## Facts | Property | Value | |---|---| | Global ambient carbon dioxide concentration | 425.64 ppm | | Concentration a closed house falls to without dosing | 150–250 ppm | | Tomato leaf photosynthesis saturation | 600 ppm | | Recommended setpoint once vents open | 400–450 ppm | | Maximum carbon dioxide an unlit tomato crop can fix | 15 kg CO₂/m² per year | | Occupational exposure limit | 5000 ppm | | Crop damage threshold for ethene in greenhouse air | 11 ppb | | Crop damage threshold for nitrogen oxides in greenhouse air | 40 ppb | Climate # CO2 enrichment. Feeding photosynthesis its raw material. ## Feeding photosynthesis its raw material Photosynthesis runs on carbon dioxide, and a healthy, actively growing crop consumes it faster than the air inside a closed greenhouse can replenish. On a bright morning with the vents shut to retain heat, CO₂ levels inside can fall below the outdoor atmospheric concentration, and at that point the light and warmth are wasted because the crop has run short of its raw material. CO₂ enrichment solves this directly: by dosing carbon dioxide back into the greenhouse air, concentrations are lifted to levels where photosynthesis — and therefore growth and yield — measurably increases. For many crops it is one of the most cost-effective yield levers available. The source of that CO₂ is itself a design decision with real economic weight. Where a combined heat and power (CHP) unit is installed, its cleaned exhaust gases are rich in CO₂ and can be captured and delivered to the crop — turning a by-product of generating heat and electricity into a valuable input, the essence of the Dutch approach of making every stream do more than one job. Alternatively, liquid CO₂ is bought in, stored and vaporised on demand: simpler and cleaner, but a direct running cost rather than a recovered by-product. The real subtlety is that enrichment and ventilation pull in opposite directions. The crop needs high CO₂, but it also needs cooling, and the moment the vents open to release heat, the enriched air — and the money spent creating it — escapes with it. The climate computer therefore weighs dosing against ventilation losses hour by hour, enriching hardest when the greenhouse is closed and light is plentiful, and easing off when the vents must open, so CO₂ is spent where it does the most good rather than blown out of an open window. Getting that balance right — the source, the delivery system and the control strategy — is what turns CO₂ from a cost into a return. DutchGreenhouses® designs the enrichment system and integrates it with the heating, CHP and climate-control strategy so photosynthesis is fed efficiently across the whole day. Get in touch to design CO₂ enrichment for your greenhouse. From the knowledge base ## Reads you might find interesting ceacultivationbusiness-case ### Grow Like a Pro: Starting Smart, Growing Strong How Grow Like a Pro combines smart farming, CEA technology and local partnerships for eco-friendly, profitable, pesticide-free greenhouse pr Read article education ### The Case for a College Greenhouse Why a college greenhouse belongs in the curriculum: teaching science, craftsmanship, business logic and sustainability, and preparing studen Read article education ### The Case for a High School Greenhouse Why every high school greenhouse matters: how it makes STEM tangible, builds responsibility and teamwork, and helps students discover their Read article education ### Greenhouses in Education: The Case for Schools Greenhouses in education reconnect students to reality — the full case for why every school, high school, college and trade program should h Read article historyconstruction ### The Origins of Greenhouse Horticulture: My Backyard A tour through greenhouse horticulture history: from 19th-century Westland fruit walls to the “City of Glass” and today’s international high Read article company ### DutchGreenhouses Rebranded: A New Corporate Identity Announcing our new corporate identity — a visual style reflecting our dedication to advanced, high-quality greenhouse projects and The Futur Read article ## FAQ **What evidence is there that CO2 enrichment increases yield?** Measured, and smaller than the market believes. In a Wageningen trial, halving the carbon dioxide dosed cost under six percent of tomato yield. The response saturates early, so the first purpose of dosing is preventing depletion rather than chasing high concentrations. **What CO2 level should a greenhouse run?** Two setpoints, not one. Around eight hundred parts per million with the vents shut, stepping down to four hundred to four hundred and fifty once they open past a tenth. Chasing a high setpoint with the vents open sends the gas outside. **How is CO2 added to a greenhouse?** Most Dutch growers dose cleaned flue gas from their own boiler or engine, distributed through perforated hoses laid along the crop rows. The remainder buy pure carbon dioxide, delivered by pipeline in the western Netherlands or by tanker elsewhere. **Is CO2 dosing dangerous for greenhouse workers?** Dosing setpoints sit four to ten times below the legal eight-hour exposure limit, so normal operation is not the hazard. The risk lies in failure modes: a bulk liquid release, or accumulation in pits and confined spaces, where carbon dioxide pools because it is heavier than air. **Can flue gas damage the crop?** Yes, if cleaning fails. Ethene and nitrogen oxides harm crops at concentrations far below what protects an engine, and duct alarms are typically set well above the level that damages plants. The meter that matters hangs at plant level, not in the flue. ## Related [Climate](/climate.md) · [Heating](/climate/heating.md) · [Cooling](/climate/cooling.md) · [Humidity Control](/climate/humidity-control.md) · [PAR (Photosynthetically Active Radiation)](/glossary/par-photosynthetically-active-radiation.md) · [Climate Computer](/glossary/climate-computer.md) · [Tomatoes](/vegetables/tomatoes.md) ## See also https://aims.fao.org/aos/agrovoc/c_35921