CO2 enrichment

Inside an unenriched greenhouse, the CO2 concentration drops below the atmospheric level whenever the CO2consumption rate by photosynthesis is greater than the supply rate through the greenhouse vents. CO2 can be enriched by-

• increasing the ventilation rate through forced air
• improving design and management of the ventilation system
• or providing CO2 enrichment.

The principal source of CO2 enrichment in the greenhouse used to be pure gas; nowadays more frequent use is made of the combustion gases from a hydrocarbon fuel, for example, low sulphur paraffin,propane, butane or natural gas and more recently also from biogas.

In these cases, attention should be given to monitoring the SO2, SO3 and NOx levels, which can damage the crops even at very low concentrations.