Automatic carbon dioxide enrichment strategies in the greenhouse: A review

Exhaust gases from fossil fuels

Enriching greenhouses with CO₂ generated from burning fossil fuels has been commonly used, particularly in cooler northern areas. In rudimentary modes of greenhouse cultivation, growers directly burn coal to heat and fertilise greenhouses during the winter. A more advanced cultivation mode employs natural gas and other hydrocarbons as heat and CO₂ sources (Dion, Lefsrud, Orsat, 2011). Additionally, it is generally accepted that natural gas can produce clean CO₂ if proper combustion occurs. Chalabi, Biro, Bailey, Aikman, and Cockshull (2002b) used CO₂ from the exhaust gases of boilers burning natural gas to enrich greenhouse atmospheres, and their results showed that this method increased financial margins after control had been optimised. Bailey (2002) enriched a tomato greenhouse with CO₂ obtained from the combustion of natural gas by the greenhouse heater and by combined heat and power units. Both methods produced good economic benefits, and the financial margins of the latter increased when heat storage was used.

Enrichment with fossil fuels can increase profits; however, other gases such as carbon monoxide, which is harmful to plants and humans, are inevitably present because incomplete combustion occurs under empirical conditions (Jerzak, 2014). Therefore, an additional purification system is necessary to remove particulates and noxious gases from the flue gas. Additionally, little heating is required in warm areas, so producing CO₂ from fossil fuel emissions is not cost effective in such conditions.

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