Query: Growers regularly pump CO2 into greenhouses, raising levels to three times that of the natural environment, to produce stronger, greener, healthier plants.”

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Carbon dioxide <=SEP=> Carbon dioxide ( chemical formula ) is a colorless gas with a density about 60 % higher than that of air ( 1.225 g/L ) that is odorless at normally encountered concentrations . Carbon dioxide consists of a carbon atom covalently double bonded to two oxygen atoms . It occurs naturally in Earth 's atmosphere as a trace gas at a concentration of about 0.04 percent ( 400 ppm ) by volume . Natural sources include volcanoes , hot springs and geysers , and it is freed from carbonate rocks by dissolution in water and acids . Because carbon dioxide is soluble in water , it occurs naturally in groundwater , rivers and lakes , ice caps , glaciers and seawater . It is present in deposits of petroleum and natural gas .   As the source of available carbon in the carbon cycle , atmospheric carbon dioxide is the primary carbon source for life on Earth and its concentration in Earth 's pre-industrial atmosphere since late in the Precambrian has been regulated by photosynthetic organisms and geological phenomena . Plants , algae and cyanobacteria use light energy to photosynthesize carbohydrate from carbon dioxide and water , with oxygen produced as a waste product .   Carbon dioxide is produced by all aerobic organisms when they metabolize carbohydrates and lipids to produce energy by respiration . It is returned to water via the gills of fish and to the air via the lungs of air-breathing land animals , including humans . Carbon dioxide is produced during the processes of decay of organic materials and the fermentation of sugars in bread , beer and winemaking . It is produced by combustion of wood and other organic materials and fossil fuels such as coal , peat , petroleum and natural gas .   It is a versatile industrial material , used , for example , as an inert gas in welding and fire extinguishers , as a pressurizing gas in air guns and oil recovery , as a chemical feedstock and in liquid form as a solvent in decaffeination of coffee and supercritical drying . It is added to drinking water and carbonated beverages including beer and sparkling wine to add effervescence . The frozen solid form of , known as `` dry ice '' is used as a refrigerant and as an abrasive in dry-ice blasting .   Carbon dioxide is the most significant long-lived greenhouse gas in Earth 's atmosphere . Since the Industrial Revolution anthropogenic emissions - primarily from use of fossil fuels and deforestation - have rapidly increased its concentration in the atmosphere , leading to global warming . Carbon dioxide also causes ocean acidification because it dissolves in water to form carbonic acid .

Cannabis cultivation <=SEP=> This article presents common techniques and facts regarding the cultivation of the flowering plant Cannabis , primarily for the production and consumption of cannabis flowers ( `` buds '' ) . Cultivation techniques for other purposes ( such as hemp production ) differ .

Vertical farming <=SEP=> Vertical farming is the practice of producing food and medicine in vertically stacked layers , vertically inclined surfaces and/or integrated in other structures ( such as in a skyscraper , used warehouse , or shipping container ) . The modern ideas of vertical farming use indoor farming techniques and controlled-environment agriculture ( CEA ) technology , where all environmental factors can be controlled . These facilities utilize artificial control of light , environmental control ( humidity , temperature , gases ... ) and fertigation . Some vertical farms use techniques similar to greenhouses , where natural sunlight can be augmented with artificial lighting and metal reflectors .

Hydroponics <=SEP=> Hydroponics is a subset of hydroculture , the method of growing plants without soil , using mineral nutrient solutions in a water solvent . Terrestrial plants may be grown with only their roots exposed to the mineral solution , or the roots may be supported by an inert medium , such as perlite or gravel . The nutrients in hydroponics can be from fish waste , duck manure , or chemical fertilizer .

Greenhouse <=SEP=> A greenhouse ( also called a glasshouse , or , if with sufficient heating , a hothouse ) is a structure with walls and roof made chiefly of transparent material , such as glass , in which plants requiring regulated climatic conditions are grown . These structures range in size from small sheds to industrial-sized buildings . A miniature greenhouse is known as a cold frame . The interior of a greenhouse exposed to sunlight becomes significantly warmer than the external ambient temperature , protecting its contents in cold weather .   Many commercial glass greenhouses or hothouses are high tech production facilities for vegetables or flowers . The glass greenhouses are filled with equipment including screening installations , heating , cooling , lighting , and may be controlled by a computer to optimize conditions for plant growth . Different techniques are then used to evaluate optimality-degrees and comfort ratio of greenhouse micro-climate ( i.e. , air temperature , relative humidity and vapor pressure deficit ) in order to reduce production risk prior to cultivation of a specific crop .