Comparison and appraisal of four different methods for CO2 enrichment

Three methods for CO2 enrichment-chemical reaction (H2SO4 + NH4HCO3), briquet combustion, granular CO2 fertilizer were comparatively studied in free tunnels and solar greenhouses for cucumber cultivation, and the yearly total cost of different methods (including pure liquid CO2) were compared. Chemical reaction had higher CO2 releasing velocity and relatively lower equipment depreciation charge; honeycomb briquet combustion produced CO2 at moderate rate, and the raw material cost was the least; granular CO2 fertilizer having highest raw material cost released CO2 slowest. When the re-use of by-product of chemical reaction was concerned, annual cost of chemical reaction was similar with that of briquet combustion and liquid CO2. Comprehensively evaluated from viewpoints of ecology, energy-saving, cost and effect, briquet combustion was in more accordance with the present situations in China including facility type, economic situation, resource condition and technique level, and so on.