Analyses of CO2 Concentration and Balance in a Closed Production System for King Oyster Mushroom and Lettuce

Abstract

The large amount of CO2 emitted from mushrooms during incubation and developmental stages can be utilized in plant production systems as a CO2 source. The objectives of this study were to measure the CO2 emission and absorption rates of mushroom and lettuce, respectively, and to analyze the CO2 concentrations at various ratios of mushroom and lettuce in a closed production system. The CO2 emission rate of king oyster mushrooms (Pleurotus eryngii (D C.) Quel) and CO 2 absorption rate of lettuces (Lactuca sativa L. cv. Asia Heuk Romaine) were measured by using two closed acryl chambers (1.0 m × 0.8 m × 0.5 m) in which indoor temperatures were maintained at 18°C and 22°C, respectively. The lettuce was grown at a light intensity of PPF 340 mol·m -2 ·s -1 and with nutrient solution at EC 1.2 dS·m -1 . The air was periodically circulated between the two chambers using a diaphragm pump. The CO2 emission rate of the mushroom increased until the 15 th day after scratching (DAS) and then decreased. The rate also increased with increased indoor temperature. In particular, the CO2 emission rate per fresh weight of fruit body increased by about 3.1 times after thinning compared to before thinning. In terms of CO2 balance, the CO2 emission rates from a bottle (950 mL) of the mushroom at 9, 12, and 14 DAS were equivalent to those of 3, 4.5, and 5.5 lettuce plants at 7, 10, and 12 DAT (days after transplanting), respectively. This work shows that balance in CO2 concentration could be achieved using an appropriate ratio of the two crops in a closed production system.