FEASIBILITY STUDY OF AN EFFECTIVE USE OF CARBON DIOXIDE HYDRATE IN GREENHOUSE PRODUCTION

Carbon dioxide is a serious contributor to climate change processes, and fundamental measures to reduce its emission are sought worldwide. The authors have previously proposed a method for separating carbon dioxide from industrial exhaust gases. On the other hand, many horticultural growers artificially elevate the concentration of carbon dioxide within greenhouses in 600 to 1,000 ppm during the daytime to boost growth and yields. Here, we propose a system that takes carbon dioxide gas captured from exhaust gases using our technique, stores it as carbon dioxide hydrate, and supplies it to a greenhouse. We describe the system and its energy-use efficiency. We conducted an experiment with small plant growth chambers equipped with a heat-exchange unit. The chambers were placed in an air conditioned room with lighting provided by a metal-halide lamp. Four cucumber seedlings were placed in each of two chambers. Carbon dioxide from liquefied carbon dioxide was mixed with cold water in a high-pressure vessel (1.0 L volume) at 2.0 MPa and stored at -20°C overnight. Carbon dioxide from the carbon dioxide hydrate was directed into the chambers via a tube to maintain the concentration above 1,000 ppm. Cold thermal energy from the hydrate was transferred to the chamber via a heat-exchange unit which maintained the air temperature below 25°C. We demonstrated that cucumber seedlings could be grown using carbon dioxide hydrate as a source of carbon dioxide and to supplement cooling. Larger trials are needed to demonstrate the feasibility of commercial-scale operation and the potential for capturing carbon dioxide from industrial emissions.