CO₂ Emission and Cost Analysis in Asparagus <i>Fusekomi</i> Forcing Culture with Wood Pellet Boiler

Abstract

Domestic fresh asparagus is demanded in Japan from late autumn to winter. Asparagus production in greenhouse in winter needs a large amount of oil or electricity for heating, leading to CO 2 emissions and high costs, and an alternative heating system with low carbon emission is therefore required for winter cultivation of asparagus. Three heating systems were prepared for the asparagus fusekomi forcing culture (FFC) in a plastic greenhouse in midwinter in Hokkaido, i) conventional system i.e. electrically heated wire system for soil heating, ii) a hot water system for soil heating only, iii) a hot water system for both soil and air heating. Hot water was produced by using wood pellet boiler. Average soil temperature at 14 cm depth in the culture bed remained within 15-20°C in each system. Freeze injury of emerged spears was avoided by the hot water heating, especially in the heating of both soil and air even when the outside temperature fell to-18°C. Hot water heating systems generated larger heat and the marketable spear yield showed 1.1-1.3 times of that in the electrically heated wire system. The CO 2 emission and annual cost for 1 kg marketable spear production in the hot water heating system was obviously higher than those in the electrically heated wire system, however the small improvement of spear productivity was recognized in the hot water heating system. Scale of the wood pellet boiler in the present examination, prototype boiler, was excessive for the asparagus production in 9 m-length bed, and suitable scale of wood pellet boiler asparagus production should be installed in future.