CO₂ ENRICHMENT WITH NATURAL GAS FIRED HOT-AIR HEATERS

When greenhouses are heated by means of hot-air blowers not only CO₂ but NO_x is blown into the greenhouse.
Using a physical model based on the NO_x emission from the hot-air blower, the ventilation rate of the greenhouse, and absorption of NO_x by the crop it was shown to be possible to predict a concentration gradient in the greenhouse which matched the gradient actually measured.

The model was used to establish a relationship between the average outside temperature and the NO_x concentration in the greenhouse, given a certain cultivation temperature.
This enables prediction of the NO_x concentration in greenhouses during very cold spells, when hot-air blowers are used for long periods.

The results show that even a ‘low-NO_x‘ hot-air blower with an NO_x emission of only 8 ppm can produce NO_x levels in the greenhouse which exceed a possible crop damage threshold of 250 ppb.

IV International Symposium on CO2 in Protected Cultivation

A. Kiel

https://doi.org/10.17660/ActaHortic.1990.268.9