Abstract

Ensuring access to sufficient high-quality irrigation water is crucial for hydroponic greenhouse cultivation, especially when recirculation systems are applied. Water demand of greenhouse cultivation per square meter is expected to continue increasing due to the intensification of crop production and as a result of external factors such as climate change. To meet this growing demand, growers are looking toward alternative water sources. An alternative water source is condensate water from the combined heat and power (CHP) installation. Preliminary research indicates that CHP condensate water could supply 5 to 10 % of the total water requirement of a hydroponic greenhouse cultivation. Depending on the material, design and specific working conditions of the CHP installation, this condensate water might contain heavy metals. Furthermore, the pH can vary from 4 to 6. In this study, 10 % unpurified or purified (via a Lubron filter unit) CHP condensate water was added to the fertigation schedule of a year-round tomatocrop. This was compared with a control where the fertigation schedule was based off 100 % rainwater. Although differences were not significant, yield was slightly higher for the control. The purified CHP water treatment produced 8 % less with a slightly lower fruit weight. The unpurified CHP water treatment produced 11 % less with a slightly lower fruit weight. Plant characteristics did not differ significantly. More importantly, there was no accumulation of heavy metals in the fertigation water or fruits, even when unpurified condensate water was used. Nevertheless, purification is still recommended as CHP condensate water quality varies between installations.