A airplane pilot written report was lead on the effects of CO2 dosing and ventilation system on CO2 assiduity and crop photosynthesis in the glasshouse . After all , in the ( penny-pinching ) future , CO2 will become scarce due to horticulture becoming fossil - free . As a result , CO2 will become increasingly expensive , and CO2 dosing will have to be more economical . How can you attain the high possible concentration in the greenhouse while dosing as little as possible ? Dennis Medema shares the final result of the archetype subject on ' Kas Als Energiebron ' .
Saving on CO2 by by artificial means increasing the ventilation charge per unit in the greenhouse?Can you in reality get CO2 from outside by increasing ventilation ? And what exactly is the effect of alter CO2 concentration on photosynthesis and thus craw production ? An answer to these enquiry was receive through a archetype study of the effects of CO2 dosing and ventilation on CO2 concentration and harvest photosynthesis in the greenhouse .
Air exchange with extraneous air travel ( ventilation ) , CO2 dosage , and CO2 consumption by the harvest ( for photosynthesis ) are the three main components to be calculated . The glasshouse must be ventilated to cool the greenhouse or remove moisture . As a issue , much of the dosed CO2 escapes to the extraneous air . If lilliputian or no dosing have property , the CO2 concentration before long drops below the outside value and ventilation system can also be used to raise the CO2 absorption to that of the outside atmosphere ( 400 - 420ppm ; 400 ppm has been calculated ) . Partly by open up window further and partly by mechanically increase public discussion .
These situations of no or low dosing were put into a mannikin by researchers using cucumber as an example harvest and further calculate to suffice the above interrogation , initially at some fixed short intensities such as 200 , 500 , and 1000 μmol / m2 / s and then some sampling solar day with varying igniter . Calculations were made with a 6 - beat - high greenhouse so the airing rate ( number of arrant air changes per hr ) differ by a factor of 6 from the ventilation rate in m3 / m2 / hour . Read the cogitation by Botany on proficiency to increase ventilation rates to save CO2here ( In Dutch ) .
MisunderstandingFirst of all , a lasting misunderstanding needs to be cleared up . Photosynthesis does not answer to the kilos of dosage put into the nursery but to the effect of the kilos of dosage on the CO2 immersion in the greenhouse . For most crops , the impregnation stratum is around 800 ppm , and for cuke , it is more likely to be 700 ppm . So dose more than 800 ppm commonly makes no sense . This produces roughly 30 % more craw photosynthesis for most crop .
However , reach out 800 ppm may require niggling or many kilos of dosing depending on the external respiration charge per unit and light level . If dosed and ventilated piddling , the CO2 concentration in the nursery will quickly drop towards 300 ppm , causing a 20 % reduction in photosynthesis compare to a flora place upright at 400 ppm . Ventilating more in that post will bring more CO2 from the outside air into the nursery , which will increase CO2 concentration . However , because of CO2 uptake by photosynthesis , the outside time value is never reach and they have to settle for some production going . If the glasshouse CO2 density could be increased to 380ppm via airing , this would provide a red ink of photosynthesis of 2.5 % compared to 400ppm .
Unfortunately , accomplish this concentration ( 20 ppm less than the outside air concentration ) turns out to be very unmanageable . Indeed , calculate on the light-headed point , this requires a ventilation pace of 15 to 25 /hour ( airing rate of 90 - 150 m3 / m2 / minute , see Figure 1 ) . This is very much . In fact , the natural ventilation rate is more probable to be around 9 /hr ( windows fully unfastened and wind speed of 3 - 4 m/s ) and drops by using louse netting . If you take a red ink of photosynthesis of 5 % liken to photosynthesis at out-of-door melodic phrase concentration , a ventilation system rate of 14 /hour is still need , irrespective of PAR stage . This have in mind an additional mechanical breathing of 6 - 8 /hour ( 36 - 48 m3 / m2 / minute ) is needed on top of natural ventilation to contain production losses . For extension , the flow charge per unit of dehumidification plants is around 10 - 15m3 / m2 / hour .
Since this growth in airing rate is quite substantial and also costs some production , researchers have continued to direct the effect of very low doses . If a small amount of CO2 is dosed anyway ( say 30 kg / ha / hr ) , much less ventilation is already need to get cheeseparing to 400 ppm . At a CO2 dosage of 60 kg / hour angle / hour , the CO2 concentration in the nursery is always higher than in the outside strain because the dosage is high than the crop photosynthesis of cucumber at 1000 μmol / m2 / s PAR , resulting in a passing of CO2 to the outside air . If a CO2 concentration of 400 ppm is control , breathing no longer has any issue on the concentration in the glasshouse because there is no longer a absorption difference with the outside air . The dose required for this is tantamount to the CO2 intake ( photosynthesis ) of the crop . This dosage is between 0 and 60 kg / ha / hour and depends on light chroma . From a sustainability point of view , it seems optimal if CO2 dose and ingestion are equal and no CO2 is lose to the outdoor air . But because up to 30 % more crop photosynthesis takes place at higher CO2 concentration , from an economic point of view a high dosage will still be more suitable as long as the damage of CO2 allows it .
Free CO2In short , write out back on CO2 will quickly cost product , according to the study . The effectiveness of dosed kilos depend heavily on airing rate and light intensity . Theoretically , mechanically increasing the ventilating system rate is an option to tap liberal CO2 from the outside gentle wind but it requires a substantial air displacement mental ability to carry production losses . presently , command for the same assiduity of CO2 as in the outside air is the simplest way to economize ( a lot of ) CO2 . But even this is not without production losses compare to the optimal concentration . Meanwhile , research is already being conducted into ' unmediated air gaining control ' , among other thing . The cost of CO2 and that of the product will ultimately decide which method will be used in the future .
This consultancy was carry out by Plant Lighting and funded and organise by Kas als Energiebron , an innovation program of LVVN and Glastuinbouw Nederland . Made potential in part by Kennis in je Kas ( KijK).Click herefor the full final paper ( in Dutch),Source : Kas als Energiebron
