Question
I am currently writing a report on the post harvest handling of lychee. I was just at your lychee postharvest website looking for information on respiratory heat generation. The conversion you give is what I was looking for [a factor of 122 to get from ml CO2 / (kg.h) to kcal / (tonne.day)] but I'm not familiar enough with the expression of such things to know to what temperature ml CO2 is standardized to (0 oC? 20 oC?). I would appreciate it if you could clarify this for me. I would also be interested to know how the figure was arrived at. (T.O.)
Answer
The conversion factor is derived as follows:
Since 1 mole of sugar yields 673,000 calories of energy and 6 moles of carbon dioxide, 1 mole of carbon dioxide (44 grams = 44,000 mg) is associated with 673,000/6 = 112,166 calories, and thus, 1mg of carbon dioxide is associated with 2.549 calories.
Respiration rate in mg/kg.hr X 2.549 calories/1000 cal/kcal X 1000 kg/metric ton X 24 hr/day = 61.176 = 61.2 kcal/metric ton.day
Respiration rate in mg/kg.hr X approximately 2 = ml/kg.hr; thus the conversion factor from ml/kg.hr to kcal/metric ton.day is 61.2X2 = 122.
The conversion factor from mg to ml carbon dioxide is temperature dependent (1.98 at 0C to 1.84 at 20C), but I used 2 as an approximate conversion factor at temperatures between 0 and 20C.
-Adel Kader