Financial and Energy Consumption Analysis

The total costs of growing red spinach in this study were comprehensively calculated. All calculations were based on Singapore’s electricity standard price of S$0.2255/kW-1 h-1 and Singapore’s National Water Agency standard price of S$1.52 per m3 of water. Growing red spinach requires about 5 L of water per machines (9 plants), which is equivalent to approximately S$0.01 for one growing cycle. The gardening machines only utilizes light source for 16 h in a day; thus, in one growing cycle, the electricity cost is approximately S$2.33. Furthermore, to grow one spinach, the water and electricity cost S$0.001 and S$0.26, respectively. In sum, the total cost for grow one red spinach using gardening machines is approximately S$0.27. Additionally, the carbon footprint of growing red spinach is also calculated. The Operating Margin (OM) GEF, which is the average CO2 emissions emitted per unit net electricity generated in Singapore, is 0.4085 kg COkW-1 h-1. The total carbon footprint per gardening machine and per plant are approximately 4.22 kg CO2 and 0.47 kg CO2, respectively. Details of the aforementioned calculations are tabulated in Table 4.

Discussion

Rapid Optimization and Re-Optimization of Compound Combinations