Table 7 Energy indices for producing 1 m2 of lettuce in System-I and System-II.

From: Sustainable hydroponic production using solar energy and treated greywater within the water-energy-food-environment nexus

Input

Abbreviation

System-I

System-II

Energy ratio

ER

0.05

0.11

Energy productivity

EP (kg/MJ)

0.07

0.16

Specific energy

SE (MJ/kg)

14.89

6.14

Net energy gain

NEG

− 161.53

− 61.93

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