Emergy Evaluation of a Production and Utilization Process of Irrigation Water in China

Table 1

Emergy indices used in this study.

Number	Emergy indices	Expression	Signification
1	Solar transformity	Tr = Y/E	The ratio of the total emergy yield of a system divided by the energy of the products
2	Renewability ratio	%R = R/Y	The ratio of the renewable inputs divided by the total emergy yield
3	Emergy yield ratio	EYR = Y/(M + S)	The ratio of the total emergy yield divided by the purchased emergy from the outside economy
4	Emergy investment ratio	EIR = (M + S)/(R + N)	The ratio of the purchased emergy to the total environmental emergy
5	Environmental load ratio	ELR = (M + N + S)/R	The ratio of the sum of nonrenewable environmental resources emergy and purchased emergy to the emergy of renewable environmental resources
6	Environmental sustainability index	ESI = EYR/ELR	The ratio of the emergy yield ratio to the environmental load ratio