Emergy Analysis and Sustainability Efficiency Analysis of Different Crop-Based Biodiesel in Life Cycle Perspective

Table 1

Emergy indices and corresponding calculated methodology used in this paper.

Name (abbreviation)	Formula	Note
Renewable environmental resources	R	Renewable resources provided by the environment
Nonrenewable environmental resources	N	Nonrenewable resource
Economic inputs	F	The purchased emergy
Product (mass or energy)	P	The mass or energy of the product
Yield	Y = R + N + F	The output emergy
Transformity	Tr = Y/P	The ratio of the total emergy inputs to the mass or energy of the product
Emergy yield ratio	EYR = Y/F	The ratio of the output emergy to the purchased emergy
Environmental load ratio	ELR = (F + N)/R	The ratio of nonrenewable emergy plus the purchased emergy to the renewable environmental emergy
Environmental investment ratio	EIR = F/(R + N)	The ratio of the purchased emergy to the renewable environmental emergy plus the nonrenewable emergy
Emergy index of sustainability	ESI = EYR/ELR	The ratio of the emergy yield ratio to the environmental load ratio