Evaluation of suppliers in the tannery industry based on emergy accounting analysis: implications for resource conservation in emerging economies

Figures & data

Figure 1. Locations of the selected companies.

Table 1. Basic characteristic of the suppliers.

Company	Characteristic
Focal company	Located in Chennai, India. Engaged in the manufacturing of leather bags for the past 40 years.
Supplier 1	Located in Maharashtra with an area of 24,545 m^2. It has five working days with forty-five labourers. It processes 1200 pieces per day. Follows vegetable tanning. Transport the leather to the focal company by railway.
Supplier 2	Located in Uttar Pradesh with an area of 18,985 m^2. It has five working days with sixty-five labourers. It processes 1400 pieces per day. Follows chrome tanning. Transport the leather to the focal company by railway.
Supplier 3	Located in Kerala with an area of 20,000 m^2. It has six working days with sixty labourers. It processes 1300 pieces per day. Follows vegetable tanning. Transport the leather to the focal company by roadway.
Supplier 4	Located in West Bengal with an area of 30,000 m^2. It has six working days with fifty labourers. It processes 1500 pieces per day. Follows chrome tanning. Transport the leather to the focal company by ship.

Figure 2. Emergy system diagram of a typical supplier.

Table 2. Emergy accounting for each supplier. (All data refer to the annual consumption).

Note	S.No	Item	Raw amount				Unit	UEV (sej/unit)	Reference for UEV	Solar emergy (sej)
			Supplier 1	Supplier 2	Supplier 3	Supplier 4				Supplier 1	Supplier 2	Supplier 3	Supplier 4
Renewable resources (R)	1	Solar	1.65E+14	1.21E+14	1.15E+14	1.37E+14	J	1	Tian and Sarkis (2020)	1.65E+14	1.21E+14	1.15E+14	1.37E+14
	2	Rain	5.34E+10	4.37E+10	3.38E+10	3.56E+10	J	7.0 x 10^3	Santagata et al. (2020)	3.74E+14	3.11E+14	2.36E+14	2.49E+14
	3	Wind	3.96E+9	5.24E+9	2.50E+9	2.64E+9	J	8.0 x 10^2	Santagata et al. (2020)	3.16E+12	4.19E+12	2.00E+12	2.11E+12
Total (R)										5.42E+14	4.36E+14	3.53E+14	3.88E+14
Non-renewable resources (N)	4	Water	40,000	30,00	28,000	30,000	kg	4.10 x 10^4	Bastianoni and Marchettini, (2000)	1.64E+9	1.23E+9	1.14E+9	1.43E+9
Total (N)										1.64E+9	1.23E+9	1.14E+9	1.43E+9
Imported inputs (F)	5	Machinery	2.14E-1	3.21E-1	2.75E-1	2.45E-1	g	2.49 x 10^9	Geng et al. (2017)	5.32E+9	7.98E+9	6.84E+9	6.14E+9
	6	Electricity	7.67E+9	3.68E+9	8.88E+9	6.65E+9	J	2.21 x 10^5	Zhong et al. (2018)	1.70E+15	8.13E+14	1.96E+15	1.50E+15
	7	Chemicals	3.00E+5	3.30E+5	2.80E+5	3.50E+5	g	1.12 x 10^10	Li and Brown (2017)	3.36E+15	3.69E+15	3.14E+15	3.92E+15
	8	Labour	1.40E-3	1.20E-3	1.80E-3	1.60E-3	Ppl/ yr	3.20 x 10^13	Tian and Sarkis (2020)	4.48E+10	3.84E+10	5.76E+10	5.12E+10
Total (F)										5.11E+15	4.50E+15	5.10E+15	5.40E+15
Total emergy (U) U = R + N + F										5.60E+15	4.93E+15	5.45E+15	5.77E+15

Assume that the tannery processes 1,500 pieces per day (source: http://agriexchange.apeda.gov.in/MarketReport/Reports/Hides_Skins%20-%202016_New%20Delhi_India_6-9-2016.pdf). The number of working days is 6 days per week and 52 weeks per year. So, the tannery processes 4, 68,000 pieces per year. The lifetime of the machine used for the tanning process is 20 years. That means the machine processes 9,360,000 pieces in its lifetime. To calculate the machine’s weight for the processing of each piece, we must divide the full weight of the machine by 9,360,000 pieces. The average weight of the machine is 2000 kg, i.e. 2,000,000 g. Therefore, the weight of the machine per piece processed is 2.14 × 10⁻¹ g. All the UEVs values used in this study are based on the baselines of Brown et al. (2016).

Figure 3. Total input resources consumed by each supplier.

Table 3. Calculated emergy indicators.

Emergy indicators	Supplier 1	Supplier 2	Supplier 3	Supplier 4
EYR	1.09	1.11	1.07	1.08
ELR	9.43	10.32	14.45	13.92
ESI	0.12	0.11	0.07	0.08
% R	9.68%	8.84%	6.48%	6.72%
ESR	0.10	0.09	0.06	0.07
ED (U/Area (m^2))	1.87 x 10^11	2.01 x 10^11	2.87 x 10^11	2.89 x 10^11

Figure 4. Sensitivity analysis of the emergy indicators. (a)Emergy flow when the parameters are increased 20%. (b)Emergy flow when the parameters are decreased 20%.

Table

Abbreviations and Acronyms
%R	Percent renewable
ED	Emergy flow density
EE	Eco-efficiency
EFA	Ecological footprint analysis
EIA	Environmental impact assessment
EIR	Emergy investment ratio
ELR	Environmental Loading Ratio
EMA	Emergy accounting
^EP	Emergy of product P
EMS	Environmental management system
ESI	Emergy Sustainability Index
ESR	Emergy self-support ratio
EYR	Emergy Yield Ratio
F	Imported renewable and non-renewable resources
GEB	Global Emergy Baseline
IOA	Input-output analysis
ISAER	International Society for the Advancement of Emergy Research
ISO	International Standards Organization
L	Labour
LCA	Life cycle assessment
M	Mass or energy
MFA	Material Flow Analysis
N	Non-renewable resources
NEAD	National Environmental Accounting Database
R	Indigenous renewable resources
SEA	Strategic environmental assessment
sej	Solar emergy
SLCA	Social life cycle assessment
U	Total emergy used
UEV	Unit Emergy Value
^UEVP	UEV of product P

Table A1. Emergy based flows and indicators.

Factor	Symbol/Expression	Explanation
Indigenous renewable resources	R	Emergy of renewable resources that are directly available to the industry like solar radiation, wind, and rain within the boundary of the system under investigation.
Indigenous non-renewable resources	N	Emergy of local resources that take more time for rejuvenation than the time in which the investigation is carried. These resources include groundwater, fossil fuel, and minerals.
Imported resources	F	Emergy of resources that can be availed by the system through trade from outside. These resources include chemicals and raw materials.
Labour	L	Emergy value of activities performed within the system while executing the assigned tasks.
Total emergy used	U = R + N + F	Total emergy used in the system in the reference time (in general annually).
Percent renewable	% R = R/U	Ratio of renewable inputs divided by total emergy of the system.
Emergy Yield Ratio	EYR = U/F	Ratio of total emergy used to the emergy invested from outside the system.
Environmental Loading Ratio	ELR = (F + N)/R	Ratio of non-renewable and imported emergy to indigenous renewable emergy.
Emergy Sustainability Index	ESI = EYR/ELR	Ratio of the emergy yield ratio to the environmental loading ratio highlighting the balance between the emergy produced by the system and the environment.
Emergy self-support ratio (ESR)	ESR = (R + N)/U	Ratio of emergy inputs to the total emergy.
Emergy flow density (ED)	ED = U/Area	Ratio of emergy flow supporting the system divided by its area.
Emergy investment ratio (EIR)	EIR = F/(R + N)	Ratio of purchased emergy input to the indigenous emergy input.

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