A Novel Integrated Eco-Factory Model for Sustainable Textile Manufacturing: Multi-Vector Waste Valorization and Closed-Loop Process Automation

1. Introduction

1.1. Industrial Context and Environmental Degradation

The textiles and readymade garments (RMGs) industry acts as an essential economic driver in developing nations in South Asia. But the wet process is not environmentally sustainable because 200 liters of freshwater is used for processing each kilogram of textile produced. In the major production cities of Gazipur and Dhaka, there is excess extraction from the aquifers that leads to the depletion of the groundwater table to the extent of 2.0 to 3.0 meters each year. The industrial chimneys emit black carbon (soot), sulfur oxides and carbon dioxide into the environment.

1.2. Failure Modes of Conventional Remediation in SMEs

BIOLOGICAL EFFLUENT TREATMENT PLANTS (ETPS). The biological effluent treatment plants use delicate bacteria, which cannot survive under the highly fluctuating pH values of the wastewater (ranging between 4.0 and 11.5), in addition to the toxic metals present in the wastewater from the process of dyeing textiles. Besides, the air pollution control devices such as the wet scrubber appear to be a complete “sunk cost” without any ROI to SMEs.

1.3. Statement of Novelty and Research Gap

Although there are many individual studies on individual technologies for remediating air, water, or solid waste such as electrocoagulation or cyclonic filtration, there is nothing that takes all four vectors of industrial pollution together into an integrated sustainable industrial concept. This article introduces the Integrated Eco-Factory, a novel multi-vector system that is developed to turn industrial pollution control into a profit-generating business plan. Table 1 compares this model’s uniqueness to current literature.

2. Materials and Methods

The architectural model of the Integrated Eco-Factory operates on a closed-loop framework.

2.1. Module A: Carbon Capture and Eco-Ink Synthesis

Industrial chimney exhaust is intercepted using a high-efficiency cyclonic separator designed according to Lapple standard ratios (Diameter D = 20 cm, Height H = 80 cm, Inlet Velocity v = 12 m/s). The cut-point particle diameter (d50) collected at 50% efficiency is modeled as:

$$d_{50}= \sqrt{{\displaystyle \frac{\left(9 \mu b\right)}{2 \pi N_e{v}_i\left({\rho }_p- {\rho }_g\right)}}}$$

where μ is gas dynamic viscosity (1.8 × 10^-5 kg/m·s), b is inlet width (0.05 m), Ne ≈ 5, and ρp = 1800 kg/m^3.

Figure 1. Prototype Overview of the Integrated Eco-Factory Setup.

Figure 1. Prototype Overview of the Integrated Eco-Factory Setup.

Figure 2. Process Flow Diagram from Chimney Exhaust to Ink Synthesis.

Figure 2. Process Flow Diagram from Chimney Exhaust to Ink Synthesis.

Captured soot undergoes solvent washing in a 1:1 Isopropyl Alcohol (IPA) and distilled water solution at 600 RPM for 45 minutes, followed by thermal desorption at 120 °C for 120 minutes. The dried carbon is ball-milled to 30–50 nm and formulation proceed per Table 2.

2.2. Module B: Electrocoagulation (EC) Wastewater Treatment

Biological ETPs are replaced by an electrochemical reactor (Volume = 15 L) utilizing sacrificial aluminum (Al) anode and cathode plates with a 2.0 cm electrode gap.

Anode: Al(s) → Al³⁺_(aq) + 3^e-

Cathode: 2H₂O_(l) + 2^e- → H_2(g) + 2OH^-_(aq)

$$\mathit{Theoretical}\mathit{electrode}\mathit{consumption}(m)\mathit{follows}\mathit{Faraday}\text{’}s\mathit{Law}\text{:} m ={\displaystyle \frac{(I · t · M) }{(z · F)}}$$

Treated water is recirculated back to internal factory operations, achieving zero liquid discharge.

Figure 3. Technical Schematic of Wastewater EC with TEG & Solar.

Figure 3. Technical Schematic of Wastewater EC with TEG & Solar.

Figure 4. Operational Unit Showing Micro-Hydro Turbine and EC Tank.

Figure 4. Operational Unit Showing Micro-Hydro Turbine and EC Tank.

2.3. Module C: Sludge Stabilization & Eco-Brick Manufacturing

Chemical sludge from the EC tank is dewatered, dried at 105 °C, and incorporated into a concrete matrix (1:2:4 Cement: Sand: Sludge/Aggregate) at a 10% replacement ratio. Solidification/Stabilization (S/S) encapsulates heavy metal ions within the Calcium-Silicate-Hydrate (C-S-H) crystal lattice.

2.4. Module D: Tri-Hybrid Energy System & Smart IoT Automation

Energy autonomy (ΣP_load ≈ 18 W) is achieved via a Tri-Hybrid setup:

1. Thermoelectric Generators (TEG): Bismuth Telluride (Bi₂Te₃) arrays harvest boiler manifold waste heat (ΔT = 125 °C) via Seebeck Effect (V=α.ΔT).

2. Micro-Hydro Turbine: Captures kinetic energy from in-pipe effluent discharge (P = η·ρ·g·Q·H).

3. Solar PV Array: 100W Monocrystalline PERC panel with MPPT controller.

An ESP32 microcontroller logs real-time pH, turbidity, and sludge level data. An automated relay activates a SIM800L GSM alert if parameters exceed safety limits (pH < 6.0 or > 8.0, Turbidity > 5 NTU).

Figure 5. Thermoelectric Generator (TEG) Assembly Diagram (AI Generated).

Figure 5. Thermoelectric Generator (TEG) Assembly Diagram (AI Generated).

Figure 6. ESP32 Microcontroller Unit Mounted on Sensor Array.

Figure 6. ESP32 Microcontroller Unit Mounted on Sensor Array.

Figure 7. Circuit Diagram of Smart Valve Control.

Figure 7. Circuit Diagram of Smart Valve Control.

3. Results and Discussion

3.1. Characterization of Synthesized Eco-Ink

Evaluation across n=3 independent trials demonstrate high compatibility with standard commercial inkjet requirements

Figure 8. Particle Size Distribution Histogram of Carbon Particles.

Figure 8. Particle Size Distribution Histogram of Carbon Particles.

Figure 9. Cyclonic Separator Capture Efficiency vs Inlet Airflow Velocity.

Figure 9. Cyclonic Separator Capture Efficiency vs Inlet Airflow Velocity.

Parameter	Unit	Synthesized Eco-Ink	Commercial Ink Standard	Test Method
pH Level	--	7.8 ± 0.1	7.5 – 8.5	Digital pH Probe
Viscosity (25 °C)	cP	3.18 ± 0.15	2.5 – 4.5	Rotational Viscometer
Surface Tension	mN/m	38.5	30 – 40	Tensiometer
Avg. Particle Size	nm	45	< 100	DLS Analysis
Optical Density	Abs	1.45	1.40 – 1.60	Spectrophotometer

Parameter	Unit	Synthesized Eco-Ink	Commercial Ink Standard	Test Method
pH Level	--	7.8 ± 0.1	7.5 – 8.5	Digital pH Probe
Viscosity (25 °C)	cP	3.18 ± 0.15	2.5 – 4.5	Rotational Viscometer
Surface Tension	mN/m	38.5	30 – 40	Tensiometer
Avg. Particle Size	nm	45	< 100	DLS Analysis
Optical Density	Abs	1.45	1.40 – 1.60	Spectrophotometer

3.2. Wastewater Treatment Efficiency & Reuse Validation

Electrocoagulation achieved rapid pollutant removal within 30 minutes runtime at 15V DC.

Figure 10. Bar Chart of Contaminant Removal Efficiency Pre- vs Post-Treatment.

Figure 10. Bar Chart of Contaminant Removal Efficiency Pre- vs Post-Treatment.

Parameter	Unit	Raw Effluent	Treated Effluent	Removal Efficiency (%)	DoE Bangladesh Limit
pH	--	11.5 (Alkaline)	7.2 (Neutral)	--	6.5 – 9.0
Turbidity	NTU	350	12	96.5%	< 20
Color (Pt-Co)	TCU	2400	45	91.1%	< 150
COD	mg/L	1800	160	91.1%	< 200
TDS	ppm	2200	450	79.5%	< 2100

Parameter	Unit	Raw Effluent	Treated Effluent	Removal Efficiency (%)	DoE Bangladesh Limit
pH	--	11.5 (Alkaline)	7.2 (Neutral)	--	6.5 – 9.0
Turbidity	NTU	350	12	96.5%	< 20
Color (Pt-Co)	TCU	2400	45	91.1%	< 150
COD	mg/L	1800	160	91.1%	< 200
TDS	ppm	2200	450	79.5%	< 2100

The post-treatment COD (160 mg/L) satisfies official environmental standards, confirming suitability for closed-loop industrial reuse.

3.3. Mechanical Integrity of Upcycled Eco-Bricks

Structural testing of Eco-Bricks (10% sludge substitution) verified construction compliance=

Figure 11. Stress-Strain and Load-Bearing Curve of Eco-Brick Specimen.

Figure 11. Stress-Strain and Load-Bearing Curve of Eco-Brick Specimen.

Parameter	Unit	Eco-Brick Value	Red Clay Brick Standard	ASTM Standard (ASTM C62)
Compressive Strength	MPa	14.2 ± 0.8	15.0 – 20.0	Min. 10.3 MPa
Water Absorption	%	11.5%	15.0 – 20.0%	Max. 17.0%
TCLP Heavy Metals	mg/L	Passed	N/A	Safe Limit (EPA 1311)

Parameter	Unit	Eco-Brick Value	Red Clay Brick Standard	ASTM Standard (ASTM C62)
Compressive Strength	MPa	14.2 ± 0.8	15.0 – 20.0	Min. 10.3 MPa
Water Absorption	%	11.5%	15.0 – 20.0%	Max. 17.0%
TCLP Heavy Metals	mg/L	Passed	N/A	Safe Limit (EPA 1311)

3.4. Tri-Hybrid Energy Autonomy Performance

Power output stats over a 24-hour cycle confirm complete system autonomy.

Figure 12. Voltage Output Profile Comparison across Generation Sources.

Figure 12. Voltage Output Profile Comparison across Generation Sources.

Figure 13. Combined Power Generation vs. Time Graph.

Figure 13. Combined Power Generation vs. Time Graph.

Sub-System	Peak Voltage (V)	Peak Power (W)	Daily Yield (Wh)	Functional Role
Solar PV	18.5 V	98 W	450 Wh	Daytime Peak Supply
TEG Array	14.2 V	48 W	380 Wh	Continuous Thermal Baseload
Micro-Hydro	12.8 V	15 W	120 Wh	Fluid Flow Recovery
Total System	--	161 W	950 Wh/day	24/7 IoT & Controller Autonomy

Sub-System	Peak Voltage (V)	Peak Power (W)	Daily Yield (Wh)	Functional Role
Solar PV	18.5 V	98 W	450 Wh	Daytime Peak Supply
TEG Array	14.2 V	48 W	380 Wh	Continuous Thermal Baseload
Micro-Hydro	12.8 V	15 W	120 Wh	Fluid Flow Recovery
Total System	--	161 W	950 Wh/day	24/7 IoT & Controller Autonomy

3.5. Techno-Economic Justification and ROI Analysis

Financial feasibility was evaluated for a pilot setup producing 100 liters of Eco-Ink monthly:

Monthly Net Ink Profit = 1,20,000 BDT (Gross Sales) - 36,000 BDT (OpEx) = 84,000 BDT/month

Factoring in Eco-Brick sales and fresh water savings, total monthly net benefit reaches ~89,000 BDT.

$$\mathbf{Payback} \mathbf{Model}\text{:}\mathit{Payback}\mathit{Period}={\displaystyle \frac{Capital Expenditure (\mathrm{6,24,000} BDT) }{Monthly Net Profit (\mathrm{89,000} BDT) }}\approx 7.0 Months$$

4. Conclusions and Future Scope

4.1. Conclusions

This research developed and validated a new integrated eco-factory system specifically for textile small-medium enterprises. The major accomplishments of this work are listed as follows:

1. Air-to-Ink: 92.4% collection of flue soot for production of inkjet ink (viscosity: 3.18 cP).

2. Zero Discharge Water Loop: 91.1% COD removal using electro-coagulation process to reuse the wastewater 100%.

3. Solid Upcycling: Conversion of chemical waste into Eco-Bricks meeting ASTM requirements (14.2 MPa strength).

4. Energy and Profitability: Production of 950 Wh/day of electricity through Tri-hybrid system with payback of 7 months.

4.2. Future Scope

Future work will focus on implementing AI-driven machine learning algorithms for predictive electrode passivation management in the EC tank.