Biodegradable Cup from Tea-Factory Waste

Introduction

  • Conventional cup materials: PE, PP, PET, PS, Al-foil, paper/cardboard\text{PE, PP, PET, PS, Al-foil, paper/cardboard}
  • Issues: chemical leaching, endocrine disruption, micro-plastics, resource depletion, pollution
  • Need: biodegradable, food-safe, high-performance alternative

Knowledge Gap

  • Limited data on cups made from tea-factory waste (TFW)
  • Performance of pectin coatings (from citrus-peel waste, CPW) on such cups unexplored

Aim & Objectives

  • Develop fully biodegradable cup using agricultural wastes
    • Base: TFW + organic binder
    • Coating: pectin from CPW
  • Achieve mechanical, barrier, and safety properties that meet common standards

Materials & Key Processing Steps

  • TFW → washed, blanched, oven-dried, ground, sieved
  • CPW → soaked, layer-separated, dried, ground → acid-extracted pectin (yield 16±2%16\pm2\%)
  • Base-layer mixes (B1–B3): cellulose + glycerol + water at ratios 1:1,  1:2,  2:11{:}1,\;1{:}2,\;2{:}1 (TFW : residue)
  • Coatings (C1,C2): cellulose/pectin/glycerol blends with minor formulation shift
  • Six treatments: T<em>1-T</em>6=B<em>1−3×C</em>1−2T<em>1\text{-}T</em>6 = B<em>{1-3}\times C</em>{1-2}

Core Tests & Standards

  • Moisture (oven 105 ∘C105\,^{\circ}\text{C})
  • Drop test (GB 18006): 0.8 m0.8\,\text{m} height
  • Weight-load: 3 kg3\,\text{kg} static load, height change
  • Thickness (8-point vernier)
  • Burst & tensile strength (GB/T 50081-2002)
  • Thermal resistance: 95±5 ∘C95\pm5\,^{\circ}\text{C} liquid, 60 ∘C60\,^{\circ}\text{C}/30 min
  • Water leakage (cold 23∘23^{\circ}, hot 80±5∘80\pm5^{\circ})
  • Soil biodegradation (30 d; pH 6.8; 24 ∘24\,^{\circ}C)
  • Food-safety: colour shift ΔE∗\Delta E^*; pH drift of filled liquid

Key Performance Results

  • Moisture: all 10−11%10{-}11\% (ideal)
  • Thickness: uniform 0.20−0.25 mm0.20{-}0.25\,\text{mm}
  • Drop test: zero cracks in all treatments
  • Weight-load height change: low in T<em>1T<em>1; moderate T</em>2,T<em>4,T</em>5T</em>2,T<em>4,T</em>5; high T<em>3,T</em>6T<em>3,T</em>6
  • Burst strength: highest T<em>4 (∼20 MPa)T<em>4\,(\sim20\,\text{MPa}); T</em>2,T6T</em>2,T_6 moderate; others lower
  • Tensile: highest T<em>4 (∼24 kN cm−2)T<em>4\,(\sim24\,\text{kN cm}^{-2}); moderate T</em>1,T<em>2,T</em>6T</em>1,T<em>2,T</em>6
  • Thermal: T<em>3,T</em>6T<em>3,T</em>6 showed deformation & leakage; others stable
  • Water-leakage (first-drop time): T<em>2,T</em>5≈40 minT<em>2,T</em>5\approx40\,\text{min} (best)
  • Biodegradation (30 d): T<em>3,T</em>6≥60%T<em>3,T</em>6\ge60\%; T<em>1,T</em>4≈45%T<em>1,T</em>4\approx45\%; T<em>2,T</em>5≈35%T<em>2,T</em>5\approx35\%
  • Food safety: minimal colour & pH change in T<em>2T<em>2 (best), moderate T</em>5T</em>5

Statistical Outcome

  • Overall ranking (Minitab): T2 > T4 > T1 > T5 > T6 > T3
  • Optimum treatment: T<em>2 (B</em>2+C1)T<em>2\,(B</em>2+C_1)

Characterisation of Optimum Layers (T2)

  • FTIR (Coating C1): strong O–H\text{O–H}, C–H\text{C–H}, C=C\text{C=C} bands ↔ pectin/cellulose matrix
  • FTIR (Base B2): additional C=O\text{C=O} ester band ↔ better inter-layer adhesion
  • TGA: three events; major mass loss at ∼251∘\sim251^{\circ}C (coating) & ∼150∘\sim150^{\circ}C (base) → safe for hot beverages

Consolidated Specs of Best Cup (T2)

  • Moisture 10.2%10.2\%
  • Appearance score 4.88/54.88/5
  • Force at break 17.5 N17.5\,\text{N}; burst 144.5 N144.5\,\text{N}
  • Hot-liquid stability, no leakage ≈40 min\approx40\,\text{min}
  • Biodegradability 35%35\% in 30 d30\,\text{d}
  • Negligible colour (\Delta E^*<0.2) & pH drift

Conclusions

  • Feasible to manufacture biodegradable, food-safe cups from tea-factory waste with pectin coating
  • T2 formulation met or exceeded baseline standards across mechanical, barrier, thermal and safety tests

Future Work (Authors’ Suggestions)

  • Test with varied beverage chemistries (acidic/basic)
  • Explore alternative moulding (vacuum, pressure)
  • Further standardisation & quality certification