Figures (9)  Tables (3)

    • Figure 1. 

      Schematic representation of the TPAD system showing that A: R1 operated with or without biochar supplementation; B: R2 operated with or without biochar supplementation.

    • Figure 2. 

      Effect of biochar addition on H2 production rate.

    • Figure 3. 

      Effect of biochar addition on pH during H2 production.

    • Figure 4. 

      Effect of biochar addition on VFA during H2 production. A is the reactor without biochar, and B is the reactor with biochar addition.

    • Figure 5. 

      Effect of biochar addition on CH4 production rate.

    • Figure 6. 

      Effect of biochar addition on pH during CH4 production.

    • Figure 7. 

      Effect of biochar addition on VFA during CH4 production. A is the reactor without biochar, and B is the reactor with biochar addition.

    • Figure 8. 

      Microbial distribution in the first phase of TPAD, A with, and B without biochar addition during semi-continuous operation.

    • Figure 9. 

      Microbial distribution at the family level in the second phase of TPAD with (a), and without (b) biochar addition during semi-continuous operation.

    • Parameter Food waste Biochar 650 °C
      Carbon (%) 42.7 67.37
      Nitrogen (%) 2.3 0.75
      Hydrogen (%) 9.1 1.05
      Sulphur (%) 0.3 0.1
      C/N ratio 18.6 89.8
      Total solids (%) 61.2 96.6
      Volatile solids (%) 59.5 83.7
      pH 4.9 8.47
      Particle size distribution (µm) ND 3.5–25.9
      BET surface area (m2/g) ND 265.34
      Pore volume (cm3/g) 0.108
      ND: not determined.

      Table 1. 

      Characteristics of the food waste and biochar

    • Reactor Stage OLR
      (g VS/(L·d))      		 HRT (d) Operation time (d) Biochar addition (g/L)
      R1 without biochar I 0.5 3 30 0
      II 1 3 10 0
      III 2 3 10 0
      IV 3 3 10 0
      V 4 3 10 0
      VI 4 3 20 0
      VII 6 3 10 0
      R2 without biochar I 0.5 10 30 0
      II 1 10 10 0
      III 2 10 10 0
      IV 3 10 10 0
      V 4 10 10 0
      VI 4 10 20 0
      VII 6 10 10 0
      R1 with biochar I 0.5 3 30 15
      II 1 3 10 15
      III 2 3 10 15
      IV 3 3 10 15
      V 4 3 10 15
      VI 4 3 20 15
      VII 6 3 10 15
      R2 with biochar I 0.5 10 30 15
      II 1 10 10 15
      III 2 10 10 15
      IV 3 10 10 15
      V 4 10 10 15
      VI 4 10 20 15
      VII 6 10 10 15

      Table 2. 

      Summary of experimental conditions

    • Reactor Stage Gas composition Biogas production rate (L·d) YH (mL/g VS) YM (mL/g VS) pH
      H2 (%) CH4 (%) CO2 (%)
      R1 without biochar I 30.26 0.63 69.15 302 92.74 0 4.9 ± 0.1
      II 33.61 0.37 66.01 480 81.71 0 5.0 ± 0.3
      III 43.76 0 56.23 682 81.40 0 5.1 ± 0.1
      IV 47.82 0 51.96 1,116 82.59 0 5.1 ± 0.1
      V 49.38 0 50.61 1,488 93.72 0 5.0 ± 0.3
      VI 50.44 0 49.55 1,647 107.82 0 5.1 ± 0.2
      VII 41.47 0 51.53 1,510 90.96 0 4.8 ± 0.3
      R2 without biochar I 14.04 37.71 48.24 147 0 99.97 6.2 ± 0.1
      II 0 64.77 35.22 353 0 140.20 6.7 ± 0.2
      III 0 74.14 25.86 564 0 152.96 6.8 ± 0.3
      IV 0 73.26 26.73 1,062 0 172.71 6.7 ± 0.1
      V 0 72.62 27.38 1,736 0 212.69 6.8 ± 0.3
      VI 0 74.41 25.58 1,801 0 227.63 6.8 ± 0.1
      VII 0 62.13 28.87 1,621 199.71 6.2 ± 0.4
      R1 with biochar I 37.37 0.35 61.31 467 138.36 0 5.4 ± 0.1
      II 45.17 0 54.82 1158 146.25 0 5.5 ± 0.2
      III 50.71 0 49.28 1,462 164.24 0 5.5 ± 0.3
      IV 50.14 0 49.85 1,890 168.24 0 5.5 ± 0.1
      V 51.58 0 48.41 2,115 176.51 0 5.6 ± 0.1
      VI 53.15 0 46.84 2,320 189.73 0 5.6 ± 0.2
      VII 52.42 0 47.58 2,329 183.59 0 5.4 ± 0.3
      R2 with biochar I 14.51 39.66 47.44 648 0 199.13 6.8 ± 0.1
      II 0 74.04 25.96 1,104 0 224.27 7.1 ± 0.2
      III 0 76.36 23.63 1,654 0 312.48 7.2 ± 0.1
      IV 0 77.63 22.36 1,867 0 315.16 7.3 ± 0.1
      V 0 80.24 19.75 2,215 0 394.54 7.3 ± 0.2
      VI 0 81.21 17.24 2,383 0 407.17 7.4 ± 0.2
      VII 0 80.65 19.35 2,361 0 374.24 7.3 ± 0.2

      Table 3. 

      Performance of reactor during H2 and CH4 production