1. Development of Activated Hydrochar from Paddy Straw
for Nutrients Adsorption and
Crop Water Management
G.A.G.Kavindi
Supervisor : Prof. Zhongfang Lei

2. Content Paddy straw Hydrochar Mechanism Justification Objectives
Material and Methodology
Result and Discussion
Conclusion
Future studies
References 2

3. Paddy Straw Paddy - world’s third largest cereal crop
Rice - Staple of Sri Lanka
paddy straw is abundant lignocellulose waste material
Total straw production in Sri Lanka
3.4 million tonnes/year
Source:
Uses -
paper production construction materials compost
energy source animal feed
Burning in the fields- cost-effective but environment pollution 3

4. Hydrochar Paddy straw hydrochar - reduce crop waste generation
Reduce CO2 emission with carbon sequestration
Hydrochar production- hydrothermal carbonization process under subcritical water condition
microporosity
ion exchange capacity water holding capacity large specific surface area low H:C and O:C ratios
Characteristics – 4

5. Mechanisms
Source : Oliveira et.al, 2017 5

6. Hydrochar Advantages over Biochar
Cost Effective due to less energy consumption
Applicable for wet biomass
Applications
Moisture conservation technique
Soil conditioner (saline and acidic soil)
Improve soil Bulk density (Crop and root growth)
Enhance microbial growth
Removal of Hazardous chemicals
Renewable energy production 6

7. Justification
In Sri Lanka annual rainfall decrease and irregular rainfall cause crop water management problems
Degradation of arable lands and population growth
Crop intensification
Limitations of nutrient availability (Phosphorus)
Leachate of nutrients
Agriculture – responsible for eurtophication
Required proper moisture conservation and nutrient management techniques
Source: 7

8. Objectives
Determine the P and N adsorption capacity of the produced hydrochar
To determine the water holding capacity of hydrochar as a moisture conservation technique
Optimal procedures for hydrochar production from paddy straw

9. Materials and Methodology
Hydrochar production
10 g Paddy straw : 100 ml DW
1:10 w/v
HTC
temperature (C)
HTC holding time (min) 60
120
100 T1 T2 T3
200 T4 T5 T6
250 T7 T8 T9
Hydrothermal Reactor
Capacity 200ml

10. M hydrochar/M paddy straw*100
Methodology
Parameter
Methodology
Yield
M hydrochar/M paddy straw*100 pH
pH meter EC
EC meter
Bulk Density
Weight of sample (g)/ Volume of sample (ml)*100
Moisture absorption capacity
(M2-M/M1-M ) *100 (M1- initial wt, M2- wt after absorption, M- wt of container)
Volatile matter content
Muffle furnace at 600 0C for 4 hrs
Nutrient adsorption
Batch adsorption test and adsorption isotherm

11. Result and Discussion
Table 1 : Hydrochar yield, Bulk density and Solid percentage
HTC
Temperature (0C)
Holding Time (min)
Yield (%)
Bulk density (%)
Volatile Matter (%)
Ash + Fixed carbon (%) T0
paddy straw -
18.9
88.0
12.0 T1
100
81.5
14.6 T2 60
15.2
86.0
14.0 T3
120
81.4
14.9
88.2
11.8 T4
200
78.2
15.3
84.0
16.0 T5
60.1
16.8
82.0
18.0 T6
58.2
14.2
78.0
22.0 T7
250
56.5
29.5 T8
50.5
39.0
72.0
28.0 T9
45.0
33.0
70.0
30.0

12. Result and Discussion With increasing temperature and holding time,
Yields declined and rapid decline observed above 200 0C
Bulk Density decreased compared to feedstock
Porosity tend to increase with increasing temperature
Contrary Higher bulk density observed at 250 0C
Volatile matter content decreased with organic matter removal
Fixed carbon content increased with breakage of lignocelulose
T0- paddy straw
T4 – 200 0C, 0 min
T C, 0 min T C,60 min
T C, 120 min
Figure 1: Hydrochar at different temperature and exposing time

13. Result and Discussion
Table 2 : Hydrochar pH and Electrical conductivity changes
Temperature (0C)
Time (min) pH
EC (ms/cm) T0
paddy straw
7.7
2.76 T1
100
6.5
2.48 T2 60
6.3
2.69 T3
120
5.6
2.86 T4
200
5.1
3.30 T5
4.8
4.50 T6
5.7
2.11 T7
250
5.4
3.02 T8
5.8
3.82 T9
3.63

14. Result and Discussion
pH Change from neutral to Slight acidic condition
Minimum pH in (T5)200 0C for 60 minute holding time
EC increased with increasing temperature
Maximum EC observed for T5 followed by T8
EC and pH depend on production process and feedstock type
pH and EC is important as per the application
Figure 2: Prepared hydrochar samples for pH and EC measurement

15. Moisture absorption rate (g/1g of
Result and Discussion 6
T0- paddy straw T1- 100°C, 0min T2-100°C, 60min T3-100°C, 120min T4-200°C, 0min T5-200°C, 60min T6-200°C, 120min T7-250°C, 0min T8-250°C, 60min T9-100°C, 120min
Moisture absorption rate (g/1g of
hydrochar) 5 4 3 2 1 15
Time (hours) 5 10 20 25 30
Figure3 : Moisture absorption rate of different hydrochar over time
Maximum absorption T g/ 1g of hydrochar followed by
5.17 g/ 1g of hydrochar T9
Minimum absorption feedstock g/ 1g of hydrochar
Water holding capacity increase with increasing porosity
Micro-pores and meso-pores are responsible for water holding

16. Conclusion Char Yield negatively correlated with HTC temperature
Least yield 45% at T9- (250 0C 120 minutes)
Lowest pH (4.8) and maximum EC (4.5 ms/cm) in T5 (200 0C for 60 minutes)
Maximum Water holding capacity in T g/ 1g of hydrochar
Water holding capacity – two times higher than feedstock
Total pore volume of hydrochar increase with increasing HTC temperature
T5 most suitable hydrochar type as moisture conservation measure

17. Future Studies
Determination of the P and N adsorption capacity of the produced hydrochar
Study the P and N adsorption kinetics and Isotherms

18. Figure 4: Hydrochar at moisture absorption test
Figure 5: Hydrochar samples after drying

19. References
Ahmad, M., Rajapaksha, A. U., Lim, J. E., Zhang, M., Bolan, N., Mohan, D., … Ok, Y. S. (2014). Biochar as a sorbent for contaminant management in soil and water: A review. Chemosphere, 99, 19–23.
Oliveira, F. R., Patel, A. K., Jaisi, D. P., Adhikari, S., Lu, H., & Khanal, S. K. (2017). Environmental application of biochar: Current status and perspectives. Bioresource Technology, 246(August), 110–122.
Qambrani, N. A., Rahman, M. M., Won, S., Shim, S., & Ra, C. (2017). Biochar properties and eco-friendly applications for climate change mitigation, waste management, and wastewater treatment: A review. Renewable and Sustainable Energy Reviews, 79(November 2016),

20. Thank You 20