Development of Activated Hydrochar from Paddy Straw for Nutrients Adsorption and Crop Water Management G.A.G.Kavindi 201726054 Supervisor : Prof. Zhongfang Lei

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

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: www.newsclick.in Uses - paper production construction materials compost energy source animal feed Burning in the fields- cost-effective but environment pollution 3

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

Mechanisms Source : Oliveira et.al, 2017 5

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

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: www.open.edu 7

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

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

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

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

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 T7- 250 0C, 0 min T8- 250 0C,60 min T9 -250 0C, 120 min Figure 1: Hydrochar at different temperature and exposing time

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

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

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 T5 5.39 g/ 1g of hydrochar followed by 5.17 g/ 1g of hydrochar T9 Minimum absorption feedstock- 2.41 g/ 1g of hydrochar Water holding capacity increase with increasing porosity Micro-pores and meso-pores are responsible for water holding

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 T5 - 5.39 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

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

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

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),

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