This research studies the characterization of activated carbon from tamarind seed with KOH activation. The effects of 0.5 : 1–1.5 : 1 KOH : tamarind seed charcoal ratios and 500–700°C activation temperatures were studied. FTIR, SEM‐EDS, XRD, and BET were used to characterize tamarind seed and the activated carbon prepared from them. Proximate analysis, percent yield, iodine number, methylene blue number, and preliminary test of Fe(III) adsorption were also studied. Fe(III) adsorption was carried out by 30 mL column with 5–20 ppm Fe(III) initial concentrations. The percent yield of activated carbon prepared from tamarind seed with KOH activation decreased with increasing activation temperature and impregnation ratios, which were in the range from 54.09 to 82.03 wt%. The surface functional groups of activated carbon are O–H, C=O, C–O, –CO₃, C–H, and Si–H. The XRD result showed high crystallinity coming from a potassium compound in the activated carbon. The main elements found in the activated carbon by EDS are C, O, Si, and K. The results of iodine and methylene blue adsorption indicate that the pore size of the activated carbon is mostly in the range of mesopore and macropore. The average BET pore size and BET surface area of activated carbon are 67.9764 Å and 2.7167 m²/g, respectively. Finally, the tamarind seed based activated carbon produced with 500°C activation temperature and 1.0 : 1 KOH : tamarind seed charcoal ratio was used for Fe(III) adsorption test. It was shown that Fe(III) was adsorbed in alkaline conditions and adsorption increased with increasing Fe(III) initial concentration from 5 to 20 ppm with capacity adsorption of 0.0069–0.019 mg/g.

The production of activated carbon from eucalyptus wood chips by steam activation in a 2000 kg batch intermittent rotary kiln with continuous carbonization–steam activation process conducted at 500 °C to 700 °C was studied. The activated carbon products were characterized by FTIR, SEM–EDS, Raman spectroscopy, and BET analysis. Percent yields, iodine number, and methylene blue number of the produced activated carbon materials were measured as well. It was shown that the percent yields of the activated carbon materials made in the temperature range from 500 to 700 °C are 21.63 ± 1.52%–31.79 ± 0.70% with capacities of 518–737 mg I₂/g and 70.11–96.93 mg methylene blue/g. The BET surface area and micropore volume of the activated carbons are 426.8125–870.4732 m²/g and 0.102390–0.215473 cm³/g, respectively. The steam used in the process could create various oxygen containing surface functional groups such as –CO and –COC groups. In addition, it could also increase the amorphous nature of the activated carbon product. These properties of the activated carbon products are increased with increasing steam activation temperature from 500 to 700 °C. As a result, the activated carbon materials produced at activation temperatures of 600 °C and 700 °C exhibit higher adsorption.

The charcoal briquettes from banana peel and banana bunch wastes from dried banana industry for household heating were characterized and evaluated. A 200 L pyrolyzer was used for charcoal and wood vinegar production at 350° pyrolysis temperature. The percent yield of charcoal and wood vinegar were determined. The effects of clay binder (0-15% w/w) on the properties of charcoal briquettes such as ash content, hardness, combustion calorific value, emissions data, burn time and combustion efficiency were evaluated. It was found that the percent yields of charcoal and wood vinegar from pyrolysis of banana peel and banana bunch are 57%, 7.53% and 58.6%, 6.76%, respectively. The banana bunch charcoal retained some functional groups to a higher degree than the banana peel charcoal. These include -OH, C = O, C = C, C-H and C-C groups. The porous shapes of banana peel charcoal and banana bunch charcoal are honeycomb and tube structure, respectively. The calorific value of both charcoal briquettes decreased with increasing ratios of clay and ash content. The values range from 5,115.51 to 6,396.66 cal g-1. The hardness obtained with 5% clay binder is 23.31 kg and 25.90 kg for banana peel charcoal briquette and banana bunch charcoal briquette, respectively. Both charcoal briquettes containing 5% clay are smokeless during combustion and result in red-brown ash after combustion. The dust and total CO emissions of banana peel charcoal briquette and banana bunch charcoal briquette during combustion are 15.38 µg m-3 and 3463 ppm and 11.97 µg m-3 and 1568 ppm, respectively. The maximum temperatures of water are 88 and 84° and times needed to reach the maximum temperatures were 36 and 48 min for banana peel charcoal briquette and banana bunch charcoal briquette combustion, respectively. The maximum burning times and combustion efficiencies are 114 min and 9.10% and 92 min and 8.38% for banana peel charcoal briquette and banana bunch charcoal briquette, respectively.

Rice husk biochars were prepared by carbonization at 400–600°C. The products were analyzed by FTIR, SEM-EDS, BET, and approximate analysis in order to find final products with the best properties and the lowest carbonization temperature. It has been found that the biochar prepared at 500°C, which has 37.86 ± 0.11% yield, 341.0776 m²/g of BET surface area, and 0.136639 cm³/g of micropore volume, is suitable for use as a root supplement in the aquaponic system. The aquaponic systems consist of aquaculture and a hydroponic system with and without biochar supplement. The control experiment consists of an aquaculture and planting panel with biochar supplement disconnected from each other. Tilapia and Chinese morning glory were used for growth studies. The water quality from all aquaculture ponds has also been analyzed at an interval of 10 days for 47 days. The results showed that the growth rates of Tilapia and Chinese morning glory in the aquaponic system with biochar were clearly higher than in the control experiment, which is in accordance with the water quality in each aquaculture pond. However, the growth rates of Tilapia (23.5 g/body vs. 22.7 g/body) and morning glory (3.907 g/stem vs. 2.609 g/stem) in supplemented biochar system tend to be higher than the nonsupplemented biochar system. It has been shown that rice husk biochar can help in treating water in the aquaponic system by increasing the amount of dissolved oxygen in the aquaculture water and conversion of toxic compounds to those beneficial for plant growth.