Biochar is produced from the pyrolysis of organic matter (waste and biomass of agriculture) e.g young coconut waste (YCW). However, there is little information describing methods for producing biochar as an ameliorant for agriculture. Therefore, research is needed to determine the biochar characteristics of the Kon-Tiki, Drum, and Soil-Pit methods. This study was conducted using a Completely Randomized Design with three replications. The results of biochar production with methods significant on temperature (682°C), moisture (81.27 %), dry weight (2.09 kg) and yield ratio (20.87%) of biochar, and characteristics of biochar from YCW on pH (10.82 unit), liming potential (5.50% CaCO3), proximate analysis (moisture of 38.80%; volatile matter of 62.73%; ash of 19.50% and fixed carbon of 43.22%), CEC (457.13 mmol kg−1), cation base (K of 356.14 and Na-exch of 131.28 mmol kg−1), Cárgame (0.35 g kg−1), and C Organic (14.27 g kg−1), with the recommended method of YCW biochar production using the Kon-Tiki method.

Waste from agricultural products will be a problem if it is not used properly. Optimization of waste-biomass agriculture as ameliorant e.g biochar from young coconut waste for sustainable agriculture. The particle size of biochar will have a different effect when applied to the soil, then it is necessary to study the characteristics of biochar particle size from young coconut waste (YCW). The biochar particle size (A) 4.75 − 2.80 mm; (B) 2.80 − 2.00 mm; (C) 2.00 − 1.00mm; (D) 1.00 − 0.50 mm; (E) < 0.50 mm The treatment units were allocated based on a Completely Randomized Design with three replication. The results showed that the chemical characteristic of biochar particle size from YCW has a significant on electrical conductivity, liming potential, proximate analysis, CEC, cation base, C Inorganic, and C Organic. The best characteristics of biochar particle size from YCw is < 0.50 mm on pH (10.09 units), EC (1.11 dS m−1), liming potential (7.11 %), proximate analysis (34.5% moisture; 57.77% volatile matter); CEC (780.69 mmol kg−1), cation base (393.49 K; 430.31 Ca; 124.37 Mg and 173.42 mmol kg−1 Na); GInorganic (0.376 g kg−1), COraganic (17.93 g kg−1). With the best particle size of biochar YCw using 0.5 mm − 2 mm.

One of the qualities of biochar is determined by the method in biochar production. The development of methods is carried out in traditional (Soil-Pit), conventional (Drum), and modern ways (Kon-Tiki). Thus, it is necessary to study the characteristics of the method in biochar production. The treatment units were allocated based on a Completely Randomized Design with three replication. The results showed that the characteristics of bamboo biochar based on the method of biochar production has a significant on the duration of firing and moisture of biochar and chemical properties of bamboo biochar on pH, EC, liming potential, proximate analysis, CEC, and cation bases (K, Ca and Na-exch), C Inorganic and C Organic. The best method of production of biochar bamboo is modern ways (Kon-Tiki) because it has effective time in the process production, high moisture, yield ratio compared to other methods, and less smoke so it can reduce air pollution.

Contamination of mercury (Hg) in ex-gold mining soil is the impetus for the development of amelioration technology that utilizes Indonesian sub-bituminous coal to study the soil surface charge and the chemical properties of ex-gold mining soil. This research was aimed to study surface charge and chemical properties of ex-gold mining soil ameliorated with Indonesian sub-bituminous coal. The experimental design used in this study was a Completely Randomized Design with three replications. The treatment was implemented in a pot with the equivalent dose: A = 0 (0.0g); B = 10 (0.5g); C = 20 (1.0g); D = 30 (1.5g), and (E) 40 t ha−1 (2g 100g−1 soil). The results showed amelioration technology with Indonesian sub-bituminous coal, at the application of 40 t ha-1 on ex-gold mining soils, could increase the soil surface charge (ΔpH) by 0.60 through changes in chemical properties of the ex-gold mining soil, where there was an increase in pH (H2O) EC, CEC, and SOM, respectively of 0.37; 0.04 dS m−1; 2.14 cmol kg−1 and 7.83% compared to the control. Soil surface charge was supported by soil minerals [Quartz (SiO2)] and an increase in the chemical properties of the ex-mining soil ameliorated with Indonesian sub-bituminous coal which caused Hg to decrease by 2.50 mg kg−1 compared to the control.

Improvement the characteristics of acid mineral soil [Ultisols] is needed to support plant productivity. However, the utilization of biochar combined with sub-bituminous in improving ultisol is still limited. Therefore, this research was conducted by using treatments: 1] Control 0% Sub-bituminous [SBC] + 0% Bamboo Biochar [B]; 2] 100% SBC [20 ton.ha−1]; 3] 75% SBC + 25% B; 4] 50% SBC + 50% B; 5] 25% SBC + 75% B; and 6] 100% B [20 ton.ha-1] This study was designed using Completely Randomized Design [CRD] with 3 replications. The results showed that the application of combined biochar and sub-bituminous had a significant effect in improving ultisol’s fertility characteristics. There are two treatments that provide the most significant results for improving soil properties, namely 100% sub-bituminous treatment with a significant effect in increasing pH [1.3 pH units], Organic carbon [3.34%], Total N [0.12%], CEC [10.87 cmol/kg and Ca2+ [1.2%]. However, 50% sub-bituminous + 50% bamboo biochar treatment have a significant effect in increasing Available P [1.1 ppm], CEC [9.04 cmol/kg K+ [0.51 cmol/kg], Ca2+ [1.37 cmol/kg], and Mg2+ [1.27 cmol/kg]. In addition, application of 50% sub-bituminous + 50% bamboo biochar gave the best result for the plant height, branches and leaves of the coffee plants.