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Volcanic deposits are abundant in the vicinity of an active and inactive volcano. They are produced from the cooling of magma during explosive volcanic eruptions. They have varying physical properties and can range in size from sub-millimetric ash up to boulder size. As Indonesia is considered as an active volcanic region, volcanic materials are abundant but they are still unexploited to full capacity such as geopolymer raw material. Geopolymers are generally understood as alkali-activated aluminosilicates. They may be considered as an inorganic two-component system which consists of: [1] a reactive solid source of SiO2 and Al2O3, and [2] an alkaline activation solution. The aim of the research is to identify the chemical and mineralogical properties of Merapi and Mt. Sinabung volcanic ashes as the raw material of geopolymers. Results showed that Mt. Merapi contained amorphous volcanic glass and crystalline [feldspar] minerals with 61.13% SiO2; 17.78% Al2O3; 3.47% Fe2O3; 6.22% CaO. Mount Sinabung deposit contains amorphous volcanic glass also and crystalline [feldspar] minerals with an oxide content of 49.33% SiO2; 15.93% Al2O3; 6.48% Fe2O3; 5.87% CaO. The high content of silica and alumina in this material showed that it was pozzolan material which can be synthesized to geopolymers. The molar ratio of SiO2/Al2O3 was high, Merapi is 5.84 and Sinabung is 5.26.

Universitas Internasional Semen Indonesia (UISI) disposes abundant amount of woody waste, such as leaves, twigs, and brunches from the pruning of woody plants. The aim of this research is to convert of this waste into combustible biomass briquettes by varying the particle size and binder ratio. A hydraulic press with 2 tons power and a cylindrical iron mold with diameter of 3.5 cm and height of 3 cm were used for the briquetting process. The physical characteristics of woody waste briquette, such as moisture content, ash content, volatile matter and carbon fix were evaluated using proximate analysis. The caloric value of briquetted fuel was measured by bomb calorimeter. The combustion test was conducted to determine the combustion characteristic of briquettes. The general result shows that the caloric value of developed briquettes was between 3402 and 3630 kcal/kg. The moisture content of briquette ranged from 1.080-1.16 %. Volatile matter was found in the range of 22.2 to 39.4 %. Ash content was 31.2-35.9 %, and carbon fix was 23.54-45.52%. The shortest ignition time was 229 s. The longest burning time was 78 minutes. Based on TG/DTA results, woody waste briquette decomposition occurred from 49°C to 801°C.

The volcanic ashes are an abundant natural resource in Indonesia, but they are still little is used optimally, such as geopolymer raw material. Geopolymers are a class of inorganic polymer that be able by the reaction of an aluminosilicate material with an alkaline solution. The research aims to investigate the synthesis of geopolymers using two types of volcanic ash (Mt. Merapi and Mt. Sinabung). The synthesis of geopolymer was carried out at variation of solid/liquid ratio at 65% : 35% and 70% : 30%, with two alkaline solutions (NaOH and KOH) under different alkaline concentration (8, 9, and 12 M). A multi-analytical approach is proposed: chemical (XRF) and spectroscopic (FT-IR) analyses. The Results showed that geopolymer is influenced by volcanic ash-type and SiO 2 /Al 2 O 3 ratio. Geopolymers are formed when volcanic ash of Sinabung mix with NaOH 10 NaOH with ratio of 65% : 35%, and the polymers are relatively stable. The FTIR spectra of the synthesized geopolymers showed broad absorbance bands, between wave 972-962 cm −1 and 931-976 cm −1 assigned to the internal vibrations of Si–O–Si, and Si–O–Al respectively. Both volcanic ash materials from the Merapi and Sinabung volcanoes can be utilized for making geopolymer, suitable for both engineering and agriculture applications.