Biogas production from various organic wastes such as corn stover can be used as an alternative fuel. Corn stover is one of the agricultural wastes that are widely generated in Indonesia. It contains cellulose which has the potential to be used as raw material for producing biogas. The biogas production process was carried out in solid-state anaerobic digestion (SS-AD), i.e., a biological process that occurs naturally by a microorganism that breaks down molecules of organic material with a total solid content greater than 15%. This research was aimed to investigate the effect of EM-4 concentration on biogas yield. The volatile solids (VS) reduction was also measured in this study. The results of the study showed that EM-4 concentration had a significant effect on biogas yield (p < 0.05). The positive linear relationship was found between EM-4 concentration and biogas yield. The highest biogas yield of 597.98 L/kg VS was obtained at EM-4 15%. The main source of biogas production during SS-AD of corn stover was the reduction of VS.

This paper aims to provide an overview of the use of educational technology in learning akidah akhlak as subject. This study uses a type of qualitative research with the semiotic analysis method by examining the figure of KH. Ahmad Dahlan in the film 'Sang Pencerah'. The result of this research is the strengthening of technology by utilizing the media has long been exemplified by KH. Ahmad Dahlan. Therefore, the use of technology in learning is not new and has strong historical roots as the da'wah strategy that KH has carried out. Ahmad Dahlan in broadcasting Islamic teachings. The implication is that Islam and technology should not be contradicted but should be further harmonized. If the era of KH. Ahmad Dahlan has been balancing it for a long time, so this era should move, namely by being a consumer of technology and starting as a producer because teaching Islam cannot be separated from the use of technology in the learning process.

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The shortage of fossil fuel can be minimized by developing renewable energies such as biogas. The raw material of biogas can be derived from corn stover. Biogas was produced under solid-state anaerobic digestion (SS-AD) and liquid anaerobic digestion (L-AD). The objectives of this study were to compare the biogas yield and analyze the pH value and VS degradation. The results reported that the SS-AD generated a higher biogas yield than L-AD. SS-AD could improve the biogas yield of 71%. Both SS-AD and L-AD had a higher final pH than the initial pH. Moreover, the VS degradation was proportionate to the biogas yield. The highest VS reduction was achieved on SS-AD. Keywords: anaerobic digestion, biogas, liquid state, solid state, volatile solid, renewable energy