Key Engineering Materials Vol. 877

Abstract: This study focused on the feasibility of utilizing waste rubber tyre as coarse aggregate in concrete as a partial replacement of brick aggregate (BA). Within this context, fresh and hardened properties were investigated on concrete made with three different percentage replacements (0, 10 and 20% by volume) of BA by waste rubber tyre aggregate (WRTA). The WRTA was washed with tap water (H₂O) and treated with 20% sodium hydroxide (NaOH) for 2 hours. It was found that the workability and dry density of concrete decrease with an increasing percentage of WRTA. In case of mechanical properties, the compressive strength decreases with the increasing content of both treated and untreated WRTA. The maximum decrease was observed for 20% of both treated and untreated WRTA, which was 41-46% for treated and 47-54% for untreated lower than the reference concrete for all curing ages. It was observed that the concrete made with tyre treated with NaOH provides better strength than untreated tyre aggregate. This behavior could be attributed to the better bonding between cement paste and rubber aggregates as a result of the increased surface roughness by NaOH.

Abstract: The available of conventional fuels are fluctuating depend on distribution from the source production to consumer. The availability of biogas as renewable energy is increasing due to establishments of many organic wastes processing worldwide. The need of electricity to support daily life activity is a must, but the availability of electric source in remote area is limited especially for a farm that far away from commercial line distribution of electricity. This work is dedicated to solve this problem. The single cylinder 4 stroke spark ignition engine (83 cc) was designed to be able to be fuelled flexibly by using biogas or liquefied petroleum gas (LPG), or gasoline if sometime the biogas not available during initiation of the process or during maintenance of anaerobic digester. The engine is still can be run to provide electricity by using conventional fuel such as LPG or gasoline. The full consumption as well as emission of this flexible fuel engine was investigated. It is found that the fuel consumption is 9.97 L/mint for Biogas, 0.004 L/mint for gasoline and 2.24 L/mint for LPG. Surprisingly by using biogas the emission of carbon monoxide (CO) was down to almost zero (0.02 ppm), comparing gasoline 0.32 ppm, and LPG 0.4 ppm.

Abstract: Biogas quality in many installation of anaerobic digester for processing organic waste are found not optimum, especially in developing country where understanding of anaerobic processing is not well known. The methane content in the biogas are usually low that make it not possible to be utilized as a fuel of the engine. Biogas Purification usually will be introduced as a solution. But this idea is about complicated for simple or small anaerobic digester. Other solution is suggested by using enrichment of biogas by using other fuel such as hydrogen or blended with city gas such as LPG gas. But for preparing hydrogen gas or commercial will also costly. This research introduces simple technique for biogas enrichment by using denatured alcohol. The biogas contents were found around 30% vol. methane (CH₄) and around 2% Carbon dioxide (CO₂). The price of denatured alcohol is relative cheap because the selling tax is not as much as drinking alcohol. Engine with bigger combustion (420 cc) chamber was prepared for this purpose to make possible to be fueled with biogas. The compression was set to reach 10 bar. The clearance of the both intake and exhaust valve was set in order to be possible to be running by using biogas. The biogas-air mixer was design for this purpose. The carburetor was set for use of denatured alcohol. It is found that the engine is running well by using biogas fuel that is enriched by using denatured alcohol. The emission was found better comparing using gasoline for the same engine. The fuel consumption is reported for future economic analyses.

Abstract: Used cooking oil is potential as raw material to produce biodiesel. We discovered fatty acid ethyl esters (FAEEs) and methyl esters (FAMEs) as biodiesel content indicator from esterification and trans-esterification reactions of used cooking oil with sulphuric acid and toluene sulphuric acid as catalysts. The purpose of this study was to examine some characteristics of FAEE and FAME synthesis from used cooking oil. The FAEEs and FAMEs were detected by separation in thin layer chromatography (TLC) and Fourier Transform Infrared (FT-IR) and compared to laurate standar. The used cooking oil was produced after frying of meat chicken for seven hours in a household. The Retardation Factor (R_f) of TLC of FAME of methyl laurate was 0.36 and FAEE of ethyl laurate was 0.23. The wavenumber indicating specific functional group of =CH was 3392 cm^-1, while of alcohol as ester compound was 1739.79 cm^-1. The wavenumber of C-C and CO groups were 1635.64 cm^-1 and 1165 cm^-1, respectively. These indicate the ester group in used cooking oil, which reflects the formation of bio-diesel.

Abstract: This document it is established that 2 types of biogas anaerobic digester that usually found in developing country. First type is fixed dome type of anaerobic digester and secondly is floating drum biogas anaerobic digester. Both of this type have draw back that the anaerobic process is not completed with agitation process that yield low rate of biogas production. Other serious problem is the release of slurry cannot optimal. Some of the slurry will still remain stay in the anaerobic digester especially scum. To drain and cleaning the fixed dome or floating drum biogas anaerobic digester is mandatory to be done regularly that consume time and cost. The fixed dome types as well as floating drum type are usually not portable which cause no possibility to relocate in the new site. It is the purpose of this work to introduce portable biogas anaerobic digester that suitable for developing country with volume of digester around 500 liter of slurry. The requirement of agitator is facilitated, and the anaerobic digester is possible to be operated in batch system or continuous system. The material that is used for anaerobic digester is stainless steel 304 with tungsten inert gas welding technology that is used for the manufacturing. With this design the anaerobic digester are easy to be maintenance. The batch system can keep producing biogas until 52 day with total production of biogas around 3320 liters. The continuous system was conducted by releasing for about 5 liters slurry from the outlet and after that filled with new slurry with stirring with agitator was conducted for about 10 minutes for 3 times in a day (morning, noon, and evening). The result for continuous system is a linear biogas production with rate biogas production is around 51.7 liter/day (1550 liter/30days).

Abstract: The 2 stroke single cylinder (63 cc) engine of 750 watt electric generator is very popular in the application because providing enough amount of electricity for small house hold with compact size, light weight with reasonable price. Usually this type of electric generator is fuelled with gasoline that mixed with oil as lubricant. The cylinder volume of the engine is usually around 63 cc. This type of engine can be fuelled with biogas with addition component to mix biogas together with air and lubricant, and set the compression pressure at 10 bar. Biogas mainly contain methane (CH4), carbon dioxide (CO2), moisture (H2O), and hydrogen sulfide (H2S). The CH4 is combustible gas and can be used as a fuel for internal combustion engine. Moisture and H2S are easily removed from biogas. To remove CO2 from biogas is about difficult and costly, therefore acceptable content of CO2 in the biogas should be investigate related with the fuel consumption. This research is conducted to understand the influent of ratio CH4 and CO2 in the biogas to fuel consumption of the 2 stroke single cylinder engine of 750 watt electric generator. The variations ratio of CH4 and CO2 were obtained from anaerobic digester with batch system. The results indicate that the CH4 and CO2 ration in the range 1.667-1.967 will yield optimum efficiency that reach biogas consumption in the range of 9.1-9.8 liter/minute.

Abstract: Fatty acids composition in used cooking oil vary that need to analyze before making biodiesel to meet the requirement of a diesel engine. The purpose of this study was to identify and characterize fatty acid ethyl ethers in used cooking oil refined using various acids after a one-stage transesterification process using a heterogeneous CaO catalyst to produce biodiesel. The analytical method applied was spectroscopic technique by using Fourier Transform Infra Red (FTIR) and Gas Chromatography-Mass Spectrometry (GC-MS) instruments. The results showed that the characteristics of fatty acid ethyl esters from used cooking oil that refined using phosphoric acid were superior to than sulfuric acid and hydrochloric acid. Six peaks with m/z 88 fragments as markers of fatty acid ethyl esters and two peaks identified as ethyl linoleate and ethyl oleate as unsaturated fatty acids characterize by GC-MS. FTIR showed an increase of intensity at wavenumber of 2500-1500 cm^-1 which was a weak bond. A similar functional group identified by FTIR in biodiesel from refining used cooking oil obtained lower intensity than commercial diesel fuel.