Judul: Sistem Sirkulasi Lindi pada Digester Anaerobik untuk Produksi Biogas dari Limbah Sayuran
Abstrak: Biogas is an alternative energy that can be used as a substitute for fossil fuels. Biogas can be produced from the fermentation of organic matter carried out anaerobikally. Vegetable waste is organic material that can be used as raw material for biogas production. . In addition to the availability of abundant, this waste also has a suitable C/N ratio if added to other materials like cow dung. This study aims to evaluate the utilization of vegetable waste as raw material and comparing the effectiveness of biogas circulation and non- circulation in biogas production and rate of decline COD. Fermentation process conducted in anaerobik digester that have volume 50 Liter for digester with leachate circulation and volume 25 liter for digester without leachate circulation. Fermentation process is done by using the starter of cow dung 20 % of the total material volume for 40 days. Specific production of biogas from digester circulation by controlled pH is 219 L/kg TS of material with rate of decline COD is 24 %, digester circulation without pH control is 117 L/kg TS of material with rate of decline COD is 28 %. Meanwhile, biogas specific production in the digester without leachate circulation have specifik biogas production and rate of decline COD lower than digester with leachate circulation.the spesicific biogas production is 24 L/Kg TS with rate of decline COD is 18 %. The highest specific of biogas production is conducted by digester with leachate circulation and pH control. Leachate circulation and pH control have considerable influence of biogas production.
Keyword: Bogor Agricultural University (IPB), Circulation Leachate, C/N ratio, manure, fermentation

Judul: Pembuatan Biogas Dari Sampah Buah-Buahan Melalui Fermentasi Aerobik Dan Anaerobik
Abstrak: Solid wastes and energy crisis are created by high growing rate of people. An alternative solving for both problems is biogas technology. Municipal waste can be proceed into biogas and fertilizer by biogas technology. In general, the process of conventional biogas technology has long time about 40 days (in tropical countries) and 100 days (in subtropical countries). The main goal of the research was to shorten the retention time of biogas production by combining its aerobic and anaerobic processes with optimized environmental condition (temperature) and substrate composition (C:N ratio) in anaerobic phase. Hydrolysis and acidogenesis were set in aerobic phase, while asetogenesis was set in anaerobic phase. Fruits waste were set into pre-treatment, minimized waste size between 1-2 cm2 and water addition (1: 1). The mixed ingredients was added by E~ microorganism culture and took into digester to start aerobic process. After 5 days, the process was stopped then substrate took to anaerobic digester to produced biogas (methano~enesis). Anaerobic process was set at different temperatures (30,35 and 40 C) and C:N ratios (20,25 and 30). The beginning of water content and C:N ratio of substrate were 86,24 % and 70,32: 1. Respectively, in aerobic process substrate was degraded by microorganism into simple compound. This process can be analyzed by C:N ratio change of total solid (TS), total volatile solid (TVS), chemical oxygen demand (COD), volatile fatty acid (VF A) and acidity degree (pH). Methanogenesis (anaerobic process) was monitored by the volume of biogas produced and analyzed COD, VF A and pH. The optimum of production rate and volume ofbiogas produced was achieved by treatment in 35°C temperature and 30: 1 C:N ratio, which biogas has produced 26,5 ml in the ftrst day and 42,5 ml biogas in the end of biogas production with the highest production rate was 9,6 mVday. It showed that activity of methanogenic microbe was optimum in that treatment condition.
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Judul: Socioeconomic and psychological variables influencing household debt
Abstrak: The overall objective of this study was to examine factors influencing total debt, total debt payment, and patterns of debt payments. The study examined the impacts of both psychological (credit attitudes and perception of future income) and socioe- conomic variables on total debt, total debt payment and patterns of debt payments. A conceptual model for this study was developed by incorporating the theory of borrower risk, the economic and psychological economic theory of borrowing, and the results of previous studies. This model identifies socioeconomic and psycholog- ical variables that influence total debt, total debt payment, and patterns of debt payments. Socioeconomic variables included in the model are gender, race, mari- tal status, employment status, household size, age, education, and household assets. Psychological variables are credit attitudes toward the use of credit, and perception of future income. This study used data from the 1989 Survey of Consumer Finances. The survey was sponsored by the Federal Reserve in cooperation with some other federal agencies. Data for the survey were collected by the Survey Research Center at the University of Michigan between August 1989 and March 1990. dst ...
Keyword: Gender