Vol. 13 Issue 3 Jul.-Sep. 2022

Chuleeporn Sriyam, Amnat Chidthaisong*, Kazuyuki Yagi, Sirintornthep Towprayoon and Sudarut Tripetchkul

Abstract: This study aimed to determine the rates of N2O and CO2 production under different soil temperature and moisture conditions. Soil samples were collected from the 46-years long-term fertilizer experiment plots in Lopburi province. Three treatments were included in the present study; control or no fertilizer (NF), chemical fertilizer application (CF) and organic fertilizer application (OM). The soils were incubated at 25°C, 30°C, and 35°C under moisture content of 60 and 80% water-filled pore space (%WFPS) for 14 days. Long term fertilizer experiment (46 years) revealed that the application of cow or chicken manure has increased soil carbon stock (SOC) by 5-7 MgC ha-1 compared to that of no fertilizer and chemical fertilizer application. The N2O production rate from all treatments was increased 2-9 times under 60% WFPS and 5-18 times under 80% WFPS when the temperature was increased from 25° to 30°C, but was decreased when the temperature was increased from 30° to 35°C, except the CF which was increased. The OM had highest N2O and CO2 at any temperatures investigated. Only the temperature above 30°C that the effects of moisture on N2O production was observed. The mean value of N2O production in OM under 60% WFPS and 80% WFPS differed only under 25°C. On the other hand, CO2 production rates was enhanced 1-2 times along with increasing temperature and moisture. These results indicate that the longterm fertilizer application has significantly changed the production potential of N2O and CO2, and so their sensitivities to temperature and moisture changes.

Keywords: Long-term experiment, N2O and CO2 production, soil temperature, soil moisture.

Damson Daniel Kadete, Pipat Chaiwiwatworakul* and Surapong Chirarattananon

Abstract: This paper presents an investigation of the daylighting from external multiple shading slats integrated with photovoltaics (PV). Experiments were carried out at an outdoor chamber with a south-facing window. Based on the measured results using various sensors, the daylighting characteristics were analyzed for an office environment under varying tropical sky conditions. Relationships of the exterior daylight illuminance and the interior daylight distribution could be empirically formulated, and they were used to determine the required artificial light from electric lamps to supplement the transmitted daylight from the window. In the assessment of the daylighting potential of the PV shading slats, a monthly adjustment scheme of the slat angle to fully intercept the direct sunlight from the south window was proposed together with the task-ambient lighting concept. By using our experimental room as the demonstration case, the analysis showed that the daylighting of the PV slat system could reduce the lighting energy consumption by 80% compared to the typical office case designed with the uniform lighting concept. The generated solar energy from the PV array on the slat surface was estimated to be sufficient for the lighting by the direct-current LED lamps. However, battery storage was required due to the time mismatch between the solar power generation and the required electricity for supplement lighting.

Keywords: Daylighting, dimmable lighting, PV slats, tropical climate, workplane illuminance.

Asama Tavornpongstid, Sudarut Tripetchkul*, Sirintornthep Towprayoon, Chart Chiemchaisri and Komsilp Wangyao

Abstract: During the municipal solid waste mechanical separation process, the wastes with sizes >50-100 mm, excluding magnetic items and dense materials, are transformed into refuse-derived fuel. The remainder of the two waste streams can be disposed of in landfills, including materials with a size of ≤50 mm (rejected material 1) and heavy materials with a size of >50-100 mm (rejected material 2). The use of rejected materials for refuse-derived fuel (RDF) production in Thailand has not been investigated. This research aimed to convert the rejected materials into RDF using a biodrying process. The results revealed that rejected material 1 contained both plastic and organic waste. It had low moisture content, high volatile solid content, and high heating values (about 2,074.20-2,680.30 kcal/kg) compared to the rejected material 2. It is indicated that the rejected material 1 was a more suitable raw material for RDF production. For studying the effect of continuous aeration rates on the biodrying process for rejected material 1, three experiments were performed using lysimeters and operated at three different aeration rates, 2.27, 2.77, and 3.02 L/min/kg, for 14 days. At the aeration rate of 2.27 L/min/kg, the biodrying process of rejected material 1 had the highest average temperature (45.9-50.76°C) during the thermophilic phase and the highest accumulated temperature integration value (241.05°C). As a result, the moisture, volatile solids, and ash contents could be reduced to 21.67%, 81.21%, and 18.95%, respectively, with a lower heating value of 3,558.12 kcal/kg. However, the ash content from these RDFs exceeded the quality criteria. Therefore, this produced RDF, which was classified as a low-grade RDF. At the three aeration rates, the biodrying process emitted greenhouse gases between 0. 0.0053-0.0295 kg CO2e/kg waste, which was significantly less than the landfill of rejected material.

Keywords: Biodrying, Greenhouse gas emissions, MSW rejected materials, Aeration rate, Refuse-derived fuel.