Globally, there is growing concern about the problem of plastic waste. The majority of plastic waste is dumped into landfills, where it occupies space, reducing landfill capacity and causing a variety of environmental issues. Plastic waste pyrolysis has gained popularity because it can reduce the volume of plastic waste while also producing alternative fuels. This study assessed the feasibility of producing fuel oil from plastic waste using the catalytic pyrolysis process. Polyethylene (PE), polypropylene (PP), and polystyrene (PS) waste samples were collected from municipal solid waste (MSW) landfills on Samui Island, Surat Thani Province, Thailand. Pyrolysis was carried out in a 3-L bench-scale reactor at 450ºC using a 3% spent FCC catalyst. PE, PP, PS, and mixed plastic waste were used as feedstocks. The results showed that the pyrolysis of PS produced the most liquid product (91.44 wt%), whereas the pyrolysis of PE produced the highest percentage of diesel range product (36.60 wt%). Furthermore, the results of the analysis revealed that the characteristics of diesel from improved PE pyrolysis oil by naphtha removal were similar to those of commercial diesel B7. According to the cost-benefit analysis, the operating costs of pyrolysis oil and improved diesel were 0.37 and 0.65 USD/L, respectively, which were lower than the current market price of diesel B7. The findings of the study demonstrated the feasibility of converting plastic waste from MSW on Samui Island into alternative energy using eco-friendly and cost-effective technology.

Burning sunflower stalks after harvesting could pose a significant environmental risk due to particulate matter 2.5 pollution. The use of low-cost recycled materials in building products is on trend. In this study, two distinct methods, hot oven, and hot compression, were used to form a bio-composite from sunflower stalks and bark, using natural latex as a binder. The physical, mechanical, thermal, and acoustic properties of the bio-composite were determined. The test box was used to evaluate the thermal performance of bio-composites. The bio-composites had a density of 515.67–864.24 kg/m3, similar to flat-pressed particleboards (400–900 kg/m3). The moisture content varied from 6.01 to 14.20%, with only the 1:5 and 1:6 sunflower stalk bio-composite by hot compression having a moisture content higher than 13%. Thickness swelling ranged from 5.63% to 12.03%. All composites had a fire resistance of less than 33 mm/min. As natural latex increases, the water absorption of sunflower stalks decreases while at the same time increasing fire resistance. The thermal conductivity coefficient ranged between 0.117 and 0.161 W/mK. The noise reduction coefficient (NRC) of 1:4 sunflower stalks in a hot oven and 1:6 sunflower bark in a hot compression were 0.233 and 0.241, respectively. The hot-compressed 1:6 sunflower bark bio-composite exhibited a room temperature profile that was similar to that of the MDF board. The hot compression method revealed better results in density, water absorption, flexural strength, and flexural modulus than the hot oven method.

Using carbon dioxide (CO2) as a carbon source for renewable energy production has potential applications for CO2 sequestration and greenhouse gas (GHG) emission reduction. In biological conversion, CO2 can be transformed into methane (CH4) by hydrogenotrophic methanogens with hydrogen (H2) as an energy source. In this study, zero-valent iron (ZVI) of 16, 32, 64, and 96 g/L was used as the H2 energy source for a bioconversion of CO2 to CH4. When the ZVI dosage was increased, a decrease in CO2 in the headspace occurred simultaneously with the increase in CH4. The presence of CH4 in both CO2/H2 and CO2/ZVI indicates that hydrogenotrophic methanogens can utilize both ZVI and H2 as electron donors and convert CO2 to CH4. The highest methane yield of 1.728 mmol CH4/mmol CO2 was observed for the CO2/ZVI 96 g/L. The modified Gompertz equation fitted the cumulative CH4 production curves of CO2/H2 and CO2/ZVI very well, where R² was 0.9915 and 0.9903-0.9968, respectively. 16S rDNA high-throughput sequencing results revealed that ZVI addition facilitated the increase of the family Methanobacteriaceae, which became the most abundant among other archaea. It points out that this family favors ZVI and utilizes electrons more effectively from ZVI than H2.

This study analyzes the contributions of greenhouse gas (GHG) emissions in the wastewater treatment plants (WWTP) at Pattaya City to the areas of Naklua, Pattaya City, and Jomtien. This analysis was carried out 2021-2023 by visiting the sites, interviewing plant managers, filling out scientifically designed questionnaires and by processing the data obtained using computational methods developed by the Intergovernmental Panel on Climate Change. It was found that the total carbon footprint (CF) from both the Pattaya City and Jomtien WWTPs had the potential to contribute 5,610.61-6,020.18 tCO2eq/year and that carbon intensity ranged between 0.45-0.47 kg CO2eq/m3 in treated wastewater. The study found that the main sources of emissions were the wastewater collection system (34.47-44.61%), activated sludge process (43.02-45.74%), and electricity consumption (30.02-39.48%). Therefore, the study suggests three options for GHG reduction. Installing solar cells on the office building roof could generate 156,780 kWh annually, resulting in a reduction of CO2 emissions by 108.70 tCO2eq/year, and a savings of 35,658.52 USD. This is equivalent to a 2.38% reduction in the WWTP’s GHG emissions. Installing solar cells in the plant could also generate 823,680 kWh annually, leading to a reduction in GHG emissions of 571.06 tCO2eq/year, or 12.50%, and a savings of 187,304.58 USD. Installing a WWTP at station PS12 with a capacity of 60,874.65 m3/day could also reduce the GHG footprint from the wastewater collection system by 1,219.44 tCO2eq/year, or 36.41%, and result in a savings of 239,091.57 USD. To reach carbon neutrality and energy sustainability, the approaches for resource recovery, nutrient recycling, water reuse, and energy production on-site with combined heat and power (CHP) from biogas should be investigated in the future.