Virin Kittithammavong

Thailand is among the countries most vulnerable to climate change, ranked 8th by the Global Climate Risk Index (CRI) for the period 1999–2018. In response, the National Strategy 2018–2037 outlines pathways for both adaptation and mitigation. The waste management sector is a notable contributor to greenhouse gas (GHG) emissions, accounting for more than 16,000 Gg CO2-eq, approximately 4–5% of Thailand’s total emissions. Municipal solid waste (MSW) management is particularly relevant in developing countries, where emissions vary considerably across municipality types. This study aims to determine GHG emissions from MSW management in Phitsanulok Province, Thailand, using questionnaire-based data collected from municipalities. Emissions were calculated for both end-of-life treatment and transportation stages. The results reveal significant differences across municipality types. City municipality generated the highest average emissions (26,531 tonnes CO2-eq/year), followed by town municipality (4206 tonnes CO2-eq/year), subdistrict municipality (1837 tonnes CO2-eq/year), and subdistrict administrative organization (1168 tonnes CO2-eq/year). While total emissions were greatest in the city municipality, per capita emissions did not scale proportionally, reflecting differences in population density, waste generation, and management practices. This province-scale analysis provides new insights into the role of municipality type in shaping waste-related emissions. The findings underscore the importance of differentiated climate mitigation strategies in the waste sector to develop more sustainable, low-carbon MSW management systems in Thailand and other developing countries.

Thailand generated 27.2 million tons of municipal solid waste in 2024, of which 12% was plastic waste, predominantly single-use plastics. The mismanagement of plastic waste can lead to significant long-term environmental issues, including the release of toxic chemicals through open burning and air pollution, posing risks to human health. Effective and efficient plastic waste collection and recycling are therefore essential to address the reduction and management of plastic waste, as well as to support a low-carbon energy transition. This study assessed three community-driven initiatives by conducting a comparative sustainability assessment of plastic bag recycling under real-life conditions in Thailand using a multi-criteria decision-making framework. The results of the assessment in three municipalities showed that the actual collection rates in all initiatives remained extremely low (0.0014–0.1555%). The highest rankings were observed with recycling initiatives driven by superior collection rates and favorable economic returns. The hindrances to promoting sustainability are found to be due to policy inconsistency, ineffective leadership, and behavioral barriers. The practical collection rates should increase to at least 25% to be more sustainable in terms of economic, social, and environmental aspects compared to those without the recycling initiative. These findings, thus, provide specific targets for improving plastic waste separation and management strategies in all regions facing similar challenges.

Plastic waste is an environmental crisis that is becoming increasingly well-documented. The rapid expansion of plastic manufacturing and consumption has led to a harmful cycle of pollution and greenhouse gas emissions due to petroleum-based production and plastic waste disposal. Plastic production and disposal depend on the consumption behavior of people. This study aimed to examine the plastic consumption behavior in Thailand and its impact on climate change at the end-of-life stage. The general information, plastic consumption, and plastic waste management were collected via questionnaires for each product lifetime, including single-use, medium-use, and long-use plastics. Based on 567 questionnaires, the results showed that people consumed single-use plastic, e.g., plastic bag, food container, cutlery, straws, and bottles, at a rate of about nine pieces/household/day or three pieces/cap/day. The medium-use and long-use plastic were 10 pieces/household/month and 50 pieces/household/year, respectively. It should be remarked that population density, education, and number of household members affected plastic consumption behavior, especially for single-use plastic. Regarding the disposal of end-of-life plastics, Thai people, on average, contribute 0.15 kg CO₂eq/household/day to climate change. Many households have mismanaged waste by open dumping and open burning. Therefore, practicing proper waste management will help Thailand on the path to carbon neutrality in the future.

Optimal condition-based microemulsion is key to achieving great efficiency in oil removal. One useful empirical equation to predict an optimal condition is a hydrophilic–lipophilic deviation (HLD). However, the K constants of each surfactant should be the same to combine the HLD equations for the mixed surfactant. Recently, a normalized hydrophilic-lipophilic deviation (HLD_N) was presented to avoid this limitation. This work sought to determine the phase behaviors and predict the optimal salt concentrations, using HLD_N for the mixed surfactant. Sodium dihexyl sulfosuccinate (SDHS) as an anionic surfactant, and alcohol alkyl polyglycol ether (AAE(6EO4PO)) as a nonionic surfactant, were both investigated. Alkanes and diesel were used as a model oil. The results showed that AAE(6EO4PO) enforced both the hydrophilic and the hydrophobic characteristics. The Winsor Type I-III transition was influenced by the ethylene oxide, while the propylene oxide presence affected the Winsor Type III-II inversion. For the HLD_N equation, the average interaction term was 1.82 ± 0.86, which markedly showed a strong correlation with the fraction of nonionic surfactant in the mixed systems. The predicted optimal salt concentrations using HLD_N of SDHS-AAE(6EO4PO) in the diesel systems were close to the experimental results, with an error of <10% that is significantly beneficial due to the shorter time required for optimal determination.

The phase behavior of microemulsions stabilized by a binary anionic–nonionic surfactant mixture of sodium dihexyl sulfosuccinate (SDHS) and C12‐14 alcohol ethoxylate (C_{12 − 14}E_j) that contains an ethylene oxide (E_j) group number, j, of either 1, 5, or 9 was investigated for oil remediation. The oil–water interfacial tension (IFT) and optimal salinity of the microemulsion systems with different equivalent alkane carbon numbers (EACN) were examined. The anionic–nonionic surfactant ratio was found to play a pivotal role in the phase transition, IFT, and optimal salinity. The minimum IFT of mixed SDHS − C_{12 − 14}E_j systems were about three times lower than those of neat SDHS systems. A hydrophilic–lipophilic deviation (HLD) empirical model for the mixed anionic–nonionic surfactant system with the characteristic parameter was proposed, as represented in the excess free energy term . The results suggested that the mixed system of SDHS − C_{12 − 14}E₁ was more lipophilic, while SDHS − C_{12 − 14}E₉ was more hydrophilic than the ideal mixture (no excess free energy during the microemulsion formation), and the SDHS − C_{12 − 14}E₅ system was close to the ideal mixture. The findings from this work provide an understanding of how to formulate mixed anionic–nonionic microemulsion systems using the HLD model for oils that possess a wide range of EACN.