Bioplastics (i.e., bio-based and biodegradable plastics) are attracting attention as a sustainable alternative to conventional fossil-based plastics. However, their use in Japan, the fifth-highest per capita disposal of single-use plastics, has not become as widespread as planned by the Japanese government, and an increase in consumer awareness is necessary to promote the use of bioplastics and increase the demand for sustainable products. In addition, to promote social implementation, it is also necessary to understand the difference between bio-based and biodegradable plastics and use them correctly. Through an online questionnaire survey, this study found that the Japanese public's knowledge of bioplastics was low: there was a major difference between subjective and objective knowledge, but their perception of bioplastics was more positive than that of conventional plastics. However, they had little experience in using bioplastics. Therefore, we investigated whether providing information would promote the intent to use bioplastics. As a result, information provision is likely to be effective in increasing the willingness to use bioplastics in addition to promoting positive perceptions. The participants indicated a significantly greater willingness to pay a higher price for single-use plastics (such as a 500 ml bottle of water), but not for durable plastics (such as a three-color ballpoint pen).

Urban sanitation is a major challenge during the rapid urbanization being experienced by developing countries, as a low sewerage infrastructure capacity and irregular onsite wastewater treatment raise the risk of surface water contamination. The application of specific sewage markers to characterize contaminant sources is therefore essential for managing urban sanitation issues. In this study, we investigated the concentrations of eight sewage markers (acetaminophen, caffeine, carbamazepine, cotinine, sulfamethoxazole, sulfapyridine, atenolol, and acesulfame) in various water sources within urban area of the Galle City, Sri Lanka. The total concentration of the eight markers was in the order of hospital discharge > sewage treatment plant (STP) influent > surface drainage system. Among the eight selected markers, acetaminophen was dominant in hospital discharge (70.2–123.6 µg/L) while caffeine was the largest contributor to STP influent (16.2–68.7 µg/L) and surface drainage (0.95–21.73 µg/L). We then proposed and tested a set of criteria for evaluating the applicability of markers, including removal efficiency, concentration magnitude, excretion rate, and wastewater burden. The labile markers caffeine and acetaminophen were suitable for characterizing domestic gray and black wastewater, respectively. These results imply that the city’s drainage system receives both domestic graywater and human excretion, likely due to insufficient on-site sanitation systems. The conservative marker carbamazepine was useful for tracking hospital residues over long distances; these results imply that hospital wastewater treatment was not working properly, accounting for pharmaceutical residues reaching surface water via a hidden discharges connected to the drainage system.

In the area where household water use exceeds the capacity of the public water supply, rainwater is considered as one of the alternative water resources. Many researchers studied rainwater potential to cover the specific value of water demand in households having the average catchment area, so that the estimated potential expresses that of the average population. In this research, the possibility of rainwater use for toilets was investigated more realistically using the probability distributions of water demand and catchment area, and precipitation in case of Hanoi, Vietnam. Monte Carlo simulations were conducted throughout this simulation and the distribution of the possibility of rainwater use was estimated. The effect of household size and seasonal variations on the potential of rainwater utilization was also assessed. These results showed that our new approach exhibited that approximately 60% of the households failed to achieve the potential that was estimated using the conventional approach. Therefore, our new approach should be useful to understand the manner in which the potential of rainwater utilization differs in a given area, and it could be applied to other areas for consideration on the rainwater use potential and the suitable tank size when the distributions of variables and precipitation are clear.