3R strategies for the establishment of an international sound material-cycle society

Focusing on the promotion of the “3Rs” – reduce, reuse, and recycle – the authors summarize the policy that Japan has evolved in waste management and recycling policy over the years. To realize an international sound material-cycle society (SMS), the 3R approaches should first be implemented in each individual country. After each country has established an SMS to the best of its ability, contribution toward reducing the environmental load internationally, especially across all of East Asia, will be achieved by having waste and recyclable resources that cannot be handled in one country effectively used or processed in other countries. The current situation of international resource circulation is described and a concept of SMS at an international level is proposed. The views expressed herein are those of the authors and are not necessarily the official views of the organizations with which the authors are affiliated.     

Enzymatic Degradation of Poly(l-Lactic Acid): Effects of UV Irradiation

Amorphous and crystallized poly(l-lactic acid) (PLLA-A and PLLA-C, respectively) films were prepared, and the proteinase K-catalyzed enzymatic degradation of UV-irradiated and non-irradiated PLLA-A and PLLA-C films was investigated for periods up to 10 h (PLLA-A) and 60 h (PLLA-C). The molecular weights of both the PLLA-A and PLLA-C films can be manipulated by altering the UV irradiation time. The enzymatic weight loss values of the UV-irradiated PLLA films were higher than or similar to those of the non-irradiated PLLA film, when compared with the specimens of same crystallinities. UV irradiation is expected to cause the PLLA films to undergo chain cleavage (a decrease in molecular weight) and the formation of C=C double bonds. It seems that the acceleration effects from decreased molecular weight on enzymatic degradation were higher than or balanced with the disturbance effects caused by the formation of C=C double bonds. After enzymatic degradation, a fibrous structure appeared on the spherulites of the UV-irradiated PLLA-C film. This structure may have arisen from chains containing or neighboring on the C=C double bonds, which were enzymatically undegraded and assembled on the film surface during enzymatic degradation. The results of this study strongly suggest that UV irradiation will significantly affect the biodegradation behavior of PLLA materials in the environment.     

Hydrolysis of di-n-butyl phthalate, butylbenzyl phthalate and di(2-ethylhexyl) phthalate in human liver microsomes

Diester phthalates are industrial chemicals used primarily as plasticizers to import flexibility to polyvinylchloride plastics. In this study, we examined the hydrolysis of di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBzP) and di(2-ethylhexyl) phthalate (DEHP) in human liver microsomes. These diester phthalates were hydrolyzed to monoester phthalates (mono-n-butyl phthalate (MBP) from DBP, mono-n-butyl phthalate (MBP) and monobenzyl phthalate (MBzP) from BBzP, and mono(2-ethylhexyl) phthalate (MEHP)) by human liver microsomes. DBP, BBzP and DEHP hydrolysis showed sigmoidal kinetics in V-[S] plots, and the Hill coefficient (n) ranged 1.37-1.96. The S₅₀, V_max and CL_max values for DBP hydrolysis to MBP were 99.7 μM, 17.2 nmol min⁻¹ mg⁻¹ protein and 85.6 μL min⁻¹ mg⁻¹ protein, respectively. In BBzP hydrolysis, the values of S₅₀ (71.7 μM), V_max (13.0 nmol min⁻¹ mg⁻¹ protein) and CL_max (91.3 μL min⁻¹ mg⁻¹ protein) for MBzP formation were comparable to those of DBP hydrolysis. Although the S₅₀ value for MBP formation was comparable to that of MBzP formation, the V_max and CL_max values were markedly lower (<3%) than those for MBzP formation. The S₅₀, V_max and CL_max values for DEHP hydrolysis were 8.40 μM, 0.43 nmol min⁻¹ mg⁻¹ protein and 27.5 μL min⁻¹ mg⁻¹ protein, respectively. The S₅₀ value was about 10% of DBP and BBzP hydrolysis, and the V_max value was also markedly lower (<3%) than those for DBP hydrolysis and MBzP formation for BBzP hydrolysis. The ranking order of CL_max values for monoester phthalate formation in DBP, BBzP and DEHP hydrolysis was BBzP to MBzP ? DBP to MBP > DEHP to MEHP > BBzP to MBP. These findings suggest that the hydrolysis activities of diester phthalates by human liver microsomes depend on the chemical structure, and that the metabolism profile may relate to diester phthalate toxicities, such as hormone disruption and reproductive effects.     

An international comparative study of end-of-life vehicle (ELV) recycling systems

End-of-life vehicles (ELV) have become a global concern as automobiles have become popular worldwide. An international workshop was held to gather data and to discuss 3R policies and ELV recycling systems, their background and present situation, outcomes of related policies and programs, the framework of recycling and waste management, and case studies on related topics in several countries and regions, as well as the essential points of the comparison. Legislative ELV recycling systems are established in the EU, Japan, Korea, and China, while in the US, ELV recycling is managed under existing laws on environmental protection. Since automobile shredding residue (ASR) has a high calorific value and ash content, and includes heavy metals as well as a mass of unclassified fine particles, recycling ASR is considered highly difficult. Countries with a legislative ELV system commonly set a target for recovery rates, with many aiming for more than 95 % recovery. In order to reach this target, higher efficiency in ASR recovery is needed, in addition to material recycling of collectable components and metals. Environmentally friendly design was considered necessary at the planning and manufacturing stages, and the development of recycling systems and techniques in line with these changes are required for sound ELV management.     

Current results and future perspectives for Japanese recycling of home electrical appliances

The Japanese system of recycling home electrical appliances has several unique aspects, including (1) a limited number of target appliances, (2) a recycling fee system that requires consumers to pay a recycling fee at the time of disposal, and (3) a direct recycling obligation for manufacturers, who have a physical, rather than a financial, responsibility for their end-of-life products. We studied data from 2001 to 2007 and found that the amount of four specified home electrical appliances and their materials that was recycled increased from about 319,249 tonnes in 2001 to about 447,262 tonnes—or 3.5 kg per inhabitant—in 2006. Recycling yield and development of recycling technologies have also improved. New recycling technologies have enabled a higher rate of material recycling of plastics (i.e., a closed-loop recycling). Improved eco-design, such as design for easier disassembly, has been promoted, and the higher quality of discarded appliances has enhanced the reuse market. Hazardous substances and fluorocarbons are being well managed. Problems with the recycling system include inelastic recycling fees, illegal dumping, illegal transfer by retailers, and the limited number of target appliances. Recycling fees could be reduced; this move might reduce the incidence of illegal dumping, as would engage stakeholders in collaborative efforts against illegal dumping. Illegal transfers could be reduced by improved traceability for retailers. Products such as liquid crystal displays, plasma display panels and clothes dryers have become increasingly common and should be also be targeted for recycling.     

Hygroscopicity of particles generated from photooxidation of α-pinene under different oxidation conditions in the presence of sulfate seed aerosols

Smog chamber experiments were conducted to investigate the hygroscopicity of particles generated from photooxidation of α-pinene/NOx with different sulfate seed aerosols or oxidation conditions. Hygroscopicity of particles was measured by a tandem differential mobility analyzer （TDMA） in terms of hygroscopic growth factor （Gf）, with a relative humidity of 85%. With sulfate seed aerosols present, Gf of the aerosols decreased very fast before notable secondary organic aerosols （SOA） formation was observed, indicating a heterogeneous process between inorganic seeds and organic products might take place as soon as oxidation begins, rather than only happening after gas-aerosol partition of organic products starts. The final SOA-coated sulfate particles had similar or lower Gf than seed-free SOA. The hygroscopicity of the final particles was not dependent on the thickness but on the hygroscopicity properties of the SOA, which were influenced by the initial sulfate seed particles. In the two designed aging processes, Gf of the particles increased more significantly with introduction of OH radical than with ozone. However, the hygroscopicity of SOA was very low even after a long time of aging, implying that either SOA aging in the chamber was very slow or the Gf of SOA did not change significantly in aging. Using an aerosol composition speciation monitor （ACSM） and matrix factorization （PMF） method, two factors for the components of SOA were identified, but the correlation between SOA hygroscopicity and the proportion of the more highly oxidized factor could be either positive or negative depending on the speciation of seed aerosols present.     

Waste prevention for sustainable resource and waste management

Although the 2Rs (reduce and reuse) are considered high-priority approaches, there has not been enough quantitative research on effective 2R management. The purpose of this paper is to provide information obtained through the International Workshop in Kyoto, Japan, on 11–13 November 2015, which included invited experts and researchers in several countries who were in charge of 3R policies, and an additional review of 245 previous studies. It was found that, regarding policy development, the decoupling between environmental pressures and economy growth was recognized as an essential step towards a sustainable society. 3R and resource management policies, including waste prevention, will play a crucial role. Approaches using material/substance flow analyses have become sophisticated enough to describe the fate of resources and/or hazardous substances based on human activity and the environment, including the final sink. Life-cycle assessment has also been developed to evaluate waste prevention activities. Regarding target products for waste prevention, food loss is one of the waste fractions with the highest priority because its countermeasures have significant upstream and downstream effects. Persistent organic pollutants and hazardous compounds should also be taken into account in the situation where recycling activities are globally widespread for the promotion of a material-cycling society.     

Effects of two transition metal sulfate salts on secondary organic aerosol formation in toluene/NO x photooxidation

Aerosol phase reactions play a very important role on secondary organic aerosol (SOA) formation, and metal-containing aerosols are important components in the atmosphere. In this study, we tested the effects of two transition metal sulfate salts, manganese sulfate (MnSO₄) and zinc sulfate (ZnSO₄), on the photochemical reactions of a toluene/NO _x photooxidation system in a 2 m³ smog chamber. By comparing photochemical reaction products of experiments with and without transition metal sulfate seed aerosols, we evaluated the effects of transition metal sulfate seed aerosols on toluene consumption, NO _x conversion and the formation of ozone and SOA. MnSO₄ and ZnSO₄ seed aerosols were found to have similar effects on photochemical reactions, both enhance the SOA production, while showing negligible effects on the gas phase compounds. These observations are consistent when varying metal sulfate aerosol concentrations. This is attributed to the catalytic effects of MnSO₄ and ZnSO₄ seed aerosols which may enhance the formation of condensable semivolatile compounds. Their subsequent partitioning into the aerosol phase leads to the observed SOA formation enhancement.