Microplastic Pollution Prevention: The Need for Robust Policy Interventions to Close the Loopholes in Current Waste Management Practices.

Plastic materials that are less than 5 mm in size are defined as Microplastics (MPs). MPs that are intentionally produced are called primary MPs; however, the most abundant type in the environment consists of the remainder created by the fragmentation of large plastic debris through physical, chemical, and oxidative processes, which are called secondary MPs. Due to their abundance in the environment, poor degradability, toxicological properties, and negative impact on aquatic and terrestrial organisms, including humans, MP pollution has become a global environmental issue. Combatting MP pollution requires both remediation and preventive measures. Although remediation is a must, considering where the technology stands today, it may take long time to make it happen. Prevention, on the other hand, can be and should be done now. However, the effectiveness of preventive measures depends heavily on how well MP escape routes are researched and understood. In this research, we argue that such escape routes (rather, loopholes) exist not only due to mismanaged plastic waste, but also due to cracks in the current waste management systems. One known MP loophole is facilitated by wastewater treatment plants (WWTP). The inability of existing WWTP to retain finer MPs, which are finally released to water bodies together with the treated wastewater, along with the return of captured larger MPs back to landfills and their release into the environment through land applications, are a few examples. Organic waste composting and upcycling of waste incineration ash provide other MP escape pathways. In addition, it is important to understand that the plastics that are in current circulation (active use as well as idling) are responsible for producing MPs through regular wear and tear. Closing these loopholes may be best attempted through policy interventions.

Crop Residue Burning in India: Policy Challenges and Potential Solutions.

India, the second largest agro-based economy with year-round crop cultivation, generates a large amount of agricultural waste, including crop residues. In the absence of adequate sustainable management practices, approximately 92 seems a very small number of metric tons of crop waste is burned every year in India, causing excessive particulate matter emissions and air pollution. Crop residue burning has become a major environmental problem causing health issues as well as contributing to global warming. Composting, biochar production and mechanization are a few effective sustainable techniques that can help to curtail the issue while retaining the nutrients present in the crop residue in the soil. The government of India has attempted to curtail this problem, through numerous measures and campaigns designed to promote sustainable management methods such as converting crop residue into energy. However, the alarming rise of air pollution levels caused by crop residue burning in the city of Delhi and other northern areas in India observed in recent years, especially in and after the year of 2015, suggest that the issues is not yet under control. The solution to crop residue burning lies in the effective implementation of sustainable management practices with Government interventions and policies. This manuscript addresses the underlying technical as well as policy issues that has prevented India from achieving a long-lasting solution and also potential solutions that have been overlooked. However, effective implementation of these techniques also requires us to look at other socioeconomic aspects that had not been considered. This manuscript also discusses some of the policy considerations and functionality based on the analyses and current practices. The agricultural waste sector can benefit immensely from some of the examples from other waste sectors such as the municipal solid waste (MSW) and wastewater management where collection, segregation, recycling and disposal are institutionalized to secure an operational system. Active stakeholder involvement including education and empowerment of farmers along with technical solutions and product manufacturing can also assist tremendously. Even though the issue of crop residue burning touches many sectors, such as environment, agriculture, economy, social aspects, education, and energy, the past governmental efforts mainly revolved around agriculture and energy. This sectorial thinking is another barrier that needs to be broken. The government of India as well as governments of other developing countries can benefit from the emerging concept of nexus thinking in managing environmental resources. Nexus thinking promotes a higher-level integration and higher level of stakeholder involvement that goes beyond the disciplinary boundaries, providing a supporting platform to solve issues such as crop residue burning.

Organic Waste Buyback as a Viable Method to Enhance Sustainable Municipal Solid Waste Management in Developing Countries.

Many developing countries have inadequate Municipal Solid Waste (MSW) management systems due to lack of not only the awareness, technologies, finances, but also a proper governance that is able to enforce and monitor the regulations. Not all the solutions practiced by and in developed countries fit to the developing country contexts. The local conditions and limitations must always be taken into account when proposing waste management options for developing countries. The excessively high organic waste fraction in MSW and relatively inexpensive labor markets available in developing countries are two of the strengths that have not yet been utilized fully. This manuscript is an attempt to point out the benefits we receive from the above two strengths if we establish organic waste buyback programs. This can only become successful if we find solutions to: (1) collect source-separated organic waste, and then (2) find stable markets for the products made from organic waste. Compost or biogas could be the best bet developing countries can consider as products. However, there must be some policy interventions to support buyback programs at the waste collection stage as well as at the product marketing stage. Implementation of such organic waste buyback centers that can offer some incentives can indirectly motivate residents to do source separation. This will in turn also help promote more recycling, as any waste bin that has no organics in it is much easier for anyone (e.g., waste pickers) to look for other recyclables. Developing country settings such as the Green Container composting program in Cajicá, Colombia, and buyback centers in South Africa that are presented later in the manuscript are thought to be the places where the concept can be implemented with little effort. The environment, economy, and society are considered to be the three dimensions (or pillars) of sustainability. Interestingly, the organic waste buyback centers solution has positive implications on all three aspects of sustainability. Thus, it also supports the 2030 Agenda of the United Nations (UN), by making specific contributions to the Sustainable Development Goals (SDGs) such as zero hunger (SDG 2), affordable and clean energy (SDG 7), climate action (SDG 13), clean water and sanitation (SDG 6), and sustainable cities and communities (SDG 11).

Geotechnical characterization of mined clay from Appalachian Ohio: challenges and implications for the clay mining industry.

Clayey soil found in coal mines in Appalachian Ohio is often sold to landfills for constructing Recompacted Soil Liners (RSL) in landfills. Since clayey soils possess low hydraulic conductivity, the suitability of mined clay for RSL in Ohio is first assessed by determining its clay content. When soil samples are tested in a laboratory, the same engineering properties are typically expected for the soils originated from the same source, provided that the testing techniques applied are standard, but mined clay from Appalachian Ohio has shown drastic differences in particle size distribution depending on the sampling and/or laboratory processing methods. Sometimes more than a 10 percent decrease in the clay content is observed in the samples collected at the stockpiles, compared to those collected through reverse circulation drilling. This discrepancy poses a challenge to geotechnical engineers who work on the prequalification process of RSL material as it can result in misleading estimates of the hydraulic conductivity of the samples. This paper describes a laboratory investigation conducted on mined clay from Appalachian Ohio to determine how and why the standard sampling and/or processing methods can affect the grain-size distributions. The variation in the clay content was determined to be due to heavy concentrations of shale fragments in the clayey soils. It was also concluded that, in order to obtain reliable grain size distributions from the samples collected at a stockpile of mined clay, the material needs to be processed using a soil grinder. Otherwise, the samples should be collected through drilling.

Geotechnical properties of municipal solid waste at different phases of biodegradation.

This paper presents the results of laboratory investigation conducted to determine the variation of geotechnical properties of synthetic municipal solid waste (MSW) at different phases of degradation. Synthetic MSW samples were prepared based on the composition of MSW generated in the United States and were degraded in bioreactors with leachate recirculation. Degradation of the synthetic MSW was quantified based on the gas composition and organic content, and the samples exhumed from the bioreactor cells at different phases of degradation were tested for the geotechnical properties. Hydraulic conductivity, compressibility and shear strength of initial and degraded synthetic MSW were all determined at constant initial moisture content of 50% on wet weight basis. Hydraulic conductivity of synthetic MSW was reduced by two orders of magnitude due to degradation. Compression ratio was reduced from 0.34 for initial fresh waste to 0.15 for the mostly degraded waste. Direct shear tests showed that the fresh and degraded synthetic MSW exhibited continuous strength gain with increase in horizontal deformation, with the cohesion increased from 1 kPa for fresh MSW to 16-40 kPa for degraded MSW and the friction angle decreased from 35° for fresh MSW to 28° for degraded MSW. During the triaxial tests under CU condition, the total strength parameters, cohesion and friction angle, were found to vary from 21 to 57 kPa and 1° to 9°, respectively, while the effective strength parameters, cohesion and friction angle varied from 18 to 56 kPa and from 1° to 11°, respectively. Similar to direct shear test results, as the waste degrades an increase in cohesion and slight decrease in friction angle was observed. Decreased friction angle and increased cohesion with increased degradation is believed to be due to the highly cohesive nature of the synthetic MSW. Variation of synthetic MSW properties from this study also suggests that significant changes in geotechnical properties of MSW can occur due to enhanced degradation induced by leachate recirculation.

Compressibility and shear strength of municipal solid waste under short-term leachate recirculation operations.

This paper describes a comprehensive laboratory study performed to investigate the compressibility and shear strength properties of 1.5-year-old municipal solid waste (MSW) exhumed from a landfill cell where low amounts of leachate were recirculated. The study results are compared with results from a previous study on fresh MSW collected from the same landfill and data from previous studies with known MSW age to assess the variation in properties due to degradation. Laboratory testing was conducted on shredded landfilled and fresh MSW that consisted of similar particle-size distribution, with maximum particle size less than 40 mm and approximately 80% of the waste consisting of particles ranging from 10 to 20 mm. Standard Proctor, compressibility, direct shear, and triaxial consolidated undrained (CU) shear tests were conducted in general accordance with the American Society of Testing and Materials Standard Procedures. These tests were conducted with samples at an in-situ moisture content of 44% (dry weight basis) as well as elevated moisture contents of 60, 80 and 100% (dry weight basis). Standard Proctor compaction tests yielded a maximum dry density of 600 kg/m(3) at 77% optimum moisture content for landfilled MSW compared to the 420 kg/m(3) maximum dry density at 70% optimum moisture content for fresh MSW. Compression ratio values for landfilled MSW varied in a close range of 0.19-0.24 with a slight increasing trend with increase in moisture content; however, for fresh waste they were in the close range of 0.24-0.33 with no definitive correlation with moisture content. Based on direct shear tests, drained cohesion and friction angle were varied in the range of 12-64 kPa and 31-35 degrees for landfilled MSW and 31-64 kPa and 26-30 degrees for fresh MSW. Neither cohesion nor friction angle demonstrated any correlation with the moisture content. Based on triaxial CU tests, the average total strength parameters (TSP) were found to be 39 kPa and 12 degrees for landfilled MSW and 32 kPa and 12 degrees for fresh MSW, while effective strength parameters (ESP) were 34 kPa and 23 degrees for landfilled MSW and 32 kPa and 16 degrees for fresh MSW. This study was limited to small-scale laboratory testing using MSW samples with the specimen size relative to the maximum particle size in the range of 1.6 to 2.6; therefore, large-scale laboratory and field studies are recommended to systematically assess the influence of composition, particle size distribution and specimen size on the geotechnical properties of MSW.

Effects of gas and moisture on modeling of bioreactor landfill settlement.

This manuscript describes a model that can predict settlement at variable moisture and pressure conditions as encountered in bioreactor landfills. In this model mechanical compression of municipal solid waste (MSW) was accounted with the help of laboratory compression tests. To model biodegradation-induced settlement, biodegradation of MSW was assumed to obey a first order decay equation. Richards equation was used to model moisture transport in the waste mass and mass balance was used to link settlement with gas pressure. The functionality of the numerical formulation was examined using a hypothetical bioreactor landfill. Four scenarios were analyzed to demonstrate how the proposed model can be used to analyze the settlement behavior of bioreactor landfills as well as dry landfills. The model predicted higher strains when moisture and gas pressures were incorporated into the settlement process. Results also indicated that the prediction capability of a MSW settlement model can be improved by coupling the settlement mechanisms with the generation and dissipation of gas pressure and the moisture distribution. The model is also able to predict landfill density values, and the predicted MSW wet density after 25 years agreed reasonably with those reported in literature.

Geotechnical properties of fresh municipal solid waste at Orchard Hills Landfill, USA.

This paper presents the results of a laboratory investigation to determine the geotechnical properties of fresh municipal solid waste (MSW) collected from the working phase of Orchard Hills Landfill located in Davis Junction (Illinois, USA). Laboratory testing was conducted on shredded MSW to determine the compaction, hydraulic conductivity, compressibility, and shear strength properties at in-situ gravimetric moisture content of 44%. In addition, the effect of increased moisture content during leachate recirculation on compressibility and shear strength of MSW was also investigated by testing samples with variable gravimetric moisture contents ranging from 44% to 100%. Based on Standard Proctor tests, a maximum dry density of 420 kg/m(3) was observed at 70% optimum moisture content. The hydraulic conductivity varied in a wide range of 10(-8)-10(-4)m/s and decreased with increase in dry density. Compression ratio values varied in a close range of 0.24-0.33 with no specific trend with the increase in moisture content. Based on direct shear tests, drained cohesion varied from 31 to 64 kPa and the drained friction angle ranged from 26 to 30 degrees. Neither cohesion nor friction angle demonstrated any correlation with the moisture content, within the range of moisture contents tested. The consolidated undrained triaxial shear tests on saturated MSW showed the total strength parameters (c and phi) to be 32 kPa and 12 degrees, and the effective strength parameters (c' and phi') to be 38 kPa and 16 degrees. The angle of friction (phi) decreased and cohesion (c) value increased with the increase in strain. The effective cohesion (c') increased with increase in strain; however, the effective angle of friction (phi') decreased first and then increased with the increase in strain. Such strain-dependent shear strength properties should be properly accounted in the stability analysis of bioreactor landfills.