The impact of innovative technologies in construction activities on concrete debris recycling in China : a system dynamics-based analysis

As construction activities become more intensive in developing countries, increasing improperly managed construction and demolition waste (CDW) brings serious environmental impacts. Recycling is a beneficial way to dispose of CDW that reduces environmental impact and brings economic benefits, especially for concrete. China is the country that generates the most CDW in the world, but its domestic recycling rate is much lower than that of developed countries. While the efficient technologies in developed regions have helped them to achieve a well-established recycling industry, whether these innovative technologies can be used to improve the concrete debris recycling targets in developing regions is unclear. This study examines whether innovations currently widely used in construction activities and materials can have a positive effect on the recycling of End-of-Life concrete materials in China. Results from modeling system dynamics imply that the introduction of innovative technologies in the recycling system of concrete debris can probably contribute to CO2 reduction (3.6% reduction) and economic benefits (2.6 times increase, but mainly from landfill charges and fines) from 2022 to 2030. Prefabrication and 3D printing significantly impact recycled concrete production and CDW recycling, and they are recommended as a priority for promotion. In contrast, carbonation is not suggested for application due to its minor role. Nevertheless, since the market share of innovative technologies and the basic CDW recycling rates are currently low in China, fluctuations in their usage are hardly to have a substantial positive impact. We suggest that financial support from the government is needed for upcycling by recyclers and technology providers to improve the base recycling rate in order for innovative technologies to make an effective contribution to the sustainable construction industry, creating a win–win situation for both the economy and the environment of the recycling system

Characterizing the generation and flows of construction and demolition waste in China

Abstract only. Associated with the continuing increase of construction activities such as infrastructure projects, commercial buildings, and housing programs, China has been experiencing a rapid increase of construction and demolition (C&D) waste. Till now, the generation and flows of China’s C&D waste has not been well understood. This paper aims to provide an explicit analysis of this based on a weight-per-construction- area method. Our results show that approximately 2.36 billion tonnes of C&D waste were generated in China annually during the period of 2003–2013, of which demolition waste and construction waste contributed to 97% and 3%, respectively, in 2013. East China contributed over half of the total C&D waste in China due to their rapid economic development and expansion of cities, followed by Middle China (21%) and South China (11%). Potential economic values from the recycling of C&D waste were found to vary from 201 billion (the worst scenario, i.e., the current practice of C&D waste management) to 401 billion US dollars in 2013 (the most optimistic scenario, i.e., C&D waste is assumed to be well recycled); and the landfill space demands were estimated to range from 7504 millionm3 (the worst scenario) to 706 mil- lionm3 (the most optimistic scenario) accordingly. Consequently, increasing the recycling rate and reducing landfill rate of C&D waste could not only improve the potential recycling economic values, but also dramatically reduce land use and potential environmental impacts

Risk associated with microplastics in urban aquatic environments : A critical review

The presence of microplastics (MPs) has been recognized as a significant environmental threat due to adverse effects spanning from molecular level, organism health, ecosystem services to human health and well-being. MPs are complex environmental contaminants as they bind to a wide range of other contaminants. MPs associated contaminants include toxic chemical substances that are used as additives during the plastic manufacturing process and adsorbed contaminants that co-exist with MPs in aquatic environments. With the transfer between the water column and sediments, and the migration within aquatic systems, such contaminants associated MPs potentially pose high risk to aquatic systems. However, only limited research has been undertaken currently to link the environmental risk associated with MPs occurrence and movement behaviour in aquatic systems. Given the significant environmental risk and current knowledge gaps, this review focuses on the role played by the abundance of different MP species in water and sediment compartments as well as provides the context for assessing and quantifying the multiple risks associated with the occurrence and movement behaviour of different MP types. Based on the review of past literature, it is found that the physicochemical properties of MPs influence the release/sorption of other contaminants and current MPs transport modelling studies have primarily focused on virgin plastics rather than aged plastics. Additionally, risk assessment of contaminants-associated MPs needs significantly more research. This paper consolidates the current state-of-the art knowledge on the source to sink movement behaviour of MPs and methodologies for assessing the risk of different MP species. Moreover, knowledge gaps and emerging trends in the field are also identified for future research endeavours.</p

Toxicity trends in E-Waste: A comparative analysis of metals in discarded mobile phones.

Mobile phones and various electronic products contribute to the world's fastest-growing category of hazardous waste with international repercussions. We investigated the trends in potential human health impacts and ecotoxicity of waste mobile phones through quantitative life cycle impact assessment (LCIA) methods and regulatory total threshold limit concentrations. A market-dominant sample of waste basic phones and smartphones manufactured between 2001 and 2015, were analyzed for toxicity trends based on 19 chemicals. The results of the LCIA (using USEtox model) show an increase in the relative mass of toxic materials over the 15-year period. We found no significant changes in the use of toxic components in basic phones, whereas smartphones contained a statistically significant increase in the content of toxic materials from 2006 to 2015. Nickel contributed the largest risk for carcinogens in mobile phones, but the contributions of lead and beryllium were also notable. Silver, zinc and copper contents were associated with non-cancer health risks. Copper components at 45,818-77,938 PAF m3/kg dominated ecotoxicity risks in mobile phones. Overall, these results highlight the increasing importance of monitoring trends in materials use for electronic product manufacturing and electronic-waste management processes that should prevent human and environmental exposures to toxic components

Toxicity trends in E-Waste: A comparative analysis of metals in discarded mobile phones.

Mobile phones and various electronic products contribute to the world's fastest-growing category of hazardous waste with international repercussions. We investigated the trends in potential human health impacts and ecotoxicity of waste mobile phones through quantitative life cycle impact assessment (LCIA) methods and regulatory total threshold limit concentrations. A market-dominant sample of waste basic phones and smartphones manufactured between 2001 and 2015, were analyzed for toxicity trends based on 19 chemicals. The results of the LCIA (using USEtox model) show an increase in the relative mass of toxic materials over the 15-year period. We found no significant changes in the use of toxic components in basic phones, whereas smartphones contained a statistically significant increase in the content of toxic materials from 2006 to 2015. Nickel contributed the largest risk for carcinogens in mobile phones, but the contributions of lead and beryllium were also notable. Silver, zinc and copper contents were associated with non-cancer health risks. Copper components at 45,818-77,938 PAF m3/kg dominated ecotoxicity risks in mobile phones. Overall, these results highlight the increasing importance of monitoring trends in materials use for electronic product manufacturing and electronic-waste management processes that should prevent human and environmental exposures to toxic components

The dynamics of carbon accumulation in Eucalyptus and Acacia plantations in the Pearl River delta region

<a>Abstract </a> <p><a></a><a><b><i>Key message </i></b></a><b>Plantation</b><b> type and age strongly influence the quantity of carbon stored in forest ecosystems. </b><b>The marked increase in total ecosystem carbon stock achieved over time by the <i>Eucalyptus</i> and <i>Acacia</i> plantations has confirmed that the afforestation of degraded soils can contribute positively to carbon sequestration.</b><b> </b><b></b></p> <p>·<b><i>Context</i></b> Reforestation has been widely conducted to restore and protect the eroded red soil in south China in recent decades. The question as to whether the<a></a><a> content of soil organic carbon (SOC) can be boosted by establishing </a>plantations of fast-growing tree species remains unresolved. </p> <p><b><i>·</i></b><b><i>Aim </i></b>We addressed whether the afforestation of degraded soils can contribute positively to carbon sequestration, and whether the accumulation of SOC is more effective under a nitrogen fixing species such as <i>Acacia</i> than under <i>Eucalyptus</i>.</p> <p>·<b><i>Methods</i></b> Here, a study was undertaken to measure the quantity of total ecosystem carbon (TEC) accumulated by plantations of both <i>Eucalyptus </i>and<i> Acacia</i> spp. in the Pearl River Delta region of southern China. </p> <p>·<b><i>Results </i></b>The quantity of TEC increased significantly with stand age in both plantation types (<i>P</i> < 0.05). The largest single component of TEC was SOC, with stand age having a considerable effect on both SOC and overall biomass. The accumulation of SOC in the top 100 cm of the soil profile was higher under <i>Acacia</i> than under <i>Eucalyptus</i> (<i>P </i>< 0.05). <b></b></p> <p>·<b><i>Conclusion </i></b>In terms of carbon sequestration, the afforestation of <i>Eucalyptus </i>and<i> Acacia</i> represent an effective forest management practice. The accumulation of SOC is more effective under <i>Acacia</i> than under <i>Eucalyptus</i><b></b></p

Differences of methods to quantify construction and demolition waste for less-developed but fast-growing countries: China as a case study

As China and other developing countries continue to urbanize over the next decades, construction and demolition waste (CDW) management has been becoming a significant challenge for urban sustainability in terms of the environment, economy, and safety. However, accurate estimations or statistics of CDW generation are absent from the official national report in spite of their importance to devise sensible interventions to tackle CDW-related problems. This paper examines and compares the applications of three prevailing methods for estimating CDW, including the weight-per-construction-area method (WAM), buildings’ life span-based method, and weight-per-capita method. Specifically, China has been chosen as the case study. This study implies that the weight-per-construction-area method is more appropriate because of the data availability and accuracy at a city or national level. The results of WAM indicate that a total of 4.1 billion metric tons (Bt) of CDW were generated in China in 2016, mainly from demolition waste (85%). Taking the changes of buildings’ life span into account, a projection analysis reveals that the cumulative CDW generation will be 50 Bt between 2017 and 2040 in China (equal to approximately 38 years cumulative generation of global municipal solid waste). Overall, the findings provide some methodological options for scholars, practitioners, and decision-makers to more accurately estimate the amount of the CDW and to develop a more environmentally sound management strategy.status: publishe

Construction debris becomes growing concern of growing cities

How can growing cities be expanded in a sustainable way? Huge waste generation has become a major challenge in many growing cities, particularly in developing countries. China's annual C&D waste generation was and estimated 2.4 billion tonnes in the past decade, which is 15 times more than municipal solid waste generation. India has less C&D waste generation than China, yet still is as high as 530 million tons in 2013. However, only around 5% of C&D waste was reused in these countries and the rest largely ends up in dumping sites for disposal. As China and other developing countries continue to urbanize in the next decades, C&D waste management will continue to be a significant challenge for urban sustainability in terms of the environment, economics, and safety. We therefore critically reviewed the C&D waste generation, management, and challenges faced by the fast expanding cities in China and other developing countries. We also compared the current characteristics of key C&D waste systems in developing and developed countries. Recommendations for swift action are made for policy makers in growing cities