Effective waste management with emphasis on circular economy

Waste management optimization with NLP modeling and waste-to-energy in a circular economy

This work presents a methodology integrating Non-Linear Programming (NLP) for multi-objective and multi-period optimization, addressing sustainable waste management and energy conversion challenges. It integrates waste-to-energy (WtE) technologies such as Anaerobic Digestion (AD), Incineration (Inc), Gasification (Gsf), and Pyrolysis (Py), and considers thermochemical, technical, economic, and environmental considerations through rigorous non-linear functions. Using Mexico City as a case study, the model develops waste management strategies that balance environmental and economic aims, considering social impacts. A trade-off solution is proposed to address the conflict between objectives. The economical optimal solution generates 1.79M$ with 954 tons of CO2 emissions while the environmental one generates 0.91M$ and reduces emissions by 54%, where 40% is due to gasification technology. Moreover, the environmentally optimal solution, with incineration and gasification generates 9500 MWh/day and 5960 MWh/day, respectively, demonstrates the capacity of the model to support sustainable energy strategies. Finally, this work presents an adaptable framework for sustainable waste management decision-making.

Pine needle gasification-based electricity production: Understanding the effect of supply chain

Pine needles (pine tree leaves), found abundantly across continents such as North America, Asia, Europe, South America, Africa, and parts of the Southern Hemisphere, are a significant global concern due to their high susceptibility to catching fire, especially in dry and hot climates. The same issue persists in the Uttarakhand state of India, which boasts ample pine forests, yielding a substantial 1.67 × 109 kg of pine needles annually. In the present study, the annual potential emissions from forest fires in Uttarakhand were estimated to be 58.37 × 109 kg of CO2 equivalent. Therefore, the present research aims to unlock pine needles' potential via gasification for green electricity and biochar production, offering an alternative to coal-based plants while reducing forest fire frequencies. Nevertheless, obstacles hindering pine needle gasification include an unsteady supply chain, limited collection windows (100 days), and plant expenses, including transportation and operational costs. The primary focus of the research is to design and assess the performance of a gasification-based supply chain for pine needles in the Almora District of Uttarakhand. Ten plant capacity scenarios were considered, ranging from 25 to 250 kW. The study incorporated critical factors, encompassing diverse losses within the supply chain, selecting potential plant sites, minimizing transportation distance, and evaluating the supply chain's economic and environmental performance. The economic analysis revealed that the 250-kW plant scenario exhibited a minimum discounted payback period (DPP) of 3.93 years, alongside an internal rate of return (IRR) of 19% and a net present value (NPV) of 653.32 million INR without government subsidies. With subsidies included, the DPP decreased to 1.30 years, improving the IRR to 69% with an NPV of 916.17 million INR. The emission analysis indicated that gasification plant capacity scenarios could potentially reduce 44.63 × 106 to 46.16 × 106 kg of CO2 equivalent emissions annually compared to grid electricity while meeting nearly 5.5% of the electricity demand of Almora district. The present study aligns with SDG-7 (Affordable and Clean Energy), SDG-13 (Climate Action), SDG-9 (Industry, Innovation, and Infrastructure), SDG-11 (Sustainable Cities and Communities), SDG-3 (Good Health and Well-being), and SDG-15 (Life on Land).

The transition journey of EU vs. NON-EU countries for waste management

This study aims to identify macroeconomic indicators that can be used as predictors of waste management on the European continent. The study was conducted taking in account the intensification of urbanizations, the increase of standard of leaving that fuels to consumerism phenomenon, and imposed challenges for waste management. The research focuses on the interval from 2010 to 2020 for 37 European countries grouped according to EU15/EU28/non-EU and EU/non-EU members. As macroeconomic indicators, human development index (HDI), GDP/capita. GNI/capita, general government expenditure with environment protection, people at risk of poverty or social exclusion, population by educational attainment level, sex, and age (%)-less than primary, primary and lower secondary education (levels 0-2) were used. A multilinear regression model with collinearity diagnosis was applied to find out the direction and intensity of the contribution of independent variables and to hierarchy the predictors of waste management.. For multiple comparison between and inside of each grouping of countries, statistical inference methods were used: one-way ANOVA with Bonferroni post hoc test multiple comparisons and independent samples Kruskal-Wallis test with Dunn's post hoc test. The main conclusions of the study are that EU15 countries have the highest average values for most indicators of waste management, comparative with EU28 and with non-EU countries, followed by a group of EU28 countries. For indicators of recycling rate of packaging waste by type of packaging-metallic and recycling rate of e-waste, the non-EU countries have the highest values of mean compared with the EU15 and EU28 groups of countries. This can be explained by the high level of development of the some non-euro area countries (Iceland, Norway, Switzerland, Liechtenstein) that have intense concerns about waste recycling and have the necessary financial strength to carry out complex environmental protection programs.

Technology adoption path of construction and demolition waste recycling under governmental subsidy: a theoretical model

To achieve sustainable development, waste recycling is regarded as an ideal method to dispose of construction and demolition (C&D) waste. The economy is seen as the priority factor influencing recycling technology adoption. Hence, the subsidy is generally used to cross the economic barrier. To illustrate the recycling technology adoption path under governmental subsidy, this paper constructs a non-cooperative game model to investigate the impact of governmental subsidy on the C&D waste recycling technology adoption. By taking adoption profit, opportunity cost, and initial adoption marginal cost into consideration, the best time to adopt recycling technology and adoption behavior is discussed in detail in four scenarios. Results show that the governmental subsidy has a positive impact on C&D waste recycling technology adoption, and the subsidy could advance the adoption time of recyclers. If the subsidy proportion can reach 70% of the cost, recyclers will adopt recycling technology at the initial time. The results could contribute to a deeper understanding of C&D waste management by promoting the development of C&D waste recycling projects and also provide references to governments.

An integrated biorefinery approach for the valorization of water hyacinth towards circular bioeconomy: a review

Water hyacinth (WH) has become a considerable concern for people across the globe due to its environmental and socio-economic hazards. Researchers are still trying to control this aquatic weed effectively without other environmental or economic losses. Research on WH focuses on converting this omnipresent excessive biomass into value-added products. The potential use of WH for phytoremediation and utilizing waste biomass in various industries, including agriculture, pharmaceuticals, and bioenergy, has piqued interest. The use of waste WH biomass as a feedstock for producing bioenergy and value-added chemicals has emerged as an eco-friendly step towards the circular economy concept. Here, we have discussed the extraction of bio-actives and cellulose as primary bioproducts, followed by a detailed discussion on different biomass conversion routes to obtain secondary bioproducts. The suggested multi-objective approach will lead to cost-effective and efficient utilization of waste WH biomass. Additionally, the present review includes a discussion of the SWOT analysis for WH biomass and the scope for future studies. An integrated biorefinery scheme is proposed for the holistic utilization of this feedstock in a cascading manner to promote the sustainable and zero-waste circular bio-economy concept.