Display of Lignin Peroxidase on the Surface of Bacillus subtilis

Lignin peroxidase (LiP) has a good application prospect in lignin degradation, environmental treatment, straw feed, and other industries. However, its application is constrained by the high price and low stability of enzyme preparation. In this study, the Escherichia coli-Bacillus subtilis (E. coli-B. subtilis) shuttle expression vector pHS-cotG-lip was constructed and displayed on the surface of Bacillus subtilis spores. The analysis of enzymatic properties showed that the optimal catalytic temperature and pH of the immobilized LiP were 55 °C and 4.5, respectively. Compared with free LiP (42 °C and pH4.0), the optimal reaction temperature increased by 13 °C. After incubation at 70 °C for 1 h, its activity remained above 30%, while the free LiP completely lost its activity under the same conditions. Adding Mn2+, DL-lactic acid, and PEG-4000 increased the CotG-LiP enzyme activity to 313%, 146%, and 265%, respectively. The recyclability of spore display made the fusion protein CotG-LiP retain more than 50% enzyme activity after four cycles. The excellent recycling rate indicated that LiP displayed on the spore surface had a good application prospect in sewage treatment and other fields, and also provided a reference for the rapid and low-cost immobilized production of enzyme preparations.

Informal waste pickers in guayaquil: Recycling rates, environmental benefits, main barriers, and troubles

Systems for managing municipal solid waste are typically ineffective in developing nations because of governments' deficient financial and administrative frameworks, poor rules, and a lack of suitable infrastructure and human resources. The informal sector plays an essential role in these systems by reprocessing waste into secondary raw materials, reducing collection and disposal costs, and, most importantly, benefiting the environment by avoiding incineration and landfilling. However, their actual contributions remain unknown. The present paper aims to understand the role of informal waste pickers (IWPs) in the waste management system of Guayaquil City and their environmental impact through the calculations of the carbon footprint (CF) avoided due to their aid. The survey design gathered information on their personal profiles, types, and rates of collected recyclables, market conditions, their main barriers, and troubles regarding their formalization. The results of the survey demonstrate that waste picking is mostly a male-driven activity, the average daily mass collected per IWP is 13 kg, the most collected recyclable waste is polyethylene terephthalate, their average monthly income is $179, and the total avoided CF of the entire informal waste picking process is almost 14 thousand tons of CO2 eq yearly. Further, IWPs prefer to operate alone, and only 16% of them would join a cooperative, despite their numerous financial, logistical, and personal challenges.

The multidimensional effects of single-use and packaging plastic strategies on German household waste management

Single-use and packaging plastic (SUPP) strategies are intended to transform the linear make-use-dispose economy of SUPPs into a more circular, resource-efficient one. The aim of this study was to identify optimal SUPP management concepts from a circular-economy-perspective by assessing the effects of different SUPP strategies on household waste management. Data on the generation and management of SUPP-containing household waste in Germany in 2017 were compiled and a material flow model was established. Regulatory SUPP strategies were translated into scenarios (with effects on waste generation and waste composition) and implemented in the material flow model. The effects on material efficiency, waste generation and lower heating values were evaluated and trade-offs between these target dimensions were identified. In Germany in 2017, 32 kg per person and year of SUPP household waste were generated, of which 28 kg per person and year was packaging waste. From a material efficiency perspective, the combination of banning specific non-packaging SUPPs and optimizing source-separation leads to the maximum increase in final recycling rates of SUPPs in household waste, from 38% to 50%. However, in this scenario the amount of SUPP-containing household waste is hardly reduced as compared to the status quo. The trade-offs observed in different waste management target dimensions highlight the importance of understanding the systemic effects of SUPP strategies on waste management in order to identify optimal solutions from a circular-economy-perspective.

Material efficiency to measure the environmental performance of waste management systems: A case study on PET bottle recycling in Austria, Germany and Serbia

Material efficiency measures, such as recycling rates, are often used to set circular economy targets to achieve higher resource efficiency and lower environmental impact. The aim of this study was to identify material efficiency indicators suitable to reflect the environmental performance of waste and recycling systems using PET bottle waste management in three European countries with diverse waste management structures and recycling performance levels. Material flow analysis and life cycle assessment were performed to assess the material efficiency and environmental impacts of each system as a basis to analyze the relation between these two dimensions. PET bottle waste generation was 5.4 kg/person and year (pa) in Austria in 2013, 6.0 kg/pa in Germany in 2017 and 6.9 kg/pa in Serbia in 2015. Out of this waste flow 41%, 91%, and 11% were directed into PET recyclate in Austria, Germany and Serbia, respectively. For all systems, higher material efficiency translated into lower environmental impact and vice versa. However, linear regression analysis between different material efficiency indicators and environmental impacts showed that indicators targeted at actual recycling, specifically at closed loop, were better suited to reflect environmental performance than input-based indicators. Therefore, whenever data are available, output-based quality-related indicators should be used to measure the material efficiency of waste and resource systems because they correlate best with the goals of increasing resource efficiency and decreasing environmental impacts.

Technologies for chemical recycling of household plastics - A technical review and TRL assessment

Chemical recycling is considered an attractive technological pathway for reducing waste and greenhouse gas emissions, as well as promoting circular economy. In the EU, readiness to develop a full commercial plant is becoming increasingly important given the ambitious goal to recycle all plastics by 2030. Household packaging streams tend to be of lower quality and lower recycling performance compared to industrial and commercial waste streams, thus requiring particular attention. This paper assesses chemical recycling technologies available and identifies the most suitable for recycling of household plastic waste. We identify eight different technologies and compare them in terms of process temperature, sensitivity to feedstock contamination and level of polymer breakdown, three critical factors affecting the cost and attractiveness of a chemical process. In addition, we carry out a Technology Readiness Level (TRL) assessment for eight technologies based on the stage of their present development. The review is based on peer-reviewed scientific papers and information collected from technology developers and providers, as well as interviews with experts. Our analysis outlines advantages and disadvantages of technologies available for chemical plastic recycling and their TRL. The chemical recycling technologies with the highest TRL are pyrolysis, catalytic cracking and conventional gasification. However, the economic feasibility of these technologies is difficult to assess due to the low number of projects in operation and scarcity of data available for comparison. The results of this analysis provide timely information as policy makers and developers set targets for recycling, and contemplate investments on research and chemical plastic recovering plants.

'Wasteaware' benchmark indicators for integrated sustainable waste management in cities

This paper addresses a major problem in international solid waste management, which is twofold: a lack of data, and a lack of consistent data to allow comparison between cities. The paper presents an indicator set for integrated sustainable waste management (ISWM) in cities both North and South, to allow benchmarking of a city's performance, comparing cities and monitoring developments over time. It builds on pioneering work for UN-Habitat's solid waste management in the World's cities. The comprehensive analytical framework of a city's solid waste management system is divided into two overlapping 'triangles' - one comprising the three physical components, i.e. collection, recycling, and disposal, and the other comprising three governance aspects, i.e. inclusivity; financial sustainability; and sound institutions and proactive policies. The indicator set includes essential quantitative indicators as well as qualitative composite indicators. This updated and revised 'Wasteaware' set of ISWM benchmark indicators is the cumulative result of testing various prototypes in more than 50 cities around the world. This experience confirms the utility of indicators in allowing comprehensive performance measurement and comparison of both 'hard' physical components and 'soft' governance aspects; and in prioritising 'next steps' in developing a city's solid waste management system, by identifying both local strengths that can be built on and weak points to be addressed. The Wasteaware ISWM indicators are applicable to a broad range of cities with very different levels of income and solid waste management practices. Their wide application as a standard methodology will help to fill the historical data gap.