Discrete-Point Analysis of the Energy Demand of Primary versus Secondary Metal Production

Zinc Evaporation from Brass Scraps in the Atmosphere of Inert Gas

A description of the process of metal evaporation from liquid alloys at an atmospheric pressure has a practical value for both the smelting and remelting of their scraps. The quantities of volatile components that are eliminated in these processes depend on many factors of which the type of melting device, the method and conditions of the process performance, the alloy composition and the kind of applied atmosphere are of the greatest importance. In this paper, the results of the research on zinc evaporation from brass scraps containing 10.53 wt% Zn are presented. The experiments were conducted using the thermogravimetric method at 1080 ÷ 1240 °C in a helium atmosphere. In the research, the levels of zinc removal from copper ranged between 82% and 99%. The values of the overall mass transfer coefficient for zinc k_Zn, determined based on the experimental data, ranged from 4.74 to 8.46 × 10^-5 ms^-1. The kinetic analysis showed that the rate of the analysed process was determined by mass transfer in the gas phase.

Assessing China's potential for reducing primary copper demand and associated environmental impacts in the context of energy transition and "Zero waste" policies

To conserve resources and enhance the environmental performance, China has launched the "Zero waste" concept, focused on reutilization of solid waste and recovery of materials, including copper. Although several studies have assessed the copper demand and recycling, there is a lack of understanding on how different waste management options would potentially reduce primary copper demand and associated environmental impacts in China in the context of energy transition. This study addresses this gap in view of a transition to low-carbon energy system and the optimization of copper waste management combining MFA and LCA approaches. Six types of waste streams (C&DW, ELV, WEEE, IEW, MSW, ICW) are investigated in relation to various "Zero waste" strategies including reduction, reuse (repair, remanufacturing or refurbishment), recycling and transition from informal to formal waste management. Under present Chinese policies, reuse and recycling of copper containing products will lead to a somewhat lower dependency on primary copper in 2100 (11187Gg), as well as lower total GHG emissions (64869 Gg CO2-eq.) and cumulative energy demand (1.18x10^12 MJ). Maximizing such "Zero waste" options may lead to a further reduction, resulting in 65% potential reduction of primary copper demand, around 55% potential reduction of total GHG emissions and total cumulative energy demand in 2100. Several policy actions are proposed to provide insights into future waste management in China as well as some of the challenges involved.

Improved Copper Circularity as a Result of Increased Material Efficiency in the U.S. Housing Stock

Material efficiency (ME) can support rapid climate change mitigation and circular economy. Here, we comprehensively assess the circularity of ME strategies for copper use in the U.S. housing services (including residential buildings and major household appliances) by integrating use-phase material and energy demand. Although the ME strategies of more intensive floor space use and extended lifetime of appliances and buildings reduce the primary copper demand, employing these strategies increases the commonly neglected use-phase share of total copper requirements during the century from 23-28 to 22-42%. Use-phase copper requirements for home improvements have remained larger than the demand gap (copper demand minus scrap availability) for much of the century, limiting copper circularity in the U.S. housing services. Further, use-phase energy consumption can negate the benefits of ME strategies. For instance, the lifetime extension of lower-efficiency refrigerators increases the copper use and net environmental impact by increased electricity use despite reductions from less production. This suggests a need for more attention to the use phase when assessing circularity, especially for products that are material and energy intensive during use. To avoid burden shifting, policymakers should consider the entire life cycle of products supporting services when pursuing circular economy goals.

The Resource‐Energy Nexus as a Key Factor for Circular Economy

The extraction of raw materials is associated with energy input and CO2 emissions. What is obvious for extraction from mining, however, also applies to recycling. Mostly, recycling is preferred for reasons of climate protection or because of the geological scarcity of raw materials, which is controversially discussed. While in mining, the declining ore grade is a driver for the energy demand, in case of recycling it is the dissipation of materials into products or waste. As concentration decreases, the effort required also increases disproportionately. The “closing the loop” metaphor of Circular Economy is therefore inappropriate in its stricter meaning. It is rather about optimizing the overall system and finding the optimal recycling rate. However, first, it must be clarified what the political goals for Circular Economy are.