Sahil Sahni

Remanufacturing and energy savings.

Remanufactured products that can substitute for new products are generally claimed to save energy. These claims are made from studies that look mainly at the differences in materials production and manufacturing. However, when the use phase is included, the situation can change radically. In this Article, 25 case studies for eight different product categories were studied, including: (1) furniture, (2) clothing, (3) computers, (4) electric motors, (5) tires, (6) appliances, (7) engines, and (8) toner cartridges. For most of these products, the use phase energy dominates that for materials production and manufacturing combined. As a result, small changes in use phase efficiency can overwhelm the claimed savings from materials production and manufacturing. These use phase energy changes are primarily due to efficiency improvements in new products, and efficiency degradation in remanufactured products. For those products with no, or an unchanging, use phase energy requirement, remanufacturing can save energy. For the 25 cases, we found that 8 cases clearly saved energy, 6 did not, and 11 were too close to call. In some cases, we could examine how the energy savings potential of remanufacturing has changed over time. Specifically, during times of significant improvements in energy efficiency, remanufacturing would often not save energy. A general design trend seems to be to add power to a previously unpowered product, and then to improve on the energy efficiency of the product over time. These trends tend to undermine the energy savings potential of remanufacturing.

The energy required to produce materials: constraints on energy-intensity improvements, parameters of demand

In this paper, we review the energy requirements to make materials on a global scale by focusing on the five construction materials that dominate energy used in material production: steel, cement, paper, plastics and aluminium. We then estimate the possibility of reducing absolute material production energy by half, while doubling production from the present to 2050. The goal therefore is a 75 per cent reduction in energy intensity. Four technology-based strategies are investigated, regardless of cost: (i) widespread application of best available technology (BAT), (ii) BAT to cutting-edge technologies, (iii) aggressive recycling and finally, and (iv) significant improvements in recycling technologies. Taken together, these aggressive strategies could produce impressive gains, of the order of a 50–56 per cent reduction in energy intensity, but this is still short of our goal of a 75 per cent reduction. Ultimately, we face fundamental thermodynamic as well as practical constraints on our ability to improve the energy intensity of material production. A strategy to reduce demand by providing material services with less material (called ‘material efficiency’) is outlined as an approach to solving this dilemma.

Appliance remanufacturing and life cycle energy and economic savings

In this paper we evaluate the energy and economic consequences of appliance remanufacturing relative to purchasing new. The appliances presented in this report constitute major residential appliances: refrigerator, dishwasher, and clothes washer. The results show that, despite savings achieved in production, appliance remanufacturing is a net energy-expending end-of-life alternative. Moreover, we find that economic incentives can be an influential driver for consumers to remanufacture and re-use old appliances.

Why we use more materials

In this paper, we review the drivers for the high levels of material use in society, investigating both historical and current trends. We present recent national and global data by different material categories and accounting schemes, showing the correlations between materials use and different measures of human well-being. We also present a development narrative to accompany these observed trends, focusing on the strong role materials have played in economic development by industrialization and in the consumer economy. Finally, we speculate on how material efficiency might alter this pattern going forward and whether it is possible to de-couple well-being from material use. This article is part of the themed issue ‘Material demand reduction’.

Reusing personal computer devices - good or bad for the environment?

The energy saving potential of reusing / reselling personal computer (PC) devices was evaluated relative to the choice of buying new. Contrary to the common belief of reuse leading to energy savings, with the advent of more efficient laptops and liquid crystal displays (LCD), reuse of an old personal computer device can lead to relative energy expenditure. We found that in certain scenarios this expenditure could be as large as 300% of the lifecycle energy inventory for the new device. As a result, it is essential to assess the reuse of personal computer devices more critically, incorporating the different factors that influence the analysis as discussed below.

Energy saving strategies in the materials sector: The case of aluminum

In this paper we evaluate the energy saving strategies for the materials sector with a focus on the aluminum industry. An interconnected dynamic model is constructed to evaluate the strategies independently as well as in combination, such that the intertemporal effects and different interrelations within the material-energy space are accounted for. Both technical and social levers are considered. Results highlight the challenge of controlling average impact created over the rest of this century at current levels of 2010. Only full implementation of all considered strategies allows us to achieve this target for total energy demand. For other impact parameters of interest like total material or total primary material, even this proves to be inadequate calling for more severe action through either better or more strategies, or stricter rates of deployment. Interestingly results suggest focusing on social levers more than technical levers because of their potential to contribute over 50% of the targeted reductions.

Your scrap, my scrap! The flow of scrap materials through international trade

With increasing international trade of secondary materials it is imperative to start including it in our analysis of recycling systems. The goal of this work is to set a materials-flow based foundation to do so. We provide a method for calculating the flow of scrap1 materials through an interconnected network of international trade. All analysis is presented through the specific example of copper scrap collected in USA, Germany, and Japan, which are leading generators of copper scrap. Results show how the open-economy form can contrast with a closed-economy one, and how different trade networks of the three countries result in different flows, decay rates, and potential recycling returns.