Environmental dimensions of additive manufacturing: mapping application domains and their environmental implications

Additive manufacturing (AM) proposes a novel paradigm for engineering design and manufacturing, which has profound economic, environmental, and security implications. The design freedom offered by this category of manufacturing processes and its ability to locally print almost each designable object will have important repercussions across society. While AM applications are progressing from rapid prototyping to the production of end-use products, the environmental dimensions and related impacts of these evolving manufacturing processes have yet to be extensively examined. Only limited quantitative data are available on how AM manufactured products compare to conventionally manufactured ones in terms of energy and material consumption, transportation costs, pollution and waste, health and safety issues, as well as other environmental impacts over their full lifetime. Reported research indicates that the specific energy of current AM systems is 1 to 2 orders of magnitude higher compared to that of conventional manufacturing processes. However, only part of the AM process taxonomy is yet documented in terms of its environmental performance, and most life cycle inventory (LCI) efforts mainly focus on energy consumption. From an environmental perspective, AM manufactured parts can be beneficial for very small batches, or in cases where AM-based redesigns offer substantial functional advantages during the product use phase (e.g., lightweight part designs and part remanufacturing). Important pending research questions include the LCI of AM feedstock production, supply-chain consequences, and health and safety issues relating to AM

Comparison of pollutant emission control strategies for cadmium and mercury in urban water systems using substance flow analysis

The European Union (EU) Water Framework Directive (WFD) requires Member States to protect inland surface and groundwater bodies but does not directly stipulate how the associated environmental quality standards should be achieved. This paper develops and assesses the performance of a series of urban emission control strategies (ECS) with an emphasis on the scientific and technological benefits which can be achieved. Data from the literature, in combination with expert judgement, have been used to develop two different semi-hypothetical case cities (SHCC), which represent virtual platforms for the evaluation of ECS using substance flow analysis (SFA). The results indicate that the full implementation of existing EU legislation is capable of reducing the total emissions of cadmium (Cd) and mercury (Hg) by between 11% and 20%. The ability to apply voluntary reduction practices is shown to be particularly effective for Cd with the potential to further lower the overall emissions by between 16% and 27%. The most efficient protection of the receiving surface water environment is strongly influenced by the city characteristics with the introduction of stormwater treatment practices being particularly effective for one city (59% reduction of Hg; 39% reduction of Cd) and the other city being most influenced by the presence of efficient advanced wastewater treatment processes (63% reduction of Hg; 43% reduction of Cd). These reductions in receiving water loads are necessarily accompanied by either increases in stormwater sediment loadings (2.6 to 14.9 kg/year or 0.6 to 2.4 kg/year for Hg) or wastewater sludge loadings (45.8 to 57.2 kg/year or 42.0 to 57.4 kg/year for Cd)