7.2.1 Evaluating Sustainability of Unit Processes
In addition to economic, environmental and social sustainability, the technological dimension needs to be considered as a fourth dimension. Yuan et al. [YUAN12] suggest three strategies to increase sustainability in manufacturing processes: (1) Optimizing of the manufacturing technology by detecting and changing the parameters that affect material and energy streams, (2) Using clean energy, (3) Using lower impact materials.
The production of a part can be broken down from all involved production chains into discrete manufacturing processes. The unit process consists of inputs, process, and outputs of an operation. Each unit process is converting material or chemical inputs into a transformed material or chemical output. Cradle to grave views a product from raw material extraction to end of life, cradle to cradle
considers re-use and recycling, cradle to gate or gate to gate evaluates only parts of the life cycle.
The CO2PE! UPLCI-Initiative provides a framework to aquire data for unit manufacturing processes [KELL11]. The in-depth approach in the CO2PE! UPLCI-Initiative studies energy through power consumption measurements and time studies, as well as consumables and manufacturing emissions [KELL12a, KELL12b, KELL11]. The basic screening approach in the CO2PE! UPLCI-Initiative quantifies energy consumption as well as other environmental impact information of manufacturing processes, and is largely based on data from publications, catalogs, and handbooks [KELL11]. It focuses on manufacturing energy and chemicals/ materials required at the machine level and can be refined by measured data.
Energy and resource efficiency of manufacturing processes can be enhanced by reducing the machine basic and idle energy through machine setup or shorter production times or by minimizing the processing energy [DORN10].