A recent Bulgarian study has shown that production scheduling – commonly used to optimise manufacturing efficiency – can also be used to reduce a plant’s environmental impact.
A study from the Institute of Chemical Engineering (IChE) – part of the Bulgarian Academy of Sciences (BAS) – has proposed an approach for the more environmentally friendly management of multipurpose batch chemical or biochemical plants.
Multipurpose batch plants are designed to be flexible enough to produce a number of similar products at any given time. By implementing production schedules a plant can be optimised to ensure raw materials and other inputs are sent to particular items of equipment in the right processing sequence. By doing so, manufacturers maximise the use of a plant’s equipment.
Such scheduling helps manufacturers achieve certain objectives, such as lowering costs, increasing quality or reducing production time. This study set out to prove that scheduling could also be used to minimise the environmental impact of a particular production process.
While the use of production scheduling is nothing new, the idea of applying it to meet environmental rather than economic goals is innovative. Traditionally production schedules do not take environmental factors into account. In contrast, this study used life-cycle analysis and process systems engineering approaches to incorporate environmental considerations.
While this system could be implemented in any type of batch plant, the study’s authors took a dairy plant as their case study. Their research, which was part funded by the European Social Fund (ESF), aimed to optimise scheduling to ensure the plant had the least possible environmental impact. To this end, the study analysed the waste generated by each of its processing recipes.
In the case of dairy plants, the most important environmental indicator in terms of waste analysis is biochemical oxygen demand (BOD). The level of the BOD is determined by the make-up of the milk. BOD is used to measure the strength of organic pollutants in discharged wastewater. Moreover, it can give a firm indication of the amount of waste produced from the raw materials and processing tasks, as well as the losses of by-products and final products.
By analysing the data collected, two pollutants which were responsible for more than 40% of BOD were identified. Furthermore, by implementing their modelling approach the researchers were able to make recommendations on how to improve the dairy plant’s environmental impact. This involved reducing the damage caused by wastewater from the manufacture of curds by targeting losses from whey acidification and drainage tasks.
Bulgarian Academy of Sciences (BAS):
Institute of Chemical Engineering (IChE):
European Social Fund:
‘Cleaner manufacture of multipurpose batch chemical and biochemical plants. Scheduling and optimal choice of production recipes’; Vaklieva-Bancheva, N. G., Kirilova, E.G. (2010) Journal of Cleaner Production. 18:1300-1310: