We compare the exergetic performance of a conventional industrial mushroom production chain with a mushroom production chain where part of the compost waste is recycled and reused as raw material. The critical exergy loss points (CEPs) identified are the cooking-out process of the spent mushroom substrate, and the phase I composting process which are related to chemical and physical exergy losses, respectively. The total exergy input requirements for the conventional chain are higher (24 GJ per three flushes of mushrooms) than for the alternative chain (17 GJ per three flushes of mushrooms) since more raw materials are required. The largest exergy losses are due to unclosed material balances, i.e. chemical exergy losses, which represent 69% of the total exergy losses for the conventional chain, and 56% for the alternative production chain. Therefore, it only makes sense to reduce any avoidable physical exergy losses after utilizing all mass streams maximally that translate into chemical exergy flows. Further comparison of exergetic indicators (e.g. specific exergy losses, and exergetic cost) shows that recycling material streams would improve the resource efficiency of the industrial mushroom production chain considerably. The variations in the assumed electricity consumption values for the ventilation in phase I composting and for the ammonia scrubbing process affect greatly the exergetic indicators and the number of critical exergy loss points indicating that any further improvement on the exergetic performance of the mushroom production chain should focus on these two process variables. This study shows that variability in data can influence both quantitatively and qualitatively the outcome of exergetic analyses of food production chains since it can lead to the calculation of different values for the selected indicators as well as to the identification of completely different critical exergy loss points.
- Exergy analysis
- Food industry