Life cycle assessment of expanded clay granulate production using different fuels

Straw can be valorised through a set of unconventional applications other than the traditional ones being mainly related to livestock breeding. It can be utilised in bioenergy field as renewable feedstock for anaerobic digestion and other biological processes, or as fuel for direct combustion. However, it can also find suitable application in buildings as a multiple-function material (i.e. enveloping and insulation) or for production of other building materials. This paper investigates an Expanded Clay Granulate (ECG) production system in Sicily where straw is used as fuel in the cooking/expansion process, and so contributes both fields: buildings and bioenergy. In this study, the authors carried out a comparative Life Cycle Assessment (LCA) according to the subject International Standards, to environmentally validate shifting from hard coal to Durum Wheat (DW) straw as fuel for cooking and expansion of input fresh clay in a rotary kiln line. Study development provided the definition of the system functional unit and boundaries: the former was represented by the production of thermal energy as required for the making of 1 m3 ECG, depending upon whether the kilning phase is fuelled with hard coal or DW straw. Whilst, the latter were designed to include all processes for which differences were recorded due to the change in the fuel utilised. The study documented that, despite the environmental impacts associated with DW straw production, the hard coal fuelled system is far more impacting than that providing straw utilisation, mainly because of the related huge emissions of carbon dioxide.