# Cleaner Design and Production of Lightweight Aggregates (LWAs) to Use in Agronomic Application
## 4 Conclusions  
In this research, lightweight aggregates were successfully manufactured from two different clay matrices using brewery wastewater sludge as a pore-forming agent, and fer  
Figure 7: LWA leaching test results (ppm) in water (H2O) 30 min for whole samples (WS) and 30 min and 21 days in citric acid (C6H8O7) for whole and powdered samples (PS). tilizer glass and cattle bone flour ash as a means to give the materials fertilizing properties, studying the physical and mechanical properties of the aggregates obtained. On the basis of the results of this study, the following specific conclusions can be drawn:  
* MIP results showed how brewery sludge can be efficiently used as pore-forming agent for LWA manufacturing, representing savings in virgin raw materials and energy consumption, as well as an alternative to landfill disposal. * The addition of FG or CBA produced a slight decrease in the open porosity and water absorption of the materials with respect to aggregates obtained only from BS. However, the open and interconnected porosity structure of the aggregates remained practically intact, as shown in the SEM images and the pore size distribution curves obtained by MIP. * Although some other materials were close to the limits, only WC\({}_{\text{FG}}\) and WC\({}_{\text{CBA}}\) were light aggregates according to the standard UNE-EN-13055-1:2003. Furthermore, these products had high water absorption values and crushing strength of the same order as commercial products such as Arlita Leca L used in gardening, horticulture, and roof insulation applications. Furthermore, they presented adequate pH and E.C. values, indicating their potential use as growth substrates in agronomic applications. * The results of the leaching tests showed the importance of grain size in the release of nutrients. For longer times (21 days) comparing clay aggregates with the same clay but containing FG instead of CBA, the former had a better capacity in the release of nutrients, showing the positive effect of the presence of the fertilizer glass. * The results indicate that the different clay minerals and waste/by-products had the potential for manufacturing high-quality, lightweight aggregates for agronomic purposes using low sintering temperature with less environmental impact and higher economic savings. * The use of brewery wastewater sludge and cattle bone flour ash for the production of lightweight aggregates brought about many environmental and economic benefits. Among the most important were the reduction of waste and energy savings. In addition, it allowed materials to be obtained that met the requirements set by the regulations to be declared as lightweight aggregates with new fertilizing properties. This approach to waste recovery makes it possible to reduce the consumption of non-renewable raw materials and the space allocated to waste disposal. This strategy is aligned with the principles of Circular Economy and Sustainable Development Goals. Conceptualization, C.M.-G. and M.T.C.-P.; methodology, M.T.C.-P., L.B., F.A. and I.L. ; validation, M.T.C.-P., L.B. ; formal analysis, C.M.-G., M.T.C.-P., L.B., F.A. and I.L. ; investigation, C.M.-G., M.T.C.-P., L.B., F.A., I.L. and R.D.F. ; data curation, M.T.C.-P.; writing--original draft preparation, C.M.-G., M.T.C.-P., L.B., F.A., I.L. and R.D.F. writing--review and editing, C.M.-G., M.T.C.-P., L.B., F.A. and I.L. ; supervision, C.M.-G. and M.T.C.-P.; project administration, C.M.-G. All authors have read and agreed to the published version of the manuscript. This research was conducted as a part of the SmartMats Project (MAT2015-70034-R), \"Smart materials for sustainable construction\", funded by the Spanish Ministry of Economy and Competitiveness and FEDER (MINECO-FEDER). Not applicable. The authors thank Escavazioni Industriali Baroni S.P.A. for collaborating with this research. [PERSON] would like to express her gratitude to the University of Jaen and University of Modena and Reggio Emilia. The authors gratefully acknowledge this support.