# Inorganic Waste Generated in Kraft Pulp Mills:
## 4 Potential Applications
### Green Liquor Dregs
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Application** & **Highlights** & **Scale** \\ \hline Construction materials & & \\ \hline
**Concrete** & GLD as a replacement of part of the cement in concrete is not suitable since the loss in mechanical properties is significant [23]. Substitution of clinker up to 10\% is feasible to obtain Portland cement (CP I-S and CP II-F) [50]. & Laboratory \\
**Clinker production** & The mixture of GLD (0.13 wt \%) with standard materials is technically viable and does not present noticeable environmental effects [34]. & Industrial \\
**Geopolymer mortars** & GLD can be used as a fine filler up to 25 wt \% incorporation. The obtained mortars exhibited enhanced tensile and compressive strength [29]. & Laboratory \\ \hline Geotechnical & & \\ \hline
**Landfill cover** & Alternating layers of 0.15 m of GLD (70 wt \%) and SG (30 wt \%) covered by 1 m of MSW have the potential for replacing soil as intermediate covering in landfills [27]. & Industrial \\
**Road pavement construction** & GLD require washing before incorporation as aggregates in bituminous mixtures to guarantee stability in terms of water sensitivity [36]. & Laboratory \\
**Sealing layer in mines** & A mixture with the proportions 7:2:1 of tailings: GLD: fly ash was found to be geotechnically satisfactory to be used as a sealing layer in dry covers on mine [37]. GLD showed high water retention capacity and low hydraulic conductivity, which prevents water percolation and oxygen transport [51]. & Laboratory \\
**Hot-mix asphalt** & GLD used as filler in hot-mix asphalt leads to poor water resistance, despite displaying adequate mechanical properties (stiffness and permanent deformation) [52]. & Laboratory \\ \hline Environmental & & \\ \hline
**Neutralize acidic wastewaters** & The liming effect of GLD (39.6\% Ca eq) is similar to commercial limestone (38\%). The pH of 10.7 indicates a strong liming effect [53; 54]. & Industrial \\
**Acid mine drainage remediation Soil amendment** & GLD exhibited high buffering capacity [4] at low dosages of 1 g/[55] for remediation of acid mine drainage. & Laboratory \\
**Seil amendment** & Doses up to 20 t/ha achieved neutralization of acidic soil, not causing deterioration of soil properties or depressing crop yields [56]. After 5.5 years since application, positive effects were observed on the soil chemical attributes [57]. & Laboratory \\
**Drying adjuvant of sewage sludge** & A dose of 0.15 g GLD per g of sewage sludge reduced by 8\% the energy required for the evaporation of humidity at 130 \({}^{\circ}\)C. A reduction in phytotoxicity was also observed in tests with garden cress, revealing a good potential for agricultural applications [34]. & Laboratory \\ \hline Agricultural & & \\ \hline
**Liming material Co-composing** & Valid option to substitute commercial agricultural limestone [25; 41]. The addition of a moderate amount of GLD (5–8 wt \%) with kraft mill sludge did not show a negative effect on the biological activities during the composting process [58]. & Industrial \\ \hline \end{tabular}
\end{table} 
Table 6: Applications of GLD reported in the literature. studies at an industrial scale have shown the potential of GLD as construction materials, in geotechnical, environmental or agricultural applications. Industrial trials showed that the incorporation of GLD with standard materials for clinker production is a viable route [34]. Another noteworthy alternative could be the incorporation of GLD in the production of geopolymers, which would decrease the environmental impacts of conventional Portland cement production [29]. GLD is also being tested to replace 100% of the filler for the construction of asphalt pavement of a section of a road in Portugal [59]. In addition, GLD showed good potential to replace the soil in successive layers for intermediate covering in landfills [27].