## 2 The Role of Cellulose Waste in Sustainable Construction
### Sustainable Concrete Alternatives  
The construction industry is also exploring the use of cellulose waste in the development of sustainable concrete alternatives. Traditional concrete, while essential for modern construction, has a significant environmental footprint, particularly due to the high carbon emissions associated with cement production. By incorporating cellulose fibers, including those derived from waste streams, into concrete, researchers and engineers aim to develop materials that maintain the strength and durability of conventional concrete while reducing its environmental impact. [PERSON] et al. [95] used cellulose fibers as additives in concrete blocks to enhance their insulation properties, specifically improving their ability to limit heat transfer. Unlike other fillers, such as rubber particles, which can reduce the thermal insulating performance of cementitious composites, the use of cellulose fibers offers an ecological and environmentally sustainable alternative. The experimental results demonstrated that the incorporation of bio-cellulose significantly impacts the porous matrix structure, effectively reducing heat transfer and thermal conductivity. Cellulose-based composites can achieve thermal conductivities as low as 0.20 W/mK, which can be further optimized to 0.15 W/mK under specific conditions, such as temperature and the use of condensed phosphates. Similarly, [PERSON] et al. [96] explored the potential of waste paper concrete by incorporating waste paper into concrete mixtures, substituting fine aggregate, coarse aggregate, and cement in varying proportions (0%, 5%, 10%, 15%, and 20%). The study found that the fresh, structural, and durability properties of concrete improved with the addition of waste paper at 5% and 10%, while a decline was observed beyond 10%. At 10% incorporation, the concrete showed an increase in strength due to the presence of hydrated cement particles, outperforming standard concrete without paper. Cellulose-reinforced concrete exhibits improved tensile strength and reduced brittleness, which are critical factors in prolonging the lifespan of concrete structures. The incorporation of cellulose fibers helps to distribute stresses more evenly within the concrete, reducing the likelihood of cracking and other forms of degradation. This not only enhances the structural integrity of buildings but reduces the need for frequent repairs and maintenance, leading to lower lifecycle costs [97]. However, the majority of researchers have reported that the mechanical performance of concrete increased with the addition of fibers only up to a 1.0% concentration, while further additions of fibers decreased the mechanical performance of concrete due to reduced workability [98]. Building on the innovative usesof cellulose waste in concrete, another example of its application comes from a project at a hydropower station in China, where cellulose fiber-reinforced concrete was employed for its durability and enhanced mechanical properties. The study utilized four different fiber contents (0.6, 0.9, 1.2, and 1.5 kg/m\({}^{3}\)) to determine the optimal mix for concrete slabs exposed to extreme conditions. Particularly, the concrete with a fiber content of 0.9 kg/m\({}^{3}\) demonstrated superior compressive, splitting tensile, and flexural strengths compared to plain concrete. This optimized cellulose fiber content not only improved the concrete's structural integrity but its energy absorption capacity and toughness, making it highly suitable for the dam's face slab in challenging environments. The implementation of this modified concrete in this project showcased significant benefits, as the dam face slab maintained a stable working condition through varying temperatures and even during seismic activities. These results underline the potential of cellulose fibers to enhance the resilience and longevity of concrete structures, particularly in hydroelectric projects where durability and performance under stress are paramount [42].