# Sustainable Materials from Waste Paper: Thermal and Acoustical Characterization
## 1 Introduction  
The international energy outlook [1] predicts that global energy consumption will grow by up to 42% by the end of 2050 due to several factors, such as the increase in building construction and the fast growth of the global population. Conventional building materials, such as cement and polymeric components, are responsible for increasing the energy demand due to the huge consumption of non-renewable resources. Furthermore, plastic materials provoke 4.5% of global greenhouse gas emissions [2], significantly contributing to the pollution of oceans and seas [3]. The catastrophic scenario of a rise in the Earth's average surface temperature by about 5 \({}^{\circ}\)C by the end of 2100 is closer than expected [4, 5]. According to [6], who develop an exhaustive report on the advanced techniques of by-products transformation, municipal waste can be divided into two categories: organic and inorganic waste. The first category includes food residues, wood waste, paper, textiles, rubber and plastics; the second includes metals, ash, glass and tiles. Several applications at the industrial scale and numerous studies have been conducted using different typesof waste in the energy recovery and building sector [6; 7; 8]; for example, lignocellulosic biomasses such as sawdust are suitable residues to be converted into the new raw matter of biochemicals [6]. Recently, there has been growth in the literature on the use of organic components and natural fibers for the production of insulating panels, mortars, plasters and bricks [9; 10; 11; 12; 13]. [PERSON] et al. [9] gave a critical overview of recent technologies adopted for the conversion of different by-products from food waste. [PERSON] et al. [10] proved that the use of different fractions (and dimensions) of olive pruning fibers may affect sound absorption in chitosan-based panels. [PERSON] et al. [11] carried out a study on almond skin waste for the creation of building panels. They demonstrated the great capacity of the almond skin residues to improve thermal performance, and from an acoustic point of view, the measured normal incidence sound absorption coefficient demonstrated the great capacity of the biomass aggregation to create a typical tortuous and complex structure able to reach a value typical of porous materials. [PERSON] et al. [12] showed the results of thermal characterization and life cycle analysis of building insulation panels made with cork scraps, end-life granulated tires, rice husk and coffee chaff, demonstrating the great capacity of the biomass waste to enhance the thermal performance of the final products. Among the numerous tested mixes, the best solution was found by cross-tabulating the thermal test results with the minimum embodied energy. [PERSON] et al. [13] proposed a review of conventional and unconventional insulators considering the main parameters by which they can be compared: thermal conductivity, thermal diffusivity, specific heat capacity, sound absorption coefficient and fire reaction. Considering the current environmental need to convert waste components into new resources, supporting the re-use and recycling of by-products, the aim of the present paper is to show the potential use of waste paper with the addition of different biomass as new base components for innovative and efficient materials, demonstrating their potential suitability to be applied as thermal and acoustic insulators in sustainable buildings. Three different aggregates, considered as by-products, were used in addition to the basic mix: exhausted coffee grounds, sawdust powder and fava bean residues. The literature on the used components shown in the next sections was useful when approaching the innovative mix design. Each aggregate originated from the Apulian Region in order to use 0 km components, thus assuring a sustainable material in terms of environmental impact.