Expanded polystyrene (EPS) is a synthetic polymer that is widely applicable in the fields of food packaging, equipment protection and civil construction. Aiming to replace EPS, biofoams were developed utilizing mycelia of the macrofungi Pycnoporus sanguineus, Pleurotus albidus and Lentinus velutinus in a medium formulated with sawdust and wheat bran. Sample characterization was obtained by scanning electron microscopy (SEM), thermal analysis and infrared spectroscopy with Fourier Transform; density and compression strength were analysed as mechanical properties. The main results include that the compression strengths of biofoams from P. sanguineus, P. albidus and L. velutinus were 1.3, 0.4, and 1.3 MPa, respectively, which exceed that of EPS (0.4 MPa). The thermal stability of the biofoams was lower than that of EPS; however, they were stable up to 350
C. Biofoams are denser than EPS, with values of 0.3 and 0.03 g cm3 , respectively. The data obtained for biofoams categorize this material as sustainable substitute for EPS in some applications, while at the same time, reducing the environmental impact caused by sawdust and EPS.

Introduction

The growing search for biodegradable materials has shifted the interest of the scientific community towards the development of biodegradable products (Vaisanen et al., 2017). These materials can replace synthetic petroleum-related products, such as expanded polystyrene (EPS), which is used in a huge variety of shapes and applications (Poletto et al., 2011; Song et al., 2009; Treinyte et al., 2018). Polystyrene is a widely employed polymer (Shimomura et al., 2016; Yousif and Haddad, 2013). In its expanded form, EPS is used in the form of plates or blocks for preparing slabs, as protective packaging for domestic appliances, in crash helmets and as electrical or thermal insulators in homes, among other applications (Chen and Liu, 2004; Haghi et al., 2006). However, there are some drawbacks because it is petroleum-related and is not biodegradable, which means that it takes many years to degrade if left in the environment (Araújo et al., 2008). After its use, EPS is unduly disposed of, piling up in landfills or even in the environment, which compromises the conventional degradation processes because certain compounds present in the polymer chains can act as a barrier against degradation by organic compounds (Araújo et al., 2008). Still, EPS contains benzene, which has been classified as a human carcinogen (IARC group 1) since 1979, with sufficient evidence to support the claim that it causes leukaemia (Loomis et al., 2017). EPS also contains styrene, a substance that can also trigger the development of various neoplasms (IARC Monographs Vol 121 Group).