WASTE BIOREFINERIES: OPPORTUNITIES AND PERSPECTIVES

The progressive implementation of the circular economy concepts, the population growth and associated concerns in terms of availability of non-renewable resources, the will of many countries to diversify their strategic sources and to free themselves from the supply of materials and energy resources from areas politically and socially unstable, the fight against climate change, the need to favor delocalization of production systems and promote regional and rural development, the improvement of the knowledge of the factors that govern biological processes, entail that the context of biowaste management currently looks at more ambitious and articulated targets which find the most appropriate and complete synthesis in the concept of waste biorefinery. The potential inherent in biorefineries is huge. The global industrial production of organic chemicals accounts for a major share of the overall global chemicals industry and is estimated to amount, excluding fuels, to more than 300 Mt/year; the associated market was worth over 6 billion $ in 2014 and grew at an average of 8% per year from 2009 to 2014. The primary outputs of the chemical industrial activity are represented by a relatively limited number of building blocks used to produce a plethora of end products such as food and beverages, pharmaceuticals, pesticides, agrochemicals, water treatment, crop protection, personal care products and cosmetics, fertilizers, automotive industry, gasoline additives, polymers and chemicals, etc. Each building block can also be obtained from biomass, enabling the supply of raw materials at the local level, releasing the industrial activity from expensive and risky supplies, and opening the door to economic sustainability even in disadvantaged contexts such as, for instance, the insular ones. The demand for bioproducts from renewable sources is estimated to reach, depending on more or less favorable market conditions, 26-113 Mt/year in 2050, which would correspond to 38 and 17% of the total organic chemicals production, respectively; the associated market should account for some 7-8 billion $, with a growth rate of 15%/year which could further benefit from the increasing demand for biopolymers (IEA Bioenergy - Task 42 Biorefinery, 2012). The concept of biorefinery is not new in its more traditional meaning, and has evolved over time driven by three pivotal aspects (Akhlaghi et al., 2016): - cascade approach; - environmental sustainability; - economic sustainability. The cascade approach involves the flexible integration of different processes aimed at producing a mix of biofuels and bioproducts. The integration of processes and products according to the traditional or inverse cascade, is basically linked to economic sustainability, which requires an appropriate mix of products characterized either by significant market sizes - typical of biofuels - or high added values, but also to environmental aspects. In fact, as the number of usable and marketable outputs increases, this would logically correspond to less waste production, thus approaching the zero waste concept. The improvement in environmental sustainability is the main element underlying the hypothesis of transition towards a new generation of biorefineries: waste biorefineries. The environmental sustainability of the first and current biorefinery generations was, and still is, linked mainly to benefits related to the reduction of the consumption of non-renewable resources and CO2 emissions. To this respect, it is estimated that the production of a large share of synthetic organic compounds from renewable resources could lead to a global reduction of CO2 emissions ranging between 400 and 1000 Mt/year. The use of residual biomass would bring further environmental benefits: - first, the envi