Plastics-based materials have a high carbon footprint, and their disposal is a considerable problem for the environment. Biodegradable bioplastics represent an alternative on which most countries have focused their attention to replace of conventional plastics in various sectors, among which food packaging is the most significant one. The evaluation of the optimal end-of-life process for bioplastic waste is of great importance for their sustainable use. In this review, the advantages and limits of different waste management routes—biodegradation, mechanical recycling and thermal degradation processes—are presented for the most common categories of biopolymers on the market, including starch-based bioplastics, PLA and PBAT. The analysis outlines that starch-based bioplastics, unless blended with other biopolymers, exhibit good biodegradation rates and are suitable for disposal by composting, while PLA and PBAT are incompatible with this process and require alternative strategies. The thermal degradation process is very promising for chemical recycling, enabling building blocks and the recovery of valuable chemicals from bioplastic waste, according to the principles of a sustainable and circular economy. Nevertheless, only a few articles have focused on this recycling process, highlighting the need for research to fully exploit the potentiality of this waste management route.
In order to keep the +1.5 °C over-temperature, previously predicted with high confidence by IPPC Sixth Assessment, as minimal as feasible, it is more than vital to achieve a low-emission energy system. Polygeneration systems based on thermochemical processes involve biomass conversion in multi-output of bioenergy carriers and chemicals. Due to reduced energy input and input/output diversification, polygeneration energy systems are considered interesting pathways that can increase competitiveness of biomass-derived products. The proposed route of fast pyrolysis, sorption-enhanced biochar gasification and crude bio-oil hydrodeoxygenation to produce drop-in biofuel and hydrogen is examined. Both kinetic and equilibrium approaches were implemented in Aspen Plus to take into account the effect of the major operating parameters on the process performance and then validated against the literature data. Results show how the process integration leads to improved mass conversion yield and increases overall energy efficiency up to 10%-points, reaching the maximum value of 75%. Among the various parameters investigated, pyrolysis temperature influences mainly the products distribution while Steam/Biochar and Sorbent/Biochar affect the energy conversion efficiency.
The last Intergovernmental Panel on Climate Change (IPPC) assessment report highlighted how actions to reduce CO2 emissions have not been effective so far to achieve the 1.5 C limit and that radical measures are required. Solutions such as the upgrading of waste biomass, the power-to-X paradigm, and an innovative energy carrier such as hydrogen can make an effective contribution to the transition toward a low-carbon energy system. In this context, the aim of this study is to improve the hydrogen production process from wet residual biomass by examining the advantages of an innovative integration of anaerobic digestion with thermochemical transformation processes. Furthermore, this solution is integrated into a hybrid power supply composed of an electric grid and a photovoltaic plant (PV), supported by a thermal energy storage (TES) system. Both the performance of the plant and its input energy demand—splitting the power request between the photovoltaic system and the national grid—are carefully assessed by a Simulink/Simscape model. The preliminary evaluation shows that the plant has good performance in terms of hydrogen yields, reaching 5.37% kgH2/kgbiomass, which is significantly higher than the typical value of a single process (approximately 3%). This finding demonstrates a good synergy between the biological and thermochemical biomass valorization routes. Moreover, thermal energy storage significantly improves the conversion plant’s independence, almost halving the energy demand from the grid.