The growing scarcity of material resources for energy production and other industrial activities, and the huge impacts of the waste management activities led to introduction of the circular economy concept as a fundamental strategy for sustainable development.

According to the Waste Management Hierarchy, prevention and reduction of waste generation are the major waste management priorities but those policies only limit the growth rate of waste production in the different societal activities. Reusing and Recycling wastes are the next priority waste management options, but they may be applied to a limited fraction of the generated wastes.

Recover is the only alternative before disposal and is the purpose of many  technologies, recently proposed to recover organic and inorganic components as well as energy from different waste streams.

Lignocellulosic wastes are an increasingly sought-after resource for energy and material applications, namely for selective conversion of their biopolymers into to nanocellulose, lignin, bio polyols or different liquid biofuels.

Organic wastes have been traditionally used in composting applications but the associated methane emissions press for a wider application of more advanced techniques such as anaerobic digestion or other biological conversion processes that allow the capture and use of biomethane or biohydrogen for energy production. Furthermore, the use of organic wastes in the production of biopolymers and other specialty chemicals is a growing valorization option reaching the industrial maturity level.

Polymer and mineral wastes also have recycling pathways well established that allow for an efficient reutilization of these resources, but the solutions are less straightforward when dealing with miscellaneous waste that may aggregate polymers, lignocellulosic materials, mineral components including metals and, in some cases, organic contaminants.

These complex wastes represent the biggest challenge for development of sustainable and economically feasible solutions of recovery and valorization. Unfortunately, given the growing complexity of the materials we use in our daily life, the complex and heterogeneous waste fraction is predominant in the waste streams produced in most countries around the world.

The combination of different technologies that may include chemical, biochemical, electrochemical, photochemical, and thermochemical processes has been proposed in order to define pathways for a complete recover of the waste components and their valorization in a range of marketable products and energy applications.

The recover of mineral components of critical relevance is a subject of growing interest, namely in the fields of the valorization of electric an electronic wastes and landfill mining.

Finally, some of these solutions have their inherent carbon footprint therefore emission minimization is also a concern when proposing integrated waste management strategies. Stabilization of carbon-rich materials by reincorporation in soils or use as feedstock for industrial processes is one of the options to reduce CO₂ emissions and achieve a long-term sequestration of these carbon materials. Mitigation of CO₂ emissions has also been developed  in the last years, both at the level of more efficient capture technologies but also in what concerns the CO₂ conversion techniques, either to methane, liquid biofuels, and a range of useful products with industrial relevance.

The development of efficient and sustainable solutions for waste management and valorization is one of the biggest technological challenges we face today, given the present rates of population growth and associated waste production. The solutions must be integrated, innovative, economically feasible and with no associated emissions so that we may transit from a waste management and disposal model to a zero-waste model supported by a complete recovery of waste resources.