UABDivulga - Barcelona recerca i innovació

In recent years, there has been growing concern about the limitations of the current linear economic model, based on extracting resources, producing, consuming and generating waste. In contrast to this linear system, the circular economy proposes reusing waste to convert it into new resources. In this context, organic waste (such as food scraps, agricultural waste or sewage sludge) represents a great opportunity to produce energy and useful biomaterials in a more sustainable way.

This article analyses the key role of Chemical Engineering in the development of a circular bioeconomy based on organic waste. The bioeconomy seeks to transform this waste into bioproducts (such as fertilisers, biopesticides and biosurfactants, among others) and bioenergy (biogas or biomethane) through biological processes that can be complemented by other physicochemical processes. To this end, the concept of biorefinery is introduced: an advanced facility that integrates various technologies to maximise the potential of waste, going beyond the traditional approach of simple waste treatment.

The article reviews the main current biotechnological technologies. Composting and anaerobic digestion are already widely implemented and enable the production of compost and biogas, respectively. However, it highlights the need to go further and incorporate emerging processes such as solid-state fermentation, which can generate bioproducts with higher added value. It also analyses technological combinations, for example, anaerobic digestion followed by thermal processes such as pyrolysis, which produce biochar, a material with multiple environmental and energy applications.

One of the main challenges is to ensure that these systems are truly sustainable from an environmental and economic point of view. To this end, Chemical Engineering provides essential tools such as material and energy balances, which enable facilities to be reliably dimensioned, as well as life cycle analyses and technical-economic studies, which are fundamental for decision-making by administrations and companies.

The following table groups together the main elements that the discipline can apply to contribute to the sustainability of these technological systems:

The article also highlights future challenges: managing large quantities of digestate, difficulties in scaling up emerging technologies, the need for better models and simulations, and the growing role of artificial intelligence in the design and optimisation of biorefineries. Finally, it concludes that the combination of circular economy and chemical engineering can be decisive in transforming organic waste into a key pillar of a more sustainable economy, although more research and, especially, real-scale or pilot-scale experiences are still required.