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Front. Chem. Eng. | doi: 10.3389/fceng.2019.00001

The current role of Chemical Engineering in solving environmental problems

  • 1Autonomous University of Barcelona, Spain

Chemical Engineering (CE) has demonstrated to be a powerful tool to have comprehensive solutions to a wide range of environmental problems. Classical disciplines of CE have been extensively applied to typical and emerging environmental technologies such as wastewater treatment, anaerobic digestion, biofiltration, etc. Among them, it is important to highlight these CE classical topics: chemical reactors design, kinetics, simulation, control, modelling and especially, heat and mass balances.

Through these are CE fundamentals, numerous environmental processes have been described and designed. However, environmental science and technology is evolving so rapidly that certain processes need a CE approach.

A key area in need of CE methods and tools is waste biological treatment. From composting, which is a robust and well implemented technology in which most of the decisions are based on “rules of thumb” criteria, to solid-sate fermentation, the new paradigm of circular economy to convert wastes into new bioproducts, there are only first approaches to use the CE paradigms. Some studies on composting modelling, or even the use of Computational Fluid Dynamics (CFD) can be found in literature, but it is not a general rule. Perhaps, solid-state experiments could be closer to reality when using some grams of substrate under controlled and sterilized lab conditions.

Nevertheless, some recent studies are being presented when scaling-up solid waste treatments. Microbiology seemed to be a drawback for these studies, but recent papers have adapted modern techniques to complex solid matrices, such as those found in composting and solid-state fermentation. The future for this important part of environmental studies is clear and many rigorous studies are necessary to consolidate it.
Water and wastewater treatments are a couple steps ahead. Complex models are being presented and analysed, and some of them implemented at the full-scale. Today, researchers are focusing these emerging studies not on the treatment of these wastewaters, but on the recovery of their compounds. A paradigmatic research trend is the recovery of phosphorous, which has important and relevant advances. In this same trend, the transformation of wastewater into bioplastics is another top research line, although the behaviour of these biodegradable plastics needs further research.

Considering the three main pollutant sources, gaseous emissions have been, without any doubt, the topic of many studies related to the use of CE tools to provide reliable and consistent information about their abatement and transformation. From chemical processes (scrubbers) to more complex biological processes (biofiltration and biotrickling filters, especially), researchers have an extensive collection of realistic studies to treat and model this equipment. Microbiology has been easily incorporated to these biological treatments, giving consistency to the models developed.

Another important emerging trend is the use of nanotechnology to solve environmental problems. This multidisciplinary approach has a lot of problems to be published: is this a nanotechnology or and environmental paper? The answer to this question is: it is both, but it seems that some journals are not prepared for that. It is the responsibility of researchers to change this mentality, and important efforts are being made. All of these are welcome. CE is, by definition, a multidisciplinary approach to real problems.

After these brief considerations about the state-of-the-art of the three main issues considered in environmental problems: liquid, gas and solid, two main topics appear as major questions in deciding technologies for environmental treatments and involving all the stakeholders (some of them are not familiar with the research field): Life Cycle Assessment (LCA) and Circular Economy.
LCA is a developed version of the typical CE mass and heat balances of a technology or product (or even more than this, “from cradle to grave”) to define the environmental impacts that are often expressed as some pollution categories. Being a powerful tool, and recommended for making decisions, scientific papers such consider that this analysis, to be consistent and reliable, need the use of realistic data. This is not what happens sometimes, and it is the role of scientists to enlarge the databases of environmental processes to have concluding results. An enormous field of research is awaiting.

The second and most transversal is the relatively recent term of “circular economy” (previously known with other names). Although the definition and need for a circular economy is unanimously understood within environmental engineering, the element of economy is usually omitted in studies focused on this topic. This term is related to the need of closing cycles, especially when dealing with energy and materials. Being a fashionable term, one wonders if the composting and anaerobic digestion studies performed thirty years ago do not deserve to be considered circular economy. However, if they are within the scope of circular economy, why do most of the published papers on this topic lack a simple cost analysis? There is a urgent need to fill this gap which is as big as the controversial use of the term. Especially since all current CE courses and projects include an economic evaluation. Unfortunately, economic analyses are not always well received by scientific journals, yet, if they are consistent and rigorous, they are an essential part of any environmental solution. It is an ongoing and ubiquitous frustration for researchers since the lack of clarity of economic terms can make a good technical solution seem unfeasible.

In this framework, it is relatively easy to deduce the general areas where CE principles can be used for the complete solution of environmental problems:

1) Application of CE consolidated paradigms: among them, mass and heat balances should be primordial.

2) Multidisciplinarity: most environmental problems do not have a unique solution. Biological treatments do no discard the help of other physico-chemical treatments.

3) Shifting the mindset from disposal to recovery: a typical example of this problem is the use of adsorption to “remove” pollutants from water. What then happens to those pollutants? Most studies lack a follow-up and have thus only created a pollutant transport.

4) Approximation using LCA principles: when applicable and if built with realistic data, it can indicate whether a research proposal is actually useful.

5) Estimation of the economic viability of a proposal.

In summary, CE tools are a powerful tool to explain, interpret and model environmental problems, from the mere technological point of view to more complex LCA and circular economy analyses.

Keywords: Chemical Engineering, Environmental Engineering, Waste treatment, Life Cycle Assesment, Circular economy, Wastewater treament, Circular economy (CE)

Received: 16 Aug 2019; Accepted: 11 Oct 2019.

Copyright: © 2019 Sánchez. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Antoni Sánchez, Autonomous University of Barcelona, Barcelona, 08193, Catalonia, Spain, antoni.sanchez@uab.cat