Biorefining and Circular Economy: Innovative Processes for Waste Valorization

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Energy Systems".

Deadline for manuscript submissions: 15 December 2026 | Viewed by 972

Special Issue Editors


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Guest Editor
Department of Chemical Engineering, Howard University, Washington, DC 20059, USA
Interests: green chemistry; sustainable chemical and biochemical processes; process intensification; green extraction; enabling technologies (ultrasound, microwaves, hydrodynamic cavitation, ball milling, flow chemistry); process design, simulation, and optimization; reactor engineering; separation processes; bioprocess engineering; integrated biorefineries; biomass and residue valorization; biofuels, biodiesel, and sustainable aviation fuel; methane valorization; circular bioeconomy; techno-economic analysis (TEA); life cycle assessment (LCA); sustainability assessment; decarbonization and carbon-efficient process systems
Special Issues, Collections and Topics in MDPI journals
Chemical Engineering Department, Howard University, Washington, DC 20059, USA
Interests: biomass; biocomposites; 3D printing; waste utilization
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

A circular economy can be achieved by transforming today’s wastes and side streams into tomorrow’s fuels, chemicals, materials, and nutrients. Biorefining is a rigorous systems-level approach that can link feedstock preprocessing, biocatalysis and thermocatalysis, separations, energy and water integration, and end-of-life strategies. Across agriculture, food and beverage, pulp and paper, municipal services, and bioenergy, there is a pressing need for innovative process solutions that are scalable and sustainable.

This Special Issue, “Biorefining and Circular Economy: Innovative Processes for Waste Valorization,” invites original research and critical reviews that advance process concepts converting residual biomass and other waste streams into higher-value products. We particularly welcome contributions that integrate rigorous experimentation with modeling and simulation; demonstrate process intensification and integration; quantify techno-economic performance and life-cycle impacts; and chart viable scale-up and deployment pathways, including industrial symbioses.

Topics include, but are not limited to, the following:

  • Novel pretreatment, biocatalytic/thermocatalytic conversion, hybrid processes, and intensified reactors.
  • Valorization of agro-industrial residues and aqueous side streams (e.g., stillage, vinasse, whey, glycerol), forestry and food wastes, wastewater sludges, and fiber rejects into fuels, chemicals, biopolymers, and advanced materials.
  • Separation, purification, and solvent/reagent recycling; mass/energy/water integration and heat recovery.
  • Digital tools for process design and operations: modeling and simulation, optimization and control, AI/ML, and digital twins.
  • Techno-economic analysis, life-cycle assessment, carbon/water footprints, and sustainability metrics; circular business models, supply chain design, and policy/regulatory considerations.
  • Scale-up case studies, pilot/demonstration results, quality assurance, product standards, and safety.

We welcome original research articles, reviews, communications, and perspectives. We look forward to your contributions to this Special Issue.

Dr. Cristiano E.R. Reis
Dr. Anqi Ji
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access semimonthly journal published by MDPI.

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Keywords

  • biorefinery
  • circular economy
  • waste valorization
  • process integration
  • process intensification
  • agro-industrial residues
  • techno-economic analysis (TEA)
  • life cycle assessment (LCA)
  • hybrid biocatalysis–thermocatalysis
  • digital twins and process modeling

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Published Papers (1 paper)

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Review

22 pages, 840 KB  
Review
Methanotrophic Technologies for Low-Concentration Methane: Reactor Designs and Performance
by Ajani A. Moss, Isaiah Thompson, John Tharakan and Cristiano E. Rodrigues Reis
Processes 2026, 14(6), 969; https://doi.org/10.3390/pr14060969 - 18 Mar 2026
Viewed by 640
Abstract
Low-concentration methane emissions from landfills, manure management, wastewater treatment, and ventilation streams are difficult to mitigate using conventional capture and oxidation because of high air-to-fuel ratios, variable flows, and unfavorable economics. Methanotrophic bioreactors provide an aerobic biological route to oxidize methane at ambient [...] Read more.
Low-concentration methane emissions from landfills, manure management, wastewater treatment, and ventilation streams are difficult to mitigate using conventional capture and oxidation because of high air-to-fuel ratios, variable flows, and unfavorable economics. Methanotrophic bioreactors provide an aerobic biological route to oxidize methane at ambient conditions and, in selected cases, enable valorization into biomass and bioproducts. This review synthesizes methanotrophic reactor technologies for dilute methane, emphasizing the design and operational constraints that control performance. We classify systems into (i) fixed-film gas–solid configurations (biofilters, biocovers, biotrickling filters, and bioscrubbers), (ii) suspended-growth gas–liquid reactors (stirred tanks, bubble columns, and loop/airlift designs), (iii) membrane-based and intensified contactors that decouple methane and oxygen delivery and enhance mass transfer, and (iv) hybrid and in situ approaches for diffuse sources. This review presents key metrics and discusses how mass transfer, moisture and temperature control, nutrient supply, and microbial ecology interact to define achievable removal. We further summarize recent techno-economic and life-cycle studies to identify dominant cost drivers, particularly air handling and gas–liquid transfer, and the concentration regimes where biological oxidation is competitive with catalytic or thermal alternatives. Full article
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