Special Issue "Waste-to-Energy Systems in Standalone, Integrated and Hybrid Configurations"

A special issue of Resources (ISSN 2079-9276).

Deadline for manuscript submissions: closed (15 June 2021).

Special Issue Editors

Dr. Michela Costa
E-Mail Website
Guest Editor
Istituto di Scienze e Tecnologie per l’Energia e la Mobilità Sostenibili, CNR STEMS, Via Guglielmo Marconi, 4 – 80125 Naples, Italy
Interests: renewable energy systems; biomass thermo-chemical conversion; energy efficiency; waste heat recovery; computational fluid dynamics; modeling of reacting and non-reacting thermo-fluid systems; combustion kinetics
Dr. Daniele Piazzullo
E-Mail
Co-Guest Editor
Istituto di Scienze e Tecnologie per l’Energia e la Mobilità Sostenibili, CNR STEMS, Via Guglielmo Marconi, 4 – 80125 Naples, Italy
Interests: CFD; Numerical Modeling; Internal Combustion Engines; Renewable Energy; Cogeneration

Special Issue Information

Dear Colleagues,

The need to resort increasingly to renewable energy sources is currently forcing governments and distribution network service providers (DNSPs) to grapple with how to manage the costs of electricity supply with the prospect of distributed generation while still meeting the social objectives of access and affordability in remote areas. In developed countries, the so-called prosumer, simultaneously producing and consuming electricity, is spreading, thus making concrete the diffusion of micro-grids and the need for their development in the light of demand–response optimization. The electric power distribution networks of many undeveloped countries, on the other hand, today reveal an insufficient or null supply to many remote communities. This often implies the need to resort to solar power or thermoelectric generators burning diesel oil. The latter, in particular, is expensive, environmentally damaging, and fails to exploit the vast renewable resources available. A symbolic example is the majority of off-grid energy supply to the Brazilian northwest region, largely dominated by the rainforest, which alone accounts for about half of the nation’s territory. In most cases, sole market mechanisms are not sufficient to guarantee the economic sustainability of remote electrification projects. Moreover, despite local DNSPs encouraging renewables from the “bottom up” by often providing feed-in tariffs to reduce the supply cost and environmental damage from fossil fuel generation, a range of barriers still currently frustrates a dynamic and adaptive approach that fully recognizes local challenges and provides pathways to be followed to optimize valorisation.

Actions must be therefore undertaken toward a more intensive exploitation of bioenergy, in standalone configurations or by multi-source-integrated systems along with solar, wind, and hydro power. Resorting to off-grid solutions of hybrid energy generation and storage today constitutes a viable route not only to supply services to remote districts but also to lower the load over national networks and to increase the resilience of territories exposed to natural disasters or climate change effects.

Submissions addressing technical and economic challenges to a more rationale and sustainable use of resources, especially of residual materials, that discuss costs of management and disposal are welcome.

Dr. Michela Costa
Dr. Daniele Piazzullo
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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. Resources is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • waste-to-energy
  • biomass
  • integrated renewable generation
  • hybrid energy systems
  • off-grid power systems

Published Papers (2 papers)

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Research

Article
Greenhouse Gas Emission Assessment of Simulated Wastewater Biorefinery
Resources 2021, 10(8), 78; https://doi.org/10.3390/resources10080078 - 28 Jul 2021
Viewed by 773
Abstract
A wastewater treatment plant (WWTP) can be considered a system where dirty water enters and fresh water (by means of treatment processes) and other co-products such as sludge and biogas exit. Inside the system, typically, the following steps occur: preliminary treatment, primary treatment, [...] Read more.
A wastewater treatment plant (WWTP) can be considered a system where dirty water enters and fresh water (by means of treatment processes) and other co-products such as sludge and biogas exit. Inside the system, typically, the following steps occur: preliminary treatment, primary treatment, secondary treatment, tertiary treatment, disinfection, and solids handling. The system transforms biomass into several energy and non-energy products, which fall into the definition of a biorefinery. This research compares three simulated WWTP in terms of their environmental greenhouse gas (GHG) emission release to the atmosphere: a generic one (without co-product valorization), one that converts co-products into fertilizer, heat, and electricity, and a third one that converts co-products into heat, electricity, fertilizer, and bioplastic. Heat and electricity are used to provide its energy needs. The chosen impact category is GHG, and the aim is to project the best scenario to the European context in terms of GHG avoidance (savings). The scope is the upstream electricity and natural gas production, the in-use emissions, and the avoided emissions by substituting equivalent fossil-based products. The functional unit is 1 L of sewage (“dirty water”). The GHG savings are evaluated by comparing a generic WWTP scenario, without co-product valorization, with alternative scenarios of co-product valorization. Conventional LCA assuming all the emissions occurs at instant zero is compared to a more realistic environment where for each year, the average of the variable emission pulses occurs. Variable emissions pulses are taken from variable inflows data publicly available from European COST actions (COST Action 682 “Integrated Wastewater Management” as well as within the first IAWQ (later IWA) Task Group on respirometry-based control of the activated sludge process), within the later COST Action 624 on “Optimal Management of Wastewater Systems”). The GHG uncertainty is estimated based on the inputs benchmark data from the WWTP literature and by having different available global warming potential dynamic models. The conventional LCA versus dynamic LCA approach is discussed especially because a WWTP is by nature a dynamic system, having variable inputs along time and therefore variable output GHG emission pulses. It is concluded that heat needs are fully covered by biogas production in the anaerobic digester and combustion, covering its own energy needs and with a potential for heat district supply. Only 30–40% of electricity needs are covered by combined heat and power. Bioplastics and/or fertilizer yields potentially represent less than 3% of current European needs, which suggests the need to reduce their consumption levels. In comparison to generic WWTP, GHG savings are 20%, considering the uncertainty in the benchmark input assumptions. The former is much higher than the uncertainty in the dynamic global warming potential model selection, which means that the model selection is not important in this case study. Full article
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Article
CFD Simulation of an Internally Cooled Biomass Fixed-Bed Combustion Plant
Resources 2021, 10(8), 77; https://doi.org/10.3390/resources10080077 - 23 Jul 2021
Viewed by 691
Abstract
The reduction of bed temperature in fixed-bed biomass combustion is an effective measure to lower pollutant emissions. Air staging and bed cooling solutions are active strategies to decrease the fuel bed temperature. This work presents a CFD study of a biomass fixed-bed combustion [...] Read more.
The reduction of bed temperature in fixed-bed biomass combustion is an effective measure to lower pollutant emissions. Air staging and bed cooling solutions are active strategies to decrease the fuel bed temperature. This work presents a CFD study of a biomass fixed-bed combustion plant that is equipped with an internal cooling bed system. Eight different cases are calculated to analyze the effect of the total airflow, air staging ratios and bed cooling system on biomass combustion. The findings are validated against experimental data from the literature. The results show good accordance between the numerical results and the experimental data. The primary airflow rate has the biggest influence on the bed’s maximum temperatures. The internal bed cooling system is able to achieve an average bed temperature reduction of 21%, slowing the biomass thermal conversion processes. Bed cooling techniques can be combined with air staging and primary airflow reduction to reduce bed temperatures in order to reduce pollutant emissions and other undesirable phenomena, such as fouling or slagging. Full article
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