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Valorization of Wastes for Energy Production by Thermal and Biological Processes

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A4: Bio-Energy".

Deadline for manuscript submissions: closed (10 January 2022) | Viewed by 16469

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Dr. Margarida Gonçalves

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Mechanical Engineering and Resource Sustainability Center, Faculty of Science and Technology, NOVA University of Lisbon, 2829-516 Caparica, Portugal
Interests: biofuels; biomass; thermochemical processes; waste valorization; microalgae; biorefineries
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Prof. Dr. Cândida Vilarinho

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Mechanical Engineering and Resource Sustainability Center; Department of Mechanical Engineering, University of Minho, 4710-057 Braga, Portugal
Interests: waste management and treatment; biomass; thermochemical processes; life cycle analysis; circular economy
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Special Issue Information

Dear Colleagues,

Wastes are produced by most of the essential activities of modern society, and their adequate disposal or valorization are challenges of sustainable development. Waste-to-energy systems may give a fundamental contribution for waste valorization due to their diverse nature as well as their capacity to process large amounts of materials. Innovation in catalysts, reactor design, genetic engineering of microorganisms, or downstream processing techniques has been a driver for progress of technologies for waste conversion.

This Special Issue invites original research papers to address new applications of thermochemical, biological, or integrated technologies for the conversion of organic, lignocellulosic, or polymeric wastes to energy or fuels. Additionally, the authors are encouraged to submit papers addressing the state-of-the-art and recent advancements in these areas, providing useful guidelines for future research directions.

Biorefinery approaches combining material and energy valorization are some of the pathways for achieving waste valorization solutions that are both economically viable and environmentally friendly.

Finally, the emerging technologies for carbon dioxide capture, storage, and conversion to gas or liquid fuels are the ultimate weapon to lower greenhouse gas emissions and valorize this gaseous waste.

Efficient waste-to-energy solutions are necessary to reduce our consumption of essential raw materials but also to preserve the quality of air, water, and soils that constitute our supporting ecosystem.

Thermochemical processes such as combustion, carbonization, pyrolysis, or gasification have been mainly applied to lignocellulosic or polymeric wastes, while biological processes such as anaerobic digestion or fermentation have been used to convert organic and lignocellulosic materials.

Potential topics include but are not limited to the following:
Conversion of wastes to solid biofuels;
Production of liquid biofuels from lipidic wastes, lignocellulosic wastes, or polymeric wastes;
Production of gaseous biofuels by thermochemical or biological processes;
Production of alcohols from organic or lignocellulosic wastes;
Production of hydrogen from wastes;
Catalytic upgrading of waste-derived fuels;
Waste biorefineries;
Microalgae-based biorefineries;
Carbon dioxide capture, storage, and conversion to gas or liquid fuels;
Life cycle analysis of waste-to-energy systems.

Prof. Margarida Gonçalves
Prof. Cândida Vilarinho
Guest Editors

Keywords

Waste-to-energy systems
Thermochemical processes
Biological processes
Biorefineries
Microalgae
Carbon dioxide conversion
Life cycle analysis.

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Published Papers (6 papers)

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Research

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18 pages, 5140 KiB

Open AccessArticle

Individual Phenolic Acids in Distillery Stillage Inhibit Its Biomethanization

by Wioleta Mikucka and Magdalena Zielinska

Energies 2022, 15(15), 5377; https://doi.org/10.3390/en15155377 - 25 Jul 2022

Cited by 10 | Viewed by 1528

Abstract

Polyphenols that are abundant in various organic wastes can inhibit anaerobic degradation of these wastes. This study investigated the effect of the concentration of individual phenolic acids (p-OH benzoic, vanillic, ferulic, sinapic, syringic, and p-coumaric acids) and their mixture on the methane potential of distillery stillage. An increase in phenolic acid concentration adversely affected biogas production and composition, as well as the methane-production rate. The inhibition constants for methane production were 0.5–1.0 g/L of individual phenolic acids and 1.5 g/L of the mixture of these acids. At lower concentrations, the phenolic acids were utilized as a carbon source, but the process was impeded when their concentrations exceeded the threshold value, due to their negative effect on microbial growth. When distillery stillage was spiked with vanillic acid, two-phase methane production was observed. Spiking distillery stillage with vanillic, p-coumaric, syringic, or ferulic acids affected anaerobic digestion the most; 2 g/L of these acids completely inhibited methane production. With 4.0 g/L of all individual phenolic acids, no methane production was observed. As the concentration of these phenolic acids increased from 0.5 to 4.0 g/L, the abundance of methanogenic Archaea, in which acetoclastic methanogens predominated, decreased by about 30 times. Full article

(This article belongs to the Special Issue Valorization of Wastes for Energy Production by Thermal and Biological Processes)

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23 pages, 3258 KiB

Open AccessArticle

Optimization of Biochar Production by Co-Torrefaction of Microalgae and Lignocellulosic Biomass Using Response Surface Methodology

by Catarina Viegas, Catarina Nobre, Ricardo Correia, Luísa Gouveia and Margarida Gonçalves

Energies 2021, 14(21), 7330; https://doi.org/10.3390/en14217330 - 4 Nov 2021

Cited by 19 | Viewed by 2946

Abstract

Co-torrefaction of microalgae and lignocellulosic biomass was evaluated as a method to process microalgae sludge produced from various effluents and to obtain biochars with suitable properties for energy or material valorization. The influence of four independent variables on biochar yield and properties was evaluated by a set of experiments defined by response surface methodology (RSM). The biochars were characterized for proximate and ultimate composition, HHV, and methylene blue adsorption capacity. HHV of the biochars was positively correlated with carbonization temperature, residence time, and lignocellulosic biomass content in the feed. Co-torrefaction conditions that led to a higher yield of biochar (76.5%) with good calorific value (17.4 MJ Kg⁻¹) were 250 °C, 60 min of residence time, 5% feed moisture, and 50% lignocellulosic biomass. The energy efficiency of the process was higher for lower temperatures (92.6%) but decreased abruptly with the increase of the moisture content of the feed mixture (16.9 to 57.3% for 70% moisture). Biochars produced using algal biomass grown in contaminated effluents presented high ash content and low calorific value. Dye removal efficiency by the produced biochars was tested, reaching 95% methylene blue adsorption capacity for the biochars produced with the least severe torrefaction conditions. Full article

(This article belongs to the Special Issue Valorization of Wastes for Energy Production by Thermal and Biological Processes)

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19 pages, 4191 KiB

Open AccessArticle

Experimental Assessment of the Performance and Emissions of a Spark-Ignition Engine Using Waste-Derived Biofuels as Additives

by Joaquim Costa, Jorge Martins, Tiago Arantes, Margarida Gonçalves, Luis Durão and Francisco P. Brito

Energies 2021, 14(16), 5209; https://doi.org/10.3390/en14165209 - 23 Aug 2021

Cited by 4 | Viewed by 2494

Abstract

The use of biofuels for spark ignition engines is proposed to diversify fuel sources and reduce fossil fuel consumption, optimize engine performance, and reduce pollutant emissions. Additionally, when these biofuels are produced from low-grade wastes, they constitute valorisation pathways for these otherwise unprofitable wastes. In this study, ethanol and pyrolysis biogasoline made from low-grade wastes were evaluated as additives for commercial gasoline (RON95, RON98) in tests performed in a spark ignition engine. Binary fuel mixtures of ethanol + gasoline or biogasoline + gasoline with biofuel incorporation of 2% (w/w) to 10% (w/w) were evaluated and compared with ternary fuel mixtures of ethanol + biogasoline + gasoline with biofuel incorporation rates from 1% (w/w) to 5% (w/w). The fuel mix performance was assessed by determination of torque and power, fuel consumption and efficiency, and emissions (HC, CO, and NOx). An electronic control unit (ECU) was used to regulate the air–fuel ratio/lambda and the ignition advance for maximum brake torque (MBT), wide-open throttle (WOT)), and two torque loads for different engine speeds representative of typical driving. The additive incorporation up to 10% often improved efficiency and lowered emissions such as CO and HC relative to both straight gasolines, but NOx increased with the addition of a blend. Full article

(This article belongs to the Special Issue Valorization of Wastes for Energy Production by Thermal and Biological Processes)

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11 pages, 2154 KiB

Open AccessArticle

Hydrocarbon Toxicity towards Hydrogenotrophic Methanogens in Oily Waste Streams

by Bruno P. Morais, Valdo Martins, Gilberto Martins, Ana Rita Castro, Maria Madalena Alves, Maria Alcina Pereira and Ana J. Cavaleiro

Energies 2021, 14(16), 4830; https://doi.org/10.3390/en14164830 - 8 Aug 2021

Cited by 5 | Viewed by 1966

Abstract

Hydrocarbon-containing wastes and wastewaters are produced worldwide by the activities of the oil and gas industry. Anaerobic digestion has the potential to treat these waste streams, while recovering part of its energy potential as biogas. However, hydrocarbons are toxic compounds that may inhibit the microbial processes, and particularly the methanogens. In this work, the toxicity of hexadecane (0–30 mM) towards pure cultures of hydrogenotrophic methanogens (Methanobacterium formicicum and Methanospirillum hungatei) was assessed. Significantly lower (p < 0.05) methane production rates were only verified in the incubations with more than 15 mM hexadecane and represented up to 52% and 27% inhibition for M. formicicum and M. hungatei, respectively. The results obtained point out that 50% inhibition of the methanogenic activity would likely occur at hexadecane concentrations between 5–15 mM and >30 mM for M. formicicum and M. hungatei, respectively, suggesting that toxic effects from aliphatic hydrocarbons towards hydrogenotrophic methanogens may not occur during anaerobic treatment. Hydrocarbon toxicity towards hydrogenotrophic methanogens was further assessed by incubating an anaerobic sludge with H₂/CO₂ in the presence of a complex mixture of hydrocarbons (provided by the addition of an oily sludge from a groundwater treatment system). Specific methanogenic activity from H₂/CO₂ decreased 1.2 times in the presence of the hydrocarbons, but a relatively high methane production (~30 mM) was still obtained in the assays containing the inoculum and the oily sludge (without H₂/CO₂), reinforcing the potential of anaerobic treatment systems for methane production from oily waste/wastewater. Full article

(This article belongs to the Special Issue Valorization of Wastes for Energy Production by Thermal and Biological Processes)

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16 pages, 2232 KiB

Open AccessArticle

Hot Compressed Water Pretreatment and Surfactant Effect on Enzymatic Hydrolysis Using Agave Bagasse

by Marcela Sofia Pino, Michele Michelin, Rosa M. Rodríguez-Jasso, Alfredo Oliva-Taravilla, José A. Teixeira and Héctor A. Ruiz

Energies 2021, 14(16), 4746; https://doi.org/10.3390/en14164746 - 4 Aug 2021

Cited by 18 | Viewed by 2326

Abstract

Agave bagasse is a residual biomass in the production of the alcoholic beverage tequila, and therefore, it is a promising raw material in the development of biorefineries using hot compressed water pretreatment (hydrothermal processing). Surfactants application has been frequently reported as an alternative to enhance monomeric sugars production efficiency and as a possibility to reduce the enzyme loading required. Nevertheless, the surfactant’s action mechanisms in the enzymatic hydrolysis is still not elucidated. In this work, hot compressed water pretreatment was applied on agave bagasse for biomass fractionation at 194 °C in isothermal regime for 30 min, and the effect of non-ionic surfactants (Tween 20, Tween 80, Span 80, and Polyethylene glycol (PEG 400)) was studied as a potential enhancer of enzymatic saccharification of hydrothermally pretreated solids of agave bagasse (AGB). It was found that non-ionic surfactants show an improvement in the conversion yield of cellulose to glucose (100%) and production of glucose (79.76 g/L) at 15 FPU/g glucan, the highest enhancement obtained being 7% regarding the control (no surfactant addition), using PEG 400 as an additive. The use of surfactants allows improving the production of fermentable sugars for the development of second-generation biorefineries. Full article

(This article belongs to the Special Issue Valorization of Wastes for Energy Production by Thermal and Biological Processes)

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15 pages, 2259 KiB

Open AccessEditor’s ChoiceReview

Turning Waste Cooking Oils into Biofuels—Valorization Technologies: A Review

by Lucas Nascimento, André Ribeiro, Ana Ferreira, Nádia Valério, Vânia Pinheiro, Jorge Araújo, Cândida Vilarinho and Joana Carvalho

Energies 2022, 15(1), 116; https://doi.org/10.3390/en15010116 - 24 Dec 2021

Cited by 14 | Viewed by 4226

Abstract

In search of a more sustainable society, humanity has been looking to reduce the environmental impacts caused by its various activities. The energy sector corresponds to one of the most impactful activities since most energies produced come from fossil fuels, such as oil and coal, which are finite resources. Moreover, their inherent processes to convert energy into electricity emit various pollutants, which are responsible for global warming, eutrophication, and acidification of soil and marine environments. Biofuels are one of the alternatives to fossil fuels, and the raw material used for their production includes vegetable oils, wood and agricultural waste, municipal waste, and waste cooking oils (WCOs). The conventional route for WCO valorization is the production of biodiesel, which, as all recovery technologies, presents advantages and disadvantages that must be explored from a technical and economic perspective. Despite its successful use in the production of biodiesel, it should be noticed that there are other approaches to use WCO. Among them, thermochemical technologies can be applied to produce alternative fuels through cracking or hydrocracking, pyrolysis, and gasification processes. For each technology, the best conditions were identified, and finally, projects and companies that work with this type of technology and use WCO were identified. Full article

(This article belongs to the Special Issue Valorization of Wastes for Energy Production by Thermal and Biological Processes)

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