Potential Valorization Research Articles

Assessing bioenergy prospects of algal biomass and yard waste using an integrated hydrothermal carbonization and pyrolysis (HTC–PY): A detailed emission–to–ash characterization via diverse hyphenated analytical techniques and modelling strategies

Hydrothermal carbonization (HTC) presents a promising method for converting carbonaceous waste into renewable fuels, facilitating energy recovery. This study focuses on the HTC pretreatment of microalgae (Chlorella sorokiniana) and yard waste, examining their physicochemical structural changes, component migration, and potential for valorization via integrated HTC and pyrolysis processes. HTC notably enhances the carbon content while reducing oxygen and nitrogen levels in these feedstocks, producing a clean solid fuel with high energy density. The study investigates the pyrolytic behavior of hydrochars and their blends using different analytical techniques, kinetic modeling, and fixed–bed reactor experiments. The blends with 90% and 70% of microalgae hydrochar (CSH) exhibited the most significant synergistic effects during co–pyrolysis, evident in its devolatilization behaviors and reduced activation energies. Integrating artificial neural networks and response surface methodology models facilitated optimization of pyrolysis parameters and accurate prediction of bio–oil, biochar, and gas yields. The analytical techniques enabled characterization of pyrolysis products, revealing notable changes in bio–oil and biochar compositions, suggesting potential enhancements. The study comprehensively evaluates the HTC–pyrolysis approach’s potential for converting microalgae and lignocellulosic biomass into eco–friendly biofuels for industrial applications.

Comparative analysis of hydrogen production pathways for emethanol synthesis to decarbonise industry

Methane pyrolysis and water electrolysis offer alternative hydrogen pathways to methane reforming that utilise renewable power and avoid generating carbon dioxide (CO2). On a scope 1 and 2 basis, both technologies have the potential to generate carbon neutral emethanol fuel when combined with biogenic CO2. However, pyrolysis requires significantly less energy and has a lower capital expenditure (CAPEX). Being a more nascent technology, it also has upside potential for cost reductions and valorisation of the solid carbon by-product can yield lower hydrogen costs than the incumbent technology, however, limited demand from existing markets is a potential constraint. Industry decarbonisation is constrained due to a lack of available renewables and hydrogen infrastructure. Pyrolysis offers a potential cost-effective use of the available renewable assets in the early stages while the carbon by-product is not a constraint and until sufficient renewable infrastructure is in place to support water electrolysis at a cost-effective scale.

The effects of microalgae use as a biofertilizer on soil and plant before and after its anaerobic (co-)digestion with food waste

The increase in food waste generation has resulted in significant challenges for its sustainable management. Anaerobic digestion coupled with microalgae-based ponds for digestate treatment can be used as a low-cost eco-friendly technology approach. In this case, microalgal biomass harvested from the ponds may be valorized into bioenergy (biogas) and soil conditioner and/or biofertilizers. The aim of the present study was to evaluate the microalgal biomass produced from a food waste digestate treatment ponds as agricultural fertilizer. For this purpose, microalgal biomass was tested before and after anaerobic digestion and co-digestion with food waste, exploring its potential for valorization. The inorganic fertilizer urea and soil with no fertilization were also used as treatments. The experimental design consisted of applying the treatments in pots cultivated with hybrid grass Brachiaria cv. Sabiá and distributed in randomized blocks in a controlled greenhouse. Microalgal biomass was mainly composed by Scenedesmus sp.. The assessed parameters showed comparable results on plant growth (i.e. number of tillers, fresh and dry matter and Chlorophyll content index) for fresh and digested microalgal biomass and inorganic fertilizer. Furthermore, it was observed that fresh microalgae provided the highest Phosphorus content in the leaf (21 %). Additionally, there were increases of 9 % in Nitrogen and 12 % in organic matter in the soil after applying digested microalgae compared to the control group without any fertilization. Finally, experimental data obtained suggests that microalgae-based biofertilizer holds the potential to replace inorganic fertilizer as a nutrient source. Moreover, it contributes to the valorization of by-products from organic waste treatment.

Industrial byproduct pine nut skin factorial design optimization for production of subcritical water extracts rich in pectic polysaccharides, xyloglucans, and phenolic compounds by microwave extraction

Pine nut skin (Pinus pinea L.) is a poorly explored industrial byproduct with potential to be utilized as a food ingredient. Subcritical water extraction (SWE), an eco-friendly extraction technique with higher efficiency than hot-water extraction (HWE), was studied to evaluate its suitability in producing extracts rich in soluble fiber and phenolic compounds. For this, a factorial design was developed considering temperature (120–180 °C), time (2–10 min), and mass/volume ratio (1–3 g/60 mL) under microwave irradiation. This design aimed to maximize the extraction of carbohydrates, while achieving the highest content of phenolic compounds and antioxidant activity. SWE produced higher yields (2.6-fold in relation to HWE) of extracts rich in polysaccharides, determined by methylation analysis, oligosaccharides, determined by GC-qMS as alditol acetates, and phenolic compounds, determined by HPLC-ESI-MS. SWE increased the recovery of pectic oligosaccharides (10-fold) and xyloglucans (2-fold), and allowed to recover pectic polysaccharides, type II arabinogalactans and insoluble-bound phenolic compounds. Mono-, oligo- and polysaccharides were not hydrolyzed during in vitro gastrointestinal digestion, showing potential prebiotic functionality. Although phenolic compounds suffered a 23 % (gallic acid equivalents) decrease, phenolic acids and aldehydes were released or conserved upon intestinal phase. These results highlight the potential of PNS valorization as functional food ingredients through the subcritical water solubilization of polysaccharides and phenolic compounds.

Prospects of crambe for the bioeconomy of the Swabian Alb in southwest Germany

Crambe (Crambe abyssinica Hochst. ex R.E.Fr.) is a drought-tolerant, non-edible annual oil crop with low fertilization needs, and there are compelling opportunities for crambe to capitalize on market growth in natural cosmetics and the regional sustainability. It is therefore proposed for cleaner biomass production on marginal land, and the development of novel value chains and webs in rural areas. Therefore, this study assesses the prospects for growing and processing crambe in the Swabian Alb, a rural area in southwestern Germany large parts of which are characterized by marginal shallow stony soil. A literature review, stakeholder questionnaires, and a SWOT analysis were used to assess crambe's potential in the region. This informed a locally adapted value web, which combines multiple value chains and stakeholders into one interlinked diagram showing present potential valorization opportunities for crambe in the region. However, it was found that it is not currently possible to implement a value web for crambe in the Swabian Alb. Instead, a single value chain involving farmers, cosmetics companies, and biogas plants is possible. To expand this value chain opportunity into a value web, more information is needed for all stakeholders. European Innovation Action projects could help by providing more information about crambe cultivation and by ensuring ecologic and social sustainability. Economic sustainability, however, will require the involvement of other stakeholders in the value web, so that supply matches demand. Local institutions and networks can share knowledge to grow the currently possible value chain into a broader value web. This approach could also be used in other regions to assess the sustainability of novel biobased value chains across social, economic, and environmental dimensions.

Valorisation potential of low-grade fly ash as a sustainable MgO source for iron ore sintering: Insights from in situ X-ray diffraction and tablet studies

CaO- and MgO-rich fly ash derived from low-grade coals is typically discarded due to its incompatibility with existing large-scale valorisation technologies. This study demonstrates the potential of such low-grade fly ash as a substitute for flux and MgO sources in the iron-ore sintering process, a critical step in producing feedstock to yield ∼1 Gt/yr of crude steel globally. In situ X-ray diffraction (XRD) analysis confirmed the supply of fine MgO particles from fly ash via thermal decomposition. Aligned with other MgO sources, fly ash suppressed the formation of calcium ferrites while increasing spinel content. Notably, the addition of fly ash enhanced the physical strength of sinter tablets due to the high reactivity of the MgO particles, which is in marked contrast to the detrimental effect of conventional MgO sources. Removal of sulphur from the fly ash further augmented the physical strength of the tablets by enhancing the reactivity of MgO. Further, detrimental elements for sintering, i.e., Na, K, P, and Cl, were negligible in the fly ash. These findings highlight the potential role of fly ash in supplying MgO without compromising the physical strength of the sinter, offering insights into sustainable steel production.

Agricultural Waste Valorization: Exploring Environmentally Friendly Approaches to Bioenergy Conversion

The pursuit of sustainable energy production through the conversion of agricultural waste into different bioenergy resources is of paramount importance given its potential to mitigate environmental impact while meeting energy demands. In this review, a comprehensive overview of the technologies for the biochemical and thermochemical conversion of agricultural waste into bioenergy is provided. A summary of the process of its conversion into different bioenergy products such as biogas, bio-oil, and biofuel is provided, in addition to the potential advantages and challenges faced using different biomass conversion technologies. The review highlights the potential of agricultural waste valorization to address the current energy demand while at the same time contributing to environmental benefits and greenhouse gas emission reductions. Moreover, this review highlights some significant gaps for improvement. These include the challenges in the pretreatment of agricultural waste biomass in optimizing the conversion rates and lowering the required energy consumption throughout the process while enhancing both the quantity and quality of the output. Some recommendations are proposed to address the identified challenges. These include the need for further studies for a thorough assessment to evaluate the efficacity and sustainability of agricultural waste valorization technologies. Assessment methods such as life cycle assessment (LCA), life cycle analysis (LCA), net energy ratio (NER) calculations, life cycle costing (LCC), as well as techno-economic assessment (TEA), are recommended, together with collaboration among governments, farmers, and researchers, as well as the integration of cutting-edge technologies to enhance various aspects of agricultural waste, optimizing the conversion process, cost efficiency, time management, and labor requirements, consequently boosting the conversion efficiency and product quality.

Potential valorization and transformation of plastic biomass waste into useful fertilizers in agricultural Mediterranean soils under extreme climate conditions

Plastics are widely used in agricultural practices, although recently they have been recognized as a new emerging risk in soils. Polyethylene (PE), is commonly used by farmers to cover agricultural practices; geotextile, is used mainly for ground and crop covering; and polyvinyl chloride (PVC) is considered the main material contained in irrigation hoses. The present study aimed to assess the effects of three plastics (polyethylene, geotextile, polyvinyl chloride) on the soils’ fertility. Several pot experiments were conducted in soil samples from the study area (Thessaly) contaminated with adequate amounts of each plastic type (PE, geotextile: 2% v/v and PVC: 5% v/v). Water was added in two quantities: one to maintain typical soil moisture levels according to the crops’ requirements and an elevated amount to form supersaturating soil conditions similar to those following a flood event. Furthermore, temperature effect was also investigated to assess its impact on plastics’ behavior and soil fertility. The levels of all nitrogen forms and the microbial activity were determined at 10, 30, and 60 days. Significant changes were observed in the concentrations of nitrate, nitrite, and ammonium ions under ambient soil moisture conditions especially when the microplastics were incubated for a longer period. PE addition resulted in greater changes, followed by geotextile, although PVC addition did not induce significant changes in the nitrification process during the experimental time. PE and geotextile microplastics appeared to enhance microbial colonization and total microbial activity. In addition, soil characteristics were notably altered when moisture stress conditions were reached (85%) and when soils were flooded for two months, leading to a severe decrease in the availability of all nitrogen forms. The results showed that alterations in soil nitrogen forms in the presence of plastics study are crucial for maintaining the health and improving the productivity of Mediterranean soils.

Carbon derived from orange peel waste for preparation of benign bimetallic catalyst in organic reactions

In this work, a convenient approach has been applied to discover the potential valorization of biomass waste such as orange peel in which PdCu-based nanostructured systems were synthesized via a one-step in-situ dry-milling approach to obtain the benign bimetallic catalysts with different palladium(Pd) and Copper(Cu) loadings on the orange peel support (Pd1%Cu1%, Pd0.3%Cu0.7%, Pd0.5%Cu0.5%, Pd0.5%Cu1%). Catalytic applications of these new composites were investigated in the Sonogashira-Hagihara coupling reaction as well as the Sonogashira–click reaction sequence to the preparation of substituted 4-aryl-1,2,3-triazoles and reduction of nitroaromatics under mild reaction conditions. Catalytic tests with the four activated carbons catalysts showed that the C@Pd1%Cu1% catalyst was the most active in the Sonogashira-Hagihara coupling reaction compared to the other catalysts. Also, the C@Pd0.5%Cu0.5% catalyst showed the highest catalytic activity in the reduction of 1-chloro-4-nitrobenzene and 4-nitrophenol in comparison with other prepared carbon catalysts.

Valorization of oil palm empty fruit bunches into activated carbon: A mini-review

This paper aimed to comprehensively review the potential valorization of oil palm empty fruit bunches (OPEFBs) into activated carbon and its potential application. Activated carbon is carbon processed through dual phases, including carbonization and activation. Firstly, this process converts biomass into carbon thermally with zero to little oxygen conditions. Next, the carbon needs to be activated to stimulate the formation of pores and reduce impurities. The activated carbon’s quality is influenced by the activation process, which can be done physically, chemically, or physiochemically. Activated carbon has an amorphous structure and abundant internal pore structure, thus increasing the surface area. In Indonesia, the quality of active carbon is regulated by Indonesian National Standards or SNI 06-370-1995. The factors influencing the activation step include activator agent type, activator agent concentration, activation ratio and time, etc. . Generally, activated carbon can be widely applied to various sectors, such as agriculture (i.e., slow-released fertilizer, fertilizer, etc.), waste treatment (i.e., adsorbent, activator in anaerobic digestion/AD, bioremediation, etc.), gas purification, ceramic membrane, etc. However, further in-depth investigation is required to determine potential scaling-up and commercialization.

Towards a zero liquid discharge process from brine treatment: Water recovery, nitrate electrochemical elimination and potential valorization of hydrogen and salts

This research addresses the issues related with treatment and valorization of brines and nitrate decontamination of surface and ground waters. The objective was to approximate to zero liquid discharge (ZLD) minimizing the environmental impact of brines of an electrodialysis reversal water treatment plant (EDRWTP) as an example. The innovative in flow process was developed from lab to pre-industrial scale and joined several main concepts: ion-exchange equilibrium for softening or demineralization of brines; reversed osmosis to recover suitable water and to enrich the waste in nitrate for efficient electrochemical reduction of NO3− to N2; valorization of subproducts by direct use or by precipitation; and assessment of the whole process by measuring in-line several parameters. The achieved softening was around 98 % and the recovered water from this current by reversed osmosis was 75 %. The brine of this step (25 %) contained around 1500 mg/L of nitrate and it was treated by electrochemical reduction with a Bi/Sn cathode providing a gas current of 60 % of initial nitrate reduced to N2, O2, H2O, NH3 and at least 97 % of H2. The aqueous current contained around 40 % of initial nitrate as ammonium and nitrite lower than 50 and 5 mg/L, respectively. Hypochlorite was added to this last current for oxidizing ammonium and nitrite to N2 and nitrate, respectively, being nitrate and ammonium lower than 50 and 5 mg/L, respectively. After the obtained water was demineralized and conducted to the EDRWTP inlet. The recovery of insoluble salts as calcium carbonate, reuse of saline solutions for the regeneration of process resins and the potential use of hydrogen generated as a by-product during the electrochemical reduction are other possible utilities.

Valorization of Rejected Macroalgae Kappaphycopsis cottonii for Bio-Oil and Bio-Char Production via Slow Pyrolysis.

Kappaphycopsis cottonii, a prominent macroalgae species cultivated in an Indonesian marine culture, yields significant biomass, a portion of which is often rejected by industry. This study explores the potential valorization of rejected K. cottonii biomass through slow pyrolysis for bio-oil and biochar production, presenting an alternative and sustainable utilization pathway. The study utilizes a batch reactor setup for the thermal decomposition of K. cottonii, conducted at temperatures between 400 and 600 °C and varying time intervals between 10 and 50 min. The study elucidates the temperature-dependent behavior of K. cottonii during slow pyrolysis, emphasizing its impact on product distributions. The results suggest that there is a rise in bio-oil production when the pyrolysis temperature is raised from 400 to 500 °C. This uptick is believed to be due to improved dehydration and greater thermal breakdown of the algal biomass. Conversely, at 600 °C, bio-oil yield diminishes, indicating secondary cracking of liquid products and the generation of noncondensable gases. Chemical analysis of bio-oils reveals substantial quantities of furan derivatives, aliphatic hydrocarbons, and carboxylic acids. Biochar exhibits calorific values within the range of 17.52-19.46 MJ kg-1, and slow pyrolysis enhances its specific surface area, accompanied by the observation of carbon nanostructures. The study not only investigates product yields but also deduces plausible reaction routes for the generation of certain substances throughout the process of slow pyrolysis. Overall, the slow pyrolysis of rejected K. cottonii presents an opportunity to obtain valuable chemicals and biochar. These products hold promise for applications such as biofuels and diverse uses in wastewater treatment, catalysis, and adsorption, contributing to both environmental mitigation and the circular economy.

The Influence of Gamma Radiation on Different Gelatin Nanofibers and Gelatins.

Gelatin nanofibers are known as wound-healing biomaterials due to their high biocompatible, biodegradable, and non-antigenic properties compared to synthetic-polymer-fabricated nanofibers. The influence of gamma radiation doses on the structure of gelatin nanofiber dressings compared to gelatin of their origin is little known, although it is very important for the production of stable bioactive products. Different-origin gelatins were extracted from bovine and donkey hides, rabbit skins, and fish scales and used for fabrication of nanofibers through electrospinning of gelatin solutions in acetic acid. Nanofibers with sizes ranging from 73.50 nm to 230.46 nm were successfully prepared, thus showing the potential of different-origin gelatin by-products valorization as a lower-cost alternative to native collagen. The gelatin nanofibers together with their origin gelatins were treated with 10, 20, and 25 kGy gamma radiation doses and investigated for their structural stability through chemiluminescence and FTIR spectroscopy. Chemiluminescence analysis showed a stable behavior of gelatin nanofibers and gelatins up to 200 °C and increased chemiluminescent emission intensities for nanofibers treated with gamma radiation, at temperatures above 200 °C, compared to irradiated gelatins and non-irradiated nanofibers and gelatins. The electron paramagnetic (EPR) signals of DMPO adduct allowed for the identification of long-life HO● radicals only for bovine and donkey gelatin nanofibers treated with a 20 kGy gamma radiation dose. Microbial contamination with aerobic microorganisms, yeasts, filamentous fungi, Staphylococcus aureus, Escherichia coli, and Candida albicans of gelatin nanofibers treated with 10 kGy gamma radiation was under the limits required for pharmaceutical and topic formulations. Minor shifts of FTIR bands were observed at irradiation, indicating the preservation of secondary structure and stable properties of different-origin gelatin nanofibers.

Investigation on trommeled legacy waste from full-scale mining of old dumpsites: Suitable for valorization or scientific disposal?

The burgeoning interest in resource recovery from old dumpsites has significantly propelled the adoption of Landfill Mining (LFM) in recent years. This study is centred around evaluating the quality of materials recovered from the full-scale LFM activities at two major dumpsites in India, focusing on the valorization potential of the segregated legacy waste. A detailed analysis was conducted on the segregated waste fractions based on particle size (−30 mm, 30 to 6 mm, and −6 mm, as sourced from the sites), employing both batch and column leaching methods across a range of liquid-to-solid (L/S) ratios (0.1–10.0 L/kg).The findings reveal a pronounced concentration of contaminants within the −6 mm fraction compared to the 30 to 6 mm and −30 mm fractions. Column leaching tests revealed a reduction in contaminant concentration, correlating with incremental changes in L/S ratio. Notably, this trend remained consistent across varying particle sizes and specific type of contaminants assessed. Notably, color intensity of leachate reduced significantly from 720 to 1640 Platinum Cobalt Units (PCU) at an L/S ratio of 0.1 L/kg to a minimal 94–225 PCU at an L/S of 10 L/kg. Dissolved salts emerged as a primary concern, marking them as significant contaminants in both leaching methods. The analysis confirmed that the segregated fractions comply with the USEPA Waste Acceptance Criteria (WAC), permitting their disposal in non-hazardous waste landfills. However, the elevated presence of dissolved salts, exceeding reuse limits by 5–35 times, limits their open or unrestricted reuse. Despite this, isolated reuse aligns with regulations from the Netherlands and Germany, suggesting viable pathways for compliant utilization. Geotechnical assessments indicate the potential for repurposing the −30 mm fraction as alternative earthfill and construction material. While heavy metal leaching does not pose significant concerns, the prevalent unscientific disposal practices near urban settlements highlight potential human health risks.This investigation enriches the understanding of the physicochemical properties, leaching behaviour, and reuse potential of segregated legacy waste, offering crucial insights for civic authorities in determining appropriate reuse and disposal strategies for such materials.

Holistic investigation of structural evolution in corn stover lignin under pretreatment with varying γ-valerolactone concentrations

Until now, research on green and sustainable γ-valerolactone (GVL) pretreatment has predominantly centered on component separation efficiency, with limited attention given to the lignin structure. Nonetheless, the lignin's structure is considerably affected by the fractionation, consequently influencing its potential valorization. Herein, we conducted a holistic investigation of the structural evolution of two fractions of lignin in corn stover, obtained under pretreatment with varying GVL concentrations: GVL lignin (GVLL) originated from pretreatment liquor and cellulolytic enzyme lignin (CEL) separated from pretreated residue. Our findings indicated a general positive correlation between the molecular weight and polydispersity index of both GVLL and CEL with the increasing GVL concentration. This phenomenon is attributed to the enhanced lignin dissolution and relocation as the GVL concentration increases. Moreover, higher GVL concentrations also increased the acidity of reaction system, leading to degradation of β-O-4 linkages from 45.2 to 34.9 and 57.6 to 37.9 per 100 aromatic units in GVLL and CEL, respectively. Compared to CEL, GVLL exhibited a more remarkable phenolics yield (33.7% vs. 22.2%) during hydrodeoxygenation due to its superior purity and lower degree of polymerization. Recycling studies demonstrated the stability of GVL at lower concentrations. These findings provide valuable insights for optimizing GVL pretreatment systems.

Hydrogen from food waste: Energy potential, economic feasibility, and environmental impact for sustainable valorization

Globally, inefficient management of municipal solid waste, composed primarily of food waste poses concern for human and environmental well-being. Food waste can be converted into hydrogen gas, which can be utilized to generate power without emitting any harmful pollutants. This solution would also help with the issue of disposing of food waste. The conversion of food waste into hydrogen is a practical energy source with potential financial benefits. This study explores the transformative potential of converting food waste into renewable energy through hydrogen production, focusing on Bangladesh from 2023 to 2042. Notably, the study forecasts a surge in food waste from 23 million tons in 2023–110 million tons by 2042. By 2042, food waste is expected to generate 2480 MW of power, a rise from 489 MW in 2023. Based on the results of the economic study, the food waste into hydrogen via gasification project is financially viable in all of Bangladesh's main cities. Metrics such as internal rate of return, payback period, levelized cost of energy, net present value, and total life cycle cost were used to assess economic viability. The hydrogen production cost, payback period, and internal rate of return are 2.05 $/kg, 11 years and 14% respectively. It was discovered that using the available electricity from hydrogen gas may displace 1428 M liters of diesel fuel combustion. The quantity of diesel fuel saved can cut carbon dioxide emissions by 3.85 million tons. It was also found that using hydrogen as a source of energy generation has an attractive ecological efficiency of 99.98%. This research provides novel and pertinent data for investors contemplating gasification-based energy projects in Bangladesh. It pioneers a path toward eco-friendly waste management, reduced greenhouse gas emissions, and the adoption of sustainable energy solutions for the country.

Taguchi optimisation of the synthesis of vine-pruning-waste hydrochar as potential adsorbent for pesticides in water

This research aimed to synthesise an effective hydrochar adsorbent from vineyard pruning wastes to remove emerging contaminants as a potential valorisation product. The adsorption capacity of the hydrochar was optimised using the Taguchi method. Four synthesis variables were evaluated: hydrothermal reaction temperature, use of H3PO4 as a catalyst, number of acetone washes, and type of chemical cold activation. The simultaneous adsorption of five model pesticides (clothianidin (CTD), acetamiprid (ACE), 2,4-D, metalaxyl (MET), and atrazine (ATZ)) at an initial pH of 7 was studied. At optimum conditions, the hydrochar presented a total adsorption capacity of 22.7 μmol/g, representing a 2.7-fold improvement with respect to pristine hydrochar performance. High percentage removals were achieved for all pollutants (85 % CTD, 94 % ACE, 86 % MET, and 95 % ATZ) except for 2,4-D (4 %). This research provides a valuable reference for developing hydrochar adsorbents for pollution control and the valorisation of biomass wastes.

Reservoir siltation and sediment characterization for reuse as construction material in a semi-arid area

Anibi S, Ellouze S, Zairi M. 2024. Reservoir siltation and sediment characterization for reuse as construction material in a semi-arid area. Lake Reserv Manage. 40:159–176. In this study, we investigated the siltation rate, evolution, and spatial distribution of sediments within the Siliana Dam reservoir, north-west Tunisia. We analyzed the geotechnical, chemical, mineralogical, and trace metal content properties of sediment samples collected from the reservoir. Additionally, we examined the potential valorization of reservoir sediments in road construction and the effects of hydrated lime treatment on their bearing characteristics. The Siliana dam reservoir is currently 50% silted up, and the sedimentation rate is approximately 1.52% per year. The sediments are mainly fine-grained, low organic with medium to high plasticity and high content of calcium carbonate. The sediments consist of calcite and quartz, with minor amounts of dolomite, hematite, and phyllosilicate minerals. Chromium, zinc, and copper contents in the sediments exceed environmental standards. The lime treatment improved the materials bearing capacity. Adding lime (5% by weight) resulted in an immediate bearing ratio of 26%, a higher ratio compared to the raw sediments. The study of the spatial and temporal evolution of sediment accumulation provides information to develop strategies for mitigating the accumulation of sediments. The sediment characterization evaluated the suitability of sediments to be used as construction materials, offering potential cost savings and contributing to informed decision-making for reservoir management.

Innovation and Networks in the Bioeconomy: A Case Study from the German Coffee Value Chain

The transition to a circular bioeconomy requires innovation across many sectors, but social dynamics within a sector’s network may affect innovation potential. We investigate how network dynamics relate to the perceptions and adoption of bioeconomy innovation using a case study from the food processing sector. Our case study of the German coffee value chain represents a technologically advanced sector with a strong sustainability focus and potential for residue valorization, which is an important dimension of a sustainable circular bioeconomy. We identify three distinct views (pioneers, traditional and limited users) related to residue valorization, map linkages between actors using social network analysis, and highlight barriers to innovation. We collected data through an online survey and semi-structured interviews with key actors in the coffee roasting sector. Within the social network analysis, we find that public waste managers are closely linked to the most influential actors, state actors such as the customs and tax offices can quickly interact with others in the network and promote the spread of information (highest closeness centrality) and specific roasters play an important role as intermediaries for efficient communication (highest betweenness centrality). Finally, we identify four main barriers including the structure of the coffee network, inconsistencies in federal waste regulations, economies of scale, and visions of sustainability. To support a sustainable bioeconomy, we recommend that policy makers revise the primary regulatory frameworks for waste (e.g., German Recycling Act) to clarify how to classify food residues, their disposal structures and broaden their use streams.

Optimization of the Process for Obtaining Antioxidant Protein Hydrolysates from Pumpkin Seed Oil Cake Using Response Surface Methodology

Pumpkin seed cake, a byproduct of cold-pressed oil production, represents a food waste material with a great potential for valorization. The objective of the present study is to optimize the papain enzymatic hydrolysis process of pumpkin seed cold-pressed oil cake (CPC) to obtain protein hydrolysates with the highest antioxidant activity. Box–Behnken Response Surface Methodology (RSM) was used to optimize the simultaneous effects of an enzyme concentration of papain, a temperature, and a reaction time on the process of enzymatic hydrolysis on pumpkin seed cold-pressed oil cake (CPC). For these three input factors, different values are used—1, 2, and 3% for papain concentration, 20, 30, and 40 °C for temperature, and 60, 120, and 180 min for hydrolysis time. Thus, the design generated a total of 21 experimental runs. The aim is to obtain protein hydrolysates with the highest antioxidant activity. The responses DPPH and ABTS were calculated and the determined regression models were statistically analyzed and validated. The results revealed that optimal conditions included a papain concentration of 1.0%, a temperature of 40 °C, and a hydrolysis time of 60 min to retrieve the highest level of bioactive compounds.