Valorization Technologies Research Articles

Present scenario and future scope of food waste to biofuel production

AbstractFood waste is the outcome of different food processing practices that have not been reused and are disposed of as waste. Food wastes are rich in a wide variety of organic constituents including starches, proteins, oils, fats, phosphates, nutrients, amino acids, and natural acids. Food waste is a zero‐value and nonconsumable resource. In this context, the valorization of food waste to different sorts of biofuels, for example, biodiesel, bioethanol, biohydrogen, bio‐oil, biochar, and biomethane by employing well‐structured and efficient valorization technologies can be an attractive and viable approach to counter the current global energy crisis and in establishing a sustainable bioeconomy. This type of food waste management not only resolves the serious pollution problem but also helps to reduce the dependency of the energy sector on fossil fuels. This review discusses the characteristics of food waste, common strategies for food waste management, food waste as a feedstock, biofuels as a renewable energy source, valorization of food waste to various types of biofuels, microbes‐assisted valorization of food waste, biofuels and bioeconomy, and future scope and challenges in the valorization of food waste to biofuels.

Sequencing batch airlift reactors (SBAR): a suitable technology for treatment and valorization of mineral oil wastewaters towards lipids production

Produced water (PW) and spent oil-based wastewaters are some of the largest mineral oil wastewaters produced. Due to the high toxicity of hydrocarbons, several countries set stringent discharge limits and its treatment is compulsory before discharge. In this work, biological treatment of mineral oil wastewaters coupled with the production of bacterial lipids is demonstrated in sequential batch airlift reactors (SBAR). Two SBAR (2 L working volume) were used for treatment of PW and lubricant-based wastewater (LW), inoculated with Alcanivorax borkumensis SK2 (SBARAb+PW) and Rhodococcus opacus B4 (SBARR.o+LW), respectively. A total petroleum hydrocarbon removal (TPH) efficiency up to 96% and 80% were achieved for SBARAb+PW and SBARR.o+LW, respectively. Intracellular lipids production in SBARAb+PW increased when lower TPH/N ratios and higher feast stage duration were applied (up to 0.74 g g-1 cell dry weight (CDW)), whereas in SBARR.o+LW higher lipids production was observed for higher TPH/N ratios (0.94 g g-1 in CDW). Triacylglycerols (TAG) were the main intracellular lipid accumulated in both SBARAb+PW and SBARR.o+LW operations, while wax ester (WE) production was only observed extracellularly in the SBARAb+PW.

A review on the valorisation of food waste as a nutrient source and soil amendment.

Valorisation of food waste offers an economical and environmental opportunity, which can reduce the problems of its conventional disposal. Food waste is commonly disposed of in landfills or incinerated, causing many environmental, social, and economic issues. Large amounts of food waste are produced in the food supply chain of agriculture: production, post-harvest, distribution (transport), processing, and consumption. Food waste can be valorised into a range of products, including biofertilisers, bioplastics, biofuels, chemicals, and nutraceuticals. Conversion of food waste into these products can reduce the demand of fossil-derived products, which have historically contributed to large amounts of pollution. The variety of food chain suppliers offers a wide range of feedstocks that can be physically, chemically, or biologically altered to form an array of biofertilisers and soil amendments. Composting and anaerobic digestion are the main large-scale conversion methods used today to valorise food waste products to biofertilisers and soil amendments. However, emerging conversion methods such as dehydration, biochar production, and chemical hydrolysis have promising characteristics, which can be utilised in agriculture as well as for soil remediation. Valorising food waste into biofertilisers and soil amendments has great potential to combat land degradation in agricultural areas. Biofertilisers are rich in nutrients that can reduce the dependability of using conventional mineral fertilisers. Food waste products, unlike mineral fertilisers, can also be used as soil amendments to improve productivity. These characteristics of food wastes assist in the remediation of contaminated soils. This paper reviews the volume of food waste within the food chain and types of food waste feedstocks that can be valorised into various products, including the conversion methods. Unintended consequences of the utilisation of food waste as biofertilisers and soil-amendment products resulting from their relatively low concentrations of trace element nutrients and presence of potentially toxic elements are also evaluated.

DatabencArt and EDUBBA: digital infrastructures for cataloguing and sharing cultural heritage content

The paper presents DatabencArt and EDUBBA, two strictly integrated digital infrastructures designed and developed to cope with the increasing demand of a smart use of cutting-edge technologies in the Cultural Heritage (CH) realm. DatabencArt has been primarily designed to facilitate the cataloguing of CH objects while EDUBBA is focused on educational purposes. These platforms are the results of a long-term research effort made in the last five years by DATABENC Consortium (Distretto ad Alta Tecnologia per i Beni Culturali) and treasuring the experiences gained with the exploitation of many research projects in the field of of ICT technologies for Cultural Heritage knowledge, preservation, valorization and sustainable fruition.

The Use of Heterogeneous Catalysis in the Chemical Valorization of Plastic Waste

Plastic solid waste (PSW) is an ever-growing environmental challenge for our society, as it not only ends up in landfills but also in waterways and oceans and is consequently entering the food chain. A key strategy to overcome this problem while also preserving carbon resources is to use PSW as a feedstock, evolving towards a circular economy. To implement this, mechanical as well as chemical recycling technologies must be developed. Indeed, owing to the high volume of PSW generated each year, mechanical recycling alone is not adequate for addressing this global challenge. Because of this, chemical recycling via thermal and heterogeneous catalytic conversion has received growing attention. This process has the potential to take PSW and convert it into usable monomers, fuels, synthesis gas, and adsorbents under more sustainable conditions than thermal degradation. This Review highlights the recent research advances in catalytic technologies for PSW conversion and valorization.

Performance analysis of a 2.45 GHz microwave plasma torch for CO2 decomposition in gas swirl configuration

Microwave plasmas are a promising technology for energy-efficient CO2 valorization via conversion of CO2 into CO and O2 using renewable energies. A 2.45 GHz microwave plasma torch with swirling CO2 gas flow is studied in a large pressure (20–1000 mbar) and flow (1–100 L min−1) range. Two different modes of the plasma torch, depending on the operating pressure and microwave input power, are described: at pressures below 120 mbar the plasma fills most of the plasma torch volume whereas at pressures of about 120 mbar an abrupt contraction of the plasma in the center of the resonator is observed along with an increase of the gas temperature from 3000 K to 6000 K. The CO outflow is generally found to be proportional to the plasma effective power and exhibits no significant dependence on the actual CO2 flow injected into the reactor but only on the input power at certain pressure. Thermal dissociation calculations show that, even at the lowest pressures of this study, the observed conversion and energy efficiency are compatible with a thermal dissociation mechanism.

Understanding the Structural Changes of Lignin Macromolecules From Balsa Wood at Different Growth Stages

Lignin is the most abundant aromatic polymer in nature, that makes it an attractive raw material for producing chemicals, materials, and fuels that are currently obtained from fossil resources. However, the structural complexity, heterogeneity, and variability of the lignin macromolecules hinder the development of efficient valorization technologies for different sources of raw materials. In this study, double enzymatic lignin (DEL) was isolated from different tree-age balsa tree to understand the structural variations of lignin macromolecules during the growth of balsa for the first time. Confocal Raman microscopy (CRM) and component analysis were used to monitor the accumulation of lignin in the plant cell wall. Meanwhile, the structural characteristics and chemical reactivity of DELs were synthetically characterized by advanced NMR techniques. Results showed that the lignin is almost composed of β-O-4 linkages and its content is elevated as the increasing tree-age. Interestingly, carbon-carbon linkages (e.g., β-β and β-5) in these DELs isolated from 3 and 5-year balsa are gradually disappeared. Considering the increasing molecular weight of DELs with the tree-age, it was concluded that lignin macromolecules in balsa wood was gradually polymerized with the increasing growth years. Furthermore, abundant C-O linkages with less C-C linkages in the DELs from 3 and 5-years balsa wood suggested that these feedstocks are promising feedstock in current lignin-first biorefinery scenario. Meanwhile, these lignin fractions from these feedstocks are beneficial to the downstream conversion of lignin into aromatic chemicals. In short, understanding the structural changes of lignin during the growth of balsa wood will facilitate the deconstruction and value-added applications of this kind of feedstock.

Thermochemistry of the lignin broken bits

The hydroxy- and methoxy substituted benzaldehydes are the simplest broken bits from the lignin valorization technologies. Comprehensive thermochemical study of these compounds was performed including vapour pressure measurements, combustion and differential scanning calorimetry. A large number of primary experimental results on vapour pressures, phase transitions, and enthalpies of formation have been collected from the literature and evaluated with help of empirical and quantum-chemical methods. The consistent sets of thermodynamic data were utilised for developing the simple GA method for prediction of enthalpies of vaporization and enthalpies of formation of di-substituted benzenes in the gas phase. Parameters of GA procedures are expected to be transferable for prediction of thermochemical properties of poly-hydroxy and poly-methoxy substituted benzenes appearing in reaction products during of the lignin valorization.

Advancement in valorization technologies to improve utilization of bio-based waste in bioeconomy context

The world today is not only facing the problem of depleting energy sources but also generation of waste from anthropogenic activities. While waste is a risk, it is also an opportunity to solve this dual problem through utilization of waste as a potential source of energy and products. In order to reconcile the management of waste to the scale of its production, several researches are being pursued. Establishment of bioeconomy is a great way to achieve this goal. But inherent challenges associated with biowaste include manageability of by-products and sludge, wide variety in waste composition, efficiency of the process and economic viability of treatment technologies to scale-up and industrialize beyond laboratory setup. Recent advancements have been made in this regard with the use of new techniques, synergistic catalysts, combination of technologies and novel treatment materials to remediate the challenges and maximize the value of waste by utilizing it as a feedstock to produce industrial chemicals, fuels and materials. This review provides an insight into these developments, along with the critical discussion, limitations and economic feasibility of waste valorization technologies to provide new understanding for the advancement of bioeconomy.

How do novel and conventional agri-food wastes, co-products and by-products improve soil functions and soil quality?

Agriculture is estimated to generate about 700 million tons of waste annually in the EU. Novel valorization technologies are developing continuously to recover and recycle valuable compounds and nutrients from waste materials. To close the nutrient loop, low-value agri-food wastes, co-products and by-products (AFWCBs) produced during the valorization process, need to be returned to the soil. However, knowledge on their reaction in soils that is needed to allow efficient and environmentally sound recycling is largely lacking. To this end, we set up a series of laboratory incubation experiments using 10 AFWCBs including insect frass residues made from three different feedstocks, anaerobic digestates from two feedstocks, potato-pulp, rice bran compost, duckweed and two reference crop residues (wheat straw and sugar beet) and measured net N release, C mineralization, dehydrogenase activity (DHA), microbial biomass C (MBC) and community structure. The suppressing potential of frasses and digestates against Rhizoctonia solani was determined using bean. The digestates released the highest net mineral N (50–70%) followed by rice bran compost (55%) and duckweed (30%), while frass made from general food waste and potato-pulp immobilized N like the reference straw for 91 days after incubation. All AFWCBs except digestates significantly increased MBC compared to the control while frasses, potato-pulp and duckweed increased DHA. Frasses and digestates significantly suppressed the development of Rhizoctonia solani in bean plants. AFWCBs from emerging valorizing technologies have the potential to improve microbial activities, C sequestration and may play a significant role in closing the nutrient loop.

Food Waste Valorization Based on Anaerobic Digestion

The rapid urbanization that took place in the last 60 years has led to a dramatic increase in the generation of Municipal Solid Waste (MSW). The biodegradable fraction of MSW mainly consists of food waste (FW) and corresponds to about 50% of the total MSW. The disposal of FW in the environment has become a significant challenge. On the other hand, FW is an excellent substrate for anaerobic digestion (AD). This manuscript reviews the different AD technologies for the treatment of FW. Different types of bioreactors and pretreatment methods used to enhance methane production through AD of FW are discussed. The current review gives special emphasis on the methods for biogas upgrading and on technologies for FW digestate valorization. Food waste valorization through anaerobic digestion offers a wide variety of options in all process steps. From the pre-treatment of the feedstock and the selection of the suitable anaerobic digestion technology to the configuration of the process based on the desired products and the valorization of the generated digestate, the design of an integrated anaerobic digestion plant is a challenging task, which necessitates a systematic design. A systematic approach is necessary for FW valorization. The simple single-stage AD process leads to underutilization of the feedstock. There are plenty of available technologies that could be combined for the development of an integrated biorefinery that will be optimized in terms of FW valorization towards the production of biofuels and high-added value products, while introducing a circularity in the nutrients contained in the FW. FW-to-biofuel conversion technologies are high Technology Readiness Level (TRL—9) technologies and anaerobic digestion is applied worldwide at commercial scale.

Lignin from Tree Barks: Chemical Structure and Valorization.

Lignins from different tree barks, including Norway spruce (Picea abies), eucalyptus (Eucalyptus globulus), mimosa (Acacia dealbata) and blackwood acacia (A. melanoxylon), are thoroughly characterized. The lignin from E. globulus bark is found to be enriched in syringyl (S) units, with lower amounts of guaiacyl (G) and p‐hydroxyphenyl (H) units (H/G/S ratio of 1:26:73), which produces a lignin that is highly enriched in β‐ether linkages (83 %), whereas those from the two Acacia barks have similar compositions (H/G/S ratio of ≈5:50:45), with a predominance of β‐ethers (73–75 %) and lower amounts of condensed carbon–carbon linkages; the lignin from A. dealbata bark also includes some resorcinol‐related compounds, that appear to be incorporated or intimately associated to the polymer. The lignin from P. abies bark is enriched in G units, with lower amounts of H units (H/G ratio of 14:86); this lignin is thus depleted in β‐O‐4′ alkyl–aryl ether linkages (44 %) and enriched in condensed linkages. Interestingly, this lignin contains large amounts of hydroxystilbene glucosides that seem to be integrally incorporated into the lignin structure. This study indicates that lignins from tree barks can be seen as an interesting source of valuable phenolic compounds. Moreover, this study is useful for tailoring conversion technologies for bark deconstruction and valorization.

Hydrochars production, characterization and application for wastewater treatment: A review

Hydrothermal carbonization (HTC) of wet solid wastes has been pointed out as an eco-friendly, flexible and highly efficient technology for the sustainable valorization of multiple sourced wastes. In this review paper, most recent studies on hydrochars (solid residue of the HTC process) production, characterization and application for wastewaters treatment was summarized and deeply discussed. The role of initial feedstock source nature and characteristics as well as the HTC experimental conditions including the temperature, the residence time and the pH media was assessed. Physical and chemical activation methods including the use of oxygen, steam, microwave, acids, alkaline, organics and salty solutions for the improvement of the physicochemical properties of the produced hydrochars are compared. The efficiency of these raw/modified hydrochars along with the involved mechanisms during organic (dyes) and mineral pollutants (heavy metals and nutrients) removal from aqueous solutions is also reviewed. Finally, this paper addresses the main challenges and also demonstrates insights on new directions for hydrochars research and development in the future.

Novel Drying Methods for Sustainable Upcycling of Brewers’ Spent Grains as a Plant Protein Source

Brewers’ spent grains (BSGs) are the most important by-product of the brewing industry and are rich in protein and fiber. However, abundant amounts of BSGs are discarded annually worldwide. This project aimed to employ and compare innovative drying techniques to introduce snacks with protein sources derived from leftover BSGs. This study explored the dehydration kinetics of BSGs and the effect of three different drying methods—oven drying (OD), freeze drying (FD), and vacuum microwave drying (VMD)—on their protein content and functionality. Then, an energy and exergy analysis for the drying methods was given. Accordingly, a snack product (baked chips) using the dehydrated BSGs was developed by a sensory panel study to assess consumer acceptability of the final products. It was found that the VMD process took less drying time (48 min) compared to OD (50 min), with higher effectiveness as a drying process. VMD-treated BSG also showed moderate protein functionality and the highest overall acceptability when used in baked chips. Thus, VMD might be used as a sustainable drying technology for thermal treatment and valorization of BSG. In addition to having implications for dietary health, findings can help improve the economy of the breweries and other industries that deal with the processing of grains by valorizing their process waste and contributing to sustainability.

The Cultivation of Lipid-Rich Microalgae Biomass as Anaerobic Digestate Valorization Technology—A Pilot-Scale Study

The aim of the study was to determine the use of digestate from anaerobic digestion of dairy wastewater as a culture medium for microalgae to obtain bio-oil. The experiments were conducted at a small scale in a closed raceway pond. The efficiency of the microalgae biomass production, the digestate treatment efficiency as well as the content and properties of the bio-oil obtained from the microalgal cells were analyzed. The produced biomass concentration was about 3000 ± 10.5 mg dry biomass/L, with an average growth rate of 160 ± 6.6 mgdm/L·d. The efficiency of organic compound and nutrient removal was above 90%. The bio-oil content in the biomass was about 20%. Based on the results of the study, a concept for technical-scale technology was developed.

Realization of a solar hydrothermal carbonization reactor: A zero-energy technology for waste biomass valorization

Research around hydrothermal carbonization (HTC) has seen a huge development in recent years, materializing in the first pilot and industrial plants. Even though HTC reactions are slightly exothermic, the overall process entails energy consumption to both reach operating conditions and tackle heat losses. To face this issue and to develop a zero-energy process, this work proposes an innovative solution: the coupling of an HTC reactor with a solar concentrator, designed to fully cover the HTC energy needs. A 300 ml stainless steel HTC reactor was constructed and positioned on the focus of a parabolic dish concentrator (PDC), consisting of one parabolic mirror of 0.8 m2. To maximize the light absorption, the illuminated side of the HTC reactor was coated with a thin layer of nanostructured copper oxide, realized via electron beam deposition. Then, the effectiveness of the hybrid solar-HTC solution was demonstrated by carrying out an experimental campaign on a residual agro-biomass (grape seeds), which was treated at 180, 220, and 250 °C for 2 h. The coating confers excellent absorbing performances to the system, exhibiting an absorptance of up to 95.6% (at 300 nm wavelength). Heating times, yields, composition, and energy properties of “solar hydrochars” resemble those of studies performed in traditional HTC systems. This research work proves the feasibility of the solar-HTC prototype apparatus and opens the way to the development of a zero-energy solar-HTC technology.

Combining anaerobic digestion and hydrothermal liquefaction in the conversion of dairy waste into energy: A techno economic model for New York state

There is increasing global interest and policies being enacted to lower greenhouse gas emissions, especially from the agricultural sector. In the U.S. for example, states with large dairy operations may combine proven manure valorization technologies, such as anaerobic digestion and hydrothermal liquefaction. Sustainable manure treatment would increase the recovery of energy and other useful co-products, namely biogas, biocrude oil and hydro-char as well as lower the environmental impacts. In this study, the economic feasibility of implementing a centralized bioenergy system in New York State was investigated. The feasibility of this transformation depends on many factors, including capital costs, discount rates, and other financing arrangements, electricity selling prices, incentives and farm sizes and locations. For a large-scale implementation in New York State accounting for nearly 50% of the state’s dairy farms, our model of a distributed, hybrid anaerobic/hydrothermal system was shown to treat 590 million liters of wet manure per day, producing 607 million kWh of electricity, 162,000 L of biocrude oil and 117,000 kg of hydro-char per day. Electricity selling price is a critical factor. Increasing the electricity selling price from wholesale ($0.06/kWh) to retail ($0.18/kWh) increased the net present value from $395 million to $1.5 billion (considering a 40-year project lifetime).

Hydrodynamic cavitation-assisted continuous pre-treatment of sugarcane bagasse for ethanol production: Effects of geometric parameters of the cavitation device.

For biotechnological conversion of lignocellulosic biomass, a pre-treatment step is required before enzymatic hydrolysis of carbohydrate fractions of the material, which is required to produce fermentable sugars for generation of ethanol or other products in a biorefinery. The most of the reported pre-treatment technologies are in batch operation mode, presenting some disadvantages as dead times in the process. In this context, hydrodynamic cavitation (HC)-assisted alkaline hydrogen peroxide (AHP) pre-treatment in continuous process was proposed for pre-treatment of sugarcane bagasse (SCB). The system was designed with a main reactor containing two devices to generate cavitation by passing liquid medium through orifice plates. For SCB pretreated in continuous process, 52.79, 34.31, 22.13 and 15.81g of total reducing sugars (TRS) per 100g of SCB were released in samples pretreated using orifice plates with a number of holes of 24 (d=0.45mm), 16 (d=0.65mm), 12 (d=0.8mm) and 8 (d=1mm), respectively. Computational Fluid Dynamics (CFD) tools showed that 0.94 of vapor phase volume fraction and 0.19 of cavitation number were achieved at 31m/s of throat velocity and upstream pressure of 350,000Pa. By using pretreated SCB, 28.44g of ethanol/L (84.31% of yield respect to theoretical value) was produced by immobilized Scheffersomyces stipitis NRRL-Y7124 in a simultaneous hydrolysis and fermentation process at high solid loading (16% S/L). Thus, HC-assisted process was proved as a promising technology for valorization of lignocellulosic biomass.

University-business cooperation: directions of interaction

The article is devoted to the analysis of promising areas of university-business cooperation (UBC) based on the study of modern Russian and foreign experience. It justifies the relevance of the broad approach to the interpretation of UBC within which it is proposed to consider cooperation between universities and business not as a set of isolated transactions within a limited range of areas of interaction, but as a system of long-term mutually beneficial relations with a wide range of possible types of cooperation that can also include the state and community organizations. The article analyzes 14 types of joint activities of universities and business within four main blocks - education, research, valorization (knowledge and technology commercialization) and management, which can serve as a basis for developing a system of indicators for assessing the effectiveness of UBC. The conclusion is made about the need to adjust the state policy in the field of science and education in order to reduce the imbalance in the development of these areas of cooperation both in Russia and in Europe.

Agri‐food waste valorisation

Agri‐food waste valorisation