Biorefinery Concept Research Articles

Enhancing the Methane Yield of Salicornia spp. via Organosolv Fractionation as Part of a Halophyte Biorefinery Concept

The present research investigated the effect of organosolv pretreatment on two species of salt-tolerant Salicornia spp. biomass, Salicornia dolichostachya and Salicornia ramosissima, for increasing biomethane production through anaerobic digestion. The final biomethane yield of de-juiced green fibers of Salicornia spp. from wet fractionation increased by 23–28% after organosolv treatment. The highest methane yield of about 300 mL-CH4/gVS was found after organosolv treatment with 60% v/v ethanol solution at 200 °C for 30 min, or at 180 °C for 30 or 60 min treatment time. Furthermore, the methane production rate increased significantly, reducing the time until 95% of the final methane yield was reached from 20 days to 6–10 days for the organosolv-treated biomass. This research shows that the process of anaerobic digestion of halophyte biomass benefits from cascade processing of Salicornia fibers in a biorefinery framework by sequential wet and organosolv fractionation for full utilization of halophytic biomass.

Sustainable Management Strategies for Fruit Processing Byproducts for Biorefineries: A Review

The fruit processing industry generates enormous amounts of byproducts, which are primarily removed through landfill or incineration. However, these processes cause carbon dioxide and methane emissions and release dioxin into the environment. The management of fruit processing byproducts is important for reducing the amount of food waste that is sent to landfills and for developing strategies through the reuse of these products for valorization and economic added value. Fruit processing byproducts are rich sources of bioactive compounds and fermentable and nonfermentable sugars. Therefore, these materials are very attractive feedstocks for developing integrated multifeed biorefineries that coproduce a wide range of natural products and bioenergy. The studies presented here have shown sustainable strategies for managing fruit processing byproducts via a biorefinery approach to achieve full valorization via a circular economy. The full valorization project proposed five main phases, namely, pretreatment, extraction, dark or aerobic fermentation, anaerobic digestion, and post-treatment, as well as two additional pathways to generate additional bioelectricity. When choosing the appropriate directions for the presented concept, a technoeconomic analysis should be carried out, considering the type of biomass and its availability at the site of the biorefinery and throughout the year of production. Applying the proposed concept of biorefineries in closed-loop technology is a promising way to enhance economic efficiency and decrease environmental influence in accordance with sustainable development.

Features of the microalga Raphidocelis subcapitata: physiology and applications.

The microalga Raphidocelis subcapitata was isolated from the Nitelva River (Norway) and subsequently deposited in the collection of the Norwegian Institute of Water Research as "Selenastrum capricornutum Printz". This freshwater microalga, also known as Pseudokirchneriella subcapitata, acquired much of its notoriety due to its high sensitivity to different chemical species, which makes it recommended by different international organizations for the assessment of ecotoxicity. However, outside this scope, R. subcapitata continues to belittle explored. This review aims to shed light on a microalga that, despite its popularity, continues to be an "illustrious" unknown in many ways. Therefore, R. subcapitata taxonomy, phylogeny, shape, size/biovolume, cell ultra-structure, and reproduction are reviewed. The nutritional and cultural conditions, chronological aging, and maintenance and preservation of the alga are summarized and critically discussed. Applications of R. subcapitata, such as its use in aquatic toxicology (ecotoxicity assessment and elucidation of adverse toxic outcome pathways) are presented. Furthermore, the latest advances in the use of this alga in biotechnology, namely in the bioremediation of effluents and the production of value-added biomolecules and biofuels, are highlighted. To end, a perspective regarding the future exploitation of R. subcapitata potentialities, in a modern concept of biorefinery, is outlined. KEY POINTS: • An overview of alga phylogeny and physiology is critically reviewed. • Advances in alga nutrition, cultural conditions, and chronological aging are presented. • Its use in aquatic toxicology and biotechnology is highlighted.

Experimental Insights into the Fermentation of Pyro-Syngas to Ethanol in a Semi-Batch and Continuous Stirred Bioreactor with Mathematical Modelling and Optimization

Syngas fermentation can play an important role in implementing the concept of biorefinery as it can serve as a platform to convert high-lignin biomass to biofuels. For the utilization of this process in commercial scale, the generation of an experimental database supported by a deterministic mathematical model and optimization is necessary. In this study, a locally isolated clostridial consortium, UACJUChE1, was used to convert pyro-syngas to ethanol and acetic acid. Mathematical models were developed and validated for a 3 L stirred and gas-sparged bioreactor operated in both semi-batch and continuous modes. The volumetric productivity of ethanol was correlated with the dilution rate and the gas residence time. The performance of the bioreactor, run in both semi-batch and continuous modes, was optimized using response surface methodology. For the semi-batch operation, a maximum ethanol concentration of 13.122 g/L after 30 h operation was achieved at optimum values of pyrolysis temperature, ratio of gas to liquid volume (VG/VL), and volumetric gas flow rate of 648 °C, 0.46, and 6.7 L/h respectively. For continuous operation, a maximum ethanol concentration of 29.450 g/L after 300 h is obtained at optimum values of VG/VL and ratio of gas to liquid volumetric flow rate of 0.28 and 335.148, respectively.

Sequential catalytic lignin valorization and bioethanol production: an integrated biorefinery strategy

BackgroundThe effective valorization of lignin and carbohydrates in lignocellulose matrix under the concept of biorefinery is a primary strategy to produce sustainable chemicals and fuels. Based on the reductive catalytic fractionation (RCF), lignin in lignocelluloses can be depolymerized into viscous oils, while the highly delignified pulps with high polysaccharides retention can be transformed into various chemicals.ResultsA biorefinery paradigm for sequentially valorization of the main components in poplar sawdust was constructed. In this process, the well-defined low-molecular-weight phenols and bioethanol were co-generated by tandem chemo-catalysis in the RCF stage and bio-catalysis in fermentation stage. In the RCF stage, hydrogen transfer reactions were conducted in one-pot process using Raney Ni as catalyst, while the isopropanol (2-PrOH) in the initial liquor was served as a hydrogen donor and the solvent for lignin dissolution. Results indicated the proportion of the 2-PrOH in the initial liquor of RCF influenced the chemical constitution and yield of the lignin oil, which also affected the characteristics of the pulps and the following bioethanol production. A 67.48 ± 0.44% delignification with 20.65 ± 0.31% of monolignols yield were realized when the 2-PrOH:H2O ratio in initial liquor was 7:3 (6.67 wt% of the catalyst loading, 200 °C for 3 h). The RCF pulp had higher carbohydrates retention (57.96 ± 2.78 wt%), which was converted to 21.61 ± 0.62 g/L of bioethanol with a yield of 0.429 ± 0.010 g/g in fermentation using an engineered S. cerevisiae strain. Based on the mass balance analysis, 104.4 g of ethanol and 206.5 g of lignin oil can be produced from 1000 g of the raw poplar sawdust.ConclusionsThe main chemical components in poplar sawdust can be effectively transformed into lignin oil and bioethanol. The attractive results from the biorefinery process exhibit great promise for the production of valuable biofuels and chemicals from abundant lignocellulosic materials.

Integrated process for a new sequential valorization of corn ethanol production by-products: Production of fermented solid with lipase activity, ethyl esters, and animal feed

The use of co-products from corn ethanol production such as distillers’ dried grains with solubles (DDGS) and distillers’ corn oil (DCO) to produce a crude extract with lipolytic activity and fatty acid ethyl esters was studied in an integrated process. The dry fermented solid (DFS) with lipase activity was produced from the fermentation of the filamentous fungus Rhizomucor miehei in DDGS in tray-type reactors and column systems. The DFS was used to catalyze esterification reactions between oleic acid and ethanol, with conversions of 72% and 80% (within 4 h) for the biocatalyst produced in tray-type and fixed bed systems, respectively. The biocatalyst also converted glycerides from DCO into FAEE, with an ester yield higher than 70% after three consecutive reactions. By introducing 2 wt% of a commercial preparation (Novozym 435) in the system with the DFS, ester contents of 81% were obtained and, the yield was higher than 95% after three consecutive reactions. The biocatalyst could be reused 6 consecutive times in the esterification reactions, after washing with ethanol and 5 times after washing with hexane. In DCO transesterification reactions, reuse was less efficient with a loss of activity after the second reuse. Bromatological analysis showed that the fermented material maintained the main properties of the in natura DDGS, with a reduction in the oil and grease and an increase in protein content. The chemical composition was maintained after its use in the corn oil ethanolysis (used DFS). These findings show the potential for developing novel pathways to diversify the use and enhance the value of co-products derived from the large-scale corn ethanol industry, in a biorefinery concept.

Valorization of Food Waste into Single-Cell Protein: An Innovative Technological Strategy for Sustainable Protein Production.

The rapidly increasing population and climate change pose a great threat to our current food systems. Moreover, the high usage of animal-based and plant-based protein has its drawbacks, as these nutritional sources require many hectares of land and water, are affected by seasonal variations, are costly, and contribute to environmental pollution. Single-cell proteins (SCPs) are gaining a lot of research interest due to their remarkable properties, such as their high protein content that is comparable with other protein sources; low requirements for land and water; low carbon footprint; and short production period. This review explores the use of food waste as a sustainable feedstock for the advancement of SCP processes. It discusses SCP studies that exploit food waste as a substrate, alongside the biocatalysts (bacteria, fungi, yeast, and microalgae) that are used. The operational setpoint conditions governing SCP yields and SCP fermentation routes are elucidated as well. This review also demonstrates how the biorefinery concept is implemented in the literature to improve the economic potential of "waste-to-protein" innovations, as this leads to the establishment of multiproduct value chains. A short section that discusses the South African SCP scenario is also included. The technical and economic hurdles facing second-generation SCP processes are also discussed, together with future perspectives. Therefore, SCP technologies could play a crucial role in the acceleration of a "sustainable protein market", and in tackling the global hunger crisis.

Development of a Carotenoid-Rich Microalgae Colorant by Microencapsulation

Dunaliella salina has been recognized as an excellent biomass source of carotenoid, which can be used as a natural orange coloring agent for food products. The most eco-friendly approach for extracting carotenoid is through supercritical carbon dioxide extraction, as it yields highly concentrated extracts while preventing pigment thermal degradation. However, there are limitations when a lipophilic extract is considered a food ingredient, in particular very difficult handling and low solubility in water-based products. The aim of this study was to develop a hydrosoluble form of a natural carotenoid-rich extract recovered from algae biomass within a biorefinery concept to be incorporated in aqueous-based food products. A two-step process was developed, starting with the emulsification of the supercritical extract into a mixture of maltodextrin and gum arabic, using soy lecithin as an emulsifier. The emulsification was followed by a spray-drying step. The impact of process variables on the encapsulation yield, efficiency, emulsion properties, and particle characteristics was studied. The resulting particles exhibited an intense orange color and good water dispersibility, facilitating uniform yellow coloring when incorporated into an aqueous-based product. Overall, spray-drying emulsions containing carotenoids derived from Dunaliella salina prove to be a promising strategy for the global market demand for natural colorants.

Recycling of waste calcium carbonate in lignocellulosic biorefining chain for chiral lactic acid production

One of the major end-products of lignocellulosic biorefining chain is the solid residues containing various compounds. The present approach to solid residues treatment is combustion for generation of heat and electricity. This study investigated the potential for recycling of the combustion ash from the solid residues after lignocellulosic dry biorefining process. A range of characterizations showed that the combustion ash contained a high amount of calcium carbonate. By recycling the ash as the neutralizer in biorefining process, the waste calcium carbonate in the ash was efficiently utilized for pretreated biomass neutralization and can replace 40 % of calcium hydroxide for lactic acid production. The chiral L-lactic acid titer reached 102.4 ± 3.6 g/L from 20 % (w/w) solids loading of wheat straw. Three feasible strategies of ash recycling for the investigated biorefinery concept were further proposed base on the rigorous calcium mass calculation, which can efficiently reduce the consumption of neutralizers.

Assessment of novel biorefinery concepts for the production of biohydrogen and value-added products from industrial waste streams

The concept of biorefinery provides a promising strategy to tackle some of the most pressing challenges of our time. Biorefineries can close material loops by generating value-added products from waste, thereby contributing to the implementation of a circular economy and reducing the extraction of primary resources. Further, they can help solve the problem of waste accumulation and reduce CO2 emissions by harnessing the energy content of waste. To realize the full potential of biorefineries, however, more work is needed in process design and optimization. Uncertainties regarding economic feasibility, performance, and the reliability of new technologies often hinder their implementation. Thus, a holistic approach is needed to assess these factors in the early phases of process development. This paper presents a basis for such an approach using the example of a novel biorefinery concept. This concept uses two interconnected biological processes for the production of biohydrogen and other products with low CO2 emissions. Two waste streams from an industrial setting are used as input along with organic agricultural residues. The basis for an assessment method is developed to estimate the environmental impacts of biorefineries using the described case as an example.

Enzymatic approaches for diversifying bioproducts from cellulosic biomass.

Cellulosic biomass is the most abundantly available natural carbon-based renewable resource on Earth. Its widespread availability, combined with rising awareness, evolving policies, and changing regulations supporting sustainable practices, has propelled its role as a crucial renewable feedstock to meet the escalating demand for eco-friendly and renewable materials, chemicals, and fuels. Initially, biorefinery models using cellulosic biomass had focused on single-product platform, primarily monomeric sugars for biofuel. However, since the launch of the first pioneering cellulosic plants in 2014, these models have undergone significant revisions to adapt their biomass upgrading strategy. These changes aim to diversify the bioproduct portfolio and improve the revenue streams of cellulosic biomass biorefineries. Within this area of research and development, enzyme-based technologies can play a significant role by contributing to eco-design in producing and creating innovative bioproducts. This Feature Article highlights our strategies and recent progress in utilizing the biological diversity and inherent selectivity of enzymes to develop and continuously optimize sustainable enzyme-based technologies with distinct application approaches. We have advanced technologies for standalone platforms, which produce various forms of cellulose nanomaterials engineered with customized and enhanced properties and high yields. Additionally, we have tailored technologies for integration within a biorefinery concept. This biorefinery approach prioritizes designing tailored processes to establish bionanomaterials, such as cellulose and lignin nanoparticles, and bioactive molecules as part of a new multi-bioproduct platform for cellulosic biomass biorefineries. These innovations expand the range of bioproducts that can be produced from cellulosic biomass, transcending the conventional focus on monomeric sugars for biofuel production to include biomaterials biorefinery. This shift thereby contributes to strengthening the Bioeconomy strategy and supporting the achievement of several Sustainable Development Goals (SDGs) of the 2030 Agenda for Sustainable Development.

Bark extractives as sources of carbon-efficient functional precursors and materials

<p>Biomass residues generated in forest operations represent an abundant and renewable resource in need for valorization. Bark is becoming increasingly relevant, not only in the bioproducts sector, but also in the context of the circular bioeconomy, which is placing emphasis on underutilized residues and waste. Among these, tree bark is one of the largest forestry by-products, accessible at a megaton scale but so far mostly utilized for its solid fuel value. Bark valorization should include the isolation of valuable natural compounds that add functionalities to a variety of bioproducts. This is the subject of this review, which considers bark extractives prospects, under the biorefinery concept, placing attention on extractives' chemical profiles and properties. We introduce the most recent pathways reported for bark fractionation and the opportunities to achieve new materials by using the concepts of supramolecular chemistry, leading to special assemblies. We show that value-added chemicals and materials are possible and expected to become most relevant in efforts aimed at maximizing bark utilization.</p>

Valorizacija agro-industrijskog otpada kao potencijalnog izvora proizvoda sa dodatnom vrednošću sa aspekta cirkularne ekonomije

Agro-industrial waste has been considered to be a good source for the production of biofuels. Apart from that, it has also proven to be a valuable source of high-value-added products. The conversion of agro-industrial waste into high-value-added products allows the whole process to be designed in line with the biorefinery and zero-waste circular economy concept, especially because all parts of agro-industrial waste can be utilised. The application of the circular economy to agro-industrial systems is spreading globally and is a response to the current unsustainable model of production and consumption based on resource depletion and increased demand. This review provides a more detailed understanding of the potential of the circular economy as a response to the need to reduce the environmental impact of agro-industrial waste in organic production and to promote a more sustainable agri-food industry.

Microbes' role in environmental pollution and remediation: a bioeconomy focus approach.

Bioremediation stands as a promising solution amid the escalating challenges posed by environmental pollution. Over the past 25 years, the influx of synthetic chemicals and hazardous contaminants into ecosystems has required innovative approaches for mitigation and restoration. The resilience of these compounds stems from their non-natural existence, distressing both human and environmental health. Microbes take center stage in this scenario, demonstrating their ability of biodegradation to catalyze environmental remediation. Currently, the scientific community supports a straight connection between biorefinery and bioremediation concepts to encourage circular bio/economy practices. This review aimed to give a pre-overview of the state of the art regarding the main microorganisms employed in bioremediation processes and the different bioremediation approaches applied. Moreover, focus has been given to the implementation of bioremediation as a novel approach to agro-industrial waste management, highlighting how it is possible to reduce environmental pollution while still obtaining value-added products with commercial value, meeting the goals of a circular bioeconomy. The main drawbacks and challenges regarding the feasibility of bioremediation were also reported.

STUDY ON THE PROCESS OF GASIFICATION OF BLACK LIQUOR

This review paper describes the potential of developing a new lignocellulosic biorefinery concept integrated with the Kraft industry. To demonstrate that gasification is a sustainable and more valuable processing route than burning it in recovery boilers, additional processes of syngas cleaning and high sulfur recovery are required in order to achieve a significant reduction in operating costs to improve economic feasibility through BL gasification. BL gasification is performed using two types of gasifiers, one with a fluidized bed, which requires a higher air velocity to increase the yield of valuable products aiding to increase the calorific value of the produced gas compared to fixed bed gasifiers. Fixed-bed gasifiers produce gas with a high tar content because the heat and mass transfer between the gasifier and the biomass is low and non-uniform. BL gasification offers great potential for increased energy recovery with a reduced amount of emissions compared to that of conventional BL burning in recovery boilers.

Coproduction of Biofuel and Pigments from Micractinium sp. Using UV-Induced Mutagenesis and Adding Abscisic Acid and Salicylic Acid for Biorefinery Concepts

Coproduction of Biofuel and Pigments from Micractinium sp. Using UV-Induced Mutagenesis and Adding Abscisic Acid and Salicylic Acid for Biorefinery Concepts

MONOGRAPH: The confluence of Circular Bioeconomy, Biorefineries and Sustainable Development Goals in the olive sector

In this work, the basic concepts of Circular Economy, Bioeconomy and Biorefineries are reviewed with a special emphasis on the olive sector. The possibility of developing biorefineries in this field entails a series of advantages that affect economic, social and environmental aspects and, therefore, can have a direct impact on achieving the Sustainable Development Goals (SDGs). This article reviews the main contributions of biorefineries based on olive biomass to the SDGs, both from the industrial point of view and from the point of view of cooperatives, which represent the vast majority of the productive structures in the olive oil sector in Spain. Finally, an analysis is carried out of the barriers and opportunities that may affect the achievement of the SDGs in the area of study.

An economic and environmental assessment of guayule resin co-products for a US natural rubber industry

Guayule (Parthenium argentatum) is a natural rubber producing desert shrub that has the potential to be grown in semi-arid areas with limited water resources. Numerous studies have examined the costs and environmental impacts associated with guayule rubber production. These studies identified the need for additional value from the rubber co-products, specifically the resin, for sustainable and commercial viability of the biorefinery concept. This study developed process models for resin-based monoterpenes, insect repellant, and adhesive co-products that are integrated with sustainability assessments to understand the commercial viability. A techno-economic analysis and cradle-to-gate life cycle assessment of these three different co-product pathways assumed a facility processing 66 tonnes/day of resin (derived from the processing of 1428 tonnes per day of guayule biomass) and included resin separation through co-product formation. Additionally, a fourth pathway was evaluated, combining the insect repellent and monoterpene process models to evaluate potential advantages resulting from their integration. The evaluation outcomes were integrated into an established guayule rubber production model to assess the economic potential and environmental impact of the proposed guayule resin conversion concepts. The minimum selling price for rubber varied by co-product: $3.64 per kg for monoterpenes, $3.48 per kg for insect repellent, and $1.90 per kg for resin blend adhesive. The resin blend adhesive co-product pathway had the lowest greenhouse gas emissions. These findings show a pathway that supports the development of a biorefining concept based on resin-based adhesives that can catalyze a US based natural rubber industry.

Oleaginous Yeast Biorefinery: Feedstocks, Processes, Techniques, Bioproducts

The world climate crisis has triggered the search for renewable energy sources. Oleaginous yeasts are a potential renewable source of biofuels. However, the yeast-derived biofuels cost is still non-competitive with the fossil fuel prices. To improve the sustainability of yeast-derived biofuels, it is necessary to valorize all yeast biomass fractions, an approach based on the biorefinery concept. This review describes the present situation of the oleaginous yeast biorefinery research, emphasizing the feedstock, processes and techniques involved in this concept, as well as on potential bioproducts that can be obtained from oleaginous yeast biomass.

Toward a zero-waste microalgal biorefinery: Complete utilization of defatted Chlorella biomass as a sole heterotrophic substrate for Chlorella sp. HS2 and an improved composite filler

The concept of circular biorefinery has been promoted as a sustainable new approach for the nascent microalgae industry. In particular, solvent extraction of the lipid fraction of microalgal biomass is generally performed when aiming to recover marketable compounds from microalgae; the waste residual biomass generated by this process can provide new market opportunities for microalgae in a wide array of commercial sectors. Herein, the heterotrophic cultivation of Chlorella sp. HS2 was demonstrated using a hydrolysate recovered following the dilute acid hydrolysis of defatted Chlorella biomass (DCB). While HCl and H2SO4 in each case was found to be an effective catalyst capable of converting nearly 40% of DCB into fermentable monosugars, the results of microalgal cultivation in diluted hydrolysate indicated high cellular growth without the need for any supplemental nutrients. Notably, the highest microalgal growth was observed when neutralizing HCl- and H2SO4-treated hydrolysates with NaOH and Ca(OH)2, respectively. Furthermore, the fabrication of a polymer/residual composite using the residual material obtained after H2SO4-catalyzed hydrolysis and Ca(OH)2 neutralization suggested improved tensile capabilities, attributed to the improved dispersion of salt precipitates-containing residue in the hydrophobic polymer matrices. Considering that the leftover residual DCB could be better conditioned as an organic–inorganic filler for composite fabrication through a combined acid hydrolysis-neutralization process, the results here suggest new integrated utilization routes for underutilized byproducts from the microalgal industry. Further investigations are thus warranted with a special focus on bolstering the economic feasibility and scalability of the postulated zero-waste microalgal biorefinery.