Fossil fuel limitations and their influence on climate change through atmospheric greenhouse gas emissions have made the excessive use of fossil fuels widely recognized as unsustainable. The high lipid content, carbon-neutral nature and potential as a biofuel source have made microalgae a subject of global study. Microalgae are a promising supply of biomass for third-generation biofuels production since they are renewable. They have the potential to produce significant amounts of biofuel and are considered a sustainable alternative to non-renewable energy sources. Microalgae are currently incapable to synthesize algal biofuel on an extensive basis in a sustainable manner, despite their significance in the global production of biofuels. Wastewater contains nutrients (both organic and inorganic) which is essential for the development of microalgae. Microalgae and wastewater can be combined to remediate waste effectively. Wastewater of various kinds such as industrial, agricultural, domestic, and municipal can be used as a substrate for microalgal growth. This process helps reduce carbon dioxide emissions and makes the production of biofuels more cost-effective. This critical review provides a detailed analysis of the utilization of wastewater as a growth medium for microalgal - biofuel production. The review also highlights potential future strategies to improve the commercial production of biofuels from microalgae.

The aerobic granular sludge (AGS) biotechnology has been explored for wastewater treatment for over two decades. AGS is gaining increased interest due to its enhanced treatment performance ability and the potential for resource recovery from AGS-based wastewater treatment systems. Resource recovery from AGS is a promising approach to sustainable wastewater treatment and attaining a circular economy in the wastewater management industry. Currently, research is at an advanced stage on recovering value-added resources such as phosphorus, polyhydroxyalkanoates, alginate-like exopolysaccharides, and tryptophan from waste aerobic granules. Recently, other value-added resources, including curdlan, have been identified in the aerobic granule matrix, and this may increase the sustainability of biotechnology in the wastewater industry. This paper provides an overview of AGS resource recovery potential. In particular, the potential for enhanced curdlan biosynthesis in the granule matrix and its recovery from AGS wastewater treatment systems is outlined.

Agriculture and industries related to the agriculture sector generate a large amount of waste each year. These wastes are usually burned or dumped, causing damage to the environment, the economy and society. Due to their composition, they have great potential for obtaining high value-added products in biorefineries. This fact, added to the growing demand for energy and chemicals from fossil resources, is driving the interest of the scientific community in them. Biorefinery processes are hardly profitable when applied individually, so a better alternative is to develop integrated multi-feedstock and multi-product biorefinery schemes using all biomass fractions in a zero-waste approach. However, for industrial scale application, extensive research, scale-up studies, and techno-economic and environmental feasibility analyses are needed. This review compiles information on integrated multi-biorefinery processes from agro-industrial wastes to shed light on the path towards sustainable development and circular bioeconomy.

The potential of cellulolytic enzymes has been widely studied and explored for bioconversion processes and plays a key role in various industrial applications. Cellulase, a key enzyme for cellulose-rich waste feedstock-based biorefinery, has increasing demand in various industries, e.g., paper and pulp, juice clarification, etc. Also, there has been constant progress in developing new strategies to enhance its production, such as the application of waste feedstock as the substrate for the production of individual or enzyme cocktails, process parameters control, and genetic manipulations for enzyme production with enhanced yield, efficiency, and specificity. Further, an insight into immobilization techniques has also been presented for improved reusability of cellulase, a critical factor that controls the cost of the enzyme at an industrial scale. In addition, the review also gives an insight into the status of the significant application of cellulase in the industrial sector, with its techno-economic analysis for future applications. The present review gives a complete overview of current perspectives on the production of microbial cellulases as a promising tool to develop a sustainable and greener concept for industrial applications.

The hydrodynamic cavitation comes out as a promising route to lignocellulosic biomass pretreatment releasing huge amounts of energy and inducing physical and chemical transformations, which favor lignin-carbohydrate matrix disruption. The hydrodynamic cavitation process combined with other pretreatment processes has shown an attractive alternative with high pretreatment efficiency, low energy consumption, and easy setup for large-scale applications compared to conventional pretreatment methods. This present review includes an overview of this promising technology and a detailed discussion on the process of parameters that affect the phenomena and future perspectives of development of this area.

Biorefinery approaches offer the potential to improve the economics of the microalgae industry by producing multiple products from a single source of biomass. Chromochloris zofingiensis shows great promise for biorefinery due to high biomass productivity and a diverse range of products including secondary carotenoids, predominantly astaxanthin; lipids such as TAGs; carbohydrates including starch; and proteins and essential amino acids. Whilst this species has been demonstrated to accumulate multiple products, the development of an integrated downstream process to obtain these is lacking. The objective of this review paper is to assess the research that has taken place and to identify the steps that must be taken to establish a biorefinery approach for C. zofingiensis. In particular, the reasons why C. zofingiensis is a promising species to target for biorefinery are discussed in terms of cellular structure, potential products, and means to accumulate desirable components via the alteration of culture conditions. Future advances and the challenges that lie ahead for successful biorefinery of this species are also reviewed along with potential solutions to address them.
UNASSIGNED: The online version contains supplementary material available at 10.1007/s13399-022-02955-7.

Fermentation technology is a biorefining tool that has been used in various industrial processes to recover valuable nutrients from different side streams. One promising application of this technique is in the reclamation of nutritional components from seafood side streams. Seafood processing generates significant amounts of waste, including heads, shells, and other side streams. These side streams contain high quantities of valued nutritional components that can be extracted using fermentation technology. The fermentation technology engages the application of microorganisms to convert the side stream into valuable products like biofuels, enzymes, and animal feed. Natural polymers such as chitin and chitosan have various purposes in the food, medicinal, and agricultural industry. Another example is the fish protein hydrolysates (FPH) from seafood side streams. FPHs are protein-rich powders which could be used in animal nutrition and nutraceutical industry. The resulting hydrolysate is further filtered and dried resulting in a FPH powder. Fermentation technology holds great possibility in the recovery of valuable nutrients from seafood side streams. The process can help reduce waste and generate new value-added products from what would otherwise be considered a waste product. With further research and development, fermentation technology can become a key tool in the biorefining industry.

The production of banana peel by the food-processing industry is substantial and the disposal of this waste material has become a matter of concern. However, recent studies have demonstrated that banana peel is a rich source of biologically active compounds that can be transformed into valuable products. This review aims to explore the potential of converting banana peel into valuable products and provides a comprehensive analysis of the physical and chemical composition of banana peel. Additionally, the utilization of banana peel as a substrate to produce animal feed, bio fertilizer, dietary fibers, renewable energy, industrial enzymes, and nanomaterials has been extensively studied. According to the researches that has been done so far, it is clear that banana peel has a broad range of applications and its effective utilization through biorefinery strategies can maximize its economic benefits. Based on previous studies, A plan for feasibility of a banana peel biorefinery has been put up which suggest its potential as a valuable source of renewable energy and high-value products. The utilization of banana peel through biorefinery strategies can provide a sustainable solution for waste management and contribute to the development of a circular economy.

The world is facing problems of the increasing amount of resources wasted as the world population grows. Biowaste streams form a significant part of the overall waste generation, and a circular economy utilizing this biowaste will significantly reduce waste whilst lowering the anthropogenic carbon footprint. Due to their energy content and high concentration of hydrocarbon molecules, bio-based waste streams have the potential to be transformed into valorized products (energy, fuels, and chemicals) using biorefinery technologies. In this work, a mini-review has been conducted on available, mostly European databases on existing biomass types and biorefinery technologies to provide a framework for a desirable, comprehensive database connecting bio-based waste streams, biorefinery technologies and bioproducts, as well as the geographical distribution of feedstocks and biorefineries. The database assessment utilized the SWOT (strengths, weakness, opportunities, threats) methodology to support benchmark analysis and to identify critical gaps in underlying data structures that could be included in a single database. The results show that current databases are useful but insufficient for waste biorefineries due to limited quality and quantity as well as the usability of data. A comprehensive database or improved database cluster would be necessary, not only for technology development but for better investment and policy decisions. The development of the new database architecture would need to incorporate the aspects: expansion of database scope and content depth, improved usability, accessibility, applicability, update frequency, openness to new contributions, process descriptions and parameters, and technology readiness level.

Resveratrol, a natural organic polyhydroxyphenolic compound, has gained significant attention in the last years given its potential health benefits, including antioxidant, anti-cancer, and anti-inflammatory properties. It can be directly extracted from plants, vegetables, and related products and waste resources, but also chemically/enzymatically/microbially synthesized. However, certain process strategies have some limitations, such as high costs, reduced yield or high energy demand, thus implying significant environmental loads. In this context, the search for more sustainable and circular process schemes is key to the integration of resveratrol into the market value chain of the food, cosmetic and pharmaceutical sectors. The extraction of resveratrol has traditionally been based on conventional methods such as solvent extraction, but advanced green extraction techniques offer more efficient and environmentally friendly alternatives. This review analyses both conventional and green alternative extraction technologies, as well as its bioproduction through microbial fermentation, in terms of production capacity, yield, purity and sustainability. It also presents alternative biorefinery models based on resveratrol bioproduction using by-products and waste streams as resources, specifically considering wine residues, peanut shells and wood bark as input resources, and also following a circular approach. This critical review provides some insight into the opportunities that resveratrol offers for promoting sustainable development and circularity in the related market value chains, and thus provides some criteria for decision making for biorefinery models in which resveratrol is one of the targeted high value-added products. It also identifies the future challenges to promote the inclusion of resveratrol in value chains, with the scale-up of green technologies and its demonstrated economic feasibility being the most prominent.