Waste Valorization for Value-added Products

Depletion of fossil fuels and environmental concern has impelled to search for alternative biofuels and biobased chemicals. Biofuels have been considered an alternative clean energy carrier due to their environmentally friendly nature. Recently, research has been focused on finding a readily available, low-cost and renewable lignocellulosic biomass to produce value-added products. In this context, the plant-derived organic wastes can be transformed to produce biofuels (bioethanol, biobutanol, biogas and biohydrogen) and biochemicals (lactic acid, succinic acid, xylose and xylitol). It will be a sustainable effort to reduce the huge amount of plant waste generated. In addition, in the recent decades, several efficient conversion methods have been invented. During the past few years, a large number of chemical pretreatment methods have also been developed for efficient lignocellulosic conversion. The current chapter discusses the advanced methods for biofuels and biochemicals’ production, focusing primarily on different pretreatment methods for effective conversion of plant derived wastes.

Recent years have seen a tremendous demand in bioenergy. The technological advancements in the production of second-generation biofuels have opened a plethora of opportunities for the valorization of natural polymers. Lignin is one of the most abundant and recalcitrant materials available on earth. Advancements in genetic engineering, metabolic engineering and synthetic biology applications fueled tremendous interest in the valorization of lignin into fuels as well as platform and commodity chemicals. Though there is a growing continuum for biofuel advancements in recent years, at the same time, a rising upsurge has also been envisaged in the valorization of waste bioresources. Therefore, this chapter entails about various aspects and embodiments related to lignin bioconversion and their routes for obtaining various products. This chapter also highlights current biotechnological interventions for the improvement of the valorization process as well as the current challenges and future perspectives in this burgeoning area.

During the last few decades, food remains a primary concern throughout the world as it is depleting day by day. On the other side, its residual waste is accumulating over time. Around one-third of food produced for human consumption is wasted which escalates the environmental issues and ecological burden. Management of waste food by current methods is cost-ineffective with adverse impacts on the environment. Therefore, attempts have been made to convert food waste into high-value by-products. Being a rich source of carbohydrates, proteins, sugars, and fats, it acts as a potential source for high-value products. The organic nature of food makes it a raw material for industries related to biofuel, bioactive compounds, prebiotics, livestock food, and biodegradable plastics. Bioconversion of food waste into valuable products not only provides economic advantage but reduces stress on landfills. The valorization of low-cost, abundantly available food waste into biofuel can decrease the demand for fossil fuels and economic loss for their manufacturing. Minimum food wastage and re-utilization of wasted food can be a sustainable approach to combating this problem. In this chapter, various techniques used for bioconversion and the valuable products produced by waste food processing have been discussed with their prospects. 

The consumption of olive oil is deeply rooted in human history and the production of olive oil contributes greatly to the economy of Mediterranean countries. Olive oil is generally extracted following three different methods; the traditional pressing method, two-phase decantation system and three-phase decantation system. These extraction processes generate mainly two different types of waste which are olive mill solid waste (OMSW) and olive mill wastewater (OMWW). Olive mill by-products are considered a major environmental hazard in Mediterranean regions as they are high in phenol, lipid and organic acid content. To eliminate this problem, valorization of these waste products is the need of the hour. Phytochemical compounds like phenols, and flavonoids are important and useful for pharmaceutical industries. Other than the recovery of these value-added compounds, olive waste can be used as animal feed and a source of clean energy. Biological treatment of these wastes reduces the percentage of phenols and organic acids and then it can be used in agricultural applications. The valorization strategies of olive mill wastes depend on factors like socio-economic conditions, and agricultural and industrial environments. In this chapter, the olive oil production process, phytochemical characteristics of generated waste and their environmental impact are discussed. This discussion also emphasized the available valorization techniques of olive oil by-products, their advantages, and disadvantages.

In recent years, more studies on waste valorization are emerging due to excessive accumulation in the land, foul-smelling, and lack of conventional disposal practices to sustain a proper ecosystem. The decline in the supply of fossil fuels and their high-cost led to finding alternative technologies that use renewable resources as raw materials to manufacture value-added goods. The waste contains organic residues like carbohydrates, proteins, and fats, which are helpful in producing bio-based chemicals. However, several roadblocks ought to be crossed for adopting organic waste as nutrients for microbes to obtain high yields of desired products. Many studies have shown potential ways to solve these problems and have achieved high yields. Nevertheless, this technology has not been globally explored to manufacture commercial products, as many other issues are associated with biorefinery and product costs. This chapter addresses the organic residues present in the wastes, their use in manufacturing platform chemicals, methods for the pretreatment process, and ways to overcome the challenges.

Fruits of the date have found great value in human nutrition because of their rich content of essential nutrients. Tons of palm fruit waste are being discarded daily. Waste such as date holes represents 10% of date fruit. Within the framework of the bio-economy, there is a high potential for date waste use in ligne-cellulosic products in a broad spectrum of bio-industries. Extensive and varied biomolecules may capture energy for use in the pharmaceutical industry as an active pharmaceutical ingredient (API), or in the development of nutraceuticals without using them as substrates for mass production of bacteria, phenolic, sterols, carotenoids, anthocyanins., procyanidin, flavonoids, minerals, various vitamins, economically beneficial amino acids, organic acids, biosurfactants, biopolymers, biofuels, exopolysaccharides, probiotics with date flavors, etc. Date fruits are commonly used to prepare many kinds of products such as date juice concentrate (distribution, syrup, and liquid sugar), date products (wine, alcohol, vinegar, organic acids) and date pastes for different uses (e.g., bakery and - confectionery) without the direct use. Date seeds can be converted into high-value liquids (bio-oil), gas, and solid products (bio-char) by pyrolysis, and coal and activated carbon can be produced from date seeds. Significant progress has been made in developing specific date fruit products and using products from packaging and processing. Additional economic benefits will also increase so far as farmers increase the number of commodities they produce, as well as diversify their sources of income.

With the growing population, resource production and utilization, including citrus fruit consumption, have amplified tremendously. Citrus foods include sweet orange, sweet blood orange, tangerine, grapefruit, lemon, lime, and Seville orange. Industrial processing of citrus fruits is done to produce various end products like juice concentrates, jams, jellies, sweets, candies, marmalades, and ice creams, which simultaneously produce tons of peels and waste as well. Like all industrial waste dumping, the negligent discard of citrus waste has legal repercussions. Therefore, the global treatment seems to be a virtuous option, which results in improved earnings, thereby ultimately reducing the reprocessing expenditure. Conversely, despite the low cost, citrus waste management and valorization still have not reached a virtue that makes it an ideal candidate. Valorization technically refers to the process of industrial recycling or waste composting into commercially valuable products. To fix the citrus wast essential to understand the various ways to recycle and manage the left-over better. This requires research and knowledge of different techniques involved in the commercial utilization of citrus waste for the production of various components, counting-essential oils, flavonoids, pectin, enzymes, ethanol and methane etc., along with the applications of these bioactive components in various ventures. This study summarizes the bioactive components obtained from citrus foods and their possible industrial utilization. 

The increase in the use of plastic products caused the major worldwide disposal problem of plastic solid waste (PSW). Plastics are becoming appropriate materials of interest for everyone due to their attractive applications in households, packaging, healthcare, and industries owing to their durability and versatile functionality at affordable prices. Statistics show that a large number of waste plastics are dumped in landfills, and only a tiny amount of plastic is recycled for making valuable materials e.g., shampoo bottles, film, sheets, trash bags, kitchen-wares and packing materials. About 26,000 tonnes of plastic waste is generated in India every day, of which 40% remains uncollected and littered leading to adverse impacts on human health and the environment. Further, the incineration of plastic wastes emits many harmful gases such as nitrous oxide, sulfur oxides, dust clouds, dioxins and other toxins that pollute the atmosphere. To reduce waste plastics generation in the environment, the Indian government has implemented the Plastic Waste Management Rules, 2016 and its amendments, which explain ways for collection and management of plastic waste, its recycling, and utilization. Plastic wastes can be valorized to produce fuels using techniques such as thermal degradation, catalytic cracking, and gasification. This chapter is focused on waste plastic handling approaches, and novel routes to convert plastic wastes into energy and other valuable chemicals. This approach may compensate for high-energy demands and plastic waste management.

Wood biomass is a vital component in producing various value-added products. It can be used to produce biofuels and chemicals. Agriculture practices produce a lot of lignocellulosic biomass, a waste management concern for years. Most of this lignocellulosic biomass is considered waste. But in recent years, efforts have been made to utilize and valorize this biomass to produce value-added products. The major challenge with lignocellulosic biomass is that it cannot be used in production processes. Therefore, it requires several physical and chemical pretreatments. This chapter discusses various pretreatment technologies involved in valorizing lignocellulosic biomass. In addition, it also discusses lignin pretreatment, saccharification, and microbial biodiesel production. 

The alarming concern over the environment created due to the uncontrolled use of based petrochemical-based synthetic plastic created a research thrust on bioplastics. Bioplastics, in general, refers to the polymers derived from plants, animals, and microorganisms that have close material properties to their synthetic counterparts. Despite having good biodegradability, their commercialization still faces hurdles majorly contributed by the high production cost involved. An integrated strategy of waste valorization with bioplastic production was a sustainable approach toward their cost-effective production and commercialization. Food waste represents a continuous and rapidly available substrate containing high-value nutrients that can be exploited for the production of bioplastics through microbial fermentation and chemical treatment methods. This chapter describes the biotechnological strategies for valorizing food waste into commercially important biopolymeric components like chitosan, polyhydroxyalkanoates, HAp, and cellulose-based polymers. It presents a comprehensive outlook on their chemical nature, production strategy, and application in various fields.

The poultry industry is one of the fastest-growing markets at the global level. As the industry expands, the solid waste generated from the poultry sector increases. However, a large amount of waste are generated in poultry farms which needs proper management and disposal to avoid many serious issues like environmental pollution, the spread of diseases due to pathogens residing in the waste as well as breeding of flies and rodents near the waste. Several methods are implemented for the proper utilization and disposal of residues produced in the farms. The methodology used for management varies widely based on many factors like the type of waste generated, nutritional value, and potential hazards to humans and the environment. The techniques adapted for utilization or disposal of the waste generated have evolved from simple conventional methods to highly advanced and more reliable methods (Pyrolysis, anaerobic digestion and catalytic pyrolysis), which are practiced increasingly nowadays, especially in large-scale poultry farms. Many projects and research are being held to improvise waste management techniques in the coming years. The appropriate processing, utilization and disposal of waste and its by-products are important to prevent unwanted side effects and increase the pecuniary output. 

India is the second-largest cultivator of sugarcane worldwide, the primary source of refined sugar. Increased demand for sugar has driven this industry as a mainstream pollutant-generating industry. Every year, a tremendous amount of liquid (molasses) and solid wastes (sugarcane bagasse, filter cake) are generated, posing a major bottleneck for waste management. Although there exist traditional approaches like incineration, landfills are being employed for handling sugarcane waste which leads to the emission of greenhouse gases, and foul odour and adds more cost to running a sustainable industry. Moreover, no value-added product is formed from such traditional approaches resulting in an immense loss of bioenergy. Researchers have emphasized transforming waste into a sustainable economic generation of higher\-value products over the past few decades. Sugarcane industrial waste is a rich source of lignocellulosic organic biomass, which is used as a raw material for the production of biofuel (bioethanol, biogas), single cells proteins, enzymes, organic acids, food additives and nutraceuticals. Day by day, with advanced technology, novel applications are evolving, adding more thrust to this area. In this chapter, the potential of valorization of sugarcane waste to value-added products is discussed comprehensively.