**1. Introduction**

A sustainable growth of our society implies a continual and efficient (re)use of the available resources. At the European Union (EU) level, great efforts are made to move to a circular economy with an efficient use of resources and zero waste generation. In the latest report, member states view food, waste processing and mobility among the priority sectors in the circular economy strategies [1]. Waste from one part of the system may be a resource in other sector, matching demand and supply, while biofuels obtained from the high-growing biomass and biological wastes tackles the problem of renewable energy.

Rape or rapeseed (*Brassica napus* L. and its varieties) currently occupies the second place in the world production of oilseed and meal [2]. EU is the second major producer of rapeseed, after Canada. In Europe, the main oilseed culture consists of rapeseed, followed by sunflower seeds and soya beans. Romania is

among the top seven major producers, being responsible for almost 5.5% of the EU total RS production [3]. Crushing of oilseeds produces RS oil (for human consumption or biodiesel production) and RS meal. The latter represents almost 57% of the world total RS production [2]. Within the scope of this chapter, the terms "rape" or "rapeseed" will be used when referring to other common names or varieties, such as canola, colza, swede, swede rape, summer rape, winter rape, annual rape. Another mention is about the methods of oil extraction from rape seeds (RSs). This can be done by mechanical pressing, when RS meal is produced, with 8–20% residual oil content. The fat content could be further lowered by solvent extraction to 1–3%; then the solid waste obtained is RS cake [4]. Because we have found a great number of articles in literature where no distinction between RS meal (RSM) and RS cake (RSC) was made, we will be using these terms interchangeably here.

Valorization options for RS meal are based predominantly on the use as animal feed. Although a recognized feedstock for protein extraction, RS is still underutilized for production of commercially available protein products [5, 6]. Besides meal, other solid residues result from RS harvesting (stems and leaves). They are primarily used to obtain energy by combustion or fermentation [7] and soil amendment and fertilizer [8]. Currently at EU level, lignocellulosic and agricultural biomass (including rapeseed wastes) are the subject of some Bio-Based Industries Joint Undertaking projects [9].

An emerging valorization alternative consists of using RS wastes for the removal of pollutants from wastewater by adsorption. In order to lower the cost of activated carbon (AC) processes, abundant and readily available agricultural wastes were tested in native form or after a treatment as presented in various reviews [10–13]. The process is called *biosorption* when the waste is used in either its natural form or after some physical or chemical modification. At present, most of the work is done at laboratory scale. Although activated carbon process is an established technology at industrial scale, not many ventures can be encountered for the commercialization of biosorption [14].

This chapter aims to dive into the rapeseed waste management practices and strategies, specifically on the opportunity of valorization as a sorbent in wastewater treatment. Firstly, the sources of different rape waste biomass are identified and their valorization options are discussed from the circular economy perspective. The second part of the chapter will focus on the relation between adsorption and RS waste. After a short description of the adsorption process as a wastewater treatment technology, the characteristics that make RS a potentially suitable biosorbent are highlighted. Finally, an overview of the limited number of studies found in literature dealing with RS-based sorbents will be focusing on the types of pollutants and wastewater matrix investigated and the adsorption system configuration employed.

#### **2. Rape waste biomass sources and management strategies**

#### **2.1 Sources**

Rape is a multifunctional oily plant with yellow flowers and thin, long and branched stems. The many RS varieties are remarkable by extensive biomass, easiness in harvesting and adaptability to climatic change, their cultivation being estimated as one of the most sustainable oil crops [15]. The main applicability of the harvested component of the rape crop, the seeds, targets vegetable oils production (**Figure 1**). Rape seeds contain compounds of nutritional value (proteins and oil) and anti-nutrients, namely erucic acid and glucosinolates. The two varieties of *Brassica napus* seeds frequently cultivated - industrial rapeseed and canola- have

**143**

*Valorization of Rapeseed Waste Biomass in Sorption Processes for Wastewater Treatment*

as distinguishing feature the erucic acid content in the corresponding oils. Unlike traditional varieties of rapeseed that give oils that contain 22–60% erucic acid, the

The main sources of RS waste are agricultural activities and production of oil and biodiesel (**Figure 1**). Field residues, present after RS crop harvesting, consist of stems, stalks, leaves and seed pods. From the technological process before seed storing result impurities, broken and immature grains, stems, rotten grains etc. [16, 17]. The total RS biomass consists of 28–50% seeds, while the rest is crop residues, mainly stalks [18]. The agricultural wastes resulting in large amounts from the harvesting and postharvest of the seeds of rape are lignocellulosic materials: straws and stalks contain 15–36% cellulose, 18–25% hemicelluloses and 14–31.6% lignin [19, 20], while seeds husks contain: 13.7% cellulose, 19% hemicellulose and 25.5% lignin [21]. The processing of the rape seeds for vegetable oils yields press-cake or meal as industrial residue, which account for about 60% by weight of the input seeds [21, 22]. The RSC obtained by mechanical pressing of oleaginous seeds contains 30–40% proteins and 9.0–12.60% crude fibers [16, 23]. On the other hand, RSM resulted after the solvent extraction of the oil from the rape seeds has a content of about 37–40% proteins and 10–17.5% crude fibers [22, 24]. Authors [25] have determined the composition of deoiled canola meal (CM): 34.5% lignin, 33.5% hemicellulose and 30.2% cellulose. The RSC/RSM are currently important sources of organic matter and energy. The wide availability, low-cost, renewability, versatility, unique structure and interesting technological properties make these residual materials more than just wastes. Their resource potential for sustainable products with multi-faceted

**2.2 The circular economy approach and management of rape biomass**

Circular economy can be described as an industrial system that is restorative or regenerative by intention and design, aiming for the elimination of waste through the superior design of materials, products, systems and business models [26]. The recovery of valuable by-products can contribute to circular economy transition by reducing waste generation, maximizing resources potential and also leading to cost reduction [27]. The management of RS wastes with the possibility of their reuse in different forms is presented in **Figure 2**. Rapeseed meal/cake, the main by-product of vegetable oil and biodiesel production, has a high potential for an integrated valorization scheme [28]. For example, RSM can be transformed into a hydrolysate and used with crude glycerol to produce poly (3-hydroxybutyrate) [29]. RSM contains bioactive constituents, such as phenolic sinapinic acid and protocatechuic acid, which can be used as functional food ingredients and for use in cosmetic and pharmaceutical applications [27, 30]. Its application for animal feed is limited however due to the presence of anti-nutritional compounds (e.g. glucosinolates, phytic acid, synapine, erucic acid, tannins) and high fiber contents. Treatment with ethanol reduces phenols and glucosinolates content, while increasing the protein

*DOI: http://dx.doi.org/10.5772/intechopen.94942*

*Sources of wastes from the RS oil production process.*

**Figure 1.**

cultivars of canola produce oils with low erucic [5].

applications is still undervalued.

*Valorization of Rapeseed Waste Biomass in Sorption Processes for Wastewater Treatment DOI: http://dx.doi.org/10.5772/intechopen.94942*

#### **Figure 1.**

*Environmental Issues and Sustainable Development*

Undertaking projects [9].

of biosorption [14].

among the top seven major producers, being responsible for almost 5.5% of the EU total RS production [3]. Crushing of oilseeds produces RS oil (for human consumption or biodiesel production) and RS meal. The latter represents almost 57% of the world total RS production [2]. Within the scope of this chapter, the terms "rape" or "rapeseed" will be used when referring to other common names or varieties, such as canola, colza, swede, swede rape, summer rape, winter rape, annual rape. Another mention is about the methods of oil extraction from rape seeds (RSs). This can be done by mechanical pressing, when RS meal is produced, with 8–20% residual oil content. The fat content could be further lowered by solvent extraction to 1–3%; then the solid waste obtained is RS cake [4]. Because we have found a great number of articles in literature where no distinction between RS meal (RSM) and RS cake

Valorization options for RS meal are based predominantly on the use as animal feed. Although a recognized feedstock for protein extraction, RS is still underutilized for production of commercially available protein products [5, 6]. Besides meal, other solid residues result from RS harvesting (stems and leaves). They are primarily used to obtain energy by combustion or fermentation [7] and soil amendment and fertilizer [8]. Currently at EU level, lignocellulosic and agricultural biomass (including rapeseed wastes) are the subject of some Bio-Based Industries Joint

An emerging valorization alternative consists of using RS wastes for the removal of pollutants from wastewater by adsorption. In order to lower the cost of activated carbon (AC) processes, abundant and readily available agricultural wastes were tested in native form or after a treatment as presented in various reviews [10–13]. The process is called *biosorption* when the waste is used in either its natural form or after some physical or chemical modification. At present, most of the work is done at laboratory scale. Although activated carbon process is an established technology at industrial scale, not many ventures can be encountered for the commercialization

This chapter aims to dive into the rapeseed waste management practices and strategies, specifically on the opportunity of valorization as a sorbent in wastewater treatment. Firstly, the sources of different rape waste biomass are identified and their valorization options are discussed from the circular economy perspective. The second part of the chapter will focus on the relation between adsorption and RS waste. After a short description of the adsorption process as a wastewater treatment technology, the characteristics that make RS a potentially suitable biosorbent are highlighted. Finally, an overview of the limited number of studies found in literature dealing with RS-based sorbents will be focusing on the types of pollutants and wastewater matrix investigated and the adsorption system configuration employed.

**2. Rape waste biomass sources and management strategies**

Rape is a multifunctional oily plant with yellow flowers and thin, long and branched stems. The many RS varieties are remarkable by extensive biomass, easiness in harvesting and adaptability to climatic change, their cultivation being estimated as one of the most sustainable oil crops [15]. The main applicability of the harvested component of the rape crop, the seeds, targets vegetable oils production (**Figure 1**). Rape seeds contain compounds of nutritional value (proteins and oil) and anti-nutrients, namely erucic acid and glucosinolates. The two varieties of *Brassica napus* seeds frequently cultivated - industrial rapeseed and canola- have

(RSC) was made, we will be using these terms interchangeably here.

**142**

**2.1 Sources**

*Sources of wastes from the RS oil production process.*

as distinguishing feature the erucic acid content in the corresponding oils. Unlike traditional varieties of rapeseed that give oils that contain 22–60% erucic acid, the cultivars of canola produce oils with low erucic [5].

The main sources of RS waste are agricultural activities and production of oil and biodiesel (**Figure 1**). Field residues, present after RS crop harvesting, consist of stems, stalks, leaves and seed pods. From the technological process before seed storing result impurities, broken and immature grains, stems, rotten grains etc. [16, 17]. The total RS biomass consists of 28–50% seeds, while the rest is crop residues, mainly stalks [18]. The agricultural wastes resulting in large amounts from the harvesting and postharvest of the seeds of rape are lignocellulosic materials: straws and stalks contain 15–36% cellulose, 18–25% hemicelluloses and 14–31.6% lignin [19, 20], while seeds husks contain: 13.7% cellulose, 19% hemicellulose and 25.5% lignin [21]. The processing of the rape seeds for vegetable oils yields press-cake or meal as industrial residue, which account for about 60% by weight of the input seeds [21, 22]. The RSC obtained by mechanical pressing of oleaginous seeds contains 30–40% proteins and 9.0–12.60% crude fibers [16, 23]. On the other hand, RSM resulted after the solvent extraction of the oil from the rape seeds has a content of about 37–40% proteins and 10–17.5% crude fibers [22, 24]. Authors [25] have determined the composition of deoiled canola meal (CM): 34.5% lignin, 33.5% hemicellulose and 30.2% cellulose. The RSC/RSM are currently important sources of organic matter and energy.

The wide availability, low-cost, renewability, versatility, unique structure and interesting technological properties make these residual materials more than just wastes. Their resource potential for sustainable products with multi-faceted applications is still undervalued.

#### **2.2 The circular economy approach and management of rape biomass**

Circular economy can be described as an industrial system that is restorative or regenerative by intention and design, aiming for the elimination of waste through the superior design of materials, products, systems and business models [26]. The recovery of valuable by-products can contribute to circular economy transition by reducing waste generation, maximizing resources potential and also leading to cost reduction [27]. The management of RS wastes with the possibility of their reuse in different forms is presented in **Figure 2**. Rapeseed meal/cake, the main by-product of vegetable oil and biodiesel production, has a high potential for an integrated valorization scheme [28]. For example, RSM can be transformed into a hydrolysate and used with crude glycerol to produce poly (3-hydroxybutyrate) [29]. RSM contains bioactive constituents, such as phenolic sinapinic acid and protocatechuic acid, which can be used as functional food ingredients and for use in cosmetic and pharmaceutical applications [27, 30]. Its application for animal feed is limited however due to the presence of anti-nutritional compounds (e.g. glucosinolates, phytic acid, synapine, erucic acid, tannins) and high fiber contents. Treatment with ethanol reduces phenols and glucosinolates content, while increasing the protein

#### **Figure 2.** *Rape waste biomass as resourceful raw material in circular economy.*

level, and makes possible RSM use as feed additive or as a source for production of protein-rich ingredients with specific value and functionality [31]. The biotransformation of RSM using bacteria increases its nutritional value and enriches it with a variety of additives, including polymers, bio-surfactants and enzymes [32]. RSM has proved to be a plant-derived alternative for development of bio-plastic materials [33] and new polyurethane composites [23].

The lignocellulosic biorefinery strategies integrate physical, chemical, thermophysical, thermochemical or biological processes for the pretreatment and conversion of biomass into bio-based products [34]. In the case of RS, these processes are adapted to the characteristic content of cellulose, hemicellulose and lignin that are the main components responsible for biorefinery. The use of the whole plant of RS for production of biodiesel, bioethanol and methane into the frame of biorefinery concept resulted in a 3 times increase of the efficiency of energy recovery as compared to conventional process of biodiesel production [35–37]. RS straws, containing >50% of carbohydrates, are an interesting source of biomass for biorefineries, by conversion into bioenergy and high-value chemicals. It is also an attractive source of fermentable sugars for bioethanol production [19]. More than 50% of RS straw could be recovered as xylan, lignin and nanocellulose [38].

RS stalk and straw also present interest in pulping and papermaking industries [39–41]. The potential of RS straws as source of lignocellulosic fibers can also be valorized for the production of biocomposite materials [42, 43]. The beneficial effects of RS stalks use on the humus and nutrients content of some damaged soils have been pointed out [44, 45]. Polyphenols and proteins were extracted from rapeseed stems and leaves by pulse electric fields [46]. Another potential use for canola leaves is as annual forage for field-raised swine and poultry. RS leaves and hulls can be used in livestock (rabbits, swine, poultry, fish) feeding [17, 47], or substrate for fungi production [48]. RS shells can be used as precursors for activated carbon materials as cathode in lithium-sulfur batteries [49]. Other applications of RS wastes include the use as soil amendments for increasing crop growth, usually in biochar form [8, 50, 51].

Another interesting possibility of recycled–value added application of RS wastes involves their ability to act as efficient biosorbent for the removal of heavy metals

**145**

*Valorization of Rapeseed Waste Biomass in Sorption Processes for Wastewater Treatment*

and organic pollutants from environmental aqueous media, which will be discussed

Among the numerous wastewater treatment processes, adsorption distinguishes by efficiency, design simplicity and flexibility, operation easiness, insensitivity to toxic pollutants and economic feasibility [52]. Adsorption refers to the retention of a chemical species (adsorbate) on the surface of a solid substance (adsorbent) by means of physical and chemical interactions. The existence of weak van der Waals interactions determines the fast kinetics, low heat, monolayer or multilayer coverage, non-selectivity and reversibility of the physical adsorption. A chemisorption mechanism reaches equilibrium slower due to creation of covalent bonds, which causes a high activation energy, monolayer coverage and irreversibility. The adsorption of inorganic and organic pollutants from wastewater is most often the result of both types of mechanisms overlapping. The significance of adsorption for wastewater treatment is highlighted by the increasing range of materials used as adsorbents. The materials that can act as adsorbents are remarkable by the variety of structures and properties. They can be raw and modified materials of mineral, organic or biological origin, natural materials, synthetic materials, industrial and agricultural

The "green" subcategory of adsorption, biosorption, can be defined as the low-cost and low-tech concentration of pollutants from aqueous media on the solid surface of a biological matrix (biosorbent), achieved through a passive mechanism [54]. As a physico-chemical process, biosorption works by a combination of different interactions ranging from hydrogen forces to covalent bonds through which the targeted toxic species is retained on the biosorptive materials surface. The key concepts of biosorption have been fully decrypted by means of a large number of

Due to its quasi-perfect framing into the sustainable development coordinates, biosorption has received considerable acceptance in removing heavy metals and organic pollutants from wastewater [54, 55]. Besides the ecologic and economic advantages, biosorption is also challenging by its applicability over a wide array of operational conditions, adaptability to varied designs of systems, possibility of sequential or simultaneous removal of pollutants from large volumes of wastewaters. Biosorption is a propriety characteristic to a broad spectrum of natural or waste bio-origin materials that are cheap, abundant, ready available, renewable, recyclable and versatile [55]. The biosorption potential of biomass is mainly due to their surface functional groups (hydroxyl, carboxyl, amino, sulfhydryl, carbonyl, phosphate) able to cope with the pollutants' toxicity. Due to the functional groups, these materials developed a wide range of uptake mechanisms (electrostatic interaction, ion exchange, precipitation, complexation, chelation, reduction) that ensure high pollutants removal efficiencies from aqueous media [13, 14, 56]. Various biological materials were tested for the development as biosorbents, including: microorganisms and algae, plant materials, agro-industrial wastes and other polysaccharides materials. These categories of green adsorbents have been almost exclusively investigated from the perspective of their application for removal of heavy metals and/or textile dyes from synthetic wastewaters. The promising results have opened the way to develop environmentally friendly technologies for removal – recovery – recycling of rare earths and precious metals [57, 58]. Biosorbents must

laboratory studies addressing issues of fundamental research (**Table 1**).

*DOI: http://dx.doi.org/10.5772/intechopen.94942*

**3. Adsorption on rape waste biomass**

**3.1 Adsorption/biosorption processes**

in the second part of this chapter.

wastes and biomasses [53].

and organic pollutants from environmental aqueous media, which will be discussed in the second part of this chapter.
