Exploring the Potential of Sunflowers: Agronomy, Applications, and Opportunities within Bio-Circular-Green Economy

Abstract

The present review article is intended to provide comprehensive insights into the techniques of sunflower cultivation, methods of processing, and opportunities for value addition through a variety of applications. Sunflower (Helianthus annuus L.) is an economically valuable crop, admired for its vibrant yellow flowers and seeds rich in high-quality oil. The oil derived from sunflower seeds is nutritionally valued for its high content of unsaturated fatty acids, such as linolenic and linoleic acids, which help to reduce cholesterol levels and prevent arterial fat clots. Moreover, it contains essential vitamins A, D, E, and K. Sunflower cultivation primarily occurs in warm regions, aligning with the plant’s climatic preferences. As a short-lived plant, sunflowers demonstrate drought resilience due to their deep root system. In recent years, the use of sunflowers has significantly expanded, driving economic growth. The demand for products derived from sunflowers, including sprouts, roasted seeds, seed oil, and even sunflower-based agricultural tourism, has increased exponentially. Notably, sunflower seeds and their oil hold particular importance as they form the basis for integrated production systems, contributing to the creation of various food and non-food products. By presenting this information, we aim to provide a comprehensive guide for those interested in enhancing the utilization of sunflowers across various sectors.

1. Introduction

Sunflower (Helianthus annuus L.) is an economically significant oilseed crop that can be processed into a variety of products. It ranks as the fourth most important oil crop in the world, following soybean, oil palm, and canola [1]. The global trend in sunflower cultivation is steadily increasing. According to the data shown in 2018, the major sunflower-producing countries in 2018 include Ukraine (576,0000 ha), the Russian Federation (6,942,000 ha), Argentina (1,426,000 ha), China (957,000 ha), Romania (1,025,000 ha), Bulgaria (842,000 ha), Turkey (689,000 ha), Hungary (625,000 ha), France (634,000 ha), and the United States (618,000 ha). Global oil production and consumption, both for food and non-food uses, are expected to double over the next two decades. Specifically, there is an anticipated threefold increase for oil palm, 2.2-fold increase for sunflower, a doubling for soybean, and a 1.8-fold increase for canola [2]. Sunflower seeds are a rich nutritional source, boasting high levels of protein, fiber, minerals, and phenolic compounds [3]. Sunflower crops are drought-tolerant and can be cultivated late in the rainy season. They are also utilized in farming systems for crop rotation, alternating with rice, beans, or corn. Demand for sunflower products has substantially increased, primarily for seeds and oil. Notably, sunflower-oil sales reached USD 18.50 billion in 2020 [4]. In the subsequent year, numerous firms ventured into sunflower-seed production, leveraging advancements in seed technology to bring about physiological and biochemical modifications. These efforts resulted in an intriguing outcome: sunflower seeds that possess increased weight without a change in their shape. According to the Compound Annual Growth Rate (CAGR) report, the sunflower market is projected to grow 5.7% by 2027 [5].

During the COVID-19 outbreak, various factors such as labor shortages, lockdown restrictions, disrupted transportation, and supply-chain issues occurred and thus led to a decline in demand. However, growth is projected to resume in the medium term, with consumption predicted to be 16% higher by 2030 compared to the base period of 2018–2020 [6]. The global pandemic has also heightened consumer awareness of health concerns, leading to a growing preference for healthy cuisine worldwide [4,5]. Sunflower products play a vital role in the food industry as they can be processed into cooking oil, cereal, confections, and more. Notably, sunflower products, especially those rich in linoleic acid, are favored in most of Europe, the Asia-Pacific region, and South America. Confections and food-grade sunflower seeds are widely used as ingredients. The consumer retail sector, which dominates the food-grade seed market, is expected to expand both domestically and internationally due to increased demand for processed foods made with sunflower oil and other seeds [5].

The sunflower market is divided into two segments: seeds and oil. Oilseed has gained dominance in the market due to increasing health awareness and recognition of its numerous health benefits [7]. The seeds can be processed into various food products, catering to diverse markets and purposes. Confectionery sunflower seeds serve as raw materials for food-grade sunflower seeds, packed seeds, and ingredients. According to the Agricultural Marketing Resource Center [8], the primary market for food-grade seeds is the consumer retail sector, both locally and internationally. Packed seeds are marketed as nutritious snacks for consumers, while sunflower seeds also cater to businesses such as bread makers as an ingredient. Additionally, sunflower products like sunflower butter provide an alternative for consumers with nut allergies. Sunflowers can also be utilized as animal feed, especially for birds. Interestingly, the COVID-19 outbreak unexpectedly led to a surge in backyard bird-feeding sales, benefiting sunflower growers and processors [9].

Interestingly, the bio-circular-green (BCG) economic model, which can be applied in both industry and agriculture, is promoted for sustainable and all-encompassing economic development. The BCG will simultaneously develop a 3D economy, namely a bioeconomy system that focuses on using biological resources to create added value. By emphasizing the development of high-value products linked to the circular economy, these economies fall under the overarching category of the green economy [10]. By paying attention to every stage of sunflower production and applying knowledge, technology, and innovation to achieve business-cycle efficiency and effectiveness from the onset of sunflower cultivation privatization, added value has been created. Utilizing byproducts from manufacturing and processing, combined with environmental conservation, supports long-term economic development. Thus, acquiring knowledge about planting techniques and creating economic opportunities with sunflowers is crucial. The present review article aims at providing in-depth insights into sunflower-growing practices, processing procedures, and the possibility for value addition through a variety of uses.

2. Sunflower Agronomy

2.1. Botanical Characteristics of Sunflower

The sunflower belongs to the family of Asteraceae and is classified as a biennial plant widely grown in temperate regions. The name “sunflower” comes from the fact that its inflorescence turns to follow the sun, with the leaves facing east in the morning and west in the evening. However, this turning gradually decreases during the pollination and flowering stage [11]. The plant comprises essential structures such as roots, stems, leaves, flowers, and seeds (Figure 1). The root system is a taproot that goes about 150–270 cm deep, and these roots are quite sturdy, extending sideways up to 60–150 cm in length. The stem is stiff, plump, and can reach a height of 1–3 m [12]. While most stems are unbranched, some varieties do branch. The size, height, and branching of the stem depend on both the variety and the growing environment. Leaves are opposite along the lower stem, and the upper leaves alternate along the stem [13]. The shape of the leaves varies according to the species, and their color can range from light to dark green. The petioles remain vertical until the leaves reach 1 cm in length. The apex gradually curves downwards as the leaves mature (U). Leaf production is plentiful until the flowers bloom; afterwards, leaf formation reduces. Dish-shaped flowers are borne on top of the main stem or branches, with flower diameters ranging between 6 and 37 cm.

A sunflower head comprises numerous individual florets that display a unique pattern of maturation. During early development, these tiny flowers are organized in a continuous spiral, with the youngest at the center and the oldest at the periphery. In later developmental stages, the florets undergo a period known as anthesis. Every day for the next five to ten days, they become sexually mature, ready to release and receive pollen [14]. The sunflower’s structure resembles an inflorescence made up of many florets divided into two types. The first type includes the florets located around the periphery of the flower head. These are sterile flowers with yellow-orange petals that sprout from the flower disk, often referred to as ray flowers. The second type, or the disk flowers, are perfect flowers with both male and female reproductive parts. The male stamens mature before the female structures, readying them to fertilize. Most open-pollinated sunflower varieties self-pollinate very infrequently. Sunflower seeds are composed of a kernel encased by a sturdy shell (Figure 2). Oil seeds are small, black seeds with a thin seed coat that yields a high oil content. In contrast, edible seeds are larger than oilseeds and their thick hull does not adhere to the kernel inside. This makes them easier to crack. The kernel can be consumed after baking, added as decoration to desserts, turned into flour, or roasted with salt. Consuming the kernel after removing the seed coat is similar to the way watermelon seeds are eaten. Lastly, there are seeds specifically cultivated to be used as bird feed, which can be directly offered to birds or chickens [15].

2.2. Growth Stages

Knowledge of the sunflower’s ontogenetic cycle and the events that transpire during its growth and development allows for the adjustment of management practices to enhance seed and oil yield, antioxidant activity, and phenolic profile [16]. To increase yield, it is crucial to align the crop’s resource demands with the environmental conditions and inputs provided at various growth and developmental stages. The period required varies depending on the variety and the growing environment [17,18]. Schneiter & Miller [17] have categorized the sunflower’s development into five main stages. During the germination and emergence stage, the seed first grows a root to access underground water, followed by the appearance of shoots or above-ground growth. Sunflower seedlings are characterized as epigeal cotyledons. The vegetative phase represents the growth span between germination and flowering, marked by the development of the aerial stem and the taproot. The initiation of the floral primordia occurs around the eight-leaf stage or 30–40 days after seed germination [19]. In the flower-bud stage, the number of ovules is finalized. This stage lasts anywhere from two weeks to three months, depending on the variety and environmental conditions. Factors like temperature and sunlight levels can influence the speed at which they bloom. During the flowering stage, which typically occurs 120 to 180 days or roughly 17 to 26 weeks after sowing, the yellow petals on the outer circle of the sunflower head, known as ray flowers, fluoresce for 8 to 10 days. The disk flowers are the tiny buds found in the center of the sunflower head. Lastly, the maturing stage involves the seed-filling phase and the active synthesis of fatty acids. Physiological maturity is reached once the seeds attain 28% moisture. Despite these stages, one of the most widely adopted scales is the decimal notation introduced by Schneiter & Miller [17,19,20], as detailed in

Table 1. Growth stages of sunflower plant.

Sunflower	Days after Planting	Stage	Description
	10 days	Vegetative Emergence, VE	Seedling has emerged and the first leaf beyond the cotyledons is less than 4 cm long.
	15–35 days	Vegetative Stages (V number, i.e., V-1, V-2, V-3, etc.)	These are determined by counting the number of developed leaves at least 4 cm in length beginning V-1, V-2, V-3, V-4, etc. If senescence of the lower leaves has occurred, count leaf scars (excluding those where the cotyledons were attached) to determine the proper stage.
	40 days	Reproductive Stages, R-1	The terminal bud forms a miniature floral head rather than a cluster of leaves. When viewed directly above, the immature bracts form a many-pointed star-like appearance.
	55 days	R-2	The immature bud elongates 0.5 to 2.0 cm above the nearest leaf attached to the stem. Disregard leaves attached directly to the back of the bud.
	65 days	R-3	The immature bud elongates more than 2.0 cm above the nearest leaf.
	70 days	R-4	The inflorescence begins to open. When viewed from directly above, immature ray flowers are visible
	75 days	R-5 (decimal, i.e., R-5.1, R-5.2., R-5.3, etc.)	This stage is the beginning of flowering. The stage can be divided into substages depending upon the percentage of the head area (disk flowers) that has completed or is in flowering, e.g., R-5.3 (30%) or R-5.8 (80%).
	85 days	R-6	Flowering is complete and the ray flowers are wilting.
	95 days	R-7	The back of the head has started to turn pale yellow.
	105 days	R-8	The back of the head is yellow, but the bracts remain green.
	125–140 days	R-9	The bracts become yellow and brown. This stage is regarded as physiological maturity.

Source: North Dakota State University with some modifications data from North Dakota State University [20].

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2.3. Environmental Factors Affecting Sunflower Plant Growth and Development

Sunflower traits are influenced by both genetic and environmental factors. The environment plays a crucial role in sunflower-seed germination, seedling growth, development, seed yield, and seed-quality traits. The major factors affecting sunflower production are as follows:

2.3.1. Moisture

At the planning stage, the germination process impacts seedling survival rates and crop establishment, which are influenced by climate [21]. Sunflower seeds require a sufficiently fine and moist soil around them at sowing depths of 2 to 3 cm. In the first step of seed germination, the imbibition stage, dormant seeds absorb water and undergo hydrolysis [22]. Germination is complete when the radicle emerges from the seed coat to develop a root, and the plumule constructs a shoot system capable of absorbing inorganic substances, water, and light energy for healthy growth. The optimal water requirement for sunflower-seed development under controlled conditions has been studied. The milliliter technique and thousand kernel weight (TKW) are used to optimize the water requirements for sunflower germination. While sunflower seeds can germinate under a wide range of water availability, the optimal water volume enhances the growth of radicles, shoots, and seedlings. The optimal water range for the growth of radicles, shoots, and seedlings was 8.2–11.4, representing 1625–2250% [23]. Water influences the growth, seed, and oil yield of sunflower. Water stress decreases seed yield, yield components, and seed oil content but increases seed protein content in all sunflower hybrids such as Azargol, Alstar, Hysun 33, and Hysun 25 [24]. Water deficit or water stress can reduce plant height, stem girth, head diameter, the number of seeds per head, seed index (1000 seed weight, g), and the seed yield component of sunflower. Watering four times at intervals of 30, 45, 60, and 75 days after sowing (DAS) provides an optimal irrigation regime for achieving higher economic seed yields. Discontinuing irrigation under 2 (30 and 45 DAS) and 3 (30, 45, and 60 DAS) irrigation schedules resulted in severe negative effects on seed yield [25]. A lack of irrigation decreases seed yield and oil percentage in oleic acid, linoleic acid, linolenic acid, and palmitic acid content [26]. Drought stress affects achene yield, harvest index, crop water productivity (WPc), and the drought tolerance of sunflower cultivars (Chiara, Oscar, Fantasia, Hisun 33, and Shams) [27].

2.3.2. Temperature

Temperature plays a crucial role in sunflower germination processes. High temperatures negatively influence the germination rate and the phytochemical content of sunflower crops. Optimal temperatures for sunflower germination are determined to be between 15 and 35 °C. Seeds germinated at 25 °C have better germination and seedling development [23], and they accumulate more α-tocopherol, stigmasterol, leucine, proline, methionine, glutamine, and GABA compared to those at 35 °C [28]. In addition, high heat stress is a major factor influencing yield components and oil composition in high- and mid-oleic sunflower hybrids. The hybrid plants in a heat cabinet were exposed to 24/36 °C (night/day) temperatures during grain-filling. The head diameter and the sterile area of the head increased, but the number of filled seeds per head and seed weight were reduced. The average oil concentration decreased by 6%. Concentrations of palmitic, stearic, and oleic acids increased, whereas linoleic acid decreased [29].

2.3.3. Soils

Sunflowers can generally grow in moderate- to well-drained soil types, such as clay loam or silty clay loam soils, and they thrive best in sandy loam soil conditions. Wet and low-lying flood conditions are not suitable for sunflower crops. Numerous studies have documented that, in cases of marginal sites where field conditions may become too wet, “hipping” or “bedding” can help improve drainage and create more suitable growing conditions [30]. The suitable soil pH for the growth of sunflowers is slightly acidic, ranging from pH 6.8 to 7.5. Soil acidity is a major factor that limits sunflower yield. The yield can be reduced by 10% or more in highly acidic soil conditions (pH: 4.7 to 5.3) [31]. For saline soil conditions, tolerant varieties and increased fertilization are recommended [32]. The seed yield and oil quality also varied in the Thrace region of Turkey. The highest average yield was obtained from Vertisol (Typic Haploxerert, shrinking and swelling clay soils) soils at 2.26 t ha⁻¹, while the lowest yield was from Inceptisol (Typic Haploxerept, beginning of horizon development) soils at 2.03 t ha⁻¹. The greatest oil content was found in Vertisol soil, ranging between 31.79% and 43.69% compared with other soil types [33]. Sunflowers prefer well-drained soils with high water-holding capacity. Soil water-holding capacity was related to soil texture. The improvement of soil texture, density, bulk density, and porosity of soil by fly ash increased soil water-holding capacity under a sunflower–spinach–sunflower crop-rotation system [34].

2.4. Cultivation and Practices

2.4.1. Field Preparation

Sunflower plants have a deep root system; however, about 60 percent of the roots are located in the soil layer 0–40 cm in depth. It is recommended to plough the soil to a depth of 30–35 cm using a tractor, create raised beds to improve drainage in wet soil conditions, and clear out weeds. Adding manure or fermented compost can help enrich the soil with essential nutrients before cultivation.

2.4.2. Cultivation

Farming practices such as sowing depth, plant spacing, crop season, and soil moisture content all influence the growth and productivity of the sunflower crop [35]. Some effective practices include planting two seeds per hole at a depth of 5–8 cm covered by soil, maintaining a plant spacing of 70–75 × 25–30 cm, retaining only a single healthy plant per hole when 2–4 pairs of leaves have developed, and applying a wider planting distance for conditions with lower soil moisture content or adopting ridge planting to ensure easy water access during the dry season [36]. A past attempt at planting was unsuccessful due to the seeds withering. The low productivity was attributed to the infrequent pollination by insects of synthetic species. Choosing row and plant spacings that offer an optimal plant density can maximize seed yields and minimize seeding costs. Sunflowers should be sown to the appropriate plant density. A high plant density (80,000 plants/ha) results in maximum seed and oil yield [37]. A study conducted in 1998 investigated the effect of plant density (ranging from 38,000 to 100,000 plants/hectare) in combination with various rows (50 and 75 cm) and plant spacings (20, 25, 30, 35 cm) as illustrated in Figure 3 [38]. Research from two climatically distinct locations suggests that narrow row spacing (20 cm) combined with smaller plant spacings, resulting in high plant populations of about 100,000 plants/hectare, can produce economically viable yields in the rain-fed conditions prevalent in dry and warm regions of Iran. In semi-cold regions, plant populations ranging from 57,000 to 67,000 plants/ha appear to be sufficient. These findings align with those of other researchers focusing on dry land and similar climates. The moisture provision in both the warm and semi-cold locations (400 mm and above) was found to be sufficient to produce an economically viable yield of sunflower crops. The results also underscore the importance of choosing high-yielding varieties tailored to specific climatic conditions.

The wider planting spacing will have a positive effect on both the quantity and quality of the output. This may be attributed to the improved environmental conditions due to wider spacing, reduced competition between plants, and increased light penetration within the plant canopy, which enhances the assimilation rate and oil formation. An early planting date in April and a plant spacing of 75 × 20 cm for sunflowers are recommended for mild and humid climates, such as in the north of Iran [39]. The row spacing influences the yield components of the sunflower head differently, depending on the soil and climatic conditions. Under less favorable growing conditions, narrow rows appear to allow sunflower plants to utilize growth factors more efficiently, leading to higher values for the yield components of the head. Optimal row spacing and plant population depend on growing conditions (soil and climatic conditions). The highest yields were achieved with a row spacing of 75 cm under favorable conditions and with narrow rows under less favorable conditions, especially at a row spacing of 50 cm. Additionally, the highest yields were achieved with increased plant populations under favorable growing conditions. Increasing the plant population under less favorable growing conditions decreased the yield [40].

2.4.3. Fertilization and Irrigation

Inorganic fertilizer components, such as N, P, and K, are essential nutrients for plant growth and productivity. A balanced fertilization rate plays a role in supplying the nutrients needed to attain maximum sunflower growth. The proportion of nutrients and the amount of fertilizer vary according to the nature of the planting area. In Indonesian conditions, the soil has a pH of 6.5, C-organic of 1.66%, C/N ratio of 9.77, N-total of 0.17%, P-Olsen of 44 ppm, and K of 0.47 me.100 g-1. In general, the best growth of the plant and the highest harvest yield are obtained from an N-P-K treatment of 150–75–50 kg ha⁻¹. The application of NPK fertilizer at this level yields the highest grain yield of about 2.74 t ha⁻¹. This level of NPK fertilizer can be recommended for the cultivation of sunflower crops in dryland during the rainy season [41]. The level of N-P-K fertilizer form 120–90–60 kg ha⁻¹ affects plant growth, grain yield, and maximizes sunflower grain yield. Sunflowers are tolerant of moderate water stress and are capable of producing high yields in response to applied irrigation. Research and grower experiences indicate that sunflowers respond to irrigation with 2–3 times yield increases over dryland production. Furrow, drip, micro-sprinkler, and sprinkler irrigation are suitable for sunflower cultivation [42,43].

2.4.4. Disease and Insect Pests and Managements (IPM)

Various diseases and insects damage sunflower crops, resulting in significant losses in production and yield. Sunflowers are susceptible to many diseases. In fact, more than 90 sunflower diseases have been reported worldwide [44]. Throughout their growth, sunflowers are attacked by numerous insect pests. Diseases can reduce sunflower production by 30–100 percent, depending on the conditions and severity. These diseases directly affect the productivity and marketable price of the sunflower crop. Among the main diseases of sunflower are Sclerotinia, which can cause up to 50% yield loss and degrade oil quality; Verticillium, which can reduce yield by up to 30% and also degrade oil quality; and Mildew, which directly affects plant survival. Every infection can lead to plant loss, and in severe cases, the yield loss can be as much as 100% [45]. The primary pests for sunflowers include false wireworms, true wireworms, armyworms, cutworms, head borers, aphids, black scarab beetles, thrips, whiteflies, and black field earwigs [46]. In different countries, the same disease may be caused by different pathogens and the control measures include chemical treatments, integrated pest management (IPM), the use of resistant varieties, which might help reduce the incidence of pathogen attack in sunflowers [47].

2.4.5. Harvesting

The harvest time for sunflowers ranges from 90–100 days, depending on factors such as temperature, relative humidity, soil fertility, and the cultivar [48]. The primary indicator for sunflower harvesting is the seed moisture content at the time of harvest because it influences both yield and 1000-seed weight [49]. Sunflower seeds are considered physiologically mature when the back of the green plate turns yellow. Farmers generally harvest when the flower plates turn brown. A seed moisture content of 12–14 percent is ideal for storage. To harvest, farmers cut the flower stalks with a knife or sickle, dry them in the sun, and then shell the seeds. When harvesting with machinery, it is best to harvest when the seed moisture content is between 20–25 percent to minimize loss due to seed drop during the process and subsequently reduce the moisture content using a dryer.

2.4.6. Postharvest Process and Preservation

Oil seeds, like sunflower seeds, lose their germination rate quickly, especially when stored under unsuitable conditions. Storage conditions play a decisive role in ensuring the physiological quality of the seeds. Although their quality cannot be improved once harvested, maintaining good conditions during storage will help keep the seeds viable for longer, slowing down the deterioration process. When harvested seeds are stored in sheds or seed bins, the humidity must be reduced to about 9.5 percent. Seeds with a moisture content of 10 to 12% can be stored in bins with aeration. Any seeds with a moisture content over 12 percent will require drying [50]. Moreover, the type of packaging used for storage significantly impacts the preservation of seed viability and vigor. Suitable packages should aim to slow the deterioration process by decreasing respiration, thus maintaining the initial moisture content of the stored seeds. Sunflower seeds remain viable for 12 months when stored in a dry cold room (10 °C and 55% RH), a refrigerator (4 °C and 38–43% RH), or a freezer (−20 °C) in paper bags, multilayered paper, black polyethylene, or PET bottles. However, ambient conditions of 30–32 °C and 75% RH are not suitable for storing sunflower seeds [51]. Seeds stored in natural conditions showed a sharp reduction in germination from the third month of storage, fully losing their germinating power by the sixth month, regardless of the packaging type used [52,53]. In the dry cold room, refrigerator, and freezer, the germination of sunflower seeds remained over 80% throughout the storage period [54,55].

2.5. Propagation

Sunflower plants are classified as self-incompatible plants, and their cross-pollination depends on insects, primarily bees [56]. They can be divided into three seed types for propagation: hybrid seeds, open-pollinated seeds, and synthetic seeds. These types of seeds influence the number of seeds used for cultivation. Hybrid varieties can self-pollinate and set seeds efficiently without relying on insects for pollination because they produce 3–4 times more pollen than the open-pollinated variety. Sunflower hybrid seeds are preferred due to their drought resistance, wider adaptability to various environments, high yield, and high-quality oil production [57]. Open-pollinated varieties (OPV) have fewer pollens in the flower and lower self-fertilization rates, relying more on insects to pollinate the seeds. OPVs generally yield less than single hybrids but are valuable alternatives that can be easily produced locally, even by farmers, at a reduced cost [58]. A synthetic variety is a hybrid crossbred between more than four strains or between two or more open crossbreeds. Sunflower floral structures do not easily allow for emasculation and pollen transmission, making it challenging to produce hybrid (F1) seeds at a low cost. These issues can be addressed by breeding synthetic varieties. However, synthetic varieties typically have less uniformity than single-cross hybrids [59]. Currently, synthetic strains are not widely available commercially, but many organizations are conducting research on them. The seeding rate for one hectare is 4 to 6 kg or 70,000–75,000 seeds. Typically, sunflowers are planted with an interrow spacing of 70 or 75 cm. Still, this spacing can be reduced to 40–45 cm to increase the yield by 10–20% when using small-sized hybrid varieties [60]. Sowing with large seeds was better than that with small seeds. Large seeds showed a high germination percentage and seedlings from large seeds were vigorous seedlings with better chances of survival than those from small seeds [61]. Moreover, large seeds increase plant height, number of leaves, leaf area, stem diameter, and number of seeds of sunflower plants [62].

3. Utilization and Opportunities in the Bio-Circular-Green (BCG) Economy Model

The principle of the BCG model advocates holistic economic development, promoting growth in three simultaneous dimensions: the bioeconomy, which emphasizes the use of biological resources to add value. This dimension stresses the creation of high-value products tied to the circular economy, while maximizing the reuse of materials. Both these economies are part of the green economy, an approach to economic development that prioritizes not just economic growth, but also social progress and environmental preservation. This balanced approach ensures both stability and sustainability. Farmers and sunflower-business operators can leverage the principles of the BCG model in everything from cultivation to processing and marketing, aligning their operations with sustainable development guidelines. The BCG model integrates the value chains of five key industries: agriculture, biotechnology, pharmaceuticals, food processing, biofuels and biochemistry, comprehensive medicine, and tourism. At its core, the BCG model emphasizes parallel growth: it capitalizes on advanced scientific research for producing high-value products, such as health food ingredients and medicinal compounds. Additionally, the model fosters a grassroots economy, creating widespread value in an environmentally-friendly manner and bolstering social capital. The consideration of natural resources, cultural wisdom, and adherence to the philosophy of a sufficiency economy align the BCG model with the United Nations Sustainable Development Goals [63].

Creating added economic value for sunflowers, which is linked to upgrading the grassroots economy (see Figure 4), encompasses several measures. Farmers are encouraged to adopt smart-farm technology to enhance efficiency and productivity. This can reduce costs by minimizing the use of fertilizers and pesticides—the primary expenses for farmers. In turn, this leads to safer results, ensuring consistent quality and quantity that align with market demands and results in safe and stable products that can be upgraded to higher value. There is also a push to support the production of sunflower-based products with high added value, such as oils and health supplements. This will help absorb excess sunflower production in the market, addressing the issue of reduced prices during high-yield seasons. Another initiative promotes biochemical production to decrease the dependence on costly chemicals. Simultaneously, new tourist attractions centered on biodiversity and culture are being created. Introducing a tourist attraction management system that incorporates digital technology assists locals in crafting tourism content, managing routes, and boosting tourist numbers on their own. This creates high-quality tourist sites that direct visitors to local communities. Moreover, fostering a circular economy is emphasized. This focuses on transforming by-products and waste from sunflower production and processing into revenue streams. This not only adds value for current business entities in the system but also paves the way for new entrepreneurial opportunities. This approach exemplifies how the nation’s resources can be used more judiciously. Furthermore, it presents a solution to waste-related issues that pose environmental threats. Therefore, the BCG model aligns with at least five Sustainable Development Goals (SDGs) set by the United Nations, including sustainable production and consumption, tackling climate change, conserving biodiversity, and fostering cooperation for sustainable development [64].

3.1. The Bio Economy for Sunflower

3.1.1. Sunflower Sprouts

Seedling or sprout formation is caused by biochemical changes in metabolites within the seeds. These changes are brought about by enzyme activity during the catabolism and digestion of various biomolecules, such as carbohydrates, proteins, and fats. These compounds accumulate in the seeds, leading to an increase in sugar-free amino acids, some fatty acids like linoleic acid, organic acids, and various bioactive compounds. Simultaneously, there is a decrease in antinutritional factors such as protease inhibitors, tannins, and lectins. In addition to promoting seedling growth, this process enhances the nutritional value of seeds compared to those that have not germinated [65]. Sunflower sprouts, in particular, have a higher antioxidant capacity than their seed counterparts. They have become increasingly popular, especially among health-conscious consumers. Sunflower sprouts contain phytochemical compounds including caffeic acid, chlorogenic acid, caffeoylquinic acid, cynarine, gallic acid, and flavonoids such as heliannone, quercetin, luteolin, and kaempferol. Additionally, they contain pigments like chlorophyll, carotene, and xanthophyll, as well as vitamins like vitamin A, B, C, and E. They also boast niacin antioxidant activity and minerals like calcium, iron, magnesium, and phosphorus. The chemical constituents present in sunflower sprouts offer a plethora of bioactive properties, including antioxidant and antibacterial activities. Furthermore, antimicrobial, anti-inflammatory, and blood-pressure-reducing properties, akin to the antihypertensive effects of ginseng, are associated with them [66,67].

Sunflower sprouts are fragrant, crunchy, and sweet. They can be eaten fresh or used in cooking, in dishes such as salads, papaya salad, stir-fried with oyster sauce, stews, and curries, or added to noodles as a substitute for bean sprouts. The method for cultivating sunflower sprouts is quite simple and can be undertaken at home. The equipment needed for planting includes sunflower seeds, planting containers, seedling materials, and watering equipment. The procedure for sowing sunflower-seed sprouts is shown in Figure 5.

3.1.2. Roasted Sunflower Seed

Fat is the main component found in sunflower seeds, with a content of 44–52%, followed by protein at 28–32%. The important fatty acids found in sunflower seeds are 62–69% linoleic acid and 20–25% oleic acid [68]. Sunflower seeds are also a rich source of tocopherols (vitamin E), chlorine, betaine, lignans, arginine, and phenolic acid [69]. Roasted sunflower seeds are a product made by boiling raw sunflower seeds that have been removed from their shells and soaked in brine. They are then dried by baking or roasting to crack the shell and separate the seeds from the shell. There are two kinds of roasted sunflower seeds: roasted sunflower seeds in the shell and shelled roasted sunflower seeds. The moisture content of roasted sunflower seeds must not exceed 5% by weight [70]. Roasted sunflower seeds have a unique aroma. About 114 volatile compounds are found in roasted sunflower seeds, such as terpenes (α-pinene, β-pinene), heterocyclic compounds (2-ethyl-3-methylpyrazine, 2,5-dimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, pyridine), aldehydes (2-methylbutanal, furfural, hexanal, phenylacetaldehyde), hydrocarbons (octane, 2-isobutyl-1,4-dimethylcyclohexane, 6,6-dimethylundecane), and alcohols (3-methyl-2-propyl-1-pentanol), with γ-butyrolactone being a dominant compound. The optimum roasting temperature is 125 °C for 45 min [71].

3.1.3. Sunflower Seed Oil

The amount of oil in sunflower seeds depends on the sunflower species. Oil can be extracted from sunflower seeds using hydraulic or screw pressing, or with a solvent extractor. Sunflower seed oil is used for making cooking oil, salad oil, margarine, and shortening. The oil has a light-yellow color and a distinct smell, which can be eliminated through deodorization [72]. Sunflower seed oil’s fatty acid composition includes approximately 85% unsaturated fatty acids. Of these, oleic acid is most prevalent, followed by 4–8% linoleic acid, less than 2% linolenic acid, and approximately 15% saturated fatty acids. Refined sunflower-seed oil is obtained by removing contaminants from the fats or oils extracted from the seeds [73]. Sunflowers are classified as oil plants because sunflower seeds contain 34.26–39.13% oil. They produce high-quality oil, which includes unsaturated fatty acids such as linoleic, linolenic, and arachidonic, and vitamins A, D, and E [74]. Originally, sunflower seeds had 25% oil. However, modern plant-breeding methods like induced mutation, hybridization, and molecular breeding have created sunflower hybrids with up to 40% oil content [75]. These hybrids vary in their oil content. For instance, the Indian sunflower hybrid COH 3 (CSFH 12205) boasts around 42% oil, more than Sunbred 275 (38%) and Hybrid CO 2 (39%). This hybrid produced the highest oil yield of 716 kg/ha, outperforming Sunbred 275 (565 kg/ha) and CO₂ Hybrid (596 kg/ha) [76]. In Turkey, the LG 5585 sunflower hybrid has the highest oil yield (1820.6 kg/ha) for irrigated lands [77]. The general process of extracting sunflower oil is shown in Figure 6.

3.2. The Circular Economy for Sunflower

3.2.1. Feeds

The increasing demand for soybean meals may necessitate the exploration of other protein sources to economically balance compound feeds. Plants or plant-based protein sources alternative to high-priced proteins, such as soybean meals, are used in animal feed. Oilseeds must undergo the oil-extraction process mainly in factories. Sunflower seeds are composed of kernels and seed coats, or hulls. Sunflower hulls account for 21–30% of the seed weight, with the proportion of hulls in the sunflower seeds ranging from 13.67% to 43.47%. The weight of the hulls depends on factors such as variety, environmental conditions, seed size, and oil content. The lower values can result from ongoing efforts to increase the seed’s oil content. The hulls contain a relatively low protein percentage (7.82%). When the dehulling process is applied to the kernels, their protein content increases to 23.73%. The protein composition of the whole seeds is 33.85%, the kernels 23.73%, and the hulls 7.82%. Sunflower seeds are highly nutritious, containing 33.85% proteins. Sunflower oil cake, a byproduct of sunflower-seed oil extraction, has gained considerable attention due to its versatile applications. It is utilized as a high-protein and high-fat feed source for livestock, as well as a substrate in the production of enzymes, antibiotics, and biosurfactants. Furthermore, it shows promise in recovering bioactive compounds for the development of innovative value-added products [75]. Before storage, they are air-dried to remove moisture. Typically, they are molded into two forms: flour (ground material) and pellets. Sunflower oilcakes in pellet form have 31.88% fiber and 20.15% protein, while in cake form, they have 12.64% fiber and 21.60% protein, as per [75]. A review of the literature indicates that the chemical composition and the evaluation of the nutritional value and efficacy of high-protein sunflower meal in broiler feeding have been studied [78]. There are also studies on sunflower-meal supplementation as a complementary protein source in the diet of laying hens, focusing on productive performance, egg quality, and nutrient digestibility [79]. Es Petunija, Allium, and Albatre are sunflower oilseed hybrids adapted to European conditions, known for their high yield and tolerance to lodging and Phomopsis spp. The total protein content in the kernels was found to be higher than in the seeds. Specifically, the total protein content was 25.03%, 23.84%, and 23.84% in the seeds and 43.42%, 43.02%, and 42.73% in the kernels of Es Petunija, Allium, and Albatre, respectively [80].

3.2.2. Biodiesel

Ethanol can be produced from sunflower-seed-husk hydrolysate [81]. Charcoal briquettes can be made from sunflower-seed husks as an alternative energy source; these husks are by-products of the oil extracted from sunflower seeds and can also be used as an ingredient in animal feed [82,83]. Sunflower silage, as a replacement for corn silage, benefits lactating goats. When sunflower silage constituted 0, 34, 66, and 100% of goat feed, the fatty acid concentrations of C18:1 cis-9, C18:2 cis-9, trans-11 (CLA), C18:3n6, and C18:3 n:3 increased proportionally with the amount of sunflower silage in the feed [84]. Sunflower seeds can be used for biodiesel production, a liquid fuel derived from vegetable oils and animal fats. This oil undergoes a chemical reaction known as “transesterification” with methanol to produce an ester with properties similar to diesel, called “biodiesel.” Proteins isolated from the sunflower-seed by-products of oil production are identified as bioactive substances [85]. Phenolic compounds, such as chlorogenic acid, offer antioxidant effects and are rich in nutritional value. These compounds can be transformed into a protein isolate, which can be used as an ingredient in other food products. Furthermore, they serve as a matrix for creating edible and biodegradable films, presenting a healthy and cost-effective ingredient [3].

3.2.3. Fiber

The sunflower stalk is divided into two parts: the bark and the core. The bark contains 48% cellulose and 14% lignin, while the core contains 31.5% cellulose and 2.5% lignin [86]. The stem resembles wood pulp, and when plowed into the soil, it acts as a fertilizer, enhancing the soil’s fertility. It has been reported that leftover sunflower plants from harvested seeds have been used as raw materials, combined with other ingredients. They are effective for producing thermal insulation in buildings and can also be used to make paper and fuel [87]. One of today’s global environmental and socio-economic challenges is the transition from fossil fuels to biomass. Biomass represents a sustainable source of renewable raw materials for the industry. The increasing public awareness of the negative environmental impacts of petrochemical products has amplified the demand for alternative production chains, especially in materials science. One promising avenue is the value-added upcycling of agricultural by-products. Sunflower stalks, in particular, obtained by crushing, are viewed as natural fiber sources for engineered bio-composites. Due to their outstanding mechanical properties and the socio-economic benefits of their use, sunflower stalks make an excellent substrate for material applications. Their appeal is not just based on their physical and chemical properties but also stems from economic, social, and environmental considerations. The growing natural fiber market favors sunflower stalks because of their abundant supply, affordability, and widespread cultivation [88].

3.2.4. Dye

The extraction of dyes from sunflower petals yields a natural substance that has gained renewed interest due to its environmental friendliness, biodegradability, non-toxicity, and hypoallergenicity. To extract dyes from these petals, three different polar solvents were utilized: water, methanol, and a 1% NaOH solution. The dye extracts were subsequently examined using Fourier transform infrared spectroscopy (FT-IR) for functional group characterization. Extractions with different solvents yielded varying colors. The intensity of the dye observed on the shade of the cotton fabric ranged from yellow for the methanol extract, to light yellow for water, and black for the 1% NaOH solution extract. The FT-IR analysis revealed several useful functional groups in the extract, including N-H, C=H, O-H, and C=O [89].

3.3. The Green Economy for Sunflower

Allelopathy refers to the process by which plants produce substances that are released to affect the germination and growth of other plants. The plants that produce these substances are termed “donor plants,” while the affected plants are known as “recipient plants.” The compounds produced by the donor plants can influence various processes in the recipient plants, such as cell division, cell enlargement, respiration, photosynthesis, hormone function, and protein synthesis [90]. This biochemical interaction is not just limited to plants but also occurs among microorganisms and animals. Over 200 natural allelopathic compounds have been isolated from sunflowers. These compounds can either inhibit or stimulate the growth and biochemical reactions of other organisms in their vicinity. Such substances can be released by plants through evaporation, or when parts of the plants, be they roots, leaves, flowers, or fruits, are washed out. These compounds can also be derived from the degradation of plant remains. The effects of allelopathy using sunflower-root extract on physicochemical changes in wheat sprouts were studied by growing Margalla 99 and Chakwall 97 wheat seedlings. These seedlings were compared with those grown using distilled water (as a control sample) and those watered with a solution where 1 g of sunflower-root extract was mixed in 9 mL of water. The growth in wheat sprouts was found to be increased by allelochemical treatments in comparison to the control samples [91]. In agriculture, weeds pose a significant concern as they compete with cultivated plants for resources. Modern agricultural practices often resort to synthetic chemicals to eliminate these unwanted plants. However, due to growing concerns about the risks associated with synthetic chemicals, there has been a shift towards exploring alternative methods of weed control. One such avenue being explored is the use of plant compounds as an environmentally friendly alternative to synthetic herbicides. Allelochemicals, which are secondary plant metabolites, have been subjected to biological and toxicological screening to ascertain their potential as natural pesticides. The allelopathic potential of sunflower, as a natural herbicide, was studied on five wheat species: Phalaris minor, Chenopodium album, Coronopis didymus, Rumex dentatus, and Medicago polymorpha. The study evaluated the effects at ten different concentrations using sunflower roots, stems, and leaves and at 20, 30, 40, and 50% w/v on selected weeds. The findings highlight the potential of allelochemicals from sunflowers as a viable alternative for sustainable weed management. Lactones, which possess a cyclohexanone ring (an analog base of annuionone), and apocarotenoids, which produce sesquiterpene lactones, have been identified as highly effective herbicides in sunflower extracts [92].

Sunflower leaves contain many bioactive compounds. Studies on antimicrobial activity have been reported from sunflower-leaf extracts containing isochlorogenic acid and chlorogenic acid as components. The sunflower-leaf extract inhibited the growth of nitrogen-fixing bacteria and nitrifying bacteria in rice leaves. Bioactive compounds extracted from sunflower leaves induce auxin, gibberellins, and cytokinins in rice (Oryza sativa) and black beans (Phaseolus mungo), showing antibacterial activity against Xanthomonas oryzae pv. Oryzae. It is important to eliminate weeds, especially those prone to monocotyledonous plants, and to produce bioactive compounds that can be used as controls for infestations of pathogenic bacteria in monocotyledons, such as rice and black beans [93]. Sunflower leaves are a rich source of terpenoid species, including bisnorsesquiterpene annuionone E, 7,11-heliannane heliannuol L, and sesquiterpenes helibisabonol A and B, extracted from dried sunflower leaves. These compounds can inhibit the growth of the coleoptile apical membrane emerging from activated wheat grains [94].

4. Sunflowers in Agricultural Tourism

Ornamental sunflowers are widely cultivated for use as cut flowers, potted plants, and for landscaping in gardens. Sunflowers exhibit two types of growth. The first type grows as a single stem, producing a large flower at the top. It is commonly planted in gardens, landscapes, and is used as cut flowers. The second type features branching stems that result in shorter stems and a bush-like appearance, producing many smaller flowers on the sub-branches. This type is often planted as a potted plant. Ornamental sunflowers come in a variety of petal shapes and colors, including yellow, red, orange, and purple [95]. Some sunflowers are bred to be pollenless, meaning they are male-sterile, and their anthers produce no pollen. Pollen can cause allergic reactions in people with pollen allergies, and sunflowers, especially those in decorative plots or pots, tend to attract bees [96]. If a sunflower produces male pollen, it can facilitate pollination. Pollen can cause flowers to wither quickly. Pollenless sunflowers lack male stamens and do not produce pollen that can stick to seeds. The advantage of pollenless sunflowers is the reduction in these issues, and they prevent pollen from staining the area where a vase is placed or from soiling clothes when arranged into bouquets. Breeding has resulted in a variety of ornamental sunflowers. For instance, a study involving the crossing of four genetically diverse inbred lines of ornamental sunflower (Heliopa, Iskra, Talia, and Neoplanta) found that all lines are branching and vary in flower color [95]. The Talia × Neoplanta hybrid combination was identified as the most promising for cutting flowers due to its long and strong branches and relatively large lateral flowers. Meanwhile, the Heliopa × Iskra and Heliopa × Talia hybrids were found suitable for use as garden plants because of their robust plant habits, prolonged flowering time, and ideal plant height.

In Thailand, agro-tourism is heavily promoted. There are diverse forms of agricultural tourism activities within the community, spanning a range of short-term and long-term experiences. These activities include visiting sunflower fields to appreciate their natural beauty, camping among the sunflowers, participating in agricultural activities like planting and harvesting alongside the community, and engaging in immersive farm-stay programs within the village to understand the villagers’ way of life. These activities highlight both modern and traditional agricultural methods. The community has also set up comprehensive agricultural learning centers that encompass various stages, from planting to the processing and sale of agricultural products [97]. Community shops have been established to promote and sell a plethora of sunflower products and souvenirs. There has also been a significant push to advance product-processing techniques, turning agricultural produce into industrial goods that bring revenue to the community. These agricultural tourism activities offer enriching experiences for tourists while also contributing to the community’s economic growth, ensuring sustainable income sources (Figure 7).

Farmers in many regions have converted sunflower-growing areas into agricultural tourism sites, which provides an additional income stream due to the beauty and unique characteristics of sunflowers. These flowers are large, often growing 5–10 inches tall, with bright yellow petals and numerous pollen rings. The petals form a circle, highlighting the pollen. Sunflowers are sun-loving plants adaptable to various climates, from tropical to cold. They grow quickly after rainfall and can thrive in different soil types. They are typically planted in the post-rainy season or during the dry season. While sunflower plants are decorative, they are also cultivated for agricultural purposes. In the industrial system, there is a high demand for sunflowers, as they are processed for consumption in different forms and turned into sunflower oil. In many agricultural settings, sunflowers are seen as a secondary crop and can be planted in rotation with other crops like rice, beans, and corn [98].

4.1. Commercial Development of Sunflower Farms and Tourism

Tourism farming, also known as “Smart Agriculture” or “Smart Farms,” has gained significant popularity due to advancements in technology and data-driven farming practices. These innovations have transformed traditional farming methods, enabling better farm management. Sunflowers, a versatile crop, have undergone cross-breeding to meet commercial demands while remaining a valuable source of raw materials. This evolution in agriculture appeals to tourists seeking unique and immersive travel experiences, including farm-related entertainment [99]. In recent years, there has been a notable increase in the demand for farm-based activities among travelers, leading to the rise of ecotourism in this context [100]. Wisnumurti et al. [101] reported that sunflower gardens in ecotourism regions offer various picturesque spots for tourists, such as replicas of the Eiffel Tower and traditional Balinese ornaments, making them attractive destinations for both nature and selfie enthusiasts.

4.2. Training Courses and Educational Information on Sunflower Plantations and Products

Training sessions and providing instruction can serve as means for business expansion and for generating a secondary source of income. There is substantial untapped demand in the sunflower sector, presenting an opportunity for sunflower producers [102]. Encouraging more farmers, especially the younger generation, to cultivate sunflowers can help meet this market demand. Establishing a learning center focused on the growth and development of sunflowers could serve as a catalyst for such expansion. It would not only provide valuable knowledge but also inspire locals and individuals to explore additional job opportunities, thus stimulating the local economy and creating employment opportunities. Leveraging the existing consumption culture and local knowledge can further enhance production and generate supplementary income for the local population. Farmers and agricultural extension experts believe that training programs play a crucial role in equipping Thai farmers with practical knowledge, enhancing their effectiveness in agricultural practices [103]. Moreover, agricultural training acts as a platform for exchanging specific information and for demonstrating successful technology practices, serving as a catalyst for agricultural innovations, especially in the context of changing climates [104].

5. Conclusions

Sunflowers hold considerable economic significance and represent a promising avenue for agricultural development, highlighted by their adaptability to diverse climatic conditions. Their inherent beauty also makes them a powerful instrument for enhancing agricultural tourism, appealing to both cultivators and enthusiasts. Renowned for their high-quality oil content, sunflower seeds serve dual purposes, acting as popular dried snacks and essential ingredients in various culinary delights, meeting the global surge in demand for this versatile crop and reinforcing its importance in the agricultural sector. To boost both productivity and quality, the adoption of advanced management methodologies, such as the BCG model, the Internet of Things (IoT), and precision farming, is imperative. The Smart Farmer approach emphasizes the development of high-value products and reductions in waste through tailored production decision-making systems, considering market dynamics and regional nuances. This strategic alignment fosters economic growth and aligns with the Sustainable Development Goals (SDGs) and the overarching sustainability agenda in agriculture. Harnessing the potential of sunflowers goes beyond economic considerations, embedding environmental and societal well-being in its core principles, in harmony with the SDGs and sustainable agricultural development. The extraction of added value from sunflower by-products minimizes waste and promotes resource efficiency and environmental preservation, aligning with key SDGs like zero hunger, responsible consumption and production, and life on land. Moreover, the cultivation of sunflowers contributes to climate resilience due to their adaptability to varying weather conditions, advancing the broader sustainability goals in agriculture. Consequently, integrating sunflowers into agricultural systems unlocks economic opportunities and propels us towards a more sustainable and equitable future, anchored in the principles of the BCG model and SDGs.