Abstract
Pineapple waste has significant potential in multiple sectors, including nutrition, medicine, bioenergy, and environmental conservation, particularly within the sustainable development framework. As a source of bioenergy, pineapple wastes address the rising global energy demands while reducing the reliance on fossil fuels (FFs). This transition supports environmental conservation through lower carbon emissions, mitigating the effect of climate change and promoting efficient pineapple waste management in alignment with circular economy principles. Besides, repurposing pineapple waste for bioenergy encourages waste minimization and fosters sustainable practices within communities. The present review explores the potential of pineapple waste in bioenergy production, medicine and nutrition. Bioactive compounds such as bromelain, phenolics, and dietary fibers present in pineapple wastes and their health benefits are discussed. The sustainable utilization of pineapple waste to address critical global challenges while advancing economic resilience, alternative energy sources, human health, and environmental sustainability is revealed. Pineapple waste, rich in natural sugars and bioactive compounds, presents opportunities for research into bioethanol, pharmaceuticals, and nutrient production through various technologies. A comprehensive literature evaluation used keywords, targeted research questions, and a search strategy that included Google Scholar, academic databases, and library cataloguesa methodical screening and selection process determined search results pertinent to the subject.
Introduction
Global population growth and the increasing consumption of fruits have led to an expansion in fruit production and processing, resulting in a significant rise in fruit waste generation. 1 As demand for fruits increases, production and processing activities intensify, contributing to higher levels of waste across various stages, from cultivation to post-harvest handling, processing, and consumer use. 2 Pineapple (Ananas comosus) is one of the fruits predominant in tropical and subtropical climates worldwide.3,4 Pineapple is the third most important tropical fruit globally after citrus and banana. 5 The A. comosus is a monocotyledonous plant which belongs to the Bromeliaceae family and kingdom plantae.6,7 The perennial plant has a short and robust stem that grows in a rosette with a sharp point and thin, sword-shaped and spirally arranged leaves. 6 The pineapple plant produces small, purple to reddish flowers in a dense spike-like inflorescence. 8 Its fruit, a multiple fruit, has a cylindrical shape, tough skin, and juicy, fibrous flesh and the root system is shallow and fibrous, spreading laterally into the soil. 9 There are six main pineapple species, including A. comosus, A. bracteatus, A. lucidus, A. nanus, A. minor, and A. sativus. 6 However, the most commonly cultivated and widely recognized species is A. comosus. 10
The top five pineapple-producing countries are Costa Rica, Brazil, the Philippines, Thailand, and Indonesia. 11 The leading pineapple producer in 2019 was Costa Rica, which produced 3328.1; the Philippines, 2747.86; and Brazil, which made 2426 million metric tons of pineapple. 12 Studies show that pineapple production between 2017 and 2022 ranged between 1 706 000 and 1 808 000 tons. 13 Besides the annual output of 1 689 884 tons, pineapple processing results in 993 402.4 tons of waste, including peels, cores, stems, and crowns. 14 Such substantial production and consumption of pineapple generate a significant amount of waste. Pineapple is eaten in various forms, including fresh, cooked, or juiced, and can be preserved through canning, freezing, and drying.15,16 Most of the pineapple fruit produced is primarily used for fresh preparations intended for human consumption. 17 Thus, large amounts of pineapple waste are generated during processing and consumption consisting of peels, cores, and crowns constituting about 25%-35% of the fruit's weight. 18 Statistical data on pineapple production and waste generation are presented in Table 1.
Pineapple Production and Waste Generation.
Pineapple waste is less suitable for human use, but it remains effective in applications such as bioenergy production, contributing to sustainability and waste management in various areas. Nevertheless, fresh pineapple waste can be utilized in medicinal, nutritional, and bioenergy due to its valuable bioactive compounds.20,21
Pineapple wastes produced during processing are disposed of in the environment, and some are utilized as animal feed.22,23 Improper disposal of pineapple wastes, such as open dumping or landfilling, contributes to environmental issues, including soil degradation and greenhouse gas emissions. 19 However, with proper waste management strategies, such wastes are valorized to generate bioenergy, including bioethanol, biodiesel and biogas, minimizing the environmental waste. Still, pineapple wastes contain compounds which are used to treat a variety of illnesses. 24 They are rich in antioxidants and provide a variety of minerals, vitamins, and nutrients. 24 Pineapple waste is a significant source of bromelain, a proteolytic enzyme with various biotechnological uses in the food, pharmaceutical, and cosmetic industries. 25
Studies show that bioethanol and biogas can be generated from pineapple wastes.26-28 The current review compiles and analyses existing literature on the potential of pineapple wastes in nutritional, medicinal, bioenergy (bioethanol, biodiesel and biogas) and environmental conservation. By exploring the role of pineapple waste, the review highlights the significance of pineapple waste in promoting sustainable practices and a circular economy. Thus, the current study examines the potential of pineapple waste in producing biofuel, medicine, source of nutrients, and its contribution to environmental conservation.
Nutritional Value of Pineapple Wastes
Pineapple peels and core contain essential minerals like potassium, calcium, and magnesium, which are crucial for maintaining fluid balance, bone health, and muscle function. 24 Besides, pineapple peels and pineapple pomace contain carbohydrates, proteins, and lipids, which provide energy to the body, support body growth, and have potential in food and cosmetic products. 21 The significant ascorbic acid (Vitamin C) content in pineapple waste strengthens the human immune system, aiding the body in fighting infections and diseases. 29 Moreover, ascorbic acid protects the body against bacterial and viral infections, is a powerful antioxidant, and enhances iron absorption. 24 Besides, bromelain in pineapple waste is an anti-inflammatory enzyme that reduces the swelling associated with inflammatory conditions.30,31 Still, carbohydrates in pineapple waste are the primary energy source in the human diet, supporting various bodily functions, including blood glucose regulation, brain function, and gastrointestinal health. 32 Pineapple waste contains dietary fiber essential for promoting multiple physiological and metabolic benefits, including regularizing bowel movements, stopping constipation, and reducing glucose and cholesterol absorption in the intestines.21,33 The dietary fiber in pineapple waste reduces the intestinal absorption of cholesterol and glucose, promoting heart health and better blood sugar management.34-36 Thus, fresh pineapple peels can be incorporated into food as an ingredient to enhance the nutritional quality of various foods. 37
Medicinal Value of Pineapple Waste
Apart from nutritional value, pineapple waste contains medicinal value. Pineapple peels are an excellent source of antioxidants that protect cells from damage caused by free radicals. 32 Pineapple peels contain polyphenolic compounds that reduce the risk of diseases associated with oxidative stress. 32 The malic acid in pineapple waste contributes to oral health by averting gum diseases and inhibiting the formation of dental plaque. 38 Beta-carotene in pineapple waste supports vision as it is a precursor to vitamin A, which is essential for eye health and prevents night blindness. 39 Besides, manganese in pineapple peels and core supports bone strength, connective tissues, and gums, contributing to healthy and strong teeth. 40 Still, pineapple wastes contain vitamin C, enhancing immune function, providing antioxidant protection, aiding tissue repair, and promoting wound healing. 16 Potassium and sodium in pineapple wastes regulate and maintain balanced blood pressure levels. 41 Bromelain from pineapple waste is a natural remedy for chapped lips, prevents hair loss, and is beneficial for inflammatory scalp conditions due to its soothing and nourishing properties. 38 A study indicates that pineapple leaves are used as remedies for dyspepsia and diarrhea and are valued for their potential to aid digestion and mollify gastrointestinal discomfort. 36 Besides, bromelain in pineapple waste reduces pain and inflammation associated with surgery. 42 Still, bromelain exhibits significant anti-cancer activity against breast cancer cell lines, including Michigan Cancer Foundation-7 (MCF7), MD Anderson-Metastatic Breast-231(MDA-MB231), and Gastrointestinal-101A (GI-101A). 36 Pineapple wastes are a vital source of the enzyme bromelain, which has several uses in industry. 43 Bromelain is essential in breaking down protein due to its proteolytic properties. 44 Bromelain is used in the food industry for protein hydrolysates and meat tenderization and in the pharmaceutical industry to treat conditions like sinusitis and arthritis due to its anti-inflammatory and digestive properties. 45 Although pineapple is primarily used as food worldwide, its residues have potential applications in critical sectors such as alcoholic beverages, bioethanol and biogas generation. 26
Pineapple Wastes as a Source of Bioenergy
Bioethanol from Pineapple Waste
Bioethanol derived from renewable sources like corn, sugarcane, and agricultural waste is a sustainable alternative to finite fossil fuels (FFs). 46 Pineapple waste is a promising raw material for bioethanol generation. Pineapple waste can be used in bioenergy production, particularly bioethanol and biogas. Findings show that pineapple waste juice contains 12.0 ± 0.03 total soluble solids (TSS) following physical pretreatment. 26 Still, bioethanol of 11.65% can be achieved from pineapple waste after alkaline pretreatment, while acid pretreatment can provide 8.11%. However, studies show that pineapple waste juice treated with bakery yeast gave bioethanol of 45%,47,48 indicating a significant concentration of sugars. A high TSS level makes pineapple waste juice a valuable resource for the fermentation processes for bioethanol production. A report shows that pineapple waste juice supplemented with sorghum as an additional fermentable sugar enhances fermentation and potentially increases bioethanol yield to 25%. 26 Research shows that bioethanol is increasingly being used in the transportation sector. 49 Its blends, such as E5, E15, E85, and E100, are commonly used as transportation fuels.48,50 The blends present varying percentages of bioethanol mixed with gasoline, ranging from 5% bioethanol in E5 to 100% in E100, and is employed to reduce greenhouse gas emissions, thus, the reliance on FFs. 51 Bioethanol reduces greenhouse gas emissions by balancing the carbon dioxide (CO2) released during combustion with CO2 absorbed by plants, helping to mitigate climate change. 52 Bioethanol produces fewer harmful pollutants, improving air quality and public health. Its local production enhances energy security by reducing dependance on imported fuels and supports rural economies by creating markets for agricultural products. 53 Additionally, bioethanol's higher octane rating improves engine performance, and its biodegradability makes it safer for the environment. 54 Thus, bioethanol produced from pineapple waste is an excellent renewable fuel source. It not only helps to reduce the dependance on FFs but also significantly lowers greenhouse gas emissions, contributing to a cleaner environment. Moreover, utilizing pineapple wastes for bioethanol production helps manage waste by diverting organic material from landfills, reducing environmental pollution and promoting a circular economy. The summary through which bioethanol is generated from pineapple waste is given in Figure 1.
Steps of Bioethanol Production from Pineapple Waste.
Biogas Generation from Pineapple Wastes
Biogas is one of the renewable energy sources produced following microorganisms’ decomposition of organic materials during anaerobic digestion (AD). 27 Biogas can be recovered from various organic resources, including food waste, agricultural wastes, and animal manure, making it a flexible and sustainable energy source. 27 Furthermore, sewage sludge from wastewater treatment facilities and municipal solid waste plays a major role in the creation of biogas.27,55 Organic waste from other industries, including food processing, is beneficial for biogas generation.28,56 Besides, the different sources of biogas generation include organic waste from slaughterhouses, forestry residues, landfill gases, and aquatic biomass like algae.57,58 These biogas sources are key in harnessing renewable energy, reducing waste and mitigating environmental pollution because usable clean energy is recovered from organic materials. One of the promising cheap and environmentally friendly raw materials for biogas generation is pineapple waste. Pineapple waste is high in biodegradable organic matter and may be broken down anaerobically by microorganisms to generate biogas mainly composed of CO2 and methane (CH4). 59 The generation of biogas from pineapple waste occurs through the AD process, a series of biological steps that break down organic material without oxygen. 60 First, in hydrolysis, large organic molecules such as carbohydrates, fats, and proteins are broken down into smaller molecules like sugars, fatty acids, and amino acids by hydrolytic bacteria. 60 During biogas production, Clostridium thermocellum breaks down cellulose, bacteroides degrade proteins and carbohydrates, and Bacillus species aid in hydrolyzing organic compounds, thus enhancing biogas generation. 61 In acidogenesis, smaller molecules are converted into volatile fatty acids (VFAs), alcohols, ammonia, hydrogen (H2), and CO2 by acidogenic bacteria. 62 In acidogenesis, Clostridium butyricum ferments sugars into VFAs, H2, and CO2, Escherichia coli converts sugars into acids and alcohols, and Lactobacillus produces lactic acid, aiding decomposition. These acidogenic bacteria convert hydrolysis products into organic acids, alcohols, and gases, critical intermediates in biogas production.
During acetogenesis, VFAs are further degraded into acetic acid, H2, and CO2 by acetogenic bacteria. 62 Finally, in methanogenesis, methanogenic archaea convert acetic acid, H2 and CO2 into CH4 and CO2, resulting in biogas. 63 In methanogenesis, biogas production is influenced by methanobacterium and methanococcus species, which produce CH4 from H2 and CO2; methanosarcina uses acetate and other substrates, and methanobrevibacter aids in digesters collectively enhancing CH4 generation. Moreover, pineapple wastes can be co-digested with other organic materials to enhance biogas yield by improving system stability and microbial diversity and balancing the carbon-to-nitrogen (C/N) ratio. 64 Co-substrates such as animal manure, which provides nitrogen and buffer pH levels, are effective in the process. 64 Food waste, rich in easily degradable organic matter, can further boost biogas yields, while agricultural residues complement pineapple waste by providing a more balanced nutrient profile, optimizing the overall digestion process. 65 Thus, pineapple waste is an excellent feedstock for biogas production due to its high organic content and availability in regions where pineapple cultivation is prevalent. By recovering energy from pineapple waste in biogas, it is possible to produce renewable energy, thus reducing environmental pollution and creating additional economic value. A study shows that pineapple waste alone typically produces approximately 52% CH4 in biogas. 66 When pineapple waste is mixed with animal manure, biogas production increases due to higher nutrient content and enhanced microbial activity, resulting in 60% of CH4 in biogas. 66 The waste type and biogas production are summarized in Table 2.
Waste Type and Biogas Production.
Data in Table 2 shows that combining pineapple waste with pig dung produces a higher biogas output than pineapple waste alone. Co-digestion enhances microbial activity brought about by the addition of animal manure. Therefore, utilizing a mixture of pineapple waste, animal manure, and pig dung is advantageous, particularly because animal manure is affordable and easily accessible. The steps for biogas production are outlined in Figure 2.
Biogas Production from Pineapple Waste.
Pineapple Waste as a Source of Biodiesel
Biodiesel is a renewable fuel that is produced from sustainable agricultural materials. 67 Furthermore, biodiesel is a biodegradable and eco-friendly fuel that can replace FFs. 68 Biodiesel emissions are significantly lower than FFs, resulting in lower levels of harmful pollutants such as CO2, sulfur oxides, and particulate matter. 69 Biodiesel can be a complete or partial substitute for diesel in diesel engines without engine modifications. 70 The production of biodiesel can be improved by investigating effective technology; however, the high cost of feedstock is a challenge. An alternate solution to this problem is using agricultural waste feedstock. 71 Interestingly, 25%-40% of the solid wastes produced by fruit and vegetable processing industries can be used as an inexpensive feedstock to make biofuel, increasing the process's sustainability and viability. 72 The generation of biodiesel from pineapple waste helps to control waste and provides sustainable energy solutions by turning agricultural residues into renewable energy. 73 Pineapple wastes, mostly made up of peels, cores and crowns, are a rich source of organic substances such as sugars, fibers, and lipids that various chemical and biological processes can convert to produce biodiesel. 43 Pineapple waste is a carbon source for lipid extraction in biodiesel production due to its high sugar content, including fructose, sucrose, and glucose. 43 Biodiesel is primarily produced from triglyceride-rich biomass, the main component of which is fatty acid methyl ester (FAME) formed through transesterification. 74 Converting triglycerides into FAME requires a chemical reaction with an alcohol, typically methanol or ethanol, in the presence of a catalyst such as sodium hydroxide or potassium hydroxide. 75 However, using sodium hydroxide and potassium hydroxide as catalysts in biodiesel production is costly and environmentally unfriendly; thus, they are replaced by pineapple leaves as an alternative catalyst. 73 Bio-based catalysts derived from agro-industrial waste through simple calcination offer economic and environmental benefits by reducing waste and providing a low-cost alternative. 76 Calcined pineapple leaves exhibit strong catalytic activity and require minimal activation energy for the transesterification process. 43 Lipids extracted from pineapple waste are converted into biodiesel through the transesterification process. 74 Utilizing pineapple wastes in biodiesel production offers numerous economic, environmental, and health benefits. Economically, it reduces production costs by minimizing the need for expensive raw materials and chemicals. Repurposing such agro-industrial residue adds value and creates job opportunities in the biofuel sector. Environmentally, using pineapple wastes reduces agricultural waste, decreases landfill use, and lowers CO2 emissions because biodiesel is a renewable energy source. Additionally, pineapple-derived biocatalysts are more sustainable and environmentally friendly compared to conventional chemicals. Health benefits include improved air quality due to cleaner fuel combustion and reduced exposure to toxic chemicals, supporting healthier ecosystems and promoting more sustainable agricultural practices.
Pineapple Waste for Environmental Treatment
The presence of heavy metals in the environment77 seriously threatens people's health. Industrial processes, inappropriate waste management, and agricultural practices buildup hazardous metals in soil, water, and the atmosphere, including lead, mercury, cadmium, and arsenic, in soil, water, and the atmosphere. 77 When heavy metals find their way into water bodies or food chains, humans consume them and experience a variety of health problems. 78 Long-term exposure to heavy metals is connected to major illnesses like kidney damage, respiratory issues, neurological abnormalities, delayed childhood development, and even some types of cancer. 79 This environmental degradation must be addressed to protect public health.
Literature indicates that treating pineapple wastes effectively removes various environmental pollutants. 80 Pineapple waste is a cheap and simple means of eliminating heavy metals from the environment. 81 Different studies report that pineapple waste is the essential adsorbent of heavy metals. 82 Pineapple waste derivatives remove lead ion Pb+ from synthetic wastewater. 83 Still, pineapple leaves are processed into powder to remove chromium (Cr VI) anions from an aqueous solution. 80 Besides, pineapple waste is an adsorbent that eliminates safranin-O from water for safe irrigation activities in the agriculture sector. 84 Moreover, cellulose from pineapple waste is effective in removing dyne in an aqueous solution, as presented in Table 3. 85
Pineapple Waste and Application in Dye Removed from Water.
Pineapples and their derivatives serve as effective adsorbents for removing dyes from water, as indicated in Table 3. Therefore, inexpensive pineapple wastes can be processed and used to treat contaminated water.
Limitation of Using Pineapple Wastes in Nutrients and Medicine Production
Pineapple waste is a potential resource for nutritional and therapeutic uses since it contains rich bioactive chemicals like phenolics and bromelain. 21 However, there are obstacles to the use of pineapple waste. Complex and expensive purifying procedures are needed to extract active chemicals like bromelain, and these bioactive substances could degrade with time, decreasing their medicinal efficacy. Furthermore, pollutants like pesticides and microorganisms may impact the purity of extracts. Standardizing therapeutic products may be challenging because of differences in waste composition caused by various pineapple types and growing environments.
Regarding nutritional uses, pineapple waste is abundant in vitamins, fiber, and antioxidants, yet because of its high fiber content, preparing it for human use may be difficult. Its short shelf life also causes quick nutritional deterioration if not handled carefully. Its use may be further restricted by the disagreeable taste that organic acids and tannins can produce. The final regulatory barrier complicating pineapple waste's commercial use is the need for thorough safety testing before approval for use in food or nutrient goods.
Future Outlook of Pineapple Wastes
The importance of pineapple wastes is increasing due to their diverse applications in bioenergy generation, medicine, food and environmental sectors. 86 Pineapple wastes have potential in bioethanol, biodiesel and biogas generation. Research suggests that bioenergy production is an effective method for reducing FF use and lowering greenhouse gas emissions. 87 Bioenergy has garnered global interest due to its viability as a renewable alternative to automobile fuel. Bioethanol is increasingly used as a liquid biofuel for transportation, improving combustion and reducing greenhouse gas emissions due to its higher oxygen content. 88 Beyond bioenergy, pineapple wastes hold promise in medicine and nutrition due to their bioactive compounds, such as bromelain, which exhibits anti-inflammatory, anti-cancer, and digestive health benefits.
Additionally, these wastes can be processed into nutrient-rich supplements and functional food ingredients, contributing to food security and improved nutrition. Therefore, bioethanol, biogas and biodiesel are expected to become key and reliable energy sources in residential and transportation sectors in the future. Thus, bioethanol, biodiesel and biogas hold significant potential in achieving sustainable development goal number seven. 89 The utilization of pineapple wastes in bioenergy production supports Sustainable Development Goal 7, which aims to ensure access to affordable, reliable, sustainable, and modern energy for all, 90 as well as Sustainable Development Goal 2, which focuses on ending hunger, achieving food security, improving nutrition, and promoting sustainable agriculture. 90 Utilizing pineapple waste for bioenergy supports sustainability, reduces FF use, and promotes a circular economy principle in resource management.
Conclusions and Recommendations
The broad application of pineapple wastes in bioenergy generation, medicine, and nutritional sectors was explored. It emphasizes the untapped potential of pineapple waste resources, urging further research to investigate and realize their benefits fully. The widespread cultivation and use of pineapples could significantly enhance their prominence and economic significance. Understanding its full potential and application could lead to significant advancements in environmental conservation. Utilizing pineapple wastes and other environmental pollutants for bioenergy production significantly contributes to meeting the national energy demand while enhancing environmental quality by reducing waste in our communities and supporting a circular economy. Beyond bioenergy generation, applying pineapple wastes in medicinal, nutrition, and environmental conservation reveals the potential and need for repurposing wastes into high-value products.
Footnotes
Acknowledgements
The authors thank Mkwawa University College of Education Iringa, Tanzania, for academic support.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data Availability Statement
All data used for the research described are presented in the article.