Revista de la Facultad de Ciencias
Agrarias. Universidad Nacional de Cuyo. Tomo 57(1). ISSN (en línea) 1853-8665.
Año 2025.
Review
Overview
of garlic waste management, circular economy and upcycling
Perspectivas
de la gestión de residuos del ajo, economía circular y transformación
Juan
Pablo Heredia Martín1,
Alejandra
Beatriz Camargo1,
2 *
1 IBAM, CONICET. Laboratorio de Cromatografía para Agroalimentos.
Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo.
Facultad de Ciencias Agrarias. Alte. Brown 500. Chacras de Coria. Mendoza.
M5528AHB. Argentina.
2 Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias.
Cátedra de Química Analítica. Alte. Brown 500. Chacras de Coria. Mendoza.
M5528AHB. Argentina.
* acamargo@fca.uncu.edu.ar
Abstract
In the last three
years, 2 billion tonnes of untreated and dismissed agricultural wastes have
been accumulated without adequate management of reuse or final disposal,
resulting in dumping or burning. The circular economy concept has gained
increasing global recognition for addressing environmental and economic
challenges. Garlic, the second most common bulb vegetable cultivated worldwide,
generates significant waste during its industrial processing, including husks,
stalks, straws, and leaves. These wastes, representing 3.0 to 3.7 million
tonnes of residual biomass per year, are currently underutilised, with the
usual treatment involving dumping in landfills or direct burning, leading to
increased soil and air pollution. In this review, we aim to encourage innovation
by presenting a search for state-of-the-art garlic waste management. We
identified studies about garlic residual biomass valorisation as raw material
for obtaining different extracts and polymers, even energy or biofuels.
Finally, following circular economy principles, we propose potential uses for
garlic by-products to be repurposed or upcycled as materials within
agricultural or other production chains. The information above reveals an
increasing demand and interest in garlic waste valorisation. Future studies are
needed to exploit garlic by-products as important sources of biopolymers and
phytochemicals.
Keywords: bioactive
compounds, biopolymers, circular economy, garlic waste, organosulfur compounds,
pectin, valorisation
Resumen
En los últimos tres
años, se han acumulado 2 mil millones de toneladas de residuos agrícolas no
tratados y desechados sin una adecuada gestión o disposición final para su
reutilización, resultando en vertederos de basura o siendo quemados. El
concepto de economía circular cada vez ha ganado mayor reconocimiento mundial
para abordar desafíos ambientales y económicos. El ajo, siendo la segunda
hortaliza más cultivada en el mundo, durante su procesamiento industrial genera
cantidades significativas de catáfilas (piel), tallos, paja y hojas. Dichos
residuos, que representan de 3,0 a 3,7 millones de toneladas de biomasa
residual por año, actualmente son subutilizados. El tratamiento convencional es
disponerlos en vertederos o quemarlos directamente, aumentando la contaminación
del aire y el suelo. En este trabajo nuestro objetivo es fomentar la innovación
presentado una búsqueda del estado del arte en la gestión de residuos del ajo.
Identificamos estudios sobre la valorización de biomasa residual de ajo como
materia prima para obtener diferentes extractos y polímeros, incluso para la
obtención de energía. Finalmente, de acuerdo con los principios de economía
circular, proponemos posibles usos de los subproductos del ajo para su
reutilización o transformación como materias agrícolas o en otras cadenas
productivas. La información anterior revela una demanda y un interés creciente
en la valorización de los residuos de ajo. Se necesitan estudios futuros para
investigar y explotar aún más los subproductos del ajo como fuentes valiosas
de biopolímeros y fitoquímicos.
Palabras clave: compuestos
bioactivos, biopolímeros, economía circular, residuos del ajo, compuestos
organosulfurados, pectina, valorización
Originales: Recepción: 23/04/2024
- Aceptación: 16/12/2024
Introduction
Nowadays, there is
a global awareness of the problems derived from accumulating residues from
agricultural production and their environmental impact. For example, in only
three years, 3.9 billion tons of biomass can be produced (5,
65), accumulating 2 billion tons of untreated residues from the
agriculture industry (55, 79). Given the world
population growth and the expansion of new cultivation areas, these numbers are
expected to increase in the following years. With 10 billion people by 2050,
global waste growth will rise to 70%, increasing the impact on the food system
from 50% to 90% (39). For this reason,
the study of agro-industrial waste worldwide production, valorisation and,
employment for other purposes become important topics of study.
Among the wastes of
agricultural production, we are focusing on the by-products derived from the
cultivation and industrialisation of garlic (Allium sativum L.). The global garlic
commerce is reflected by its high consumption per capita (7.6 kg by 2018) and a
significant cultivated area (1.546.741 ha), harvesting 28.49 million tonnes
with a world average productivity of 18.4 t/ha (19). China, Spain, and
Argentina are the leading garlic producers and exporters, representing almost
90.8% of the global sales market (48). The commercial
context estimates that garlic cultivation will increase in the coming years,
reaching 31.1 million tonnes per year by Hsiao et al. (2025), with an annual
average growth of 4.72% (22). This vegetable is
sold as fresh or industrialised products such as paste, dehydrated, powder,
essential oil, oil macerated, and aged extract. However, the industrial process
dismisses 25-30% of solid waste (16, 38). Garlic harvesting
has implicit waste generation in cleaning, cutting, drying and processing, to
obtain phytochemicals and dietary supplements. These facts increase residual
biomass tons with no responsible disposal, generating over 3.7 million tonnes
of by-products annually (80).
Beyond garlic’s
culinary use, it is known for its relevant biological and medicinal properties,
contributing to its increasing demand, reaching 28 million tons in 2020 (80). Garlic properties
and biological activities have been widely studied, demonstrating its
preventive effect against chronic diseases such as cancer, antithrombotic (25), antibacterial,
antifungal, and antiviral (40, 78, 83). These properties
have been attributed to their composition in organosulfur and phenolic
compounds. This factor has significantly bolstered the surge in demand to
generate medicinal and functional products.
The emergence of
the circular economy concept gained traction in the 1980s, advocating for an
economic model that prioritizes resource optimisation, waste reduction,
environmental preservation, and fosters innovation (73). At its core lies
the principles of waste reduction, reuse, recycling, and resource recovery.
Upcycling, as a part of the circular economy, promotes waste reduction by
reusing existing materials, encouraging creativity and innovation to generate
higher-value products without relying on new resources (77). The potential of
garlic waste to generate higher-value products offers a promising outlook for
waste management. These principles aim to minimize waste and maximize value from
products, materials, and resources, inspiring strategies to mitigate ecological
issues.
Thus, in this
review, we summarize some effective strategies for waste management and explore
the potential use of garlic waste as value-added by-products, intending to
hopefully define future research direction. The data collection was conducted
using academic databases such as Scopus and Google Scholar; the information was
organised and summarised to identify research gaps and facilitate the approach
to this problem. In agreement with Elsevier’s abstract and citation database
Scopus, a search was done over the last 10 years using the keywords “garlic”
and “wastes”. We then selected studies focusing on garlic husks, straws, or
both. The previous Scopus search was complemented by another in Google Scholar,
which used keywords such as ‘garlic wastes,’ ‘garlic husks and straws,’ and
‘agro-industrial garlic wastes. Other investigations consulted in Google
Academics were also considered to discuss garlic waste treatment for the
extraction of different polysaccharides and polymers.
Garlic
wastes
Waste generation begins before the garlic harvesting process,
starting with removing garlic scapes to enhance bulb growth and development. Figure
1, details garlic residual biomass production.
Figure 1. Scheme
of wastes produced during garlic harvesting and processing
Figura 1. Esquema
de los residuos generados durante la cosecha y procesamiento del ajo.
The matured garlic bulbs are harvested, undergoing a curing
process (35°C, 2 weeks), and finally stored in sheds under ambient conditions
for 2 months. Garlic packing sheds are facilities dedicated to the processing
and preparation of garlic before distribution and sale. Some common tasks
performed in the sheds include sorting, selection, cleaning, and packaging.
Consequently, a large amount of waste is generated, mainly from stems and roots
are used for energy, animal feedstock, and bio-compost (12).
Unfortunately, a relevant part of garlic waste is disposed of in landfills (38).
Meanwhile, dry garlic is used for direct consumption and processed spice
products, an important commodity with relevant economic value (84).
Figure 1 also shows that
industrial processing starts with crushing garlic bulbs and peeling them to
obtain residual husks and straws (52). After the
peeling, 25 to 30% of inedible parts are considered solid wastes, consisting
mainly of dried stems (stalks) and peels (outer and inner husks) (16,
21). Garlic stalks represent 10%, and husks reach 25% of the total
garlic weight in these solid wastes (14, 69). In the garlic
paste industry, a dried pulpy residue called bagasse is obtained; however,
there is currently no information about the residues generated in this process.
In this way, low reuse and valorisation of garlic wastes negatively impact the
agricultural ecosystem, e.g., untreated garlic residues are directly burned
increasing the environmental impacts on soils and air (76).
Fortunately, in the
last decade, different investigations have focused on garlic by-product
valorisation for obtaining diverse bio-compounds and finding other ways to
process them to mitigate their environmental impacts. Additionally, circular
economy, as a current strategy, focusing on agro-industrial waste reduction by
using them as raw materials in other value chains. As a result, bio-products
and bio-energy are now being produced from wastes, improving the environmental
quality (6). For example, garlic residual biomass
has been used in biorefinery for energy generation and bioethanol production
due to its chemical composition.
A circular economy,
in concordance with Sustainable Development Goals (SDGs), is more specifically
on sustainable consumption and production and climate change, which has a
crucial role in waste management, changing the way from a linear economy to a
circular one (92). In this sense, figure 2 compares the
traditional and modern ways of conceiving garlic waste treatment. One of these
is based on linear economy or by-products conventional disposal derived from
garlic, resulting in dumping, burning, and even animal feeding. The second
strategy for solving the inappropriate use of garlic by-products is to consider
a circular economy, obtaining bio-products and bioenergy from them.
Figure 2. Comparison
between the current disposition of by-products vs circular economy
strategy.
Figura
2. Comparación de la disposición actual
de subproductos contra una estrategia de economía circular.
Our search covered the last 10 years of publications with the
keywords “garlic” and “wastes” on both Scopus and Google Academic databases.
The data showed that garlic husks, peels, and skins (63%) are the most studied
by-products, followed by garlic stems or stalks (23%). Finally, other garlic
wastes are either not specified or are a mixture (figure 3).
Figure 3. Results
of the bibliography search regarding the kind of garlic waste and the objective
of valorisation studied.
Figura 3. Resultados
de la búsqueda bibliográfica mostrando el tipo de residuo de ajo y el objetivo
de valorización estudiado.
Accordingly, in
recent years the main uses of garlic waste have been related to
second-generation products, minimising the negative impact on the food supply
by harnessing resources that would otherwise be considered waste. These
untreated materials are advantageously used as biomaterial and bio-adsorbent to
remediate environmental pollution. Similarly, some approaches align with the
circular economy using garlic by-products as solid substrates and in composting
processes. In this context, some studies, improving extraction techniques have
obtained bioactive compounds and bio-polymers showing innovative potential as
bio-products, given their functional and biological activity. Cellulose is the
most common bio-polymer investigated and extracted from garlic straw wastes.
However, other understudied bio-polymers are polysaccharides and dietary fibre
such as pectin.
Research on garlic
husks and straws for waste valorisation began several years ago. Research aimed
to provide potential uses for these by-products, transforming them into
value-added products, highlighting garlic biomass as a low-cost alternative.
Garlic
by-products’ main uses
Use as
biomaterial and bio-adsorbent production
According to the references detailed in table 1,
garlic waste is mainly used as biomaterial or bio-adsorbent. Husk, peel, and
skin represent 31% of raw material used for this purpose and 36% is represented
by stem, stalk, and straw. For example, biomaterials, such as carbon particles
and biochar, which also serve as bio-adsorbents, have been obtained from garlic
waste. Different biomaterials, including an aerogel with cellulose
nanoparticles (CNP), are proposed from husks, peels, and skins (26).
Garlic residual biomass has also been reported as a precursor carbon
electro-catalyst material (2).
Additionally, using garlic skins, a film’s microstructural properties have been
improved for environmentally friendly dish creation (27),
and cellulose nanofibre and nanoparticles have also been developed (56).
Garlic waste has also been used to obtain a novel shape-stable phase-change
material with garlic peels (47)
and to prepare a cobalt-garlic peel nanocomposite (88).
A study focused on generating eco-friendly biochar microparticles from garlic
stalks and stems (table 1).
Furthermore, garlic stems have produced low-cost and eco-friendly biochar
microparticles (86).
Table 1. Garlic
waste valorisation as a biomaterial and bio-adsorbent.
Tabla 1. Valorización
de los residuos del ajo como biomaterial y bio-absorbente.
Table 1 illustrates that
bio-adsorbent production from garlic waste is the second most investigated
value-added product. Garlic husks, peels, and skins have been reused mainly as
bio-adsorbents of the dyes cationic blue 41, methylene blue, and Direct Red 12B
(7,
49, 51). Additionally, garlic stalks or stems have been revalorised as
bio-adsorbents of methylene blue dye (37).
Other applications
of garlic husks and stems are related to removing heavy metals and even
pollutants as radioactive compounds from soil and water (54,
61, 62, 91). This last use has not been studied as extensively as dye
remediation. Additionally, they have been used to absorb antibiotics such as
Rhodamine B (76, 89). The effectiveness
of garlic by-products bio-adsorbents and contaminants removers is due to garlic
residual biomass high content of cellulose hemicellulose content, and some
pectic components, which hydroxyl and carboxyl groups bound to pollutant
molecules to remove them (57).
As mentioned in the
previous lines, garlic residual biomass has been commonly used in the last
years as a precursor to produce carbon materials or biochar for different
applications (18, 29, 43, 45, 46, 50, 63). Biochar results
from burning agricultural biomass organic material as an adsorbent, insulant,
and carbon electrode to store energy, packaging, and pollutant treatment in air
and water remediation (72). That means garlic
husks and stems have suitable properties for reinforcement ingredients given
their lignocellulosic composition, which is also natural, renewable, and
biodegradable (68).
Bioactive
compounds and biopolymers extraction
From ancient years garlic has been known for its medicinal
properties. These properties are attributed to phytochemicals such as
organosulfur compounds, phenolic compounds, and polymers (inulin and pectin),
among others (13, 59, 70, 85). Figure
3, depicts that 7% of related studies are focused on the
valorisation of bioactive compounds found in wastes. These works are about
different extraction processes, phytochemical activities evaluation, and food
additive production from bioactive compounds. Table 2
summarizes articles about each chemical bioactive group mentioned.
Table 2. Valorisation
of garlic wastes to obtain bio-compounds and biopolymers.
Tabla 2. Valorización
de residuos del ajo para la obtención de biocompuestos y biopolímeros.
As a result of the bibliographic search, the words aimed at
biopolymers reached 7% for husk, peel, skin waste, stem, stalk, and straw
waste. Garlic macro components are water, carbohydrates, proteins, fibres, some
fats and polysaccharides (3),
including biopolymers which have been poorly analysed. These components also
contribute to the specific organoleptic characteristics, as well as the
medicinal and nutritional properties of garlic (33).
All these characteristics make garlic and its by-products a special raw
material to use as a functional ingredient (4). Figure
4, schematizes the bio-compounds and highlights the main
obtention source from garlic residual biomass.
Figure 4. Bioactive
compounds and biopolymers extracted from garlic husks and stalks wastes.
Figura 4. Compuestos
bioactivos y biopolímeros extraídos catáfilas (piel) y tallos residuales del
ajo.
Other studies have
addressed different Alliaceae wastes in terms of their extract’s
bioactivity and composition (41, 58, 60). These studies
provide critical information to support the upcycling of products like
phytotherapeutics and food supplements. They also show that garlic stems/straws
or husks/peels by-products have potential uses given their composition in
bio-compounds and underline their diverse bioactivities.
Bioactive
compounds
Phenolic
compounds
Several garlic by-product extracts have been designed and
obtained due to their phenolic compounds’ antimicrobial, anti-inflammatory, and
antioxidant activities (table 2).
Likewise, in 2014, a study analysed polyphenols extraction from garlic husks
using five different hydroalcoholic solvents, demonstrating their antioxidant
and antimicrobial activity (34). Ifesan
et al. (2014) evaluated garlic peel crude ethanolic extract, measuring its
TPC content and antioxidant activity. The authors showed the effects on lipid
peroxidation and microbial growth, proving garlic peel’s potential use as a
natural food additive.
Recent studies have
focused on improving the extraction techniques to obtain phenolic compounds.
For this purpose, Chhouk
et al. (2017) tested a new extraction method using supercritical fluids with
carbon dioxide-expanded ethanol, measuring these extracts’ antibiotic and
antioxidant properties. Fortunata et al. (2019) tried to obtain
diverse bio-compounds from garlic peels through aqueous and alcoholic
extractions by comparing the phytochemical profiles obtained. Besides, Tahmas
Kahyaoğlu (2021) evaluated the ethanol extract from garlic cloves, husk, and
stem using an ultrasonic bath, evaluating their TPC content, total flavonoid,
and antioxidant activity. Finally, dos Santos et al. (2022) used garlic peel
as a co-product to extract bio-compounds by maceration and turbolisation. In
the study, the crushed biomass was incorporated into the solvent (water and
hydroalcoholic solutions) using a blender, evaluating the bioactive compounds
and their bio-activities.
The previous
reports illustrate garlic waste hydro-alcoholic extracts with applications in
nutraceutical, medicinal, and pharmacological fields. According to the
extractant, these investigations exhibit different alternative methods to
obtain a wide range of polyphenols. They also show potential uses as
antioxidants and antimicrobial activities against diverse pathogenic diseases
as an alternative response to the current bacteria drug multi-resistant
problem.
Organosulfur
Compounds (OSC)
Despite the
increasing interest in evaluating and finding new uses for garlic wastes to
obtain bio-compounds such as OSCs, few investigations have addressed this aim.
Of the total literature consulted, only one reported an extraction method to
isolate OSCs from garlic straws. However, a similar task using garlic peels or
husks was not reported (table
2).
It is crucial to underline the need for further research on unexplored
biopolymers and the possible novel extraction techniques and the new biological
activity assay alternatives derived from this, mainly highlighting biocidal
properties. In this way, Ferioli et al. (2020) evaluated two
extraction methods, using different solvents to identify the total OSCs and
their relative amounts in garlic clove and stem extracts. They detected the
highest OSCs amounts in garlic cloves. Another study by Martinotti
et al. (2016) evaluated the nematicide effect against Meloidogyne
incognita, employing aqueous extracts from garlic bulbils with promising
results.
Biopolymers
Cellulose
extraction
The most common
polymer extracted from garlic husks and straws is cellulose. Agustin
et al. (2013) obtained cellulose from garlic stalks through chemical
hydrolysis and sonication, obtaining nanocrystals, which were applied to
produce a bio-composite film with starch. Another investigation obtained microfibre
and nanocrystal celluloses from garlic skins by chemical hydrolysis,
characterising the polymers by FT-IR, TGA, SEM, XRD, and SEM physical methods (66). A similar and
recent study focused on the obtention of nanocellulose crystal, but in this
case from garlic straw residues. The polymer was also extracted by chemical
hydrolysis and characterised by the same analytical techniques (36). Likewise, garlic
stalks and skins were treated to determine their chemical composition and
obtain micro-cellulose fibres by alkaline hydrolysis. After a chlorite blanched
process, the micro-cellulose fibres were characterised by FT-IR, TGA, and SEM
physical assays (67). Similarly, Raimo
(2020)
studied a garlic skin extract’s cellulose structure and morphology without any
use or valorisation, evaluating it by microscopic and optical assays. Finally,
a similar and recent study focused on the obtention of nanofibre cellulose, but
in this case by a hydrothermal extraction pre-treatment (87).
In some studies, garlic husks and stalks were mainly evaluated
to obtain different kinds of cellulose given the amount of this polymer in the
residual material, which shows a novel source of cellulose fibres. For example,
garlic straw contains 41% cellulose (36),
garlic husk cellulose content reaches 19% (8).
The biopolymer extracted/modified depicted important value-added
characteristics, like tensile strength, moisture resistance, and thermal stability
(68).
Garlic husks and stalks are a potential bioresource with important
technological applications in polymer matrices. They can be used mainly as a
biodegradable film, to obtain bio-composites, or in food packaging production,
being an eco-friendly material. This potential for circular economy practices
is inspiring for the future of agricultural waste management.
Garlic
wastes dietary fibre
Dietary fibre
refers to non-digestible carbohydrates, including “resistant starch” and
non-starch polysaccharides, cellulose, and pectin, among others. Generally, it
is extracted by different hydrolysis methods using both acid and alkaline
solutions. These fibres are usually used to produce dietary supplements due to
their health benefits such as improving gut mobility, microbiota profile,
facilitating weight loss, and reducing insulin sensitivity (9). Recently, few
works have reported the soluble and insoluble dietary fibre content in garlic husks
and straws (table
2).
Of these, just one referenced garlic peel waste composition, in which dietary
fibre was the highest part of the total residual biomass weight representing
almost 62% (90). Huang et
al. (2018) achieved to modify the functional, physicochemical, and
structural characteristics of insoluble dietary fibre from garlic straw. Then,
the same authors published that is possible to alter soluble dietary fibre from
garlic straw with an energy-gathered ultrasound treatment (31). They provided
information on the physicochemical characteristics and antioxidant capacity of
the modified garlic straw dietary fibre. The most common research applied to
garlic wastes (husks and straws) considers polymer obtention, mainly cellulose.
Herein, Kallel
et al. (2015) studied the isolation from garlic straws of a new
polysaccharide mainly composed of glucose, mannose, galactose, and xylose. The
polysaccharide was extracted in hot water, and its antimicrobial and
antioxidant activities and structural conformation were assessed. According to
the previous information, focus should consider these by-products reusing, given
the fibre dietary content accessible and easily modified by conventional
methods.
Pectin
It is interesting
to explore the extraction of pectin from garlic by-products. It has been
demonstrated that pectin extraction can allow differences in the esterification
and methylation degrees, even in galacturonic acid content (75). These parameters
influence the jell formation capacity of the extracted pectin (10).
Some previous
pectin investigations from garlic peels have been retaken reporting it as a
component of garlic peels constituting 27% of its biomass (15,
74). Similar data was described in a recent investigation that
evaluated the pectin composition from garlic waste (peel, stem, and straw),
reporting a pectin content of 22.4% (75). Thus, Kumar et
al. (2022) synthesized and characterized different edible films from
pectin garlic husk, demonstrating the potential of this biomass for making food
packaging. The investigations in animal feeding have evaluated haematological
and biochemistry parameters as digestive enzymes in fishes. The research
demonstrated health benefits when the fish diet was supplemented with garlic
peels, given to pectin content (15).
Despite these
previous investigations, few findings have demonstrated that garlic peels are
an important source of biopolymers focusing on its pectin content and
functional potential. One of these emphasised the functional properties of the
dietary fibre pectin in animal feed (table 2). It is important
to further investigate other specific characteristics of the extracted pectin.
Likewise, to know pectin-specific rheological properties and establish its
potential uses as a nutraceutical assigning it a technological application in
the food industry.
Current
advancements and future trends
Though the circular
economy has several practices for reducing environmental damage and the carbon
dioxide footprint, residual biomass re-utilisation is the most extended
practice. Thus, agro-industrial reuse of wastes or by-products involves
reintegrating them into the productive system as raw material and removing
value-added products useful for other production chains. Therefore, the
productive systems must integrate into other practices if they want a circular
economy-producing approach. These practices include repairing, reassembling,
renovation, and upcycling proposed to incorporate by-products in new productive
chains. Besides, a circular economy strategy helps to close the productive
chain by obtaining bio-products and bio-energy from agro-industrial
by-products. Some projects have been planned to produce garlic sustainability
in Argentina. Burba
et al. (2021) established a cleaner garlic production process by adopting
some strategies. These include transforming tonnes of residual biomass into
fuel pellets for heat locations and reusing wood pallets, cardboard, and
residual plastics such as raw materials to produce new packaging. These
strategies should be integrated into other industrial and territorial
organisation approaches and the garlic sector’s Good Farming Practices (GFP).
Nevertheless, the planned project does not consider bio-products from this
garlic residual biomass.
Several studies
support the idea that waste valorisation is a current point of discussion and a
circular economy strategy using conventional techniques such as composting,
digestion, or biotransformation is a possible way to do it. Upcycling is a
recent innovative technique to obtain biofuel and bio-compounds and produce
microbial growth media (17, 44, 71, 82). In this way, the
revision of literature concerning garlic by-products shows the potential of
obtaining bio-polymers and bio-compounds for bio-energy and bio-products
generation. The final purpose of this review is to examine the links in the
garlic production chain as sources of inputs from which new chains could be
integrated to obtain additional by-products, thereby enhancing added value.
Conclusions
In summary, the
present work analyses the state-of-the-art of garlic by-product valorisation.
We identified references regarding garlic husk and straw valorisation as raw
materials for obtaining different extracts and polymers, even energy or
biofuels. Nevertheless, some current disposal practices of this biomass
contribute to environmental damage. As an upcycling
strategy, this raw material could be reused in production systems to exploit
garlic by-products’ physicochemical characteristics. Their reuse can diversify
the number of bio-products obtained from them. Knowing that garlic is the
second bulb worldwide distributed, and its consumption and processing have
increased by-product generation. There is a need to deepen studies that
contemplate waste treatment in considering circular economy. Fortunately, some
investigations have focused on garlic by-product valorisation in recent years.
Either extracting different bioactive compounds or seeking other ways to
process it as a strategy for agro-industrial waste reduction.
This review evidences that the valorisation of garlic
by-products can be divided into two clusters: the production of biomaterials
and the extraction of bioactive compounds. These works highlight the advantages
of reusing a discarded material such as a low-cost natural source of easy
accessibility to be applied at an industry level. Since garlic husks and straws
represent almost 10% of the total weight of garlic, reducing their amount of
worldwide solid waste could be a trending topic. Nevertheless, using this raw
material in other value chains for obtaining bio-products and bio-energy, still
represents a major underexplored topic. Bio-compound isolation is another
relevant aim in residual garlic biomass revalorisation, and it demonstrates its
potential applications in the nutraceutical, medicinal, and pharmacological
fields. Though there is increasing interest in evaluating and finding new uses
and valorisation of garlic wastes, their upcycling is scarce. More deep studies
focused on garlic peels and straws, as an important source of other unexplored
biopolymers and phytochemicals in this complex matrix, should be addressed.
Therefore, investigating new substances from garlic peels and straws will
improve the extractive techniques as the structural characterisation and the
biological screening assays. The discovery of new evidence to revalorise this
raw discarded material in diverse technological applications must consider the
SDGs and circular economy approaches.
Acknowledgements
Authors thank the people and institutions who have supported
this work, Instituto de Biología Agrícola de Mendoza - IBAM, CONICET, and
Facultad de Ciencias Agrarias - UNCuyo.
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