Do we need to shift our focus from traditional natural cellulosic textile fibres to innovative textile fibres like bagasse, pineapple leaf, cornhusk, water hyacinth? Preeti Kaur Sachdeva, Dr. Bhawana Chanana and Dr. M S Parmar examine reports and study to find out.
What is waste? As Tom Szaky said, "On looking at waste as an entirely modern, man-made idea, I stopped viewing garbage as garbage and instead started to see it as a commodity."
In India, agriculture provides 54 per cent employment in rural as well as urban India. The total share of agricultural output in terms of percentage of Gross Domestic Product (GDP) was 13.9per cent during 2013-2014 at 2004-05 prices. Total estimated agricultural crop production for the same year was 264.77 million tonnes. After the isolation of the main agricultural product, abundant solid residue is generated. Worldwide, it is common practice to dump residue as garbage. The piles of residue decompose by microbial activity and become a nuisance for the environmental health. Industries use agricultural residues for co-generation, but these residues being of low calorific value, generate smoke and pollute the environment on burning.
Burning agricultural residue in the agricultural field has been common practice throughout north India. It produces lethal smoke leading to respiratory diseases. Recently, the National Green Tribunal (NGT) banned such burning and declared such practice illegal and fineable. Now, all stakeholders have to think of novel and sustainable methods to utilise the idle, underutilized resources that are of important economic value to India.
Rice, wheat, sugarcane, soybean, corn, banana, pineapple, bamboo and okra are a few examples of crops that generate considerable residues. These contribute to the major part of the total annual production of biomass residue and are an important source of long and short fibres rich in cellulosic content.
What are agro-residues?
Agricultural residue or agro-residue describes all organic material produced as by-products after harvesting and processing agricultural crops. Agro-residues are non-wood lingo-cellulosic and a rich source of cellulose with lignin. These may include stalk, cane, seed pod and leaves. Agro-residues are annually renewable and a low cost source for natural cellulosic fibers. Agro-residues are of two types.
Figure 1: Classification of agro-residues
Field residues: These are materials left in an agricultural field after the crop has been harvested. Examples include pineapple leaves, banana pseudo stems and leaves, cornhusk, cotton seed pods, kapok seed pods and cotton stalks.
Process residues: They are materials left after the crop is processed into a usable resource. After isolation of the primary or main agricultural product, a huge volume of residue is generated simultaneously. Examples of process residues are bagasse, pea peel, wheat and rice straw.
Worldwide, leaders are discussing the alarming issue of climate change and its subsequent consequences. To promote sustainable living, nations are striving to work primarily on climate change, affordable and clean energy alternatives and efficient waste management.
Availability of agro-residues
Quantifying the amount and type of agricultural residues generated in each crop category is difficult, as it would require conducting comprehensive research with continuous updates of compiled data. The minimum worldwide availability of various agro-residues in the year 2000 as was estimated by the Agricultural Residue Committee is given in Table 1.As per the data released in 2009 by The Ministry of New and Renewable Energy (MNRE),approximately 500 metric tonnes (Mt)of crop residues are being generated every year in India. There is a wide variability in the generation of crop residues and their use across different regions of the country depending on the crops grown, cropping intensity and productivity. Generation of crop residues is highest in Uttar Pradesh (60 Mt) followed by Punjab (51 Mt) and Maharashtra (46 Mt).
Table 1: Proximate Worldwide Availability of Agro-fibres in Million Tonnes (MnTn)
Conventionally, almost all agro-residues have been burnt for energy generation in boilers. But being low-calorific fuel, they generate air pollution due to which their use for energy generation is prohibited by Pollution Control Board. Currently, they are generally disposed of either by composting or by burning in the fields. Ina developing country like India, every possible effort should be made for the proper utilisation of these agro-residues as they are rich in cellulose and renewable. As stock is abundant, the price of agro-residues is cheaper than that of conventional cellulosic fibres like cotton, jute and linen13.
Conventional
Uses of agro-residues
Conventionally, agro-residues are
used for many purposes which are often are site-specific. Depending on how and
where the crop is harvested, the ultimate use of agricultural residues varies.
Besides being used as fuel, other uses of agro-residues are as fodder,
fertiliser, fibre, and feedstock. As fertilizer and soil conditioner, coconut
coir dust is used to retain moisture in the soil and straw as a growing medium
for mushroom. Coconut husk is used as a growing medium for orchids and for
packing material. Rice husk has many uses. It is burned as fuel. Ash generated
is used by the steel industry as a source of carbon as well as insulator
(feedstock). Also rice straw is used as animal bedding (fibre) and subsequently
as part of compost (fertiliser), crop waste can be used as a feedstock for
biogas generation (fuel), with the sludge being used as fertiliser. However,
use of such agro-residues is limited or mostly unexplored in the textile
industry. As it is a technically high-end industry, sophisticated technology
needs to be devised and made available for extraction and application of the
cellulose rich fibres from agro-residues to be made and used as textile goods.
Agro-residues:
Alternative fibres for textile industry
Upkeep of the environment is of
vital concern to Indian authorities. Agriculture industry is producing
agricultural waste in million tonnes annually. Successful solid waste
management and proper utilisation of these residues is a major challenge. A
similar challenge is being acknowledged by the textile industry. It is the
second major sector providing employment in India.
The Indian textile industry is
primarily cotton-based, cotton accounting for 54per cent of total fibre
consumption in 2014. Cotton is one of the most economically and ecologically
expensive commercial crops to produce. Cotton production is the second largest
agricultural use of pesticides in the world with five of the nastiest
pesticides used. Cyanide, dicofol, naled, and propargite are mainly used in
cotton cultivation and these chemicals are known to be cancer- causing apart from
being environmentally dangerous. Cotton still accounts for 60 per cent of the
total fibre production of the world, although man-made fibres have made
significant inroads into cotton's share during the last three decades. The
population boom is pushing demand for cotton exponentially. China is a major
buyer of cotton yarn from India. A leading daily reports that the Indian cotton
industry registered a record 142,297 tonnes export latest by June 2013. A
billowing surge of 73per cent from last year in cotton export was recorded.
This has left India's domestic cotton market hand-to-mouth. This situation is
aggravated and compounded by rising price of cultivating cotton and other
natural cellulosic fibres like jute and linen. It is the need of the hour to
look out for alternative cellulose resources. To address the critical
situation, there is a requirement of substitutes to conventional cellulosic
fibres, which are environmentally expensive to produce. Some of the undervalued
but easily accessible agro-residues are being presented here.
The major constituents of all
cellulosic fibres are α-cellulose, pentosan and lignin. High α-
cellulose and low lignin content of a fibre are necessary for its application
in textiles. The cellulose availability in agro-residues is in the form of a
complex where cellulose is encrusted in the layers of hemicellulose and lignin.
Both cellulose and hemicellulose are carbohydrate polymers while lignin is an
aromatic polymer. However, to obtain natural fibres with pure cellulose, it is
imperative to process the agro-residues for the maximum removal of hemicellulose
and lignin. In utilisation of cellulose in agro-residues, these two polymers
(hemicellulose and lignin) act as impurities.
Besides the availability of pure
cellulose, other factors which influence the development and utilisation of
these lingo cellulosics in textile industry are:
a. Ability to be spun
b. Sufficient quantity
c. Cost or economy of production
d. Desirability of their
properties to consumers
The biochemical composition of
agro-residues varies owing to the composition of the crop from which they are
sourced and the crop-specific environmental conditions they are grown in. Han,
1998, has reported on how the chemical and physical properties of some non-wood
fibres are influenced by fibre growth time (days after planting), botanical
classification of fibre, stalk height, environmental conditions, rainfall, etc.
The pure cellulose component of these agro-residues has the potential to be
used in textile industry either as natural cellulosic fibre or as regenerated
cellulosics. Though it is a well-acknowledged fact,it was hardly exploited
owing to lack of dedicated research and technology.
Bagasse and bamboo are two
important stalk agro-residues, and cornhusk and banana leaves are important
leaf agro-residues. The cellulose and lignin composition of the four residues
testifies that bagasse holds the highest amount of processable cellulose (57per
cent) amongst all other residues (Table 2).
Table 2: Proximate chemical
analysis of some common agro-residues
Bagasse
One of the largest cellulosic agro-industrial
by-products is sugarcane bagasse (or bagasse). It is a fibrous residue of cane
stalks left over after the crushing and extraction of the juice from sugar
cane. The quality of bagasse is dependent on the variety of cane, age of
cutting, agronomic and soil conditions and the extent of crushing and milling
operations carried out. It is a ligno-cellulosic residue (by-product) of the
sugar industry and used by the sugar factories themselves as fuel for boilers.
India is a major producer of sugarcane bagasse which is an annual process
residue of sugar mills apart from cornhusk, wheat and rice straw.
Bagasse is a multi-cellular and
lingo-cellulosic cane fibre. Crude bagasse contains about 65-70per cent useful
fibre and about 30-35per cent pith, dirt and other water soluble material. Pith
is an undesirable fraction because it contains non-fibrous cells, which are
below 0.4mm in length. Further, pith consumes huge amount of chemicals leading
to wastage and clogging. Hence, bagasse has to be de-pithed for industrial
application. The biochemical composition of de-pithed bagasse indicates that it
contains about 57 percent α-cellulose, 19 percent lignin, 24 percent
hemicellulose, evincing its suitability for producing good quality natural
cellulose fibres and pulp under controlled conditions26. The
chemical composition of bagasse varies with sugarcane varieties, plant maturity
and soil properties24.
For every 10 tonnes of sugarcane
crushed, a sugar factory produces nearly 3 tonnes of wet bagasse. Since bagasse
is a byproduct of the sugar industry, the quantity of production of bagasse is
in line with the quantity of sugarcane produced. Studies reveal that about 54
million tonnes of dry bagasse are produced annually throughout the world. In
general, sugar mills generate approximately 270 kg of bagasse (50per cent
moisture) per metric ton of sugarcane.
Bagasse is considered as a rich
natural resource when compared to other agricultural residues because of its
high yield and annual regeneration capacity. The biochemical composition
represents bagasse as a potential and abundant cellulose resource. To put
bagasse to some useful industrial applications, it is imperative to extract
pure cellulosic fibres free off hemicellulose and lignin which act as
impurities.
Bagasse has not been the subject
of much research worldwide. Some research studies were taken up at Louisiana
State University. An important research effort in previous work was extraction
of sugarcane rind fibre for textile applications. The extraction of fibres was
done by alkalisation. Collected bagasse was subjected to sodium hydroxide under
specific pressure. The extracted sugarcane rind fibre was used for making
geotextile mats for soil erosion control. It was reported that the sugarcane
fibre mats had higher water resistance, lower light penetration, and were less
flammable than commercial geotextile products. Similarly, in various other
studies, bagasse fibre has been reported to be used for nonwovens but there is
no literature on the spinning of bagasse fibre.
Cornhusk
Corn is a member of the grass
family of plants and the most widely distributed crop in the world. It is the
largest food crop in the world and the United States produces about 40per cent
of the world corn production. Based on the annual world production of corn,
about 45 million tonnes of cornhusks are available every year. More than 9
million tonnes of natural cellulose fibres suitable for textile applications
can be extracted from them every year. This makes cornhusk fibre second only to
cotton in terms of natural cellulosic fibre. Corn husk, one of the byproducts
of corn production, contains about 39-42per cent cellulose which can be
extracted in fibrous form for various industrial applications, including
textiles. Although textile applications offer a relatively high value addition
and a huge market for cornhusk fibre, they require fibre of high quality. Reddy
(2005) has for the first time attempted to extract natural cellulosic fibre
from corn husk with strength and elongation between cotton and linen. Fibres
were extracted manually due to lack of any suitable mechanical process.
Researchers state that the extracted fibres have the potential to be the
cheapest available natural cellulosic fibre for textile applications and would
be second only to cotton in terms of availability. Hydrolysis alkalisation was
done to obtain fibre from cornhusk. Fibres were cooked at varying
concentrations of sodium hydroxide to obtain long cellulosic fibre free of
lignin and hemicellulose. In further investigation the same research group
examined the compatibility of cornhusk fibre with cotton and polyester on ring
and rotor spinning machines. Cornhusk fibre blends with cotton were developed
in the weight ratio of 80/20, 70/30 and 50/50 and with polyester in the weight
ratio of 65/35.
Socio-Economic
Perspective
There are regions where these
abundant agro-residues are still a waste. These valuable agricultural residuals
are being burnt in lack of any alternative commercial use of them. Farmers are
losing additional income while their counterparts in the region where small and
medium scale handloom industries exist and significantly contribute in income
generation.
Exploring a feasible application
of agro-residues will lead to environmental as well as socio-economic benefits
to the farmer. So, agro-residues can be instrumental in increasing farm income.
The prices received by the farmers may help them strengthen their economics.
Devising technology for efficient utilisation of these agro-residues will not
only support the rural community by adding value to their products, but also
protect the environment. We need robust cooperation between industrialists and
research groups with consistent efforts and genuine concern for the development
of use of agro-residues.
Although textile applications
offer a relatively high value addition and a huge market for consumption of
fibres from agro-residues, they require fibres of high quality. Versatile
application of agro-residues in textile industry depends on the fineness and
strength of fibres produced. Extraction of quality fibres depends to a large
extent on extraction techniques employed. Therefore, existing extraction
methods need to be supplemented with robust techniques and machinery to provide
the agro-residues like bagasse and cornhusk with value worth advocating. It is
sometimes assumed that residues are wastes and therefore, more or less free of
cost. However, it is unwise to assume so. In a monetised economy, even where
residues are freely available, everything which has a use will sooner rather
than later acquire monetary value.
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About the authors:
Preeti Kaur Sachdeva is senior research fellow at Lady Irwin College, University of Delhi, New Delhi.
Dr. Bhawana Chanana is professor and Director, School of Fashion Design & Technology, Amity University, Mumbai.
Dr. M. S. Parmar is professor and Director at Nitra Technical Campus, NITRA, Ghaziabad.
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