The biomass available after the harvest of seed cotton is rich in cellulose, hemicellulose and lignin which is akin to most of the hard woods and therefore an excellent raw material for preparing composite boards, pulp and paper and raising edible oyster mushrooms. Amongst these options, preparation of particle boards has been found to be economically feasible. CIRCOT has standardized methods to prepare composite boards. With funding from the Common Fund for Commodities (CFC), Netherlands and the supervisory Body, International Cotton Advisory Committee, Washington, U S A, CIRCOT established models for the logistics of cotton stalk supply chain to the board industry and installed a demonstration plant at the Ginning Training Centre of CIRCOT, Nagpur.

The model of the cotton stalk supply chain clearly shows that the farmer can get an additional income of US $ 1.1 per tonne of dry biomass (10-12% moisture) and on uprooting, cleaning, chipping and transportation of cleaned chips would fetch an income of US $ 4.4 per tonne provided the industry is located within 50 km radius.

Getting rid of boll rinds and adhering residual lint is normally done manually by beating the stalks gently on a wooden mallet. This is laborious and labour intensive. Alternately, a mechanical device also has been developed to remove the unwanted materials by passing the uprooted stalks through the rollers which could be adopted wherever labour is expensive or in short supply. In India, uprooting the stalks manually/ using a mechanical device is common in areas where the crop is raised under rainfed conditions. In places where it is grown under irrigated tracts, the stalks are cut above the ground level.

The presence of boll rinds and roots definitely affects the quality of the end product be it particle board, hard board, soft board or medium density fibre boards. The processing of stalks needs to be tailored depending on the requirement. In the USA and other places where seed cotton is mechanically picked, the presence of boll rinds in the stalks is minimal and mechanically cutting could produce biomass directly used for chipping.

Conclusions from the intensive work undertaken on developing a machine for compacting stalks and transportation of baled stalks to a centralized chipping centre found it to be uneconomical. However, chipping the stalks in the field then transporting directly to the board industry has been found to be feasible.

Considering the above, establishing a 20 TPD particle board plant in countries like India and other Afro-Asian countries has been found to be feasible and sustainable. Details of the logistic model of cotton stalks supply chain and the proposed viable size plant will be presented.

Keywords : Cotton Plant Stalks, Particle Boards, Cleaning System

Introduction

India has the distinction of being the seat of all the four cultivated species of cotton in addition to hybrids. India can also take pride in being the only country growing cottons that meet the quality requirements for spinning a wide spectrum of yarn counts ranging from 6s to 120s. To make cotton farming more economically viable, an alternative was considered. An alternate strategy for improving farm income is to utilise the byproducts of cotton cultivation beneficially. Cotton stalk is one of the important by­products of cotton crop.

About 23 million tonnes of cotton plant stalks are generated in India annually. On an average about 2 to 3 tonnes of stalk are generated in one hectare of land. Most of the stalk is treated as waste, though a small part of it (15%) is used as fuel. The bulk of the stalk is burnt in the fields after the harvest of the cotton crop although it is not desirable since it causes air pollution. At the same time, cotton stalks piled up in the field harbour pests and disease causing organisms. Cotton stalk is comparable to most of the common species of hard wood with regard to fibrous structure and hence can be used for manufacture of particle boards, preparation of pulp and paper, hard boards, corrugated boards and boxes, micro-crystalline cellulose and for growing edible mushroom.

Over the years, CIRCOT has been engaged in the development of cost effective technologies for production of value added products like particle boards and hard boards from cotton stalks with a view to provide supplementary income from cotton farming to cultivators and also to help entrepreneurship creation in rural areas. A brief summary of the economic potential of cotton plant stalks is given below.

In India the majority of cotton is cultivated during the period July to February and the crop is harvested from October to March. Following table gives information about the area and production of cotton and availability of stalks in various parts of the country.

The yield of biomass varies from species to species; it is highest in the case of hybrids and lowest in the case of G. arboreum. However, on average, about 3 tonnes of cotton plant stalks are available in one hectare of land. Depending upon the variety and the crop conditions the stalks are 1 to 1.75 meter long and their diameter just above the ground may vary from 1 to 2.5 cm. The specific weight of short chopped stick is about 160 kg/m³. The calorific value of cotton stalks is equivalent to poor quality wood and is about 17.40 (MJ/kg). About 23 million tonnes of cotton stalks are generated in India with an average production of 3 tonnes per hectare of land out of which leaves, boll rinds and small branches are removed during collection and cleaning. Hence it is estimated that only 2 tonnes of field cleaned stalks are available per ha.

Most of the stalk produced is treated as waste though a small part of it is used as domestic fuel. The bulk of the stalk is burnt off in the fields after the harvest of cotton crop. The following table gives the chemical composition of cotton plant stalks from different species of cotton. (WHERE IS THE TABLE?)

On average cotton plant stalk contains about 68 % holocellulose, 26% lignin and 7% ash.

It is interesting to note that in contrast to other agricultural crop residues, cotton stalks possess fibre dimension comparable to most commonly available species of hardwood. It can therefore be used for the manufacture of particleboards, preparation of pulp and paper, hard board, corrugated boards and boxes and as a source of cellulose for the manufacture of microcrystalline cellulose. Cotton stalks can also be used to grow edible oyster mushrooms.

Logistics of Cotton Stalk Collection

The following three models were tried in the first two seasons to arrive at the most suitable and economical way of collection of cotton stalks and its processing.

• Transportation of cotton stalks directly from the field to factory for chipping in the factory.

• Chipping of cotton stalks by farmers and transportation to the factory.

• Collection and transportation of cotton stalks by farmers from the field to chipping centre, chipping and subsequent transportation to the factory.

In the first year, the stalks were directly transported to GTC (Called, factory) and chipped using a drum chipper (Klockner chipper). Alternately the stalks were collected and chipped in a centralised place (chipping centre) in the field itself and chips were transported. The third option of chipping in the field itself and transportation to factory was also attempted.

Based on the first year results, the second year trial was restricted to only one centre wherein the studies were undertaken on the tractor driven mobile chipper (chaff cutter).

The cotton stalks were uprooted as being practiced by the farmers in central and South India, allowed to dry for 4-5 days and cleaned by beating the dried stalks on a wooden mallet to remove the adhering cotton lint, boll rinds and very small branches. Such cleaned stalks were chipped in the field itself employing tractor driven mobile chipper. The chips thus obtained were transported directly to the factory by using two modes of transport. In the first one, the chips were directly loaded and transported and in the second model the chips were filled in gunny bags and the bags were loaded in lorry and transported. The following flow chart (WHERE IS THE FLOW CHART ???) depicts the availability of stalk and its conversion to chip form at the end of the process.

It has been found out that the cost of cleaned chips transported to a distance of about 50 km comes to Rs. 2000/- per tonne. This has been ascertained by some interested entrepreneurs who have come forward to supply cotton stalks chips. According to their experience, the rate quoted for cleaned cotton stalk chips comes to Rs. 1500/- per tonne at the site (field where the stalks are collected and chipped) and the transportation is extra. This study has already enthused some of the entrepreneurs in Central and Northern India based on the responses received from the participants at the Awareness meets held very recently.

Presently, tractor driven mobile chippers are available and they could be hired for the purpose. Fabricating drum chippers (to be driven by power tillers) and small tractors has been found to be not viable for the following reasons.

1. Three phase motor is essential to run a drum chipper

2. Not possible to shift them from field to field as they are very heavy

3. Availability of three phase power supply in rural India is not common

Alternately, tractor driven mobile chaff cutters are ideal and economical

1. They can be taken very easily from field to field

2. They could be run on single phase power supply which is easily available in rural places.

A Model Cotton Stalk Supply Chain for 20 TPD particle Board Plant

It is assumed that for producing 1 tonne of boards, about 1.5 tonne of chips are required. For producing 1.5 tonnes of ready to use cleaned chips, 3 tonnes of biomass (including leaves, boll rinds etc) are needed. Thus for a 20 TPD particle board plant, 30 tonnes of chips are needed each day. Based on our experience it has been observed that it is possible to get about 1.5 tonnes of ready to use chips from one hectare land in and around Nagpur. In case the factory has to run only on cotton stalks it is necessary to get the material from 6000 ha i.e. 9,000 tonnes per annum (for 300 working days).

Storage

Our experience has shown that cotton stalks are normally uprooted in and around Nagpur when the plant is almost dry (devoid of leaves). Such plants, if uprooted and left in the field for three days and manually cleaned to remove the boll rinds, can then be chipped with the resulting miosture being approximately 12%. During transportation of the same to the factory, the percentage of moisture stabilizes to about 10%.

Considering that the chips have to be stored in the mill premises for at least one month, about 900 tonnes are to be stacked in the mill premises and the rest to be stored in 9 decentralised places by a group of farmers (say in 9 villages connected well with transport services)

Chipping Stations

It has been estimated that about ten chipping stations are required to be setup. Each chipping station is to be provided with one tractor driven mobile chipper (outsourcing). These chippers can provide chips of about 500 kg/h. Thus it is possible to chip about 3-4 tonnes per day or 90-120 tonnes per month. Each chipping station will have to store about 900 tonnes of chips. These chips will be stored in three stock piles of 3 meters height and each pile to be covered by polythene sheets to prevent the spoilage during rainy season. These stock piles will be separated from each other sufficiently to facilitate loading of chips in trucks.

The density of cotton stalk chips is about 0.14. The average area occupied by a 3 meter height stock pile would be around 70m². The space required in each chipping centre would be around ¼ of an acre (should be in hectare units).

Cotton Stalk Collection at Each Chipping Station

About 100 tonnes of chips are to be stored in each chipping centre. In other words stalks are to be collected from 70 hectares of land. Based on our experience four labourers can uproot and collect stalks from one acre in a day. In other words, 10 persons are required to uproot the stalk from 1 hectare. This also means 10 persons would get employment for one week for only uprooting. An equal number of people are required to clean the material also.

Supply of Cotton Stalk Chips

The chips will be transported to the factory under the direct control of the factory to ensure that adequate supply of cotton stalk chips to the plant takes place.

Cotton Stalks Cleaning System

It has been found out that the presence of boll rinds and adhering lint affects the quality of boards. This necessitates the removal of them before chipping. Manually this is done by beating the uprooted or cut stalks gently against a wooden mallet. This is labour intensive. Wherever labour is a problem, machine removal becomes necessary.

A cleaning system has been designed and fabricated. The unit has the following features.

1. Scratching system (pealer)

2. Conveyor system

3. Air blowing chamber

4. Air suction chamber

It has been observed that 90% of the boll rinds are removed in the first unit itself and about 5% are removed in the suction chamber. This indicates that the scratching system could be directly connected to a chipper to economise the process. The results obtained are given in the following Table.

Cleaning Effect on Properties

There was a feeling that the impurities viz., boll rind and the presence of bark do not significantly change the quality of the boards. Removal of either the boll rinds alone or the bark or both will definitely affect the raw material cost. In view of this a study was undertaken to establish the effect of impurities on the quality of the boards. The results are presented below.

The above study clearly brings out the following facts:

1. Significant reduction in water absorption by bark removal.

2. Enhanced Modulus of Rupture after cleaning and bark removal.

3. Improvement in Internal bond strength.

All the above indicate that the quality of the boards is enhanced after the cleaning and removal of bark.

Storage Trials

With a view to study the storage behaviour of cotton plant stalks, several trials were undertaken. Cotton stalks were stored in different forms such as whole cotton stalks and chips. Samples collected at different intervals were analysed for chemical composition to assess the deterioration if any in quality during storage. The cotton stalks as is and in chipped form were kept in open and also inside the shed. After 5 months of storage, there was no change in chemical composition in the materials stored inside. However, there was discolouration/darkening of stalks in the surface layer of the material stored in the open.

To find out any charge in chemical composition of cotton stalks stored in the open, following trials were undertaken.

(1) Stalks stored in the open over a stone-cemented platform

(2) Chipped stalks stored in the open

(3) Chipped cotton stalks placed as such inside a shed

(4) Chipped cotton stalks packed in gunny bags and stacked inside a shed

(5) In addition to this about 35 tonnes of chips filled in gunny bags were stored

outside in a factory for 7 months but covered with tarpaulin sheets

Chemical analysis was also carried out and results are produced below

The chemical analysis indicates that there was no significant change in the composition in case of chips stored inside. However, there is a slight reduction in the holocellulose content in the case of chips stored outside. This might have been due to the exposure of chips to rain. Even this could be avoided by covering the chips with polythene or tarpaulin sheets. Analysis has shown that the samples stored outside at a factory, but covered, indicated no change in the chemical constituents even after 7 months.

Installation of Particle Board Demonstration Plant

A one tonne per day demonstration plant has been commissioned at Ginning Training Centre of CIRCOT, Nagpur with indigenous machinery. This plant is meant to demonstrate the utilization of cotton plant stalks mainly and other related biomass to prepare particle boards of 4’x3’ size in a three day light hydraulic press of different thicknesses for prospective entrepreneurs. The following table shows the properties of boards which satisfies the specifications set by Bureau of Indian Standards (BIS).

Economic Analysis of Cotton Stalk based Particle Board Plant :

In order to carry out an economic feasibility analysis for cotton stalk based particle board plants, the following facts have been taken into account :

• A 20 TPD plant could be established with indigenous plant and machinery.

• This factory should ideally be located within 50 km radius from the cotton production site.

• As per prevailing prices, one tonne of cleaned, chipped cotton stalks would cost Rs.2,000/- at factory site.

• The land and building costs have been considered assuming that a factory to be set up in cotton growing tracts in India.

Though it has been established by CIRCOT Scientists in the early eighties itself that cotton plant stalk is an excellent material for preparing particle boards due to similar chemical constituents as that of hard woods, even today this precious material is mostly burnt or partly being used as fire wood.

This is mainly due to :

• Dependence on forest based material (timber) which was available in plenty.

• Lack of legislation on ecological considerations.

• Uncertainties in dry land agriculture with regard to crop yields.

• Non-availability of cotton stalk supply chain.

Benefits of using stalk as Raw Material by Board Industries :

• Established cotton stalk supply chain

• Additional income to farmers

• Renewable raw material to board industries

• Generation of Rural Employment

• As many as 250 people will be involved on daily wages in collecting, cleaning and chipping cotton stalks to supply them to one factory of 20 TPD capacity.

• Industry employs people in the factory

• Employment to transporters