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Report: rice straw collection

R. Hegazy J. Snadro

Content

No. Subject Page

1 Introduction 2

2 General situation of straw collection 3

2.1 Small/medium bales system 4

2.1.1 Rectangular small/medium size balers 4

2.1.2 Hydraulic vertical bailing system 10

2.1.3 Manual rice straw compression tools 12

2.1.4 Round small/medium size balers 13

2.2 Large bale systems 15

2.2.1 Large rectangular/square balers 15

2.2.2 Large round bale machines 17

2.2.3 Stationary straw baling machines 18

3 Other straw collecting methods 19

3.1 Field cubing 20

3.2 Stationary cubing from combine-harvested straw

20

3.3 Total rice crop processed at central plant

22

4 Current situation in other countries in Asia 22

5 Straw/bales transportation

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6 Conclusion and important points need further consideration:

24

References 26

International Rice Research Institute Crop and Environmental Sciences Division Postharvest Unit

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1. Introduction

Along with the progress in the rice production system, the amount of straw will increase. About 620

million tons of rice straw produced in 2008 in Asia and now approximately 731 million tons per year

rice straw is produced globally (Africa: 20.9 million tons, Asia: 667.6 million tons, Europe: 3.9 million

tons, America: 37.2 million tons, and Oceania: 1.7 million tons) (Gummert, 2013; Sarkar and Aikat,

2013). Only about 20% of rice straw was used for purposes such as ethanol, paper, fertilizers and

fodders and the remaining amount is either removed from the field, in situ burned, piled or spread in

the field, incorporated in the soil, or used as mulch for the following crop (Hanafi et al., 2012).

Collection and management of rice straw is still a major challenge, for the environmental and economic

reasons, rice straw should be collected and used to produce energy or to be under different

management options, a proposition that becomes unfeasible over long distances due to the low density

of rice straw. Considering the economic aspects, the amount of rice straw available for use will be very

limited if there is no better way to collect and transfer the straw compared to woody biomass, a fuel

with much better transportability.

The conversion technologies applicable to rice straw include direct combustion heating, direct

combustion power generation, gasification and power generation (gas engine, steam turbine, and fuel

cell), gasification and methanol production, flash pyrolysis, acid hydrolysis and ethanol fermentation,

and co-firing. Only two of these technologies, combustion heating and direct combustion power

generation, are now commercialized. Conventional boilers and hot water generators are applicable for

direct combustion heating, direct combustion and steam power generation have been applied to woody

biomass and municipal waste, and they can be easily applied to rice straw and rice husk as well. A small

commercial plant for rice husk was available since 2001 in Japan for 1.25 t h-1 with an efficiency of 7%

(Matsumura et al., 2005). Engine, steam turbine, fuel cell, gasification and methanol production, and

flash pyrolysis have all been demonstrated in bench scale tests, and the feasibility of high-efficiency

performance has been demonstrated even on a scale as small as several tons per day using gas engines,

fuel cells, or methanol synthesis technology. Nonetheless, heat recovery and tar treatment technology

need to be improved for practical use, particularly in the case of smaller plants, due to the greater

difficulty in operating these thermochemical conversion processes with high efficiency.

However, collection of straw comes always as the first step to start successful and attractive energy

production systems as shown and cited in Fig 1 below.

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Fig. 1 Straw utilization chart

2. General situation of straw collection

Since 1970, the collection of field crop residues has been processed under two basic approaches; 1)

collection of residue after crop harvested: post-harvest concept, 2) simultaneous collection of crop and

residue: total harvest concept. For post-harvest collection of rice straw, collection of residue after

harvest could be accomplished by either the use of small/medium baling system or large bales system,

in details these baling systems can be done by; a) conventional small/medium baling equipment to

make round or rectangular bales, these equipments are stationary or being mobile equipment, b) big

package hay making equipment, including the large round baling equipment c) buckrakes to make large

piles of residue, d) field cubing equipment, e) field chopping equipment.

For the total harvest of rice, the concept of total harvest was discussed by Horsfield et al. (1977) and

Dobie et al. (1978) however; this has not been reduced to practice. The total harvest system removes

the straw and grain in a single operation and hauls it to a designated location at the edge of the field, to

the farmstead, or to the grain terminal for separation. The major pieces of equipment needed for a total

harvest consist of collector device, stationary or modified combine, straw drying equipment, and a large

baler. The grain collected can be separated from the straw outside the field. The un-threshed rice is

unloaded to form long high piles, combine with a modified feeding device work into these piles,

threshing the rice and dropping the straw in an adjacent pile. Using total-harvest systems to collect the

straw and the grain simultaneously will avoid the problem of reentering wet and rutted fields that post-

harvest systems face.

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2.1 Small/medium bales system

Field baling is much the least expensive method for harvesting and packing rice straw (Dobie et al., 1980). Bailing can be (and commonly is) applied to improve the characteristics of agricultural residues for transportation and storage. Packed loose straws to bales of different sizes and shapes, small square bales, round large square and compact bales, can improve the low density attributed to straw. The bulk density of rice straw is around 75 kg for loose straw and 100-180 kg in packed and baled form as energy feedstock. The baled straw has relatively low moisture content and can be stored for long period without significant dry matter loss and deterioration in fuel quality (Dobie and Haq, 1980). Earlier, this system is used to a limited extent, using either push-type or self-propelled two- or three-wire balers, and mechanical bankout wagons for road-siding. Under favorable conditions, a three- wire baler can produce bales weighing about 40 kg each. Rice straw must be dry for baling, as damp straw will not feed into the baler properly. Straw windrows from the combine are slightly wider than the normal baler pickup, but can be handled by the addition of gathering wheels. Recently, there is fast growing and a lot of modification done to enhance the performance of balers and to increase their capacities with different sizes and shapes of bales. Wide ranges of equipments in these systems have been introduced to the market in different countries. 2.1.1 Rectangular small/medium size balers

In many developing countries, straw collection always was remained dependent on a handful of elderly stationary balers with top-feed ram stroke and wire/plastic twine tie design, and straw was shipped in rectangular bales for instance 0.6×0.5×1.5 m3 (width, height and length). Bale length varied up to 1.9 m. Mass was typically 100-120 kg/bale, but could be higher, which make this baling system classified as medium to large baling system. Fig 2 shows an example of stationary balers in North Africa and Middle East region. There is another smaller type of straw bale press is produced by private local small sized iron factories. It is custom made to fit the requirements of straw bale size of the client and it can be either used to press rice straw at its hay estate or in its chipped estate, its tractor drawn type. Metal string or plastic ropes can be used to tie the straw bale, the baler move from place to place near the field to bale manually collected rice straw (Fig 3) (Garas et al., 2009).

Fig 2 Example of stationary balers in North Africa and Middle East region

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Fig 3 Small bale press stationary machine locally produced in Egypt

More development done to improve the working efficiency with adequate safety, low power

consumption and minimum manufacturing &running cost for rectangular stationary balers, e.g. El-Shal

(2005) mentioned required modification to be added i.e. 1) unit of straw pick up and elevation it to be

moved to the bale-chamber entry, 2) packers to place the material in the chamber while the plunger is

on its retracted stroke, 3) reciprocating plunger to compress the straw and move it through the bale

chamber, 4) means of applying forces to resist the moving of material through the bale chamber and

thus to control the degree of material compression and resultant bale density, 5) means of separating

consecutive bales.

To overcome the problems mentioned, one stationary baler modified and following parts added or

modified:

1- Exchanging the manual feeding (feeding through the upper opening and the feeder head of the

stationary baler) by mechanical feeding device.

2- Power transmission system from the tractor to the baler is developed by using a gear box with

flexible joint at the front of the baler instead of the driven pulley and belt

3- The stationary baler is developed by adding two knives; the first knife is fixed on the plunger edge,

while the other is fixed opposite the baler chamber opining to cut straw while the feeding operation

is taking place. The plunger is driven by a heavy crankshaft and connecting rod from gear box.

The main specification became; bale size 0.45 x 0.55 x 0.14 m3, added pick up (1.45 m width, number of

teeth are 64 on four tooth bars, the number of forks is 2), modified plunger head; stroke with 0.64 m,

dimensions; height: 1.45 m, width: 2.65 m, length: 4.80 m, PTO speed 540 rpm, developed baler mass:

2100 kg (Fig 4).

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Fig 4 Developed and modified stationary baler

Summary of the modified stationary baler test included; increasing the baler feed rate, decreasing

number of broken bales and fuel consumption with no much effect of moisture content of straw on fuel

consumption, in addition to the safety working environment with the modified baler.

Mobile straw baling powered machines came later and now are commonly used in this region, the first

type for mass production was small and compact baler and was ideally suited for harvesting straw from small fields, and the bale is convenient and easy-to-handle by small-scale producers. It is generally used by the governmental straw collecting centers that provide straw baling services for the farmers. This kind of press is used only for rice straw in its hay condition (Steele et al., 2009). These machines produce smaller rectangular bales with dimensions 0.80×0.46×0.36 m3 with mass up to 25 kg. These types of rectangular balers are now produced locally in some countries e.g. in Egypt under license to foreign Italian manufacturer. Baler is assembled in Egypt and costs from $ 4,000 to 5,000 with up to 10 years of useful service life when adequately maintained. A 50 kW tractor is required to operate such balers, its capacity is 15 t/day and it is tractor-drawn with typically pick up straw from the windrow left by the combine harvester (Fig 5).

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Fig 5 Italian baler assembled in Egypt

A mobile straw baler was designed and developed at the Agricultural Mechanization Research Institute (AMRI), Multan, Pakistan during the year 2003 and modified during 2004 (Fig 6). In 2009 field performance of this baler was evaluated. The design parameters of this mobile straw baler were based on local farm size, crop wastes and field conditions. The first prototype of mobile straw baler was fabricated at AMRI’s workshop in 2003 using locally available materials, fabrication techniques and facilities. Some of important components and parts such as hydraulic pump, hydraulic jack and gears were manufactured by the local industry according to their technical specifications (Yasin, 2012).

Fig 6 AMRI’s Mobile straw baler, Pakistan

The baler made bales of size approximately 0.391 x 0.457 x 0.635 m3. Handling of the bales was simple and easy. The loading and transportation of bales with a truck and trolley was easy and cheaper than that of the straw. The cost was $ 3800. The average weight of bhoosa bale was 34.6 kg. The baler took 4.3 minutes and consumed 17 men-minutes to prepare a bale. The baler was tested on cotton sticks, corn stover and sugarcane chaff, but no data regarding usage such baler with rice straw. Baler is mounted on a small trolley which can be transported to threshing sites and bales are made right after threshing. It can be operated by a tractor PTO or 20 hp diesel engine. The overall length, width and height of the baler are 5.3 m, 1.61 m and 2.06 m, respectively. The main frame is 2.53 mm long and 1.075 m wide made from mild steel.

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The baling chamber and gear box supports are also made of M.S. channel and welded on main frame reinforced with brasses of M.S. plates.

In China, systems needed for the collection, processing, and transportation of rice straw have been

developed recently (HSCUP, 2011). However, for the reason of lacking sufficient infrastructure and

available machinery for working on wet, muddy ground currently, it will provide rice straw to off-farm

use. The operating capacity of the different harvesting systems using baling would depend on the

amount of the straw in the field, ground conditions for machinery use, and the field size; the technical

characteristics of the machinery would be less of an issue. The nature of the rice straw creates high

wear and maintenance for processing equipment, resulting in processing cost increases over that of less

harsh materials. Many square bale bundling machines are widely used in collecting and bundling straw,

wheat stalk, and corn stalk (Fig 7). It is convenient for transportation, reserve and deep processing, and

it is matched with envelop machine to achieve the enveloping of ensile.

Fig 7 Rectangular bale bundling machine in China

Table 1 presents technical data of two different small square blares

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Table 1 Specifications of two different small square blares in China market

Item Model: 9YFK-1.4 Model: 9QYK-2.0

Pickup Width (mm) 1400 2000

Size of bale HxW (cm) 35×45 35×45

Length of bale (cm) 50~120 50~135

Density of bale (kg/m³) ≥120 ≥120

Efficiency (bales/hour) 120~140 120~240

Weight (kg) 1550 1650

Power (HP) 35~50 45~60

In India, many balers are available for collecting rice straw. In most of rice growing states the mechanization retrieval of straw can be done either by use of a straw baler or a straw harvester, the commercial straw gatherer cum baler (CLASS MARCANT-55) in Fig 8 was used in many places. For this baler, the drive is taken from the tractor PTO stub. The pickup width is 1.24 m and tractor power requirement of 30 KW or larger for output up to 16 tonnes per hour and bale size of 0.46 x 0.36 m with variable length from 0.4 to 1.1 m and bale weight is from 10 to 35 kg depending on bale length and crop condition (Mangaraj and Kulkarni, 2011).

Fig 8 Straw gatherer cum baler

In some industrial states like Punjab, after using available balers in farmers’ field, the straw bales get transferred by medium and big trucks to near power plant. e.g. Ghanaur, Punjab, India, there is biomass power plant near the village that collects straw from farmers of the surrounding countryside. Farmers after harvest, they would normally burn this agricultural waste, inedible to people and animals, to clear fields for wheat crops, as farmers across India do, and in that way contribute to the country’s dire air pollution, but in this case with the power plant, 120,000 tons of rice straw in year are instead burned to generate 12 megawatts of electricity for the state’s power grid (Romana, 2013) (Fig 9).

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Fig 9 Workers collect rice straw from the fields in Baghoura village, northern India.

In some African countries, e.g. in Ghana, the rectangular balers are used now in some places for baling rice straw (Fig 10) mainly as cattle's feed (MOFA, 2013). But no local manufacturing or assembling operations running within the country, all available balers are imported.

Fig 10 Baling rice straw for dry season feeding in Ghana

2.1.2 Hydraulic vertical bailing system

Hydraulic bailing system or hydraulic bailing press is mainly used for baling scrap materials and can be applied for rice straw baling. Most of hydraulic baling press machines are available in vertical shape, e.g. one of hydraulic type of straw bale press (Fig 11 left side) available in Egypt, the press uses an electrically powered hydraulic piston with gadget to control pressing pressure values. The press is custom made to fit the client requirements through the required bale size and the desired pressing pressure (Garas et al., 2009). Specifications of one of the Hydraulic type of straw bale press are presented in table 2. Another type with 1.5 t/h to 2 t/h capacity is available and fit the use of small stakeholders (Fig 11 right side) its specification presented in table 3.

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Table 2 Specifications of hydraulic type of straw bale press (Garas et al., 2009)

Model Units KEFAC Hydraulic

KBVN-05 Compressing Force Tons 5 Tying Slots Number 3 Electric Motor HP 3 Cycle Time Dry Seconds 30 Chamber Size ( L x W x H) CM 60 x 80 x 120 Bale Size ( L x W x H ) CM 60 x 80 x Var. Productivity Bale / Hr 50-70 Bale Weight KG 30-40

Press Overall Dimensions CM 60 x 100 x 200

Fig 11 Hydraulic type of straw bale press

Table 3 Specification of a hydraulic vertical type of straw bale press machine in China

Bale size (L×W×H) Mm 1200×900×1800 Length is adjustable

Cylinder Φ125×2 Pressing force KN 400 Density kg/m3 200±20 Bale Weight kg/bale 400±50 Capacity t/h 1.5-2 Wire Line 5 Power KW 18.5 Machine Weight T 2.2 Materials Hay, Straw, Cotton stalk, Wood chip, etc.

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Another type of vertical mechanical press baler has been seen in Pakistan, but no available information regarding its use (Fig 12)

Fig 12 Stationary press type baler used in Pakistan

2.1.3 Manual rice straw compression tools

Rice straw compression tools are different from rice straw balers in construction and use; normally they are manually operated tools to form square or rectangular bales or straw blocks. These blocks are used in building eco-friendly and energy-efficient houses. Straw bale houses are extremely sustainable and earthquake-resistant structures and make alternatives for some regions. A group called PPAKSBAB (Pakistan Straw Bale and Appropriate Building) has already started a program in which durable buildings are created using local resources (Fig 13) (Ganea, 2013)

Fig 13 Rice straw compression tool being used for creating buildings in Pakistan

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2.1.4 Round small/medium size balers

There are many types of small/medium size round balers around the world, e.g. there is self-propelled small-size round baler. This baler uses a crawler instead of wheels, the crawler achieves low pressure. Therefore, it is easy to operate even if on the wet paddy field. And the full time drive crawler system is kind to the surface of the ground better than one side brake turning; this baler is common in Japan and being produced there (Fig 14), an example of the specification of a self-propelled small-size round baler presented in table 4. Table 4 Specification of Japanese self-propelled small-size round baler (SE-511)

Models SE-511

Dimensions (mm) Overall length 1990 Overall width 960 Overall height 1140

Weight (kg) 340 Engine (kW {PS}) 3.4 {4.7} Fuel Unleaded gasoline Fuel tank capacity (L) 4.0 Starter Recoil starter Speed (km/h) at rated engine speed

Forward F1 1.4 F2 2.8

Reverse R1 1.4 Operation width (cm) 70 Standard Operation speed (km/h) 1.4 Bale size (Dia x W cm) φ50 x 63 Operational efficiency (min/10a) 40 - 50

Fig 14 Two different types of self-propelled small-size round baler in Japan

In Vietnam, straw has been collected manually in most of rice growing areas; recently locally manufactured balers and imported ones have been introduced. Mainly the small size baler is the most favorable and common. Most of the balers are easily be driven by small/medium size tractor, its light body enables work on soft fields and easy handling. It has 1 point hitch as direct attaching with PTO extended shaft. The common bale size is around 75 cm width x 50 cm diameter, and easy to handle, both the accuracy of bales tying and bale height adjusting are varying Fig 15.

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Fig 15 small locally manufactured round Vietnamese baler

In addition to the round bales machine, there are rectangular bales machines which are bigger in size and need more power source, also the self-propelled balers are available and have been introduced to the farmers by importing them from Japan, or being produced locally/assembled under supervision from the main factory in Japan (Fig 16).

Fig 16 Different balers in Veitnam

China has many small size round balers available now in market, e.g. as the one shown in Fig 17 with its specifications

Fig 17 Round bale bundling machine in China

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2.2 Large bale systems

Large balers are more of a recent phenomenon. There are two main types of large balers, round and square. Large bales can range in size equivalent of approximately 20 to 45 small square bales in most cases (Agribility Project, 2008), Prior operation is required before using large baling systems e.g. raking and swathing; raking is rakes are used for windrowing rice straw prior to baling (post-harvest option) and conducted when the straw is left at a spread or windrow depth between 5 and 25 cm or an average of 15 cm after the rice grain harvest. This is normally needed when the harvester operates in lodged (fallen) rice, and the stem is cut close to the ground, yielding high straw loadings; the swathing operation ensues when the stubble height is in the range from 25 to 90 cm. During swathing operation the stubble is further cut to a height of 5-10 cm. Also, after baling, big truck should pick up large bales from field. 2.2.1 Large rectangular/square balers

Balers that produce large square bales are gaining in popularity throughout developed countries, but not in developing countries as the farms and land are limited in size. Bale dimensions start from 1 x 1 x 1.8 m, and they can weigh up to eight tons (Fig 18). Square bales are easier to stack than are round bales. Stacks created with square bales are also higher and more compact, taking up less space. The most significant problem associated with the large square balers is the high cost of the equipment; large square balers significantly surpass the round hay balers in cost.

Fig 18 Recently compressed large rectangular bales. June 2009, northern Utah, USA (Sando, 2010)

The baling system is same as the small baler with a few different additions to the process; first

difference is the pre compression chamber; second difference is strength of the twine, times it wraps

the bale and the knots tied at the end. Large square bale size is equal to about 20-40 small square bales.

Specifications of large square balers, BB9060 Packer Cutter, (Fig 19) are presented in table 5.

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Fig 19 Large rectangular baler, BB9060 Packer Cutter

Table 5 some of specifications mentioned for large square balers, BB9060 Packer Cutter

Model BB9060 Packer Cutter Bale Dimensions Width, in. (mm) 31.5 (800) Height, in. (mm) 35.4 (900) Maximum length, in. (mm) 102.3 (2600) Baler Dimensions Length chute closed, in. (mm) 284.6 (7230)

Width (single axle 600/55 x 22.5 tires), in. (mm) 101.6 (2580) Width (tandem axle 500/50 x 17 tires), in. (mm) 99.2 (2520) Height (single axle), in. (mm) 122 (3100) Height (tandem axle), in. (mm) 120 (3050) Weight (single axle), lb. (kg) 15,807 (7170) Weight (tandem axle), lb. (kg) 17,129 (7770) Feeder 3 packer fork Feeder protection Slip clutch Stuffer Fork type with 6 tines Stuffer protection Shearbolt Pre-compression chamber, volume, ft3 (m3) 8.8 (0.25) Plunger Speed, strokes/min. 42 Length of stroke, in. (mm) 28 (711) Tractor Requirements Minimum PTO power, hp 110 PTO speed, rpm 1000

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2.2.2 Large round bale machines

There are different ways to wrap the bales. Twine is the simplest wrap, but it leaves the bale exposed to nature’s elements (Fig 20 right side). In the relatively dry condition, many farmers choose to wrap their bales with twine, which is effectively less expensive than alternative methods such as plastic mesh. To offer more protection from weather and other elements, some farmers opt to wrap their hay bales with a type of net wrap (Fig 20 left side). Net wrap is a strong, plastic mesh cover that binds the bales. It is more expensive, but there are benefits to using net wrap even in a drier climate. Net wrap reduces the amount of spoilage from the collection of rain and snow. With net wrap, hay bales require fewer revolutions to wrap the bales, meaning the baler produces more bales per hour. If hay growers sell their hay, and it is transported a long distance, net wrap keeps the bales together better than twine. Even if bales are not sold, because net wrap keeps the bales together better, farmers might still opt for the more durable binding

Fig Two different ways of wrapping large round bales

In Korea, only within the last few short years have the large round baling machines (Fig 21) been in Korea. Even the machines for small square bales are fairly recent and started to be introduced in the mid-1990s but not widely used then at all. The large round ones are wrapped in plastic and left along edges of fields (Magnant, 2010).

Fig 21 Large round bales in Korean farms

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Large round balers are varied in their specification e.g. a specification of one large baler (Claas R 250) used in IRRI, Los Baños, Philippines is; Pick-up widths is 2.10 m, Pick-up (Fig. 22), guide wheels with castor and feed system is roto-feed rotor, number of compression rollers is 16, Baling chamber diameter is 1.25 m, Width is 1.2 m, tires: 15.0/55-17 10 PR with optional 19.0/45-17 10 PR.

Fig 22 large round baler (Claas R 250)

This type of balers include characteristics; steel baling chamber with the unique MPS chamber layout

guarantees extra bale density and high core compaction; MPS for extra compaction; drive chains are

designed to cope with heavy situations with plenty of stamina for long term reliability; easy to handle

and stack as well; equipped with the well-known assister feed rake behind the pick-up, this additional

rake transfers the crop from the pick-up and feeds it evenly to the baling chamber; bales are around

2.10 metres diameter with optimum wrapping security.

2.2.3 Stationary straw baling machines

New modified stationary straw balers have been introduced to the market recently in China, e.g. a

hydraulic baler equipped with one low-power motor, which provide adequate power to the continuous

running of the machine, equipped with emergency stop switch, circuit protector and safety door to

make sure safety when operating, caution boards are posted on main parts of the machine to warn

operators. Specification of such baler as below (table 6):

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Table 6 Specification of a hydraulic baler (Fig 23 left side).

Specification, unit Bale size (L×W×H)

mm 1800×900×1200 Length is adjustable

Cylinder Φ200 Pressing force KN 600 Cycle Time s 15 Density kg/m3 180-220 Bale Weight kg/bale 350±50 Capacity t/h 3-5 Feed Opening mm 1000×900 Wire line 5 Power KW 18.5 Machine Weight T 6 Materials Hay, Rice Straw, Cotton stalk

Fig 23 Stationary hydraulic balers

3. Other straw collecting methods

There are additional machines used for straw collection, some of them have been mentioned by

Tingshuang et al. (2002); straw collector: it was used to collect straw into small stacks, or to bring them

to a large one. It consists of a collecting platform, left and right handspikes, a frame and a pulley. The

collecting platform includes a collecting fork, a side bar and a fence; stacker: to gather the straw and

pushes it out, there are many types of stacker, including derrick stackers, fan stackers, conveyor belt

stackers, slide stackers and hydraulic stackers; Pick-up-and-press stacker; This consists of a flail-type

pick-up chopper, a blower tube with rectangular cross section, a directing cover, a movable top cover, a

chamber, a chamber rear door, and a chain conveyor for discharging. However, such machines are not

being used nowadays

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3.1 Field cubing

Limited experience indicates that rice straw can be cubed in the field provided: (1) the straw contains 12% or less moisture; (2) the windrows are limited to about 2 kg of straw per meter of length; and (3) a suitable bonding agent is uniformly applied to the straw. The cubes made using this process are of fair quality for handling and storage, with a bulk density of 340-420 kg/m. Very limited cubing machine tested and performance of these types of machines not clear, for its second generation bio-energy projects, PAMI (multi-faceted engineering-based research and development organization) has developed a self- contained mobile field-side cuber built on the deck of a flatbed trailer. The equipment can be moved to a field of agricultural byproduct residue such as straw for conversion and compression on site to cubes that are suitable as fuel feedstock to replace coal. Unlike other cubing processes, no steam is required which reduces input costs and power needs. The equipment is used to assess the energy efficiency of field-side cubing. A system for field cubing have been modified and tested by Shinners and Hoffman, (2012). Their target was to run in field cubing system for Switchgrass, reed canarygrass and corn stover, but not used for rice straw. Their modified machine testing showed very inconsistent process, currently not robust, spatially variable moisture content makes consistent performance difficult, cooled die ring and lime amendment, improved performance, and much development work remains (Fig 24).

Fig 24 In field cubing (Shinners and Hoffman, 2012).

3.2 Stationary cubing from combine-harvested straw

This system involves hauling combine-harvested straw from the field to a central plant, grinding the straw and mixing with feed supplements, cubing, cooling and storing the cubes. Most of these operations have been individually performed with rice straw, but have not been integrated into an operating system. The bulky nature of combine-harvested straw renders storage at a central location uneconomic. An alternative plan is to move the straw to the edge of the field with stacking wagons. Each stack contains about 2.3 tonnes of compressed long straw, providing reasonable protection from rain. However, as straw must be dry for cubing, a protective cover is beneficial. These stacks remain intact until moved to the central plant. This system allows cube production to be continued through the winter and offers much more flexibility than does a system in which cubing is restricted to the rice harvest season. There are several advantages to such an operation from the standpoint of producing and selling cubes for a particular off-farm application.

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Also, Deprez et al. (2012) presented a concept of using a small mobile machine to produce straw pellets directly on the field. The economic relevance is checked and a general concept of the machine is proposed. Measurements show that for a production capacity of 1000 kg/h a mill with a power of 35 kW is needed. As the component of this system, straw cannot be directly fed into the hammer mill, but has to undergo a downsizing step. Pre-cutting knives of a baler or the pre-cutting system of a forage harvester can be used. Under the hammer mill a ventilator creates a small vacuum to force the straw particles through the sieves of the mill. Air and partials are separated using a cyclone. The straw is fed afterwards to the pelletizing machine using a transport screw. After cooling down of the pellets on a conveyor belt, the pellets are stored in a tank. The machine is powered with a diesel engine of which the exhaust can be used to warm up the biomass (Fig 25).

Fig 25 Mobile straw pelletizing machine (Deprez et al., 2012)

In line with mobile straw pelleting machine concept, a small company in Staffordshire Moorlands in England developed a small-scale mobile pellet machine (Pelheat, 2013). This machine included a hammer mill for size reduction, cyclone separator and finally a pellet mill. The equipment was all mounted on a trailer and powered by a Perkins diesel engine (Fig 26). The mobile pellet machine was not suitable for sale due to various limitations. However, it still can provide opportunity in processing collected rice straw into pellets if it is adapted to do that.

Fig 26 Small-scale mobile pellet machine

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3.3 Total rice crop processed at central plant

This case was based on a hypothetical system in which the entire rice crop, straw and grain, were to be harvested at the same time, and the crop transferred to a stationary plant for processing. The overall process includes field chopping the standing crop into large vans, hauling it to a central plant, separating the grain from the straw, drying the grain and straw separately, and processing the straw into mixed-ration cubes. This concept differs from standard rice-harvesting practice, and involves some operations and equipment that are unproven with rice.

4. Current situation in other countries in Asia

Philippines

No clear technologies for straw collection, few balers have been used in the country. A small funded project, Improved Rice Straw Collection and Storage at the PCC National Bull Farm through the Introduction of Mechanized Rice Straw Balers (Enterprise Technology Upgrading Program CY, 2010)

Malaysia

Rosmiza et al. (2012) stated that the harvest of rice during the rainy season in Malaysia is a key factor to the degradation of the straw development industry of some regions. Based on R&D and the use of the existing baler machine technology, rice straw can only be collected and use when everything is dry. Furthermore, the imported baler machine cannot be operated in wet soil conditions. This negated the efforts of farmers to develop the straw collection methods for industry or any other use. Balers used to collect straw on farms are not appropriate to local conditions. The tires easily come stucked and unoperational in watery rice fields. Hence, it can only operate during the dry season that is during the months of February and March.

Also, the lack of baler machine caused the demand of farmers to participate in development projects in each straw harvesting season cannot be met, in addition, The inefficient transport system includes the lack of trucks to bring out the straw from the field; the small trucks cannot accommodate that many, big and heavy straw prevent the straw development. Limited period for land management for the planting of next crop affect less the development of collection straw activities, short period of time, about one and half month farmers were forced to burn the straw immediately to clear the field.

5. Straw/bales transportation

Stacking and transport to the road-side

One of simple methods to stack and transport straw, the stacking operation is comprised of filling up a stacker with bales, either large or small, and driving the stacker some distance off-field to build a large stack for subsequent hauling off site. Transport to the roadside requires the same amount of time as baling. Large stackers, which can pick up large bales, are very efficient in moving the largest amount of straw. However, these large stackers have problems in soils with higher soil moisture contents (30-62% with an average of 58%). The large bales stackers are capable of moving approximately 4 tonnes of rice straw compared to approximately 2.5 tonnes generally moved by the medium bale stackers.

Transport to the plant

Truck transportation will probably be the most feasible option in the residue collection systems, since trucks have a high degree of mobility. The bales are transported off-field to either storage or to the plant.

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Transportation of rice straw in developing countries

As long as the process of straw collection is correlated to transportation, the situation in transportation system not so far from the situation of collection in most of developing countries, mostly they depend on using two wheel tractor, animal, and small & medium trucks. Transport of baled straw can be up to 50% cheaper than transportation of loosed material and about 1% cheaper than that of wood chips (Caldwell et al., 1988). However, this method requires a good transport system to carry the baled rice straws from the field to the power plant or storage. It is also dependent to weather and soil conditions of the field. This technique can be carried out efficiently in many developing countries with simple transport devices like bullock cart where trucks and trailers are not available (Kargbo et al., 2009). 2WT can be seen to be more of powerful engine that pulls the cart where farmers can transport their straw if when need (its common in Korea) (Fig 27).

Cambodia Myanmar

Rice straw in truck, Indonesia 2WT for straw transportation in Korea

Fig 27 Rice straw transportation methods in some places in Asia

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6. Conclusion and important points need further consideration: a) Use small size bales vs. large bales

Many research work, have been done to study the potential impacts of various rice straw

management technologies as alternatives to rice straw open-field burning, however, when we come

to the comparison between these management technologies we can not find straw baling systems

included or any other mechanical collection of the straw. In the following table (table 7) you can see a

simple comparison between Small baling systems and large baling system, but separated studies

related to the visibility and economical use of both systems in different areas, especially in small-scale

farms, need to be done.

Table 7 Small baling system vs. large baling system

Comparison Conventional Small bale system Large packages (Big Round and Big Square Baler Systems

Economical More economically Economic advantage over the conventional small bale system unless more than 500 tons are harvested. Farmers who do not harvest this amount should not consider that as an option (Moggach and Weeden, 1976)

Operating Inexperienced operators can manage in conventional small bale systems

Inexperienced operators starting face many new problems when the operator tries to maximize capacity before he has developed the necessary skills to produce uniformly cylindrical bales, precision tractor driving is a must

Straw distribution

Ideal if rows of straw raked together, but can be run also in randomly distributed straw in the field

Need rows of straw raked together, prior raking and swathing required

Handling Easy to handle, transport, market and store small size bales, need small storage place

Difficult to handle, transport and store, bigger storage place is needed

For feeding Has advantage of easy delivering to animals and to control the amount of feed

Need specific feed system and highly mechanized feed distribution mechanism

Hand labor Required more hand labor Implemented based on one-person operation Storage Inside storage always better

option as outside storage need covers and losses are high

Lower losses percentage in case of outside storage compared to small conventional bale system

Safety Using small conventional bale system more safety

Large bales can be a serious safety problem, especially in transportation (Wills and Bledsoe, 1987)

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b) Straw collection in wet condition (wet season harvesting)

The feasibility of mechanical harvesting depends on the carrying or bearing capacity of the soil. In most of south Asia countries, and due to long and heavy rain, the soil often turns muddy thereby limiting the use of machinery. The problem is particularly significant in those areas. So, solutions for using specific types of baling system and/ or collecting methods in such condition are highly needed.

Also, a study indicated that potassium, chlorine and total ash are leached from rice straw by rainfall regardless of rice variety, grain harvest method, straw arrangement, or stubble length (Fig 28). While leaching of sulfur by natural precipitation was not clearly established. In selected field plots, leached straw was successfully collected with biomass yields vary from 2.2 to 3.4 Mg ha−1 and equipment had to operate in difficult conditions. Total costs for collecting leached straw on an area basis ($77:07 ha−1) are 31% higher compared to collecting crude straw in the fall ($58:67 ha−1). The feasibility of wet season collection of rice straw could be improved if straw collection equipment were better equipped to operate under wet field conditions (Bakker and Jenkins, 2003)

Fig 28 Straw in wet condition, Sacramento Valley, California, 1998 (Bakker and Jenkins, 2003)

c) Straw collection from environmental sustainability point of view

Absence of adequate straw collection and transportation systems led to unfavorable effects on farmer’s health as well the environment, burning straw in fields is just one issue but many other issues should be in focus e.g. open air threshing and its related to water and soil pollution, contribution of rice straw located around farmers’ fields to greenhouse gas (GHG) emissions, etc.

d) Timing of operation

The timeliness of straw collection is a concern of many growers. To be successful, the collection system needs to operate within the variable time constraints imposed by the weather and growers' cultivation practices for rice.

e) Available systems

Since rice straw is a low-value byproduct, systems designed to collect other field crop residues can be adapted.

f) Available power sources

As the majority of farmers in south/southeast Asia are using 2WT, it is important to study the possibilities to use 2WT as a part of the effective collection/transportation process for rice straw, and

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new designs may be needed to develop suitable small baling or collecting methods to be attached with 2WT.

g) Straw piles/threshed straw

69 % and 84 % of rice produced Philippines and Vietnam is being threshed the other amount is either being threshed manually or left in field after combine harvesting (less than 10 % and 15 % of rice area in both counties is being harvested by combines) (Viet, 2012; Mariano et al., 2012). In Cambodia Number of threshing unites increased from 3780 to 14390 unit in last 10 years, number of combine harvesters available in 2012 is around 2939(MAFF, 2013). Data from other countries related number of threshing units and combine harvester is presented as below:

Country Threshers Combine harvesters Year/source

Indonesia 201,241 (power only) NA 2010 (Unadi, 2011)

Bangladesh 155,000 + 100 2011- (Abdul-Wohab, 2011)

Myanmar 37678 NA Maung, 20112

Thailand 32,239 with 2000 unit local production yearly

41,143 2010- NSO, 2010

Srilanka 112 to 153 NA 2007 Bandara, 2012

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