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PM—Power and Machinery
Biosystems Engineering (2002) 81(1), 49}56 doi:10.1006/bioe.2001.0005, available online at http://www.idealibrary.com on PM*Power and Machinery
Development and Evaluation of Kenaf Harvesting Technology L. J. Kemble; P. Krishnan; K. J. Henning; H. D. Tilmon Bioresources Engineering Department, 264 Townsend Hall, University of Delaware, Newark, DE 19717-1303, USA Food and Resource Economics Department, 212 Townsend Hall, University of Delaware, Newark, DE 19717-1303, USA, e-mail of corresponding author: [email protected] (Received 7 November 2000; accepted in revised form 7 September 2001; published online 14 November 2001)
Laboratory and "eld tests have demonstrated that a component approach to harvesting kenaf and separating the "bre and core has a lot of potential. Machines used for harvesting kenaf required only minor, if any, modi"cation. The straw-walker from a combine harvester proved to work very well to separate the kenaf "bre and core. More work needs to be performed to expand the prototype separator into a production unit. Transportation of the whole stalk material from "eld sites to the processing facility proved to be expensive due to the low density of the material. In-"eld separation could reduce this cost by 50 per cent. 2002 Silsoe Research Institute
White et al. (1976) have summarized the work carried out on harvesting, handling and storage of kenaf in the United States. Although there are several possible harvesting methods (#ail choppers and binders), chopping the air-dried crop with a forage chopper appeared the most feasible. Regular farm balers did not satisfactorily bale "nely chopped kenaf. However, no attempt was made to bale long chopped material. Fuller and Doler (1993) mention that at least three "bre-separation systems are currently being used in the United States. These systems include: (1) a design by Harold Willett of Jeanrette, Louisiana, USA; (2) a modi"ed gin concept developed by Gordon Fisher of Agro-Fibers, Inc. of Corcoran, California, USA; and (3) a rotating driven concept marketed by the Lummus Development Corporation of Columbus, Georgia, USA. However, published information is very limited on these systems. Chen and Pote (1994) developed an in-"eld separator of kenaf based on a prototype from Tainan Fibre Crops Experiment Station in Taiwan in 1975. The whole kenaf stalk is fed into the machine comprising crusher- and beater-rollers. The crusher-rollers crush the stalk and the beater-rollers separate the bast "bre from the core. The whole length bast "bre is the end product. Also, they modi"ed a John Deere combine harvester. The
1. Introduction Kenaf (Hibiscus cannabinus L.) has the potential to be an alternative crop to be used as a rotation crop with other dryland crops. Kenaf contains two basic components: bast "bres in the outer bark and an inner core of short xylem "bres. The high-value bast "bre can be sold for paper manufacturing, either locally or for export to the Far East. The inner core can be retained either by the farmer for on-farm use as animal bedding or for processing in other markets, such as for horse bedding.
2. Review of literature In the 1950s and early 1960s the US Department of Agriculture (USDA) carried out an extensive &R&D' programme on kenaf in Florida and Cuba (Byrom, 1958, 1964; Werber & Andrews, 1995). Dempsey (1975) summarized the work carried out at the Everglades Experiment Station towards the development of a kenaf harvester}ribboner and a mechanized system for netting, working, and drying of the "bre. This "eld harvester}ribboner continued to be modi"ed and improved until the "bre crop operations were discontinued in 1965. 1537-5110/02/010049#08 $35.00/0
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2002 Silsoe Research Institute
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L. J . K EM B L E E ¹ A ¸.
separation unit was built to "t in the combine harvester. A Kemper head and a feeder house of a forage harvester were attached to the front of the separation unit. The self-propelled harvester worked satisfactorily most of the time when there was continuous feeding of kenaf. Occasionally, intermittent feeding of kenaf from the kemper head to the feeder house caused a large bundle of kenaf to pass through the separation unit. This caused breakage of roller chain or bearing housing.
3. Signi5cance In 1995, a number of farmers joined with other investors to form a company to contract with farmers to grow 100 ha of kenaf in Delaware. The seeds were obtained from Rio Farms, Inc., Monte Alto, Texas, USA. Although planted on only a limited number of acres (100 ha) in 1995, the demand for kenaf has the potential to expand rapidly over the years. As a dryland alternative crop, it could have an impact in Delaware similar to that of grain sorghum. The crop is a non-host crop for soya bean cyst nematode (SCN), making it ideal for soya bean rotations to help control SCN and improve soya bean yields on drought-prone soils. Kenaf is not subject to bird damage as is grain sorghum, making it a suitable rotation crop to soya beans in locations where potential bird damage restricts sorghum production. Also, compared with grain sorghum, kenaf o!ers higher net return on investment, thus improving farm pro"tability. Growers often resist new crops because of their unfamiliarity with the crop's cultural requirements. Research on kenaf is needed to develop local recommendations and to encourage and reassure farmers to grow the crop. Unlike grain sorghum, which was an established crop elsewhere in the country, there is no source in the United States for standard cultural practices for kenaf. Much work is needed to de"ne and re"ne the appropriate cultural practices for kenaf in the state of Delaware in USA.
(4) to modify a production model baler to receive and bale the separated "bre; and (5) to evaluate labour and transportation requirements.
5. Development of machinery A component approach was taken in the design and development of the machinery needed for harvesting whole stalk kenaf, separating the "bre and inner core, and baling the "bre (Fig. 1). The machinery developed was based on existing hay, forage and grain harvesting equipment. Each piece was evaluated as to its e!ectiveness with the kenaf material. This approach was taken to permit the commercial development of a!ordable kenaf harvesting equipment. Time to perform operations was recorded and used to develop e$ciency of production.
5.1. Kenaf ,ber}core separator 5.1.1. Description. The kenaf "bre}core separator was designed using principles already used in the grain cleaning area of a combine. The straw-walker assembly consisting of six units was utilized to provide primary separation of the "bre and core. This assembly was mounted on a frame designed to "t a modi"ed wagon running gear. The frame was attached to the running gear on both sides at the front by use of pivot points. This allowed the slope of the straw-walker to be changed. The rear of the frame was free #oating to allow for hydraulic cylinders to be installed on each side to provide for the slope change. The individual straw-walker units were modi"ed to provide speci"c placement of the core material in the core area. This was performed by cutting extended openings in the bottom of the straw-walkers and installing de#ectors to direct the core material to the centre of the core area.
4. Objectives The speci"c objectives of this project were: (1) to demonstrate the concept of a component approach to harvesting and separating the kenaf "bre and core; (2) to modify existing forage machines to harvest the kenaf plant; (3) to develop a machine to separate the kenaf "bre and core utilizing production machine components;
Fig. 1. Field arrangement for xbre}core separator
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K EN A F H A RV ES TI N G TEC H N O LO G Y
Table 1 Model numbers, speeds, 6ow rates and pressures of pumps and motors used on kenaf 5ber+core separator Hydraulic unit Pump Straw-walker motor Cross auger and Unloading auger Feed conveyor
Pressure, MPa
Capacity, ml rev\1
Rotational speed, min\1
Measured yow, l min\1
26)1 14)4
19)3 116)4
3600 200
49)3 24)6
14)4 14)4
59)0 88)6
400 100
24)6 10)9
The tops of the straw-walkers were modi"ed by putting sections of 12)7 mm expanded metal over the openings to restrict "bre from falling through. To distribute the whole stalk material over a wider area, the sawtoothed feeders were placed on angles. The wagon running gear was modi"ed to accommodate a core area under the straw-walkers. The initial design utilized a sloped bin and a combine harvester grain bin cross auger and unloading auger. A change in design incorporated a canvas and bar conveyer in the centre of the core area. This provided positive feeding of the core to the cross auger. The entire operation of the separator was based on a 9)7 kW power unit. The power unit operated a 68)0 l min\ pump that provided the hydraulic capabilities to power the straw-walkers, canvas-bar conveyer and the cross auger}unloading auger. These individual operations utilized hydraulic motors controlled by spool valves and #ow dividers to provide the desired results. Table 1 lists model numbers, speeds, #ow rates and pressures. 5.1.2. Evaluation The use of a combine harvester straw-walker demonstrated the capabilities of separating core and "bre e!ectively. The speed and angle of the straw-walker assembly were kept similar to those used as it functioned in the combine harvester. The core collection area below the straw-walkers was fabricated using technologies used on combine harvester. Initially the core was collected in a hopper below the straw-walker and removed by a combine harvester grain bin cross and unloading auger. This collection area proved unsatisfactory as material would build up, bridge and not move to the auger. To correct this problem, the bottom of the straw-walkers, near the front rock shaft, were cut and de#ectors added to make the core material drop over the cross auger (Fig. 2). A canvas and bar conveyor was also added to keep the material moving to the cross auger (Fig. 3). The canvas and bar conveyer below the straw-walker were suitable for movement of the core; however, problems did occur with "ne, damp
Fig. 2. Bottom of straw-walker at rearward deyectors
Fig. 3. Core area conveyor with side shielding removed
"bre. Damp "bre clinging to the canvas would migrate to the chain, sprockets and inside of the canvas. All this build-up increased the power to operate the conveyer. This condition improved by providing an exit door for the "ne "bre and dirt. A modi"cation that will correct this problem completely is the utilization of the open conveyer chain and bar con"guration used on a forage
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Fig. 4. Slug of xbre that entered core area
Fig. 6. Wet material poorly separated
wagon. This principle worked well for moving the material without wrapping or plugging in the forage wagon and could be incorporated into the core area. The cross auger and elevating auger worked well as long as the "bre content in the core was not in large balls. Problems occurred when large balls of "bre fell forward on the straw-walker and entered the core area under the straw-walkers creating plugging of the augers (Fig. 4). This would also happen if built-up "bre along the sides of the core area break free and enter as a slug load. The use of sections of 12)7 mm expanded metal on the top front half of the straw-walker helped to reduce the amount of small "bre entering the core area (Fig. 5). By placing the saw-toothed feeders on angles the whole stalk material was spread more uniformly across the separating area providing better #ow and reduced "bres falling through into the core area. This was not a continuous problem and can be corrected by shielding to prevent bundles of "bre from entering the core area.
Wet material proved to be the greatest challenge as it did not separate or #ow well (Fig. 6). This material also created problems at the cleaning and bagging facility. The wet core would generate condensation in the bags creating an undesirable product. The solution was not to try harvesting until the crop was dry. All things considered, the component approach used worked well for a small scale prototype machine. To expand the "bre}core separating capacity, the entire rear section of a combine has great potential. A cleaner core and "bre are possible, with the strawwalkers, fan, shoe sieves (upper and lower), return grain auger and clean grain auger. There is also the potential for separating the large and small cores through adjustment of the upper and lower shoe sieves.
Fig. 5. Fibre in core area of straw-walker when extended metal was not used
5.2. Forage harvester and rowcrop attachment 5.2.1. Description The New Holland model 718 forage harvester was a trailed, power take-o! powered unit. It was designed as a cut and direct throw machine. The length of cut was determined by the material feeding rate and number of knives on the cutter head. The machine was developed to process a wide variety of crops and provide a uniform end product. The New Holland model 824 rowcrop attachment was a low pro"le unit designed to "t the model 718 forage harvester. The unit uses rotary sickles to cut the crop and butt-grip-type gathering chains to convey it to the forage harvester feeder rolls. 5.2.2. Evaluation The New Holland model 718 harvester with New Holland model 824 rowcrop attachment worked extremely well for harvesting kenaf. Only one minor modi"cation
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K EN A F H A RV ES TI N G TEC H N O LO G Y
Table 2 Length of cut for selected number of knives and gearing combination of feed rolls No of teeth on feed roll Length of cut, sprockets mm ¹est 1 2
Knives
Front
Rear
3 6
30 30
24 24
Table 3 Time requirements for three sites; site A=one person, one tractor, one forage wagon, one trailer; site B=two people, one tractor, one forage wagon, one trailer; site C=two people, two tractors, two forage wagons, one trailer (time based on three 14)2 m3 capacity forage wagons required to 5ll a trailer) Time required, h
35)0 25)4
was made to the 718 harvester. The entire unit was taken from the maximum height clearance to the minimum (di!erence of 114)3 mm) and lowered by 50)8 mm. This reduced the slope on the header and provided for cutting the material 50)8 mm closer to the soil. This resulted in a 76)2}101)6 mm stubble versus a 127}152)4 mm stubble left in the "eld. The harvester was also tested to determine the best length of cut for processing the kenaf "bre and core (Table 2). Combination of six knives with 30 forward and 24 rear tooth sprocket con"guration for the feed rolls proved to be the best as a 25)4 mm product was produced. This worked very well for core and "bre separation and provided a desirable core size that did not require further size reduction before cleaning and bagging. The cut and throw approach of the 718 harvester worked well without problems. Di!erent forage harvesters used in other aspects of the kenaf harvest experienced problems with the core and "bre plugging the machines. This was primarily due to the cross auger and blower wrapping with "bre. However, feeder plugging and "bre wrapping at the header also occurred on several of these machines. The model 824 rowcrop attachment performed well considering one 4 ha "eld was drilled on 533)4 mm row centres (site A, Table 3) and another 2 ha "eld was drilled on 254 mm row centres (site B, Table 3). These were not the most desirable conditions for a unit designed for 762 mm row centres. Under these conditions, harvest speed was limited to 3)22}4)02 km h\ to permit feeding and prevent breaking and lodging of the kenaf stalks. This resulted in a harvest rate less than 0)4 ha h\. Another 2 ha "eld was planted on 762 mm row centres (site C, Table 3) and provided more realistic testing of the unit. Speeds in the range of 4)83}6)44 km h\ were easily obtained without lodging or plugging problems. Harvest rate exceeded 0)54 ha h\ at these speeds. The only real problem experienced with the unit was an out-of-tolerance rotary sickle on the right feeder unit. This was also towards the unharvested "eld side of the harvester. Poor cutting and feeding would result in
Operation Harvest Wagon unload Separate "bre}core Load trailer Transport and return
Site A
Site B
Site C
2)00 1)25 7)50 3)25 4)50
1)40 0)75 0)00 2)25 4)20
1)10 0)75 0)00 2)40 5)25
lodging or slug loading of the feeder unit. When this condition was corrected the unit performed as expected. All factors considered, performance of the 718 harvester and 824 rowcrop attachment was very acceptable.
5.3. Forage wagons 5.3.1. Description The New Holland model 816 forage wagon was a 540 min\, p.t.o.-powered}covered wagon with a capacity of 23)7 m. The unit had a two-speed drive for the deck chain that could supply material at 0)9 or 2)2 m min\ at a p.t.o. speed of 540 min\. The model 500 Meyer contained an optional hydraulic drive package. This eliminated the need for a p.t.o. power source. The wagon was uncovered and had a capacity of 14)16 m. 5.3.2. Evaluation The New Holland forage wagon that was used to collect the harvested material worked very well. This unit did not exhibit any problems with "bre wrapping on gears, chains or shafts. No modi"cations were made to this unit. The only disadvantage of using this unit was that it required a p.t.o. driver. In order to operate the unloading and baling during separation two tractors were required. A baler with a power unit would eliminate this problem. A second forage wagon was used and proved to work into the component system concept very well. This machine was a hydraulically operated Meyer. The unit was powered by the tractor operating the baler and was connected in series with the elevator loading the separated core into the truck. Because of the low density of whole stalk kenaf, 1)1}1)4 t of material would "ll the wagons. This was equivalent to 0)13 ha harvested, based on 1996 yield.
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L. J . K EM B L E E ¹ A ¸.
5.4. Baler 5.4.1. Description The New Holland model 575 square baler was used to bale the kenaf "bre. This baler had a 1)9 m wide pick-up containing 156 teeth on six bars to feed material into the baler operating at 540 p.t.o. speed provided 93 strokes per minute with a 0)76 m stroke of the plunger. The baler was equipped as a twine unit capable of producing 0)36 m by 0)46 m bales in varying densities. A recommended minimum of 56 p.t.o. kW tractor was needed to power the baler. 5.4.2. Evaluation The 575 baler demonstrated the ability to bale kenaf "bre. The only modi"cation made to the unit was to remove the pick-up wind guard. The baling operation was performed stationary with the baler pick-up located directly beneath the rear of the straw-walker. Fibre exiting the straw-walker fell onto the pick-up and was moved to the cross feed and bale chamber. Two minor problems arose in this feeding section. The "rst problem involved rusty and bent pick-up "ngers. Kenaf "bre was sticking to the "ngers and was pulled into the pick-up unit. After the "ngers were straightened and polished this became a minimal concern. The second problem was due to not feeding the baler enough material. This would result in non-uniform bales (Fig. 7). When material #ow was increased the bale uniformity improved (Fig. 8). Other than these problems, which were corrected, the baler worked well.
Fig. 8. Kenaf xbre after adjustments and increasing feeding rate
Testing kenaf harvesting and separating through a component system approach has been bene"cial in isolating the components that work well with the crop.
Strengths and weaknesses were quickly identi"ed with this approach. During the preliminary research on the kenaf crop and 6 months into the project, the emphasis was placed on clean "bre. As this was viewed as the primary money maker of the kenaf crop, cleanliness was important. The core material during this same period was viewed as a product of low value. However, after the design and major aspects of fabrication had been completed the demand changed. Clean core requiring very little to no size modi"cation took priority over the "bre. This possibility was considered during the design process, but budgets prevented providing a totally dirt-free core. A compromise was reached producing a clean "bre and sized core with acceptable dirt levels for minimal secondary processing (Figs 8 and 9). On testing the component system, some important cost considerations began to emerge. One such consideration was transportation cost. The need to separate the core and "bre on-site became apparent when the trucking requirements of
Fig. 7. Bales of kenaf xbre before baler adjustment
Fig. 9. Separated core
6. Discussion
K EN A F H A RV ES TI N G TEC H N O LO G Y
whole material was considered. Each forage wagon load contained 1)1}1)4 t of whole material ("bre and core) and three forage wagon loads would "t, if packed by walking on material, in a 7)9 m dump bodied trailer. Yields were ranging from 6)7 to 11)2 t ha\. Considering that 9 t ha\ yield would "ll one trailer, the trucking costs at 200 US dollars a round trip (167 km) could become prohibitive for transporting the mixture of "bre and core. Separating the "bre and core in the "eld would permit twice as much core to be shipped per trip, cutting the transportation cost in half. One "eld evaluation demonstrated this fact. Two and a half (2)5) forage wagons of whole material were separated and the core only put in a six-wheeled truck with a 4)0 m by 2)3 m grain body. The truck was "lled to a level height of 1)22 m. This was equal to 11)15 m of core. The 7)9 m dump trailers used to transport the "bre}core mixture had a 32)26 m capacity. This would permit 2)89 times the capacity of the six-wheeled truck of the separated core from 7)23 forage wagon loads of whole stalk material ("bre}core) to be transported in one 7)9 m trailer. This would result in considerable transportation savings. A time study of the harvesting was conducted at three di!erent locations (Table 3). The "rst two (sites A and B) required very similar times for the various operations when two people were involved. The times reported in Table 3 show the variation when one person instead of two people performed the operation. These operations included chopping kenaf, blowing it into a forage wagon, unloading the forage wagon, "eld separating "bre and core, elevating material into truck, packing material in truck and transporting material to processing facility. Both sites were planted with a grain drill that did not match the harvester spacing. Site A was drilled on 0)533 m row centres while site B was drilled on 0)254 m row centres. The time requirements for "eld separation were greater than harvest capabilities. With the small scale prototype "bre}core separator unit, separation of core in the "eld required 2)5 h for one forage wagon fully loaded to 1)36 t of mixture. The time was based from start-up to clean-up. This resulted in a little more than 0)4 ha per day being separated. In order to maintain separating capacity with the rate of harvest the unit needs to meet the minimum demand of tripled capacity. All of the preceding tests were performed using one wagon, one tractor and one forage chopper. This required a lot of hitching}unhitching of equipment and hydraulics resulting in lost time and decreased e$ciency. The third location (site C) of harvest did not provide access to the truck-trailer or module maker for the kenaf "eld. The distance from the "eld to the trailer}module maker was 0)644 km. Planter spacing did match the harvester spacing. In this operation, three tractors, two
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wagons and two persons were required. One person harvested while the other emptied wagons and compacted material into the trailer or module maker. When the entire day's harvest for the third location (site C) was evaluated, the time required to harvest}unload}return to harvest was 26 per cent less than the harvest of drilled kenaf (site A) using one tractor and one person. In all cases the time to harvest was greater than that of transporting and unloading wagons. Harvesting and "lling trailers for transport to the separating facility was signi"cantly faster than round trip time of trucks. A second driver and third and fourth trailer would have o!set the downtime but would also have increased the transportation cost.
7. Conclusions (1) The component approach system proved to work very well. The forage harvester, forage wagon, and baler were very adaptable to the kenaf harvest. (2) Harvest e!ectiveness and "eld e$ciency greatly improved when crop was planted on spacing dictated by harvesting equipment. (3) The separator did an excellent job in providing goodquality clean "bre. This was the design criteria for the unit. However, when greater demand was placed on good-quality core this demand was also achieved. The concepts of a straw-walker conveyer and auger system proved to be e!ective. The major limitation was capacity which was realized during design and fabrication. The width of the cross auger limited the width of the straw-walkers from six units to four. Expanding the auger width will greatly improve capacity. (4) The "eld time studies have dictated that the separating capacity needs to be at least tripled in order to keep ahead of harvesting rates. (5) In two studies a hydraulically operated forage wagon was used. This allowed the entire operation to be performed with one tractor. The tractor p.t.o. operated the baler and the tractor hydraulics were connected in series to operate the forage wagon and elevator. This worked well but required a lot of hitching and unhitching of equipment. (6) When transport time and cost to the separating facility was considered "eld separating became more desirable. Using two 32)28 m dump trailers would leave a minimum of 2 h between second trailer "ll before the "rst returned. This was due to transport and unloading time at the separating facility. The cost of transport of mixture of kenaf core and "bre also proved to be a consideration. Separated core transporting costs were less than half of the whole stalk.
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L. J . K EM B L E E ¹ A ¸.
This was due to the low density of whole stalk versus separated core. (7) For on-site use of the kenaf core, a portable separator has an advantage over the cost of trucking o!-site for processing and returning for use. (8) Research needs to be continued on the portable separator to determine whether the bene"ts of on-site separation will outweigh the transportation requirements. Acknowledgements A sincere thank you is extended to the following for their support of this project: Delaware Department of Agriculture, New Holland North America, Inc., Baker Farms, Cynthia W. Timko, Robert Uniatowski, Richard, W. Taylor, and First Farm Fibers Inc. References Byrom M (1958). Some results of engineering research on kenaf. In: Proceedings of World Conference on Kenaf, Havana, Cuba, pp 197}208
Byrom M (1964). Progress in the mechanical production of kenaf "ber. In: Proceedings Second International Kenaf, Conference, Palm Beach, FL, USA, pp 86}92 Chen L H; Pote J W (1994). In-"eld separation of kenaf. In: A Summary of Kenaf Production and Product Development Research 1989}1993 (Goforth C E; Fuller M J, eds), Mississippi Agricultural and Forestry Experiment Station Bulletin, No. 1011, pp 19}20. Mississippi State University, Mississippi, USA Dempsey J M (1975). Packaging "ber crops. In: Fiber Crops, A University of Florida Book, pp 243}257. Printed by Rose Printing Company, Tallahassee, FL, USA (ISBN 0-81300449-7) Fuller M J; Doler J C (1993). An economic analysis of kenaf separation. In: Proceedings 1993 International Kenaf Conference, Fresno, CA, USA, pp 97}101 Werber F X; Andrews B K (1995). In-"eld "ber separation. In: Applications and Processing of Kenaf. Progress Report No. 4, pp 3}4. United States Department of Agriculture*ARS, National Program Sta!, Beltsville, MD, USA February White G A; Martin J A; Cummins D G; Killinger G B; Whiteley E L; Higgins J J; Fike W T; Clark T F; Greig J K (1976). Harvesting handling, and storage. In: Cultural and Harvesting Methods for Kenaf2. An Annual Crop Source of Pulp in the Southeast. Production Research Report No. 113, pp 26}30. USDA-ARS, Washington, DC. USA April
Development and Evaluation of Kenaf Harvesting Technology L. J. Kemble; P. Krishnan; K. J. Henning; H. D. Tilmon Bioresources Engineering Department, 264 Townsend Hall, University of Delaware, Newark, DE 19717-1303, USA Food and Resource Economics Department, 212 Townsend Hall, University of Delaware, Newark, DE 19717-1303, USA, e-mail of corresponding author: [email protected] (Received 7 November 2000; accepted in revised form 7 September 2001; published online 14 November 2001)
Laboratory and "eld tests have demonstrated that a component approach to harvesting kenaf and separating the "bre and core has a lot of potential. Machines used for harvesting kenaf required only minor, if any, modi"cation. The straw-walker from a combine harvester proved to work very well to separate the kenaf "bre and core. More work needs to be performed to expand the prototype separator into a production unit. Transportation of the whole stalk material from "eld sites to the processing facility proved to be expensive due to the low density of the material. In-"eld separation could reduce this cost by 50 per cent. 2002 Silsoe Research Institute
White et al. (1976) have summarized the work carried out on harvesting, handling and storage of kenaf in the United States. Although there are several possible harvesting methods (#ail choppers and binders), chopping the air-dried crop with a forage chopper appeared the most feasible. Regular farm balers did not satisfactorily bale "nely chopped kenaf. However, no attempt was made to bale long chopped material. Fuller and Doler (1993) mention that at least three "bre-separation systems are currently being used in the United States. These systems include: (1) a design by Harold Willett of Jeanrette, Louisiana, USA; (2) a modi"ed gin concept developed by Gordon Fisher of Agro-Fibers, Inc. of Corcoran, California, USA; and (3) a rotating driven concept marketed by the Lummus Development Corporation of Columbus, Georgia, USA. However, published information is very limited on these systems. Chen and Pote (1994) developed an in-"eld separator of kenaf based on a prototype from Tainan Fibre Crops Experiment Station in Taiwan in 1975. The whole kenaf stalk is fed into the machine comprising crusher- and beater-rollers. The crusher-rollers crush the stalk and the beater-rollers separate the bast "bre from the core. The whole length bast "bre is the end product. Also, they modi"ed a John Deere combine harvester. The
1. Introduction Kenaf (Hibiscus cannabinus L.) has the potential to be an alternative crop to be used as a rotation crop with other dryland crops. Kenaf contains two basic components: bast "bres in the outer bark and an inner core of short xylem "bres. The high-value bast "bre can be sold for paper manufacturing, either locally or for export to the Far East. The inner core can be retained either by the farmer for on-farm use as animal bedding or for processing in other markets, such as for horse bedding.
2. Review of literature In the 1950s and early 1960s the US Department of Agriculture (USDA) carried out an extensive &R&D' programme on kenaf in Florida and Cuba (Byrom, 1958, 1964; Werber & Andrews, 1995). Dempsey (1975) summarized the work carried out at the Everglades Experiment Station towards the development of a kenaf harvester}ribboner and a mechanized system for netting, working, and drying of the "bre. This "eld harvester}ribboner continued to be modi"ed and improved until the "bre crop operations were discontinued in 1965. 1537-5110/02/010049#08 $35.00/0
49
2002 Silsoe Research Institute
50
L. J . K EM B L E E ¹ A ¸.
separation unit was built to "t in the combine harvester. A Kemper head and a feeder house of a forage harvester were attached to the front of the separation unit. The self-propelled harvester worked satisfactorily most of the time when there was continuous feeding of kenaf. Occasionally, intermittent feeding of kenaf from the kemper head to the feeder house caused a large bundle of kenaf to pass through the separation unit. This caused breakage of roller chain or bearing housing.
3. Signi5cance In 1995, a number of farmers joined with other investors to form a company to contract with farmers to grow 100 ha of kenaf in Delaware. The seeds were obtained from Rio Farms, Inc., Monte Alto, Texas, USA. Although planted on only a limited number of acres (100 ha) in 1995, the demand for kenaf has the potential to expand rapidly over the years. As a dryland alternative crop, it could have an impact in Delaware similar to that of grain sorghum. The crop is a non-host crop for soya bean cyst nematode (SCN), making it ideal for soya bean rotations to help control SCN and improve soya bean yields on drought-prone soils. Kenaf is not subject to bird damage as is grain sorghum, making it a suitable rotation crop to soya beans in locations where potential bird damage restricts sorghum production. Also, compared with grain sorghum, kenaf o!ers higher net return on investment, thus improving farm pro"tability. Growers often resist new crops because of their unfamiliarity with the crop's cultural requirements. Research on kenaf is needed to develop local recommendations and to encourage and reassure farmers to grow the crop. Unlike grain sorghum, which was an established crop elsewhere in the country, there is no source in the United States for standard cultural practices for kenaf. Much work is needed to de"ne and re"ne the appropriate cultural practices for kenaf in the state of Delaware in USA.
(4) to modify a production model baler to receive and bale the separated "bre; and (5) to evaluate labour and transportation requirements.
5. Development of machinery A component approach was taken in the design and development of the machinery needed for harvesting whole stalk kenaf, separating the "bre and inner core, and baling the "bre (Fig. 1). The machinery developed was based on existing hay, forage and grain harvesting equipment. Each piece was evaluated as to its e!ectiveness with the kenaf material. This approach was taken to permit the commercial development of a!ordable kenaf harvesting equipment. Time to perform operations was recorded and used to develop e$ciency of production.
5.1. Kenaf ,ber}core separator 5.1.1. Description. The kenaf "bre}core separator was designed using principles already used in the grain cleaning area of a combine. The straw-walker assembly consisting of six units was utilized to provide primary separation of the "bre and core. This assembly was mounted on a frame designed to "t a modi"ed wagon running gear. The frame was attached to the running gear on both sides at the front by use of pivot points. This allowed the slope of the straw-walker to be changed. The rear of the frame was free #oating to allow for hydraulic cylinders to be installed on each side to provide for the slope change. The individual straw-walker units were modi"ed to provide speci"c placement of the core material in the core area. This was performed by cutting extended openings in the bottom of the straw-walkers and installing de#ectors to direct the core material to the centre of the core area.
4. Objectives The speci"c objectives of this project were: (1) to demonstrate the concept of a component approach to harvesting and separating the kenaf "bre and core; (2) to modify existing forage machines to harvest the kenaf plant; (3) to develop a machine to separate the kenaf "bre and core utilizing production machine components;
Fig. 1. Field arrangement for xbre}core separator
51
K EN A F H A RV ES TI N G TEC H N O LO G Y
Table 1 Model numbers, speeds, 6ow rates and pressures of pumps and motors used on kenaf 5ber+core separator Hydraulic unit Pump Straw-walker motor Cross auger and Unloading auger Feed conveyor
Pressure, MPa
Capacity, ml rev\1
Rotational speed, min\1
Measured yow, l min\1
26)1 14)4
19)3 116)4
3600 200
49)3 24)6
14)4 14)4
59)0 88)6
400 100
24)6 10)9
The tops of the straw-walkers were modi"ed by putting sections of 12)7 mm expanded metal over the openings to restrict "bre from falling through. To distribute the whole stalk material over a wider area, the sawtoothed feeders were placed on angles. The wagon running gear was modi"ed to accommodate a core area under the straw-walkers. The initial design utilized a sloped bin and a combine harvester grain bin cross auger and unloading auger. A change in design incorporated a canvas and bar conveyer in the centre of the core area. This provided positive feeding of the core to the cross auger. The entire operation of the separator was based on a 9)7 kW power unit. The power unit operated a 68)0 l min\ pump that provided the hydraulic capabilities to power the straw-walkers, canvas-bar conveyer and the cross auger}unloading auger. These individual operations utilized hydraulic motors controlled by spool valves and #ow dividers to provide the desired results. Table 1 lists model numbers, speeds, #ow rates and pressures. 5.1.2. Evaluation The use of a combine harvester straw-walker demonstrated the capabilities of separating core and "bre e!ectively. The speed and angle of the straw-walker assembly were kept similar to those used as it functioned in the combine harvester. The core collection area below the straw-walkers was fabricated using technologies used on combine harvester. Initially the core was collected in a hopper below the straw-walker and removed by a combine harvester grain bin cross and unloading auger. This collection area proved unsatisfactory as material would build up, bridge and not move to the auger. To correct this problem, the bottom of the straw-walkers, near the front rock shaft, were cut and de#ectors added to make the core material drop over the cross auger (Fig. 2). A canvas and bar conveyor was also added to keep the material moving to the cross auger (Fig. 3). The canvas and bar conveyer below the straw-walker were suitable for movement of the core; however, problems did occur with "ne, damp
Fig. 2. Bottom of straw-walker at rearward deyectors
Fig. 3. Core area conveyor with side shielding removed
"bre. Damp "bre clinging to the canvas would migrate to the chain, sprockets and inside of the canvas. All this build-up increased the power to operate the conveyer. This condition improved by providing an exit door for the "ne "bre and dirt. A modi"cation that will correct this problem completely is the utilization of the open conveyer chain and bar con"guration used on a forage
52
L. J . K EM B L E E ¹ A ¸.
Fig. 4. Slug of xbre that entered core area
Fig. 6. Wet material poorly separated
wagon. This principle worked well for moving the material without wrapping or plugging in the forage wagon and could be incorporated into the core area. The cross auger and elevating auger worked well as long as the "bre content in the core was not in large balls. Problems occurred when large balls of "bre fell forward on the straw-walker and entered the core area under the straw-walkers creating plugging of the augers (Fig. 4). This would also happen if built-up "bre along the sides of the core area break free and enter as a slug load. The use of sections of 12)7 mm expanded metal on the top front half of the straw-walker helped to reduce the amount of small "bre entering the core area (Fig. 5). By placing the saw-toothed feeders on angles the whole stalk material was spread more uniformly across the separating area providing better #ow and reduced "bres falling through into the core area. This was not a continuous problem and can be corrected by shielding to prevent bundles of "bre from entering the core area.
Wet material proved to be the greatest challenge as it did not separate or #ow well (Fig. 6). This material also created problems at the cleaning and bagging facility. The wet core would generate condensation in the bags creating an undesirable product. The solution was not to try harvesting until the crop was dry. All things considered, the component approach used worked well for a small scale prototype machine. To expand the "bre}core separating capacity, the entire rear section of a combine has great potential. A cleaner core and "bre are possible, with the strawwalkers, fan, shoe sieves (upper and lower), return grain auger and clean grain auger. There is also the potential for separating the large and small cores through adjustment of the upper and lower shoe sieves.
Fig. 5. Fibre in core area of straw-walker when extended metal was not used
5.2. Forage harvester and rowcrop attachment 5.2.1. Description The New Holland model 718 forage harvester was a trailed, power take-o! powered unit. It was designed as a cut and direct throw machine. The length of cut was determined by the material feeding rate and number of knives on the cutter head. The machine was developed to process a wide variety of crops and provide a uniform end product. The New Holland model 824 rowcrop attachment was a low pro"le unit designed to "t the model 718 forage harvester. The unit uses rotary sickles to cut the crop and butt-grip-type gathering chains to convey it to the forage harvester feeder rolls. 5.2.2. Evaluation The New Holland model 718 harvester with New Holland model 824 rowcrop attachment worked extremely well for harvesting kenaf. Only one minor modi"cation
53
K EN A F H A RV ES TI N G TEC H N O LO G Y
Table 2 Length of cut for selected number of knives and gearing combination of feed rolls No of teeth on feed roll Length of cut, sprockets mm ¹est 1 2
Knives
Front
Rear
3 6
30 30
24 24
Table 3 Time requirements for three sites; site A=one person, one tractor, one forage wagon, one trailer; site B=two people, one tractor, one forage wagon, one trailer; site C=two people, two tractors, two forage wagons, one trailer (time based on three 14)2 m3 capacity forage wagons required to 5ll a trailer) Time required, h
35)0 25)4
was made to the 718 harvester. The entire unit was taken from the maximum height clearance to the minimum (di!erence of 114)3 mm) and lowered by 50)8 mm. This reduced the slope on the header and provided for cutting the material 50)8 mm closer to the soil. This resulted in a 76)2}101)6 mm stubble versus a 127}152)4 mm stubble left in the "eld. The harvester was also tested to determine the best length of cut for processing the kenaf "bre and core (Table 2). Combination of six knives with 30 forward and 24 rear tooth sprocket con"guration for the feed rolls proved to be the best as a 25)4 mm product was produced. This worked very well for core and "bre separation and provided a desirable core size that did not require further size reduction before cleaning and bagging. The cut and throw approach of the 718 harvester worked well without problems. Di!erent forage harvesters used in other aspects of the kenaf harvest experienced problems with the core and "bre plugging the machines. This was primarily due to the cross auger and blower wrapping with "bre. However, feeder plugging and "bre wrapping at the header also occurred on several of these machines. The model 824 rowcrop attachment performed well considering one 4 ha "eld was drilled on 533)4 mm row centres (site A, Table 3) and another 2 ha "eld was drilled on 254 mm row centres (site B, Table 3). These were not the most desirable conditions for a unit designed for 762 mm row centres. Under these conditions, harvest speed was limited to 3)22}4)02 km h\ to permit feeding and prevent breaking and lodging of the kenaf stalks. This resulted in a harvest rate less than 0)4 ha h\. Another 2 ha "eld was planted on 762 mm row centres (site C, Table 3) and provided more realistic testing of the unit. Speeds in the range of 4)83}6)44 km h\ were easily obtained without lodging or plugging problems. Harvest rate exceeded 0)54 ha h\ at these speeds. The only real problem experienced with the unit was an out-of-tolerance rotary sickle on the right feeder unit. This was also towards the unharvested "eld side of the harvester. Poor cutting and feeding would result in
Operation Harvest Wagon unload Separate "bre}core Load trailer Transport and return
Site A
Site B
Site C
2)00 1)25 7)50 3)25 4)50
1)40 0)75 0)00 2)25 4)20
1)10 0)75 0)00 2)40 5)25
lodging or slug loading of the feeder unit. When this condition was corrected the unit performed as expected. All factors considered, performance of the 718 harvester and 824 rowcrop attachment was very acceptable.
5.3. Forage wagons 5.3.1. Description The New Holland model 816 forage wagon was a 540 min\, p.t.o.-powered}covered wagon with a capacity of 23)7 m. The unit had a two-speed drive for the deck chain that could supply material at 0)9 or 2)2 m min\ at a p.t.o. speed of 540 min\. The model 500 Meyer contained an optional hydraulic drive package. This eliminated the need for a p.t.o. power source. The wagon was uncovered and had a capacity of 14)16 m. 5.3.2. Evaluation The New Holland forage wagon that was used to collect the harvested material worked very well. This unit did not exhibit any problems with "bre wrapping on gears, chains or shafts. No modi"cations were made to this unit. The only disadvantage of using this unit was that it required a p.t.o. driver. In order to operate the unloading and baling during separation two tractors were required. A baler with a power unit would eliminate this problem. A second forage wagon was used and proved to work into the component system concept very well. This machine was a hydraulically operated Meyer. The unit was powered by the tractor operating the baler and was connected in series with the elevator loading the separated core into the truck. Because of the low density of whole stalk kenaf, 1)1}1)4 t of material would "ll the wagons. This was equivalent to 0)13 ha harvested, based on 1996 yield.
54
L. J . K EM B L E E ¹ A ¸.
5.4. Baler 5.4.1. Description The New Holland model 575 square baler was used to bale the kenaf "bre. This baler had a 1)9 m wide pick-up containing 156 teeth on six bars to feed material into the baler operating at 540 p.t.o. speed provided 93 strokes per minute with a 0)76 m stroke of the plunger. The baler was equipped as a twine unit capable of producing 0)36 m by 0)46 m bales in varying densities. A recommended minimum of 56 p.t.o. kW tractor was needed to power the baler. 5.4.2. Evaluation The 575 baler demonstrated the ability to bale kenaf "bre. The only modi"cation made to the unit was to remove the pick-up wind guard. The baling operation was performed stationary with the baler pick-up located directly beneath the rear of the straw-walker. Fibre exiting the straw-walker fell onto the pick-up and was moved to the cross feed and bale chamber. Two minor problems arose in this feeding section. The "rst problem involved rusty and bent pick-up "ngers. Kenaf "bre was sticking to the "ngers and was pulled into the pick-up unit. After the "ngers were straightened and polished this became a minimal concern. The second problem was due to not feeding the baler enough material. This would result in non-uniform bales (Fig. 7). When material #ow was increased the bale uniformity improved (Fig. 8). Other than these problems, which were corrected, the baler worked well.
Fig. 8. Kenaf xbre after adjustments and increasing feeding rate
Testing kenaf harvesting and separating through a component system approach has been bene"cial in isolating the components that work well with the crop.
Strengths and weaknesses were quickly identi"ed with this approach. During the preliminary research on the kenaf crop and 6 months into the project, the emphasis was placed on clean "bre. As this was viewed as the primary money maker of the kenaf crop, cleanliness was important. The core material during this same period was viewed as a product of low value. However, after the design and major aspects of fabrication had been completed the demand changed. Clean core requiring very little to no size modi"cation took priority over the "bre. This possibility was considered during the design process, but budgets prevented providing a totally dirt-free core. A compromise was reached producing a clean "bre and sized core with acceptable dirt levels for minimal secondary processing (Figs 8 and 9). On testing the component system, some important cost considerations began to emerge. One such consideration was transportation cost. The need to separate the core and "bre on-site became apparent when the trucking requirements of
Fig. 7. Bales of kenaf xbre before baler adjustment
Fig. 9. Separated core
6. Discussion
K EN A F H A RV ES TI N G TEC H N O LO G Y
whole material was considered. Each forage wagon load contained 1)1}1)4 t of whole material ("bre and core) and three forage wagon loads would "t, if packed by walking on material, in a 7)9 m dump bodied trailer. Yields were ranging from 6)7 to 11)2 t ha\. Considering that 9 t ha\ yield would "ll one trailer, the trucking costs at 200 US dollars a round trip (167 km) could become prohibitive for transporting the mixture of "bre and core. Separating the "bre and core in the "eld would permit twice as much core to be shipped per trip, cutting the transportation cost in half. One "eld evaluation demonstrated this fact. Two and a half (2)5) forage wagons of whole material were separated and the core only put in a six-wheeled truck with a 4)0 m by 2)3 m grain body. The truck was "lled to a level height of 1)22 m. This was equal to 11)15 m of core. The 7)9 m dump trailers used to transport the "bre}core mixture had a 32)26 m capacity. This would permit 2)89 times the capacity of the six-wheeled truck of the separated core from 7)23 forage wagon loads of whole stalk material ("bre}core) to be transported in one 7)9 m trailer. This would result in considerable transportation savings. A time study of the harvesting was conducted at three di!erent locations (Table 3). The "rst two (sites A and B) required very similar times for the various operations when two people were involved. The times reported in Table 3 show the variation when one person instead of two people performed the operation. These operations included chopping kenaf, blowing it into a forage wagon, unloading the forage wagon, "eld separating "bre and core, elevating material into truck, packing material in truck and transporting material to processing facility. Both sites were planted with a grain drill that did not match the harvester spacing. Site A was drilled on 0)533 m row centres while site B was drilled on 0)254 m row centres. The time requirements for "eld separation were greater than harvest capabilities. With the small scale prototype "bre}core separator unit, separation of core in the "eld required 2)5 h for one forage wagon fully loaded to 1)36 t of mixture. The time was based from start-up to clean-up. This resulted in a little more than 0)4 ha per day being separated. In order to maintain separating capacity with the rate of harvest the unit needs to meet the minimum demand of tripled capacity. All of the preceding tests were performed using one wagon, one tractor and one forage chopper. This required a lot of hitching}unhitching of equipment and hydraulics resulting in lost time and decreased e$ciency. The third location (site C) of harvest did not provide access to the truck-trailer or module maker for the kenaf "eld. The distance from the "eld to the trailer}module maker was 0)644 km. Planter spacing did match the harvester spacing. In this operation, three tractors, two
55
wagons and two persons were required. One person harvested while the other emptied wagons and compacted material into the trailer or module maker. When the entire day's harvest for the third location (site C) was evaluated, the time required to harvest}unload}return to harvest was 26 per cent less than the harvest of drilled kenaf (site A) using one tractor and one person. In all cases the time to harvest was greater than that of transporting and unloading wagons. Harvesting and "lling trailers for transport to the separating facility was signi"cantly faster than round trip time of trucks. A second driver and third and fourth trailer would have o!set the downtime but would also have increased the transportation cost.
7. Conclusions (1) The component approach system proved to work very well. The forage harvester, forage wagon, and baler were very adaptable to the kenaf harvest. (2) Harvest e!ectiveness and "eld e$ciency greatly improved when crop was planted on spacing dictated by harvesting equipment. (3) The separator did an excellent job in providing goodquality clean "bre. This was the design criteria for the unit. However, when greater demand was placed on good-quality core this demand was also achieved. The concepts of a straw-walker conveyer and auger system proved to be e!ective. The major limitation was capacity which was realized during design and fabrication. The width of the cross auger limited the width of the straw-walkers from six units to four. Expanding the auger width will greatly improve capacity. (4) The "eld time studies have dictated that the separating capacity needs to be at least tripled in order to keep ahead of harvesting rates. (5) In two studies a hydraulically operated forage wagon was used. This allowed the entire operation to be performed with one tractor. The tractor p.t.o. operated the baler and the tractor hydraulics were connected in series to operate the forage wagon and elevator. This worked well but required a lot of hitching and unhitching of equipment. (6) When transport time and cost to the separating facility was considered "eld separating became more desirable. Using two 32)28 m dump trailers would leave a minimum of 2 h between second trailer "ll before the "rst returned. This was due to transport and unloading time at the separating facility. The cost of transport of mixture of kenaf core and "bre also proved to be a consideration. Separated core transporting costs were less than half of the whole stalk.
56
L. J . K EM B L E E ¹ A ¸.
This was due to the low density of whole stalk versus separated core. (7) For on-site use of the kenaf core, a portable separator has an advantage over the cost of trucking o!-site for processing and returning for use. (8) Research needs to be continued on the portable separator to determine whether the bene"ts of on-site separation will outweigh the transportation requirements. Acknowledgements A sincere thank you is extended to the following for their support of this project: Delaware Department of Agriculture, New Holland North America, Inc., Baker Farms, Cynthia W. Timko, Robert Uniatowski, Richard, W. Taylor, and First Farm Fibers Inc. References Byrom M (1958). Some results of engineering research on kenaf. In: Proceedings of World Conference on Kenaf, Havana, Cuba, pp 197}208
Byrom M (1964). Progress in the mechanical production of kenaf "ber. In: Proceedings Second International Kenaf, Conference, Palm Beach, FL, USA, pp 86}92 Chen L H; Pote J W (1994). In-"eld separation of kenaf. In: A Summary of Kenaf Production and Product Development Research 1989}1993 (Goforth C E; Fuller M J, eds), Mississippi Agricultural and Forestry Experiment Station Bulletin, No. 1011, pp 19}20. Mississippi State University, Mississippi, USA Dempsey J M (1975). Packaging "ber crops. In: Fiber Crops, A University of Florida Book, pp 243}257. Printed by Rose Printing Company, Tallahassee, FL, USA (ISBN 0-81300449-7) Fuller M J; Doler J C (1993). An economic analysis of kenaf separation. In: Proceedings 1993 International Kenaf Conference, Fresno, CA, USA, pp 97}101 Werber F X; Andrews B K (1995). In-"eld "ber separation. In: Applications and Processing of Kenaf. Progress Report No. 4, pp 3}4. United States Department of Agriculture*ARS, National Program Sta!, Beltsville, MD, USA February White G A; Martin J A; Cummins D G; Killinger G B; Whiteley E L; Higgins J J; Fike W T; Clark T F; Greig J K (1976). Harvesting handling, and storage. In: Cultural and Harvesting Methods for Kenaf2. An Annual Crop Source of Pulp in the Southeast. Production Research Report No. 113, pp 26}30. USDA-ARS, Washington, DC. USA April