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An alternative to field burning of pruning residues in mountain vineyards
Ecological Engineering 70 (2014) 212–216
Contents lists available at ScienceDirect
Ecological Engineering journal homepage: www.elsevier.com/locate/ecoleng
An alternative to field burning of pruning residues in mountain vineyards Raffaele Spinelli a,∗ , Carolina Lombardini a , Luigi Pari b , Liana Sadauskiene c a
CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy CRA ING, Via della Pascolare 16, Monterotondo Scalo (Roma), Italy c Lithuanian Research Centre for Agriculture and Forestry, Liepu 1 LT-53101 Girionys, Kaunas, Lithuania b
a r t i c l e
i n f o
Article history: Received 14 December 2013 Received in revised form 21 April 2014 Accepted 22 May 2014 Keywords: Baling Energy Harvesting Biomass Cost
a b s t r a c t The Authors tested a new mini-baler system designed for the recovery of pruning residues in vineyards inaccessible to conventional tractors. Under these conditions, growers manually take the residues to the field edge and burn them there. Such practice is expensive, and generates substantial emissions. Use of the new mini-baler system would substitute burning, with significant advantages on air quality and landscape amenity. The system works well, but productivity is low (mean 0.38 t per scheduled machine hour) and baling cost still too high (mean 80 D t−1 ). Productivity can be increased and cost decreased through a better preparation of the residues before collection. Farm use of the baled product may dramatically increase value recovery and is facilitated by the availability of newly designed boilers. The versatility and the small purchase cost of the mini-baler makes it an ideal machine for those cases where labour cost is low and investment capacity is limited. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Vineyards are one of the most adaptable, common and profitable crops in the temperate region. For these reasons, vineyards cover 7.4 million hectares worldwide (FAOSTAT, 2009). Vineyards require annual pruning, which generates a substantial amount of residues, estimated in the range of 1 to 2 t per hectare (Spinelli et al., 2012). Traditionally, pruning residues are disposed through open-air burning, releasing a variety of pollutants (Gonc¸alves et al., 2011). At a landscape level, agricultural burning generates much less pollution than vehicular traffic (Darley et al., 1966), but localized emissions can be substantial, especially for heavy particulate (Keshtkar and Ashbaugh, 2007). Besides, field burning is labourintensive and incurs significant cost (Magagnotti et al., 2009). Therefore, finding some use for orchard pruning residues would turn a disposal problem into a collateral production, with a potential for revenues or reduced management costs (Spinelli and Picchi, 2010). In fact, a number of machine manufacturers are now offering dedicated tractor implements for collecting vineyard pruning
∗ Corresponding author. Tel.: +39 055 5225641; fax: +39 055 5225643. E-mail addresses: [email protected] (R. Spinelli), [email protected] (C. Lombardini), [email protected] (L. Pari), [email protected] (L. Sadauskiene). http://dx.doi.org/10.1016/j.ecoleng.2014.05.023 0925-8574/© 2014 Elsevier B.V. All rights reserved.
residues (Recchia et al., 2009, Spinelli et al., 2010). However, use of these machines requires that the vineyards are accessible to tractors, which is a general characteristic of industrial crops. That is not the case of mountain vineyards, often established on steep terrain with very tight spacing (Queiroz et al., 2008). In fact, mountain viticulture is a widespread form of land use, which often yields renowned high-quality wines (Stanchi et al., 2013) representing a typical example of terroir (Cross et al., 2011). In this case, high product value is matched by high management costs, derived from the technical constraints typical of mountain environments. Mountain viticulture has the specific landscape, ecosystem and cultural values that define it as a “total human ecosystem” (Naveh and Lieberman, 1984). Under these circumstances, standard mainstream engineering solutions may backfire. Problems must be solved through an integrated multi-functional approach, typical of ecological engineering (Mitsch and Jørgensen, 2003). Extending mechanized residue recovery to these vineyards requires developing a light, cultivator-size machine that can negotiate steep terrain and tight turning space, without causing damage to soil or crop. In 2013, CAEB manufacturing (www.caebinternational.it) designed a small residue baler for mounting on light tracked carriers (Fig. 1). The goal of this study was to determine the productivity, fuel consumption and energy efficiency of this new system, used in a typical mountain vineyard, and to compare the results with the mean cost incurred with traditional field burning. If the new system proved
R. Spinelli et al. / Ecological Engineering 70 (2014) 212–216
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The machine used for the trials was the new CAEB 730 CNG minibaler, mounted on a Camisa TP 680 mini-dumper (www.fratellicamisa.it). The TP680 is a carrier powered by a Subaru 10 kW diesel engine and travels on rubber tracks. Machine width is limited to 1.2 m, which allows easy access into tightly spaced vineyards. The total weight of the carrier and the attachment was 1000 kg. The same operator ran the machine for the duration of the trial. This was CAEB’s test driver, who had tested CAEB machines for many years and had much experience with the operation of pruning residue balers.
3. Methods
Fig. 1. The minibaler at work.
functional and cost-effective, it would represent a viable option for the disposal of pruning residues in mountain vineyards using a cleaner and safer method than field burning, and without needing a radical change of crop establishment and management techniques. 2. Materials The test was conducted in March 2013 near Sondrio, in Northern Italy. Sondrio is located in Valtellina, where Nebbiolo grapes have been grown on terraced hills and cliffs since Carolingian times (900 AD). Maximum expansion was reached in the 19th century, when viticulture covered over 6000 ha, located on the hillsides (25%) and on the alluvial plain (75%). After World War II, urbanization and industrial farming occupied most of the plain and the alluvial deposits, where the terrain was flat or moderately inclined. At present, the largest majority of the approximately 2000 ha of vineyards are located on the steepest ground, on man-made terraces, which are generally inaccessible to tractors (De Lorenzis et al., 2012). Modern mechanisation is needed and it may be key for the survival of a valuable cultural landscape. For the purpose of the study, we selected 12 different fields. These were located in different areas and were meant to represent the full range of conditions encountered in Valtellina vineyards. Field characteristics are shown in Table 1, and are characterized by narrow interrow spacing, ranging from 1.8 to 2.9 m. Furthermore, maneuvering space at the field edges was quite tight (<5 m), since the fields were often enclosed by retaining walls.
The study was designed to evaluate system productivity and to identify the most significant variables affecting it. The data collection procedure consisted of a set of detailed time and motion studies conducted at the cycle level, where the harvesting of one bale was considered as a complete cycle. Time consumption was split into time elements considered to be typical of the functional process analyzed, and consisted of harvesting the residues, dumping the bale, turning, driving in and out and delays. This was done with the intent of isolating those parts of the routine that took longer or were especially problematic, so as to target future improvements. All time elements and the related time–motion data were recorded with Husky Hunter® hand-held field computers running Siwork3® time-study software. Time study sessions lasted a total of 11.5 h. Mass output was determined by individually scaling all bales produced during the tests, using portable scales. Moisture content was determined on three samples per plot, according to European standard CEN/TS 14774-2. Row spacing was measured with a tape, whereas the length of row harvested for each run and the distance covered while moving the loads to the collection point were measured with a hip chain. Harvested area was measured with a commercial-grade GPS device. Harvesting losses were estimated on one sample per plot. The sample was obtained by manually collecting all the pruning residues left on the area that had previously yielded one randomly selected bale. Percent losses were then estimated as the ratio of remaining residue weight to bale weight, for each sample. Fuel consumption was estimated by starting each work day with a full tank and refilling the tank at the end of the day. This occurred for three consecutive days. Fuel consumption was related to the hours worked each day.
Table 1 Characteristics of the test fields. Area (m2 )
Slope (%)
Rows (n◦ )
Field (no.)
Placename
1 2 3 4 5 6 7 8 9 10 11 12
San Lorenzo San Lorenzo San Lorenzo La Priora La Priora Morella Morella San Lorenzo San Lorenzo San Lorenzo Singelle Sighezzon
1215 1280 464 1698 1036 955 1266 428 761 945 1090 2114
8 4 7 15 18 10 12 5 7 5 3 3
8.5 11.5 3.0 8.0 12.0 7.0 8.0 7.5 11.0 5.5 6.0 11.5
1.9 1.8 1.8 2.9 2.9 2.2 2.4 2.0 1.9 1.8 2.6 1.9
Mean
1104
8
8.3
2.2
Total
14,356
Notes: m.c—moisture content; odt—oven-dry tonnes.
107.8
Interrow width (m)
Bales (n◦ )
Stock (t ha−1 )
m.c. (%)
Stock (odt ha−1 )
Losses (%)
31 25 5 15 9 17 25 10 18 26 24 46
4.3 3.4 2.1 1.7 1.6 3.0 3.6 3.5 3.5 4.0 3.3 3.2
46.9 46.9 46.9 40.0 40.0 47.3 45.6 45.1 45.1 45.1 41.7 48.4
2.3 1.8 1.1 1.0 1.0 1.6 2.0 1.9 1.9 2.2 2.0 1.7
13 13 13 28 27 20 21 16 7 16 14 21
21
3.1
44.9
1.7
17
272
214
R. Spinelli et al. / Ecological Engineering 70 (2014) 212–216
Table 2 Baling productivity and cost. Field (no.)
Stocking (t ha−1 )
Bale weight (kg)
Productivity Bales PMH−1
Bales SMH−1
t PMH−1
t SMH−1
Hourly cost (D SMH−1 )
Unit cost (D t−1 )
1 2 3 4 5 6 7 8 9 10 11 12
4.3 3.4 2.1 1.7 1.6 3.0 3.6 3.5 3.5 4.0 3.3 3.2
16.8 17.4 19.4 19.5 18.5 16.8 18.4 15.0 14.6 14.5 15.2 14.7
44 33 23 12 11 44 38 30 36 39 35 42
32 24 16 9 8 32 27 22 26 28 25 31
0.74 0.58 0.44 0.24 0.20 0.74 0.69 0.45 0.52 0.56 0.53 0.62
0.53 0.42 0.32 0.17 0.15 0.54 0.50 0.33 0.38 0.40 0.38 0.45
28.7 27.8 26.9 25.9 25.9 28.7 28.2 27.5 28.0 28.2 27.9 28.5
53.9 66.3 83.7 149.5 174.7 53.5 56.2 84.2 73.9 70.1 72.9 63.9
Mean
3.1
16.3
33
23
0.53
0.38
27.7
83.6
Machine rates were calculated as described by Miyata (1980), on an estimated annual utilization of 540 scheduled machine hours (SMH) and a service life of 5000 SMH. The cost of insurance, repair and service were obtained directly from the manufacturer’s best estimates, since the machine was a pre-series and no historical data were available. Fuel cost was assumed to be 1.1 D L−1 , as is customary for farmers who have access to subsidized “red-diesel”. Labour cost was set at 12 D SMH−1 inclusive of indirect salary costs. The calculated operational cost of all teams was increased by 10% to account for overhead costs (Hartsough, 2003), resulting in a total rate of 24.9 D SMH−1 . Both direct and indirect fossil energy use were estimated, using exactly the same methods described in Magagnotti and Spinelli (2011). The energy value of vineyard pruning residues was derived from previous studies, reporting a higher heating value of 18.7 MJ kg−1 (Spinelli et al., 2012). 4. Results Overall, 12 study plots were harvested. These represented a total area of 1.3 ha and yielded 4.1 t of fresh biomass. Total study time amounted to 11.2 h, of which 8.07 h were taken by harvesting, 0.63 h by delays, 1.31 h by preparation and 1.15 h by transfers. Study delays totaled 0.18 h and were excluded from analysis. Productive machine time represented 72% of the total worksite time. The remaining time was taken by transfers (12%), preparation (10%) and delays (6%). Productive machine time was cyclic and was easily allocated to individual plots. In contrast, delays, transfer and preparation times were not cyclic and could not be allocated directly to individual plots. Therefore, direct allocations of productive time were inflated by a factor 1.381, since the overall ratio of non-cyclic times to cyclic productive time was 0.381 to 1. Inflated values were used to calculate productivity per scheduled machine hour (SMH), inclusive of all delays. Within cyclic work time, actual harvesting (i.e. picking up the residues and baling them) represented 55% of the total. Time spent for the actual work steps was related to work conditions, like field
stocking, row length, slope gradient and the space available for turning at the end of the rows. Bale weight varied from 14.5 kg to 19.4 kg, with a mean value of 16.3 kg. Bale weight was inversely proportional to field stocking. The inverse correlation between bale weight and field stocking was strong (R2 = −0.67) and significant (p < 0.05). Mean bale density was 288 kg m−3 . Productivity ranged from 0.20 to 0.74 t per productive machine hour (PMH), or from between 0.15 and 0.54 t per scheduled machine hour (Table 2). Regression analysis revealed the significant influence of field stocking on machine productivity (Table 3). Baling cost varied between 53.5 and 174.7 Euro per green tonne, or between 101.5 and 291.2 Euro per oven dry tonne (odt). That corresponded to 0.9–3.2 Euro per bale. Labour was the main component of overall baling cost (42%). Twine and fuel were also important cost centres, representing 13% and 14% of total cost, respectively. Capital costs accounted for 15% of the total cost, whereas maintenance, insurance and overhead represented the remaining 16%. Mean energy use amounted to 6 MJ per bale, or 761 MJ per odt. The energy output–input ratio was 24.5. Therefore, the baling process required about 4% of the total energy contained in the pruning residues. 5. Discussion The residue yields reported in this study are almost perfectly matched to the figures reported in previous bibliography about pruning residue recovery in Italian vineyards (Laraia et al., 2001; Spinelli et al., 2010; Spinelli et al., 2012; Magagnotti et al., 2013). Concerning harvesting losses, the mini-baler offers a good performance, incurring lower losses than reported by Spinelli et al. (2012) and Magagnotti et al. (2013) for other pruning harvester types. Furthermore, stored bales incur minimal dry matter losses compared to shredded residues, which allows the maximization of the energy potential of vineyards. That is true whether the bales are covered or uncovered, although the covered option is probably safer than
Table 3 Regression model for baling productivity vs. field stocking. Productivity (t SMH−1 ) = a × lnS + b
a b
R2 −0.6759
DF = 10
Estimate
SE
T value
p Value
LCL
UCL
0.4381 0.0485
0.0959 0.1087
4.5662 0.4456
0.001 0.665
0.2243 −0.1936
0.6519 0.2907
Where: S = Field stocking (t ha−1 ); DF = Degrees of freedom; SE = Standard error; LCL = Lower confidence limit; UCL = Upper confidence limit.
R. Spinelli et al. / Ecological Engineering 70 (2014) 212–216
the uncovered one. Easy storage is especially valuable for such a wet fuel, which can be kept in storage until the moisture content has decreased through natural air drying. Nevertheless, harvesting with the mini-baler is very expensive. The baling cost is well above the 15 to 60 D t−1 , reported for fullsize tractor-powered residue harvesters (Magagnotti et al., 2013). Harvesting pruning residues with the mini-baler may not be sustainable in financial terms. The lowest delivered price for industrial biomass fuel can be estimated at 40 D t−1 (Spinelli et al., 2011), and transportation cost at 12 D t−1 . That leaves a margin of 28 D t−1 , which must compensate baling and bale collection. This margin is much smaller than the lowest baling cost recorded in this study, estimated at 53 D t−1 excluding collection. However, field burning incurs a cost in excess of 60 D t−1 , without any associated revenues (Magagnotti et al., 2009). That makes baling a much better option, with a net cost of 25 D t−1 (i.e. 53–28 D t−1 ). Much will depend on the effective organization of bale collection, whose cost may vary from 20 to over 40 D t−1 (Spinelli et al., 2010). Further research should address bale collection cost, and suggest measures for optimizing bale collection under the specific conditions of mountain vineyards. Even so, one wonders if disposal costs could be further reduced. One option is field mulching using cultivator-mounted shredders, which is a common practice with other crops. Unfortunately, mulching can favor the spread of diseases onto healthy vines. Mulched material might provide a food resource for some pathogens, acting as a reservoir for inoculum in the future. Several bacterial pathogens such as Xanthomonas sp. have been shown to survive on wood and stalks buried for several months (Schultz and Gabrielson, 1986; Vu Thanh et al., 2009). The risk associated with field mulching makes baling preferable. Hence the interest in increasing baling efficiency. Baling productivity is proportional to field stocking and could be raised by concentrating pruning residues in alternate rows, which will achieve the same practical effect as doubling the field stocking. This is a simple measure offering substantial benefits. Increasing product value may contribute to improved economic sustainability. Therefore, it may be worth looking for new uses of baled pruning, other than industrial fuel. Particle board industries (Ntalos and Grigoriou, 2002) and filter manufacturers (Ponsà et al., 2009) may offer an alternative, but they are unlikely to offer better prices than industrial energy users. Energy conversion at the farm is probably the best way for the grower to appropriate all added value. To that purpose, one may either re-process the bales by chipping them and feeding the chips to a small-scale automatic boiler, or opt for a simpler and cheaper batch-fed bale burner (Spinelli et al., 2012). In any case, bale value will be proportional to the price of the fuel being substituted, corrected for the different efficiency of the combustion plants. Mountain farms are often outside the reach of natural gas pipe works, and often resort to expensive fuel oil or propane gas. In that case, substitution with baled residues is especially attractive, and it is facilitated by newly designed residue boilers (Picchi et al., 2012). Previous studies have demonstrated that pesticide contamination is not an issue with vineyard pruning residues (Spinelli et al., 2010). Furthermore, the manufacturers believe that the mini-baler is underpowered, and they are working on a special model with a larger 15 kW engine, which is supposedly more productive. It is true that the carrier-mounted mini-baler is much less productive than the standard tractor-powered version. Its gross productivity is at best 0.54 t SMH−1 , which is three times smaller than the mean of 1.7 t SMH−1 recorded for the standard version (Spinelli et al., 2010). Smaller bale size is a handicap, because it results in a higher incidence of tie and dump times. The same applies to the shorter work width, which limits flow through the machine. These factors
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will not be affected by a power increase. However, a stronger engine may improve working speed and baling pressure, with positive effects on productivity. In any case, this machine is specifically designed for steep terrain vineyards, inaccessible to standard farm tractors. Such vineyards are relatively common: many of the most famous wine-producing regions in Europe include sizable tracts where the terrain is too steep and the spacing too narrow for tractor access. The centre for mountain viticulture lists 17 regions from 7 countries among its associates (www.cervim.org), including the producers of Beaujolais, Douro and Mosel wines. In fact, the development of specialized machinery for managing these vineyards is not unusual (Simonis, 2012), and it reflects a general trend when trying to introduce mechanization to steep terrain (Magagnotti et al., 2012). These considerations are valid for industrialized countries only. High baling costs are closely related to the high cost of labour in these countries, which represents over 40% of the total baling cost. For this very same reason, the mini-baler may represent a good machine for any country where labour costs are low, while investment costs are the main hurdle (Ruttan, 2002). The mini-baler is relatively inexpensive to buy, and the tracked carrier can be used for a variety of tasks after disconnecting the baler. The complete unit costs less than a conventional farm tractor, which is often outside the economical reach of farmers in the developing countries (Reardon et al., 2009). Here, baling may offer economical benefits at the farm level, while preventing open-air burning and relieving pressure for fire wood on natural forests (Bhatt and Sachan, 2004). In any case, cost-effective residue disposal is a crucial element for the survival of traditional mountain viticulture, which can only be conserved by use (Martin et al., 2010). Continued use is threatened by declining financial viability, and the increasingly strict regulations against field burning may give it the final blow. Under these circumstances, an ecological engineering approach can offer the best solution, offering both conservation and financial viability (Bergen et al., 2001).
Acknowledgments This project was supported by the Leonardo da Vinci Programme, within the scope of project 510138-LLP-1-2010 “Green Village” and by the COST Action FP0902 within the scope of its 5th STSM programme. Thanks are due to the Fojanini Foundation in Sondrio (www.fondazionefojanini.provincia.so.it) for their support with planning, organization and logistics.
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Contents lists available at ScienceDirect
Ecological Engineering journal homepage: www.elsevier.com/locate/ecoleng
An alternative to field burning of pruning residues in mountain vineyards Raffaele Spinelli a,∗ , Carolina Lombardini a , Luigi Pari b , Liana Sadauskiene c a
CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy CRA ING, Via della Pascolare 16, Monterotondo Scalo (Roma), Italy c Lithuanian Research Centre for Agriculture and Forestry, Liepu 1 LT-53101 Girionys, Kaunas, Lithuania b
a r t i c l e
i n f o
Article history: Received 14 December 2013 Received in revised form 21 April 2014 Accepted 22 May 2014 Keywords: Baling Energy Harvesting Biomass Cost
a b s t r a c t The Authors tested a new mini-baler system designed for the recovery of pruning residues in vineyards inaccessible to conventional tractors. Under these conditions, growers manually take the residues to the field edge and burn them there. Such practice is expensive, and generates substantial emissions. Use of the new mini-baler system would substitute burning, with significant advantages on air quality and landscape amenity. The system works well, but productivity is low (mean 0.38 t per scheduled machine hour) and baling cost still too high (mean 80 D t−1 ). Productivity can be increased and cost decreased through a better preparation of the residues before collection. Farm use of the baled product may dramatically increase value recovery and is facilitated by the availability of newly designed boilers. The versatility and the small purchase cost of the mini-baler makes it an ideal machine for those cases where labour cost is low and investment capacity is limited. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Vineyards are one of the most adaptable, common and profitable crops in the temperate region. For these reasons, vineyards cover 7.4 million hectares worldwide (FAOSTAT, 2009). Vineyards require annual pruning, which generates a substantial amount of residues, estimated in the range of 1 to 2 t per hectare (Spinelli et al., 2012). Traditionally, pruning residues are disposed through open-air burning, releasing a variety of pollutants (Gonc¸alves et al., 2011). At a landscape level, agricultural burning generates much less pollution than vehicular traffic (Darley et al., 1966), but localized emissions can be substantial, especially for heavy particulate (Keshtkar and Ashbaugh, 2007). Besides, field burning is labourintensive and incurs significant cost (Magagnotti et al., 2009). Therefore, finding some use for orchard pruning residues would turn a disposal problem into a collateral production, with a potential for revenues or reduced management costs (Spinelli and Picchi, 2010). In fact, a number of machine manufacturers are now offering dedicated tractor implements for collecting vineyard pruning
∗ Corresponding author. Tel.: +39 055 5225641; fax: +39 055 5225643. E-mail addresses: [email protected] (R. Spinelli), [email protected] (C. Lombardini), [email protected] (L. Pari), [email protected] (L. Sadauskiene). http://dx.doi.org/10.1016/j.ecoleng.2014.05.023 0925-8574/© 2014 Elsevier B.V. All rights reserved.
residues (Recchia et al., 2009, Spinelli et al., 2010). However, use of these machines requires that the vineyards are accessible to tractors, which is a general characteristic of industrial crops. That is not the case of mountain vineyards, often established on steep terrain with very tight spacing (Queiroz et al., 2008). In fact, mountain viticulture is a widespread form of land use, which often yields renowned high-quality wines (Stanchi et al., 2013) representing a typical example of terroir (Cross et al., 2011). In this case, high product value is matched by high management costs, derived from the technical constraints typical of mountain environments. Mountain viticulture has the specific landscape, ecosystem and cultural values that define it as a “total human ecosystem” (Naveh and Lieberman, 1984). Under these circumstances, standard mainstream engineering solutions may backfire. Problems must be solved through an integrated multi-functional approach, typical of ecological engineering (Mitsch and Jørgensen, 2003). Extending mechanized residue recovery to these vineyards requires developing a light, cultivator-size machine that can negotiate steep terrain and tight turning space, without causing damage to soil or crop. In 2013, CAEB manufacturing (www.caebinternational.it) designed a small residue baler for mounting on light tracked carriers (Fig. 1). The goal of this study was to determine the productivity, fuel consumption and energy efficiency of this new system, used in a typical mountain vineyard, and to compare the results with the mean cost incurred with traditional field burning. If the new system proved
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The machine used for the trials was the new CAEB 730 CNG minibaler, mounted on a Camisa TP 680 mini-dumper (www.fratellicamisa.it). The TP680 is a carrier powered by a Subaru 10 kW diesel engine and travels on rubber tracks. Machine width is limited to 1.2 m, which allows easy access into tightly spaced vineyards. The total weight of the carrier and the attachment was 1000 kg. The same operator ran the machine for the duration of the trial. This was CAEB’s test driver, who had tested CAEB machines for many years and had much experience with the operation of pruning residue balers.
3. Methods
Fig. 1. The minibaler at work.
functional and cost-effective, it would represent a viable option for the disposal of pruning residues in mountain vineyards using a cleaner and safer method than field burning, and without needing a radical change of crop establishment and management techniques. 2. Materials The test was conducted in March 2013 near Sondrio, in Northern Italy. Sondrio is located in Valtellina, where Nebbiolo grapes have been grown on terraced hills and cliffs since Carolingian times (900 AD). Maximum expansion was reached in the 19th century, when viticulture covered over 6000 ha, located on the hillsides (25%) and on the alluvial plain (75%). After World War II, urbanization and industrial farming occupied most of the plain and the alluvial deposits, where the terrain was flat or moderately inclined. At present, the largest majority of the approximately 2000 ha of vineyards are located on the steepest ground, on man-made terraces, which are generally inaccessible to tractors (De Lorenzis et al., 2012). Modern mechanisation is needed and it may be key for the survival of a valuable cultural landscape. For the purpose of the study, we selected 12 different fields. These were located in different areas and were meant to represent the full range of conditions encountered in Valtellina vineyards. Field characteristics are shown in Table 1, and are characterized by narrow interrow spacing, ranging from 1.8 to 2.9 m. Furthermore, maneuvering space at the field edges was quite tight (<5 m), since the fields were often enclosed by retaining walls.
The study was designed to evaluate system productivity and to identify the most significant variables affecting it. The data collection procedure consisted of a set of detailed time and motion studies conducted at the cycle level, where the harvesting of one bale was considered as a complete cycle. Time consumption was split into time elements considered to be typical of the functional process analyzed, and consisted of harvesting the residues, dumping the bale, turning, driving in and out and delays. This was done with the intent of isolating those parts of the routine that took longer or were especially problematic, so as to target future improvements. All time elements and the related time–motion data were recorded with Husky Hunter® hand-held field computers running Siwork3® time-study software. Time study sessions lasted a total of 11.5 h. Mass output was determined by individually scaling all bales produced during the tests, using portable scales. Moisture content was determined on three samples per plot, according to European standard CEN/TS 14774-2. Row spacing was measured with a tape, whereas the length of row harvested for each run and the distance covered while moving the loads to the collection point were measured with a hip chain. Harvested area was measured with a commercial-grade GPS device. Harvesting losses were estimated on one sample per plot. The sample was obtained by manually collecting all the pruning residues left on the area that had previously yielded one randomly selected bale. Percent losses were then estimated as the ratio of remaining residue weight to bale weight, for each sample. Fuel consumption was estimated by starting each work day with a full tank and refilling the tank at the end of the day. This occurred for three consecutive days. Fuel consumption was related to the hours worked each day.
Table 1 Characteristics of the test fields. Area (m2 )
Slope (%)
Rows (n◦ )
Field (no.)
Placename
1 2 3 4 5 6 7 8 9 10 11 12
San Lorenzo San Lorenzo San Lorenzo La Priora La Priora Morella Morella San Lorenzo San Lorenzo San Lorenzo Singelle Sighezzon
1215 1280 464 1698 1036 955 1266 428 761 945 1090 2114
8 4 7 15 18 10 12 5 7 5 3 3
8.5 11.5 3.0 8.0 12.0 7.0 8.0 7.5 11.0 5.5 6.0 11.5
1.9 1.8 1.8 2.9 2.9 2.2 2.4 2.0 1.9 1.8 2.6 1.9
Mean
1104
8
8.3
2.2
Total
14,356
Notes: m.c—moisture content; odt—oven-dry tonnes.
107.8
Interrow width (m)
Bales (n◦ )
Stock (t ha−1 )
m.c. (%)
Stock (odt ha−1 )
Losses (%)
31 25 5 15 9 17 25 10 18 26 24 46
4.3 3.4 2.1 1.7 1.6 3.0 3.6 3.5 3.5 4.0 3.3 3.2
46.9 46.9 46.9 40.0 40.0 47.3 45.6 45.1 45.1 45.1 41.7 48.4
2.3 1.8 1.1 1.0 1.0 1.6 2.0 1.9 1.9 2.2 2.0 1.7
13 13 13 28 27 20 21 16 7 16 14 21
21
3.1
44.9
1.7
17
272
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Table 2 Baling productivity and cost. Field (no.)
Stocking (t ha−1 )
Bale weight (kg)
Productivity Bales PMH−1
Bales SMH−1
t PMH−1
t SMH−1
Hourly cost (D SMH−1 )
Unit cost (D t−1 )
1 2 3 4 5 6 7 8 9 10 11 12
4.3 3.4 2.1 1.7 1.6 3.0 3.6 3.5 3.5 4.0 3.3 3.2
16.8 17.4 19.4 19.5 18.5 16.8 18.4 15.0 14.6 14.5 15.2 14.7
44 33 23 12 11 44 38 30 36 39 35 42
32 24 16 9 8 32 27 22 26 28 25 31
0.74 0.58 0.44 0.24 0.20 0.74 0.69 0.45 0.52 0.56 0.53 0.62
0.53 0.42 0.32 0.17 0.15 0.54 0.50 0.33 0.38 0.40 0.38 0.45
28.7 27.8 26.9 25.9 25.9 28.7 28.2 27.5 28.0 28.2 27.9 28.5
53.9 66.3 83.7 149.5 174.7 53.5 56.2 84.2 73.9 70.1 72.9 63.9
Mean
3.1
16.3
33
23
0.53
0.38
27.7
83.6
Machine rates were calculated as described by Miyata (1980), on an estimated annual utilization of 540 scheduled machine hours (SMH) and a service life of 5000 SMH. The cost of insurance, repair and service were obtained directly from the manufacturer’s best estimates, since the machine was a pre-series and no historical data were available. Fuel cost was assumed to be 1.1 D L−1 , as is customary for farmers who have access to subsidized “red-diesel”. Labour cost was set at 12 D SMH−1 inclusive of indirect salary costs. The calculated operational cost of all teams was increased by 10% to account for overhead costs (Hartsough, 2003), resulting in a total rate of 24.9 D SMH−1 . Both direct and indirect fossil energy use were estimated, using exactly the same methods described in Magagnotti and Spinelli (2011). The energy value of vineyard pruning residues was derived from previous studies, reporting a higher heating value of 18.7 MJ kg−1 (Spinelli et al., 2012). 4. Results Overall, 12 study plots were harvested. These represented a total area of 1.3 ha and yielded 4.1 t of fresh biomass. Total study time amounted to 11.2 h, of which 8.07 h were taken by harvesting, 0.63 h by delays, 1.31 h by preparation and 1.15 h by transfers. Study delays totaled 0.18 h and were excluded from analysis. Productive machine time represented 72% of the total worksite time. The remaining time was taken by transfers (12%), preparation (10%) and delays (6%). Productive machine time was cyclic and was easily allocated to individual plots. In contrast, delays, transfer and preparation times were not cyclic and could not be allocated directly to individual plots. Therefore, direct allocations of productive time were inflated by a factor 1.381, since the overall ratio of non-cyclic times to cyclic productive time was 0.381 to 1. Inflated values were used to calculate productivity per scheduled machine hour (SMH), inclusive of all delays. Within cyclic work time, actual harvesting (i.e. picking up the residues and baling them) represented 55% of the total. Time spent for the actual work steps was related to work conditions, like field
stocking, row length, slope gradient and the space available for turning at the end of the rows. Bale weight varied from 14.5 kg to 19.4 kg, with a mean value of 16.3 kg. Bale weight was inversely proportional to field stocking. The inverse correlation between bale weight and field stocking was strong (R2 = −0.67) and significant (p < 0.05). Mean bale density was 288 kg m−3 . Productivity ranged from 0.20 to 0.74 t per productive machine hour (PMH), or from between 0.15 and 0.54 t per scheduled machine hour (Table 2). Regression analysis revealed the significant influence of field stocking on machine productivity (Table 3). Baling cost varied between 53.5 and 174.7 Euro per green tonne, or between 101.5 and 291.2 Euro per oven dry tonne (odt). That corresponded to 0.9–3.2 Euro per bale. Labour was the main component of overall baling cost (42%). Twine and fuel were also important cost centres, representing 13% and 14% of total cost, respectively. Capital costs accounted for 15% of the total cost, whereas maintenance, insurance and overhead represented the remaining 16%. Mean energy use amounted to 6 MJ per bale, or 761 MJ per odt. The energy output–input ratio was 24.5. Therefore, the baling process required about 4% of the total energy contained in the pruning residues. 5. Discussion The residue yields reported in this study are almost perfectly matched to the figures reported in previous bibliography about pruning residue recovery in Italian vineyards (Laraia et al., 2001; Spinelli et al., 2010; Spinelli et al., 2012; Magagnotti et al., 2013). Concerning harvesting losses, the mini-baler offers a good performance, incurring lower losses than reported by Spinelli et al. (2012) and Magagnotti et al. (2013) for other pruning harvester types. Furthermore, stored bales incur minimal dry matter losses compared to shredded residues, which allows the maximization of the energy potential of vineyards. That is true whether the bales are covered or uncovered, although the covered option is probably safer than
Table 3 Regression model for baling productivity vs. field stocking. Productivity (t SMH−1 ) = a × lnS + b
a b
R2 −0.6759
DF = 10
Estimate
SE
T value
p Value
LCL
UCL
0.4381 0.0485
0.0959 0.1087
4.5662 0.4456
0.001 0.665
0.2243 −0.1936
0.6519 0.2907
Where: S = Field stocking (t ha−1 ); DF = Degrees of freedom; SE = Standard error; LCL = Lower confidence limit; UCL = Upper confidence limit.
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the uncovered one. Easy storage is especially valuable for such a wet fuel, which can be kept in storage until the moisture content has decreased through natural air drying. Nevertheless, harvesting with the mini-baler is very expensive. The baling cost is well above the 15 to 60 D t−1 , reported for fullsize tractor-powered residue harvesters (Magagnotti et al., 2013). Harvesting pruning residues with the mini-baler may not be sustainable in financial terms. The lowest delivered price for industrial biomass fuel can be estimated at 40 D t−1 (Spinelli et al., 2011), and transportation cost at 12 D t−1 . That leaves a margin of 28 D t−1 , which must compensate baling and bale collection. This margin is much smaller than the lowest baling cost recorded in this study, estimated at 53 D t−1 excluding collection. However, field burning incurs a cost in excess of 60 D t−1 , without any associated revenues (Magagnotti et al., 2009). That makes baling a much better option, with a net cost of 25 D t−1 (i.e. 53–28 D t−1 ). Much will depend on the effective organization of bale collection, whose cost may vary from 20 to over 40 D t−1 (Spinelli et al., 2010). Further research should address bale collection cost, and suggest measures for optimizing bale collection under the specific conditions of mountain vineyards. Even so, one wonders if disposal costs could be further reduced. One option is field mulching using cultivator-mounted shredders, which is a common practice with other crops. Unfortunately, mulching can favor the spread of diseases onto healthy vines. Mulched material might provide a food resource for some pathogens, acting as a reservoir for inoculum in the future. Several bacterial pathogens such as Xanthomonas sp. have been shown to survive on wood and stalks buried for several months (Schultz and Gabrielson, 1986; Vu Thanh et al., 2009). The risk associated with field mulching makes baling preferable. Hence the interest in increasing baling efficiency. Baling productivity is proportional to field stocking and could be raised by concentrating pruning residues in alternate rows, which will achieve the same practical effect as doubling the field stocking. This is a simple measure offering substantial benefits. Increasing product value may contribute to improved economic sustainability. Therefore, it may be worth looking for new uses of baled pruning, other than industrial fuel. Particle board industries (Ntalos and Grigoriou, 2002) and filter manufacturers (Ponsà et al., 2009) may offer an alternative, but they are unlikely to offer better prices than industrial energy users. Energy conversion at the farm is probably the best way for the grower to appropriate all added value. To that purpose, one may either re-process the bales by chipping them and feeding the chips to a small-scale automatic boiler, or opt for a simpler and cheaper batch-fed bale burner (Spinelli et al., 2012). In any case, bale value will be proportional to the price of the fuel being substituted, corrected for the different efficiency of the combustion plants. Mountain farms are often outside the reach of natural gas pipe works, and often resort to expensive fuel oil or propane gas. In that case, substitution with baled residues is especially attractive, and it is facilitated by newly designed residue boilers (Picchi et al., 2012). Previous studies have demonstrated that pesticide contamination is not an issue with vineyard pruning residues (Spinelli et al., 2010). Furthermore, the manufacturers believe that the mini-baler is underpowered, and they are working on a special model with a larger 15 kW engine, which is supposedly more productive. It is true that the carrier-mounted mini-baler is much less productive than the standard tractor-powered version. Its gross productivity is at best 0.54 t SMH−1 , which is three times smaller than the mean of 1.7 t SMH−1 recorded for the standard version (Spinelli et al., 2010). Smaller bale size is a handicap, because it results in a higher incidence of tie and dump times. The same applies to the shorter work width, which limits flow through the machine. These factors
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will not be affected by a power increase. However, a stronger engine may improve working speed and baling pressure, with positive effects on productivity. In any case, this machine is specifically designed for steep terrain vineyards, inaccessible to standard farm tractors. Such vineyards are relatively common: many of the most famous wine-producing regions in Europe include sizable tracts where the terrain is too steep and the spacing too narrow for tractor access. The centre for mountain viticulture lists 17 regions from 7 countries among its associates (www.cervim.org), including the producers of Beaujolais, Douro and Mosel wines. In fact, the development of specialized machinery for managing these vineyards is not unusual (Simonis, 2012), and it reflects a general trend when trying to introduce mechanization to steep terrain (Magagnotti et al., 2012). These considerations are valid for industrialized countries only. High baling costs are closely related to the high cost of labour in these countries, which represents over 40% of the total baling cost. For this very same reason, the mini-baler may represent a good machine for any country where labour costs are low, while investment costs are the main hurdle (Ruttan, 2002). The mini-baler is relatively inexpensive to buy, and the tracked carrier can be used for a variety of tasks after disconnecting the baler. The complete unit costs less than a conventional farm tractor, which is often outside the economical reach of farmers in the developing countries (Reardon et al., 2009). Here, baling may offer economical benefits at the farm level, while preventing open-air burning and relieving pressure for fire wood on natural forests (Bhatt and Sachan, 2004). In any case, cost-effective residue disposal is a crucial element for the survival of traditional mountain viticulture, which can only be conserved by use (Martin et al., 2010). Continued use is threatened by declining financial viability, and the increasingly strict regulations against field burning may give it the final blow. Under these circumstances, an ecological engineering approach can offer the best solution, offering both conservation and financial viability (Bergen et al., 2001).
Acknowledgments This project was supported by the Leonardo da Vinci Programme, within the scope of project 510138-LLP-1-2010 “Green Village” and by the COST Action FP0902 within the scope of its 5th STSM programme. Thanks are due to the Fojanini Foundation in Sondrio (www.fondazionefojanini.provincia.so.it) for their support with planning, organization and logistics.
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