The energy consumption and economic costs of different vehicles used in
transporting woodchips

Marco Manzone

⇑

, Paolo Balsari

University of Turin, Via Leonardo da Vinci 44, 10095 Grugliasco, Turin, Italy

h i g h l i g h t s

Different categories of vehicles have been considered for woodchips transportation.

The transport costs depending by the distance and the type of vehicle used.

The energy cost required for woodchip transportation is relatively small if compared to the biomass energy content.

a r t i c l e

i n f o

Article history:
Received 6 September 2013
Received in revised form 29 August 2014
Accepted 3 September 2014
Available online 22 September 2014

Keywords:
Biomass transport
Productivity
Energy consumption
Transportation costs

a b s t r a c t

One of the weak points in the energy-wood chain is the transport of woodchips from the forestry yard to
the power station. This operation is critical because the vehicles used must be very versatile to operate
under different conditions while maintaining low operating costs. The goal of this study is to implement
the information on this topic by examining the different categories of vehicles that are considered to be
appropriate for this purpose. For each category of vehicle, the working time, working rate, fuel consump-
tion, energy costs and economic costs were processed.

Tests were conducted using both ‘‘agricultural convoys’’ (tractor + trailer) and ‘‘industrial vehicles’’

(lorries).

All vehicles were tested on short itineraries of approximately 5, 15 and 25 km and on long itineraries of

50, 100 and 200 km.

The study showed that on routes longer than 25 km, lorries had the highest average transfer speed

(42 km h

1

) whereas agricultural vehicles had the lowest (24 km h

1

).

The transport costs depending on the distance, the type of vehicle used and the unit cost (€ km

1

) were

high, especially for distances less than 20 km (up to 5 € km

1

).

The application of these values to a biomass-fed thermal power unit of 1 MW with an annual use of

2000 h and a supply of biofuels in the radius of 75 km shows that 1500 h year

1

are needed for the

bestowal of chips to power the unit (3700 tss). The total cost for a lorry is approximately € 148,000 year

1

and approximately four times higher for agricultural convoys.

The energy required to transport the woodchips is approximately 90 MJ m

3

loose chips for agricultural

vehicles and 35 MJ m

3

loose chips for lorries. In both cases, these values represent a small claim (2%) of

the energy value of the biomass transported.

Ó 2014 Elsevier Ltd. All rights reserved.

1. Introduction

In recent years, the increased cost of petrol and increasing envi-

ronmental sensibility in the media have generated a great interest
for the production of renewable energy like that obtained from
agricultural and forestry biomass

[1–3]

.

In Italy, recent economic incentives for the production and use

of biofuel have generated a steady increase in the amount of short
rotation forestry conducted on agricultural lands

[4,5]

.

At present, the woodchips produced from these crops are one of

the main fuels used by large and medium-scale biomass power sta-
tions because this is interesting from an energy and economic
point of view

[6,7]

.

One of the weak points of the energy-wood chain is the transpor-

tation of biomass from forested lands to the end user

[8]

. This oper-

ation is critical because the vehicles used must be very versatile to

http://dx.doi.org/10.1016/j.fuel.2014.09.003

0016-2361/Ó 2014 Elsevier Ltd. All rights reserved.

⇑

Corresponding author.
E-mail address:

[e-mail]

(M. Manzone).

Fuel 139 (2015) 511–515

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operate under different conditions while maintaining a low operat-
ing cost

[9,10]

. The versatility of these vehicles is gauged by

whether they are capable of being loaded with woodchips directly
in the field and the possibility of using standard farm equipment
in the loading process

[11]

.

The goal of this study was to examine the different vehicle types

normally used for woodchip transportation and to evaluate the
effective convenience of their use. In detail, the productive perfor-
mance, the energy efficiency and the operating costs has been
determined for each type of vehicle.

2. Materials and methods

2.1. Vehicles considered

Field trials were conducted using both ‘‘agricultural convoys’’

(tractor + trailers) and ‘‘industrial vehicles’’ (three truck types).
The agricultural convoys consisted of 4WD agricultural tractors
equipped with five different trailer types. The study compared
trailers with two or more axles grouped together at the rear end
of the chassis to ‘‘conventional’’ farm trailers, which had turning
front axles placed on slewing rings (

Table 1

).

Four types of trucks were considered in this study: (1) a

truck and trailer road train, (2) a semi-trailer rig, (3) a truck
equipped with an open-top and hook-lift containers and (4) a
truck fitted with a light alloy body for the transportation of
cereals (

Table 2

).

In the transportation sector, trucks are defined as ‘‘large volume’’

when equipped with a container sized to reach the maximum vol-
ume allowed by road standards. Generally, these vehicles are used
for transporting loads with a low bulk density, such as woodchips.

All vehicles (agricultural convoys and trucks) were driven by

drivers with at least three years of experience.

2.2. Productivity evaluation

All vehicles were tested on shorter itineraries of approximately

5, 15, 25 and 50 km. Only trucks and trucks with trailers were
tested on longer itineraries of 100 and 200 km. Urban and extra-
urban roads were chosen for the shorter itineraries, whereas the
longer itineraries consisted of urban roads for the first 50 km fol-
lowed by travel on highways. In all itineraries, the first 500 m were
traced on dirt roads (exit simulation from the field).

The time consumption for unloading was recorded following

the methodology set up by Magagnotti and Spinelli

[12]

. Each time

element was recorded with a centesimal digital stopwatch. In this
study, productive work time was divided into the following time
elements: manoeuvring, opening and closing of the container
doors, and dumping (time necessary for tipping the container
and placing it back into the travelling position)

[13]

.

The average speed of the transport was calculated using the

analytic method as a function of travel distance and travel time.

Each distance was travelled three times (repetitions).
Productivity was estimated through detailed time-motion stud-

ies conducted at the cycle level

[14]

in which a full trailer load was

assumed to be a cycle. Productivity was expressed as the volume of
units (m

3

) transported per hour and kilometre.

2.3. Energy cost

The total energy cost was calculated as the sum of the direct

energy cost (fuel and lubricant consumption) and indirect energy
cost (energy used for the vehicle construction). Energy cost was
estimated on the basis of the primary energy content of component
materials: diesel fuel 51.5 MJ kg

1

, lubricant 83.7 MJ kg

1

, prime

mover 92.0 MJ kg

1

and trailer 69.0 MJ kg

1

[15]

. The amount of

fuel used for the whole operation was determined by filling the
tank of the vehicle before and after the test. The tank was refilled
using a 2000 cm

3

glass pipe with 20 cm

3

graduations, correspond-

ing to the accuracy of our measurements.

Lubricant consumption was determined as a function of fuel

consumption using the algorithm calculated by Piccarolo

[16]

.

2.4. Transportation cost

Transportation costs were estimated for each vehicle as a func-

tion of the machine cost and its container capacity. The machine
cost was calculated using the procedure described by Miyata

[17]

for ‘‘industrial vehicles’’ and the procedure proposed by Magagnotti
and Spinelli

[12]

for ‘‘agricultural convoys’’ (tractor + trailer). A ser-

vice life of 10,000 h was considered for all vehicles. Annual utilisa-
tion was estimated at 500 h for agricultural vehicles and 1000 h for
industrial vehicles (trucks). Repair and maintenance costs were
obtained directly by the machine owner. Labour cost was set to
18.5 € h

1

. Fuel and lubricant costs were assumed to be 1.1 € dm

3

and 5.5 € kg

1

, respectively. The total cost included 20% profit and

overhead costs

[18]

.

Table 1
Main technical characteristics of the agricultural convoys.

Trailer type

Engine power (kW)

Load volume (m

3

)

Total weight (t)

Axles (n°)

Container dumping

Opening/closing of doors

Width (mm)

Single-axle

88

18

6

1

Three sides

Hydraulic

1930

2 Axles (turning)

103

22

12

2

Rear gate

Manual

1870

2 Axles (turning)

103

25

14

2

Three sides

Hydraulic

2090

2 Axles (tandem)

95

22

14

2

Rear gate

Hydraulic

2090

3 Axles (turning)

106

35

20

3

Three sides

Hydraulic

2090

3 Axles (tandem)

103

30

20

3

Rear gate

Hydraulic

2090

Table 2
Main technical characteristics of the trucks.

Truck types

Engine power (kW)

Load volume (m

3

)

Total weight (t)

Axles (n°)

Container dumping

Opening/closing of doors

Width (mm)

Truck and trailer

308

105

44

6

Three sides

Manual

2040

Truck and Semitrailer

308

95

44

5

Three sides

Manual

2040

Container truck

191

22

25

3

Rear gate

Manual

2040

Cereal transport truck

191

25

25

3

Three sides

Manual

2040

512

M. Manzone, P. Balsari / Fuel 139 (2015) 511–515

3. Results

3.1. Productivity and time consumption

Productive working time was approximately 90% of the total

worksite time. Much of the unproductive time (80%) was caused
by paperwork at the entrance of the power station. These delays
in time were not included in the productivity calculation because
they were dependent on the power station organizations and not
the types of vehicles.

The data analysis showed that on short routes (<25 km), the tra-

vel time was about the same for all transport types, and the mean
speed was approximately 23 km h

1

. The highest productivity

(0.6 m

3

h

1

loose chips km) was obtained with high-capacity

(35 m

3

) trailers, which highlights the importance of load size even

for short distances. The time spent in manoeuvring was only 3% of
the total work time; this value can be doubled when traditional
trailers are used, and tripled when the doors are opened and closed
manually. The analysis of unproductive work times showed a con-
siderable amount (approximately 70%) of waiting time, which was
normally experienced before loading and unloading.

For long-distance transportation (>50 km), trucks had the high-

est mean speed (42 km h

1

) while agricultural convoys had the

lowest (24 km h

1

). Similar results were obtained for productivity

in which the ‘‘large volume’’ trucks had the highest performance
(0.27 m

3

h

1

loose chips km), and the agricultural convoys had

the lowest performance (0.05 m

3

h

1

loose chips km).

When transporting over long distances (>50 km), the truck and

trailer road trains were characterized by a greater amount of time
spent in loading (approximately 40% of the total time) and a lower
amount of time spent in transfer (approximately 50% of the total
time). The contrary was true for agricultural convoys. Simple
trucks offered an intermediate performance.

Regardless of vehicle type, the performance was directly propor-

tional to the load capacity and inversely proportional to the trans-
portation distance. Vehicles equipped with ‘‘large volume’’
containers offer a higher productivity but at decreasing rates with
increasing transportation lengths. In particular, these values range
from 240 m

3

h

1

loose chips at a distance of 2.5 km to 35 m

3

h

1

loose chips at a distance of 200 km. Conventional trucks have lower
performances (approximately 300%) than ‘‘large volume’’ truck and
trailer rigs but double that of agricultural vehicles (

Fig. 1

).

3.2. Transportation cost

Transportation cost was proportional to the distance and inver-

sely proportional to the container capacity of the vehicles consid-
ered. For distances of 25 km, the transportation cost was
2.34 € m

3

loose chips for agricultural convoys and 0.65 € m

3

loose

chips for 95–110 m

3

capacity trucks. For a distance of 50 km, the

transportation cost was about 5.11 € m

3

loose chips for agricul-

tural convoys and 2.72 € m

3

loose chips for 95–110 m

3

capacity

trucks (

Fig. 2

).

3.3. Energy evaluation

For all of the classes of vehicles analysed, the total energy cost

made up 10% of the indirect cost and 90% of the direct cost, includ-
ing fuel and oil consumption.

The energy cost of woodchip transportation increases linearly

with the transportation distance, ranging from 25 to 50 MJ m

3

loose chips of biomass transported for distances of 25 km to over
250 MJ m

3

loose chips transported for distances longer than

250 km.

The energy cost is also linked to the vehicle type. Assuming a

transport distance of 50 km, this value is 127 MJ m

3

loose chips

Fig. 1. Productivity of the different vehicles tested.

Fig. 2. Transportation cost relative to the volume of the unit transported.

M. Manzone, P. Balsari / Fuel 139 (2015) 511–515

513

for trucks and agricultural vehicles and only 48 MJ m

3

loose chips

for ‘‘large volume’’ vehicles (

Fig. 3

).

4. Discussion

The average travelling time depended on the type of road and

the traffic, and the driver proficiency and vehicle type could affect
the manoeuvring performance. Furthermore, it should be noted
that the unproductive times caused by waiting for the unloading
at the user plant are not predictable and can exceed 3 h in some
cases (25% of the total work time).

The transportation cost is related to the transport distance and

the vehicle type. If the value obtained from the study is applied to a
biomass fed thermal power unit of 1 MW with an annual use of
2000 h and average transportation distance of 50 km, it appears
that 1500 h year

1

are required for bestowing chips to power the

vehicle (37,000 tss). The total cost for a lorry and a trailer is
approximately € 148,000 year

1

and about four times higher for

agricultural convoys.

The results obtained in this experiment show that the use of

vehicles with high load capacities is clearly advantageous. This is
due primarily to the low density of the woodchips (approximately
0.35 t m

3

loose chips). Similar results have also been obtained in

other works in which the transportation of the biomass and for-
estry bundles were compared

[19]

.

By contrast, agricultural convoys can load the woodchips on the

field. In cases where self-propelled chippers are used such as in
Short Rotation Coppice harvesting, the convoy can follow the chip-
per because they do not need roads with high lift.

Importantly, in considering the time spent at the farm to unload

the agricultural trailer followed by the loading of the woodchips
onto lorries for their transportation to power stations, the conve-
nience of using ‘‘large volume’’ vehicles is low. In fact, for a
110 m

3

capacity vehicle that travels an average distance of 5 km

between an SRC plantation and a farm with a large landing site
for woodchip storage, this operation is quite time-consuming;
1.5–2 h are required for the agricultural convoy to travel three
times between the sites (in accordance with the data collected in
this study), and 30 min are required for loading the vehicle

[20]

.

However, if the woodchips are loaded into the agricultural con-

voys in the field, the road surface can be dirtied with pieces of land,
posing a danger to other vehicles.

Furthermore, the low forward speed of agricultural convoys,

especially in Italy (max 40 km h

1

), can cause traffic problems near

cities.

Another limitation of the use of ‘‘high-volume’’ lorries is the

height of the drop sides (4 m). In loading these lorries, specific
equipment such as a telescope handler is needed instead of con-
ventional forestry equipment such as tractor front loaders or

mechanical shovels. The use of front loaders or mechanical shovels
is possible only with ramps to raise the loader or trenches to
reduce the height of the lorries.

The energy cost required for woodchip transportation is rela-

tively small when compared with the biomass energy content.
When agricultural vehicles or standard trucks are used, it repre-
sents over 10% of the energy content of the load. With ‘‘large vol-
ume’’ vehicles, however, this value is less than 2%.

Independently of the vehicle types used, the uncovered trans-

portation of woodchips can be dangerous due to the risk of wood
pieces falling from the truck.

In conclusion, this work showed that to reduce the unproduc-

tive transport times and thereby constrain the cost of transporting
chips, it is necessary to choose vehicles that have high load capac-
ities but are nonetheless suitable for the road conditions present in
the forestry yard. A large landing site should also be used to reduce
the time spent manoeuvring as much as possible.

One highly desirable future direction is the widespread adoption

of devices that can transfer the woodchips from agricultural trailers
to lorries, which are currently used only in Northern Europe. In this
case, the working time necessary to perform this operation could be
reduced because the woodchips could be transferred directly from
agricultural trailers to lorries in the head field and the agricultural
convoys could be used exclusively in field work.

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