When compared to conventional energy sources, renewable energies is distinct for having several socioeconomic and environmental benefits. In this regard, agriculture represents a source of energy through the biomass production, which in turn is considered the fountainhead of Renewable Energy Sources in the European Union.

Five years old poplar plantations represent a fundamental source for the industrial production of paper and pulp in Northern Italy; they can be used as biomass for energy production as well.

Considering the dimension reached by the singular plant, upon felling, trees must be collected by using specific forest machines. Successively, these are chipped in a static phase, where the product is taken from piles made earlier by using a hydraulic arm having a gripper that feed the chipping machine.

The Panacea group and the National Board for Agricultural Mechanization (ENAMA) have developed, in cooperation with Spapperi srl Company (PG), a self-propelled chipper machine capable to work in a dynamic phase, collecting with a pick up head the windrowed biomass and processing it autonomously. Previously, the biomass was cut and arranged in windrows by using a prototype of cut windrower. Aim of this work was to evaluate the machine performances when it is applied for harvesting and chipping five-year old poplar plantations (Populus spp.) grown for medium rotation forestry (MRF). Using standard parameters, also the work quality of the machine and the characteristics of the wood chips have been duly analyzed.

The machine is driven by a 6 cylinders endothermic diesel engine of Iveco FPT (Fiat Powertrain Technologies). The maximum power of 260 kW is reached at 2100 rpm and a maximum torque of 1500 Nm at 1400 rpm. It is matched to a 4x4 wheel drive system, interconnected with a drive shaft with 2 speed manual transmissions driven hydraulically from the cab. The machine is equipped with four isodiametric wheels and fitted with 500/18 R22, 5 tires. The machine is designed with different driving systems. Depending on the needs, the driving systems can be modified by using an electric command placed in the cab. The driving systems are the following: front steering and fixed rear wheels, four-wheel steering, side tractor shift, crab movement.

The machine has a maximum length, width and height of 6390 mm, 2510 mm and 3910 mm respectively, a total weight of 9250 kg (see Table below), with a tank containing about 300 liters of fuel.

The prototype has a reversible drive, with a tipping for loading having the capacity of 15.7 m³. In order to unload the product directly on the trailers of trucks, it is hinged on the outer frame of the machine to 3910 mm height. Finally, the front of the machine is equipped with the PTO and with two arms connected to the chipping device as well to the pick up head.

The chopping system is designed for chipping trees up to a maximum diameter of 380 mm. It consists of a disc with diameter and thickness of 1600 mm and 60 mm respectively, which is directly connected to the PTO by a shaft. Two radial blades operate the cut with a fix counter-knife. The speed rotation of the disc during cutting is 1000 rpm, whereas specific shovels generate centrifugal airflow required for unloading the chopped product into the tipping. The chipping apparatus was designed in order to be independent from other parts, so it can be replaced quickly when mechanical breakdowns occur. Moreover, it can be substituted to obtain a product having different characteristics (eg. billet).

The pick up head is equipped with a system for conveying and powering the chipper apparatus.  

The pick-up device consists of a rotary cylinder with diameter and length of 155 mm e 1750 mm respectively. The rotary cylinder has 105 steel reliefs, each one having a thickness of 50 mm and a height of 700 mm. This tool has both gripping and lifts functions; its rotational axis is 820 mm distant from the power supply system of the machine, presenting a space of 370 mm for unloading impurities.

The conveyor system is implemented by two groups of three counter-rotating toothed drums, which help to direct the material toward the chipping apparatus. Each drum has a diameter of 250 mm and a height of 700 mm.

Parallelly above the pick-up head, there is a horizontal rotating drum having the function to compress the material and facilitating the entrance into the conveyor.

Moreover, the chipping supply system has two vertical counter-rotating drums, one fixed, the other mobile, whose motion depends on the size of the incoming product. A hydraulic system is installed on the two sides of the pick up head; this allows the contact between the collecting organ and the ground.

The rotational motion of the pick up derives from a hydraulic pump located on the left side which is protected by a metallic carter. A valve allows the regulation of the rotational velocity, which varies according to forward speed and biomass present on the ground.

During the progress along rows, the self-propelled prototype combined with the pick-up head has been capable to harvest and chipping trees from the ground, as well as to unload the product on trailers or on the rear tipping of the machine.