Technology

Mechanization and adding value for woody agro-forestry biomass for energy use

Work on the "green economy" has generated income and jobs throughout Europe. There is still very great potential associated especially with agricultural and forestry biomass for the production of energy but steady support for research and a more ample distribution of mechanization are required. The mechanization industry is today capable of manufacturing harvesters and forwaderes, chippers, shredders and bundlers along with basic machines to make the bio-energy supply chain more efficient and productive

by Matteo Monni e Raffaele Spinelli

January/February 2015 | Back

The energy policies in Europe need a commitment shared by all Member States in order to adopt those measures in line with the current process of decarbonization.

The current economic situation, that – despite the significant drop in the price of oil – is provoking a decrease of energy consumptions, must not lose sight of the interesting development scenario of renewable sources of energy and energy efficiency, especially in view of the climate conference which will be held in Paris in December.

The effective combination of technological innovation and concern about the environmental emergencies, is fueling the confidence of both industry and consumers towards new types of production.

It is a fact that in Italy, since the beginning of the crisis up to this day, approximately 20% of the most dynamic businesses believed and invested in several ways in the “green” component of economy, creating about three million new jobs and more than one hundred billion euro of added value (data from “GreenItaly 2014” Survey by Unioncamere and Fondazione Symbolia). If we extend the analysis at European level, the annual turnover of bioeconomy comes to about 2,000 billion euro and 22 million jobs distributed among agriculture, forestry, fishery, food, chemicals and energy.

In this framework, the valorisation of energy from biomass sources represents an opportunity of great importance, not only for the abundance and heterogeneity of resources, but also for the added value of the production chains generated, which allow an appropriate management of land and new perspectives of work for farmers and forest owners. From fields and forests, Europe could bring into play a huge amount of biomass, but this resource should be mobilised at competitive costs, respecting the ecosystems involved.

In recent years, the high degree of maturity of the technological systems and incentive mechanisms, have given a positive impulse for the implementation of many plants for energy conversion of biomass. Unfortunatley, many of them – especially the largest ones – are fueled with considerable shares of imported materials. If, on one side the use of extraterritorial biomass can be convenient in terms of economy and energy, on the other side an important part of the efforts directed towards sustainability and re-launch of agriculture and national forestation is being frustrated.

In fact, within the chain of biomass for energy purposes, farmers and forest owners can come into play in different ways, according to the individual inclinations or business capacity of each single company. It all starts from the simple production and sale of raw materials to third parties, to the delivery of energy services.

The subjects in question are individuals fully aware of the fact that the value and renewability of the resources they deal, are closely connected to their management, especially in a future where the raw materials supplied from land emerge as the main limitation to the development. Therefore, the most farsighted companies opting for the energy service, will be interested in keeping control of the primary resources produced from our fields and forests. On the other side from policy and scientific research are awaited the solutions that will put farmers in the condition to offer raw material at competitive conditions, thus providing a unique opportunity for the revival of many areas of our country.

The importance of scientific research

Targeted research is the best way to develop specific technical knowledge. It often happens that the same operators of agriculture and forestry seek individual solutions to technical problems by improving machines at their disposal or adopting new standards of work. Anyway, this kind of approach has considerable limits in terms of costs and likelihood of success. The recourse to the scientific research leads to oucomes which are definitely more effective and less expensive. In fact, outside an appropriate experimental project, a test provides only one answer and that is why many experiments are required in order to obtain the systematic set of knowledge necessary to be successful in a designated activity. Moreover, the various responses should be coordinated in a systematic plan, in order to formulate hypotheses with statistical procedures. Otherwise, it will be impossible to know wether the result obtained from a test really comes from the introduced innovation, or rather by a coincidence of external factors independent of this.

It is important to highlight that applied scientific research is not a theory distant from the operational reality, but it takes place in the field, is based on solid evidence and aims at obtaining applicable results. Even though the intervention of science is not necessary to prove that the time required to grind a pile of branches depends on their consistency and on the power of the machine, scientific research can certainly give a numerical value to this relation, allowing accurate estimates, such as f.ex. how many hours and euro it will take to dispose of a pile of 200 cubic meters, with a 400 horsepower shredder which costs 150 euro per hour. This is a factual information with an immediate practical value.

BOX – Communicating research findings

Communication between industry and research is becoming increasingly important, as these fields often speak different languages and operate with rarely compatible timings. In this context will be held at FAO in Rome (May 19, 2015) a prestigious conference on biomass supply chains entitled “Mobilization of woody biomass for energy and industrial use – Smart logistics for forest residues, prunings and dedicated plantations”.

This conference will illustrate the results of 3 great projects financed by the EU – with an overall budget of 15 million euro – on issues concerning the wood-energy supply chains for agriculture (EuroPruning Project), forestry (INFRES Project) and tree cultivations outside forests (LogistEC Project). These three projects connect 63 partners, among which are the most prestigious research institutes in Europe. The Conference is jointly organized by the projects' coordinators – with a particular involvement of the CNR IVALSA – and is sponsored by a large group of Italian, European, American and international organizations and institutions, among which are FederUnacoma and ITABIA.

The participation in this event is free and all the information on the programme is available at the following link: www.infres.eu/eu/en/final-conference/.

The availability of resources

In Italy, agriculture can provide large amounts of wood raw material, obtainable both from the exploitation of by-products and plantations of dedicated crops. From the periodic pruning of vineyards, olive groves and other orchards are obtained every year from 1 to 3 tons of dry matter per hectare, which represent a potential biomass, considering that the involved areas amount to several million hectares. To this vast supply basin can be added that of the dedicated cultivations, that in Italy concerns species such as poplar, black locust and eucalyptus. For example, one hectare of short-rotation poplar can produce yearly around 15 tons of dry matter and is harvested every two-three years by means of appropriately modified forage harvesters.

The Italian woods cover a surface of 11 million hectares and have a biomass potential definitely high. In woods of tall trees, the most frequent interventions are thinning operations and “maturity” cuts at the end of life cycle. From thinning operations it is possible to obtain from 25 to 40 t DM/ha, with a frequency ranging from 10 to 20 years, while from maturity cuts are obtained even larger quantities, which arrive up to 100 tons per hectare, especially when the production of wood for packaging is not affordable due to the low quality of trees. However, in relation to an increased production, maturity cuts are carried out with longer intervals ranging from 60 to 70 years, according to the growth of trees.

The timber obtained from the cut of coppice, which occurs every 15-30 years, is entirely transformed into firewood destined primarily to traditional systems (fireplaces and stoves).

Some examples of machinery

Mechanization is the only way to make timber harvesting affordable. The manual processing should all be mechanized and if this is not possible, they should be replaced with other types of processing. Technological innovation cannot solve all problems but can certainly make an essential contribution to the further development of the biomass sector. Researchers and manufacturers are studying new machines, which can make harvested biomass more effective and competitive. Some innovations are relatively simple to develop, while others require special commitment and creativity.

Harvesters and forwarders

Harvesters and forwarders are the two machines on which is based the modern forestal mechanization: the first one cuts down the trees, sets them up in trunks and arranges them in piles, possibly divided into assortments. The second machine lifts the piles, loads them onto an embedded platform and carries them until a place reachable by the means of transport. Born in Scandinavia, the couple harvester-forwarder rapidly spread all over Europe, arriving to Italy in the late '90s. Today in Italy there are over 150 machines between the one and the other type.

Even in the working conditions of the Italian mountain woods, a harvester can produce the same quantity of five chainsaws, often allowing to carry out a more accurate work than that of manual processing. Since the harvester is equipped with a crane, it is able to better direct the fall of plants.

The use of harvesters in maturity cuts allows to reduce the total cost of use of a variable rate between 30 and 40%, compared to the traditional manual processing. In thinning, the production of roundwood from chainsaw is affordable only with the use of a harvester. In this case, the mechanical pulling down of trees and handling are more expensive than the manual processing but allow a much cheaper wood hauling determining an overall reduction of the cost of harvesting. Furthermore, most of the harvesters can be used to package sections with branches or partially debranched trunks, which are easier to move and produce a chipped wood of better quality.

The forwarder instead does the same work of three tractors with trailer, thanks to the higher load capacity and better manoeuvrability: this machine can operate on land inaccessible to tractors and is perfect for hauling larger distances, where it is necessary to maximise the payload transported.

Forage harvesters

In agriculture, the most effective harvesting techniques are based on modern industrial sites. This is true both for the recovery of residues generated by traditional crops and for the harvest of dedicated cultivations. In the first case, the industrial forage harvesters have proven to be much more effective than the modified chaff cutters, allowing the halving of the costs of recovery. The same principle also applies to dedicated crops, where big forage harvesters (f.ex. Claas, Krone), offer a flexibility of use and operational efficiency significantly higher than the light equipment applied to a tractor. They also allow a drastic reduction in the cost of harvesting.

Chippers and shredders

Regardless of the techniques of harvesting, the wood biomass – before being sent to the biomass boiler – must be chopped through the use of appropriate machinery, e.g. chippers and shredders. The main difference between the two machines is the chopping unit, considering that chippers use sharp blades (knives), while shredders use tools with bevelled edges (hammers). Each alternative has obviously pros and cons. The comminution with sharp blades (chipping) offers a product of better quality and lower power consumption. In fact, cutting a trunk with an ax requires less energy than cutting it with a hammer. On the other side, a sharp blade will be much more sensitive in contact with hard objects such as stones, metal and soil particles. In this case, if the wood to be chipped is contaminated with particles of soil or contain nails, stones etc., is preferable the use of a shredder rather than a chipper. In general, for pratical reasons it is better to avoid chipping in the wood and bring the whole biomass to a stationary chopper (chipper or shredder), which is usually more productive than a movable machine. As an alternative, it is possible to resort to the mobile chopper, which can be easily transported directly on the harvest place, facilitating all the following operations. The more powerful and modern the machine is, the lower is the cost of processing, which decreases going from a tractor-mounted chopper, to a truck-mounted chopper and up to the fixed industrial installation. It is not a case that the largest biomass plants are often equipped with their own stationary chipper, which allows a huge reduction of the cost of chipping. Today, the best solution seems to be that of an industrial truck-mounted chipper, which is flexible and efficient at the same time. This type of machinery is widespread throughout Italy, from Trentino to Calabria.

Compactors

An alternative to the chipping of residual biomasses is their compaction in homogeneous units for size and weight (compact residue logs – CRL). This offers many advantages, especially with regard to their handling, transport and storage. To this purpose the branches produced by forest harvesting can be transformed in cylinders of wood very similar in form to the traditional logs. The machinery allowing this type of operation facilitate the integration of the wood supply chains for energy use with considerable savings in the costs of transport and handling. Furthermore, the storage of compacted waste turns out to be more effective than chipped wood or loose branches because it severely limits rehumidification during storage, in particular in case of snowfall. Finally, due to the morphology of CRL it is possible to transport it on the same vehicles used for logs, thus reducing the costs of transport, in particular for long-distance deliveries. The productivity of compactors varies from 10 to 30 bundles per hour, corresponding to 5-12 tons of biomass, with a cost ranging from 10 to 20 euro per ton. These costs can be reduced through more efficient operations of handling, transport, storage and shredding.

Communicating research findings

The participation in this event is free and all the information on the programme is available at the following link: www.infres.eu/eu/en/final-conference/.