Waste prunings from orchards, vineyards and olive groves could be a valuable source of biomass energy and help boost rural economies, say EU-funded researchers. The key ingredient is a sustainable supply chain.
As the EU seeks alternatives to fossil fuels, there is increasing interest in biomass for heating and power generation. Forestry waste is now recognised as an important source of biomass fuel but until now little attention has been paid to the 25 million tonnes of prunings produced each year by Europe’s orchards, vineyards and olive groves.
With only 2 % of woody material from pruning currently finding its way into biofuel, are Europe’s farmers missing an opportunity?
“Residues from pruning do not accrue any growing costs,” points out Fernando Sebastián of Spain’s Fundación CIRCE, which coordinated the EU-funded EuroPruning project. “They could be tapped at a relatively low price if effective collection systems were deployed.”
The 16-partner project set out not only to find technical solutions for the collection and processing of prunings into biomass fuel, but also to plan an entire supply chain to exploit a material that has traditionally been seen as a problem rather than a resource.
Chipping and baling
The first task was to devise machinery that could collect prunings from the narrow spaces between rows of trees in orchards, vineyards and olive groves, and do so economically.
Italian partners ONG and CRA-ING designed a chipping machine. It picks up prunings from the ground and chops them up into standard-size woodchips that can be used as fuel for biomass boilers. PIMR, a partner in Poland, built a baler to gather the prunings and roll them into standard 1.2-metre bales which can be transported for further processing or used directly as fuel for large-scale power plants.
“Another main goal was the development and implementation of an innovative logistics tool,” says Sebastián. “It optimises the handling of agricultural residues along the whole supply chain from harvesting to final transport to the end user.” The tool ensures that batches can be traced to their point of origin for quality assurance purposes and to facilitate a market in biomass trading.
The project has also made recommendations on harvesting, transport and storage, with a view to maintaining acceptable levels of moisture and ash content. Partners also looked at the life-cycle assessment of effects on the environment and on sustainable development.
Removing prunings can affect soil quality as material that was previously left to decompose and return to the soil is now being taken away. The project has drawn up guidelines on soil management, including advice on when prunings should not be removed.
The partners have run full-scale demonstrations of the entire system at three sites in Spain, France and Germany, which involved 46 farmers and produced 570 tonnes of biomass. They tested the equipment in vineyards and olive groves as well as apple, peach, plum and cherry orchards.
Users of the system are expected to be single farms and cooperatives, which could use the fuels for their own consumption but also sell their products to energy companies. About two thirds of the current production of prunings could be commercially exploited for biomass energy, the project found, contributing over €470 million to Europe’s rural economy and creating an impressive 30 000 jobs.
The project finished in the summer of 2016 but national projects are continuing in Poland and Germany, and the prototype machines used in EuroPruning are being developed by the manufacturers. The work done on logistics could be used in other biomass markets to assure quality, Sebastián says.
There are still barriers to overcome and some of the EuroPruning partners are taking part in further EU-funded projects – notably uP_running and AGROinLOG – which will help bring to fruition the potential of this neglected source of energy.
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