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Urban greenery residues, a source of energy

Subproducts left by the maintenance of parks and gardens in Italian cities can annually lead to a huge amount of biomass, sufficient to meet the energy requirements of thousand families. A succession of incompatible regulations which, over time, have led to differing definitions of residues and thus differing procedures for handling them and thus have blocked the efficient use of them as raw combustion materials

by Matteo Monni
April - May 2018 | Back

It appears that there is nothing simple and to efficiently free simplicity from complexity a great deal of understanding is needed. An example is the case of urban greenery. Imagine a monumental park, a garden or a stand of trees which often decorate our cities opening to thoughts of saving them from the dump. On the other hand, the maintenance of these areas produce two million tons of residues from mowing and pruning annually, if not taken for better purposes, can wind up in the dump with a serious impact on costs and the environment.

To be precise, now in Italy and according to regulations enacted the flow of outgoing material left behind by a production process can be managed as refuse, that “anyone with a substance or object to get rid of or intends to trash or is required to trash comes under” EU Directive 2008/98/EU of November 19 2009; or when a subproduct is something to be used without further treatment differing from a normal industrial procedure for another production process and meets all the requirements for protecting health and the environment according to DLgs 152/2006, art. 184 II comma 1.

This dual interpretation does not make clear the destination for the legitimate use of biomass derived through the maintenance operations of urban greenery creates confusion in many conditions. In summary, if this biomass is to be considered refuse its optimum use would be for compost whereas if it were a premium subproduct it could fuel plant as a renewable energy source. Both solutions would be socially and environmentally valid but from the financial point of view it would not be stupid to identify the most advantageous solution for Italian homes between the two. Moreover, the financial angle is at the center of debate among the stakeholders of compost and fer-Energy advocates. For the former, the exclusion of urban residues would produce a drastic cut in the percentages of cities, differential collection and strongly alienate the target of fixed collection as the national norm. Also, if prunings were sold rather than discarded they could be sold for compost on the market instead of being paid for removing them the result would be increased costs for sending them to plants. The bioenergy sector, on the other hand, maintains leaving urban prunings out of refuse leads to municipal earnings on sales of biomass to plants at a price of € 20 per ton with a compost per ton of urban greenery costing € 100.

These considerations must be greatly untangled by political decision makers because over the last ten years Italy has seen a succession of contradictory regulations through which juridical features on refuse and subproducts, the question of residues has been changed as many as four times.

At present, mowing and pruning urban greenery exclude a refuse regime and can be used as renewable energy sources for bioenergy. But these issues are not settled because a new chapter has been opened by approval of 2018 EU legislation eliminating modifications in 2016 on “Associated Agriculture” which does not confirm to the Directive on refuse. The risk of enabling EU infraction of procedures brings everything back to the table of discussion. An example is law 129/2010 which allows urban greenery pruning to be acquired for energy purposes in supply contracts with municipality agencies for the selection and withdrawal of biomass. This was a good way to activate good systems, especially for public agencies because the costs of managing residues were replaced by earnings by the sale of biomass with a very real advantage for the people involved. The change in the classification of biomass from urban greenery led to a break in supply contracts and higher costs for combustible fuel without serious repercussions on those planning the use of this resource. Finally, it must be pointed out that the chemical-physical characteristics of wood obtained in the maintenance of urban greenery is totally similar to forestry biomass.

The City of Rome, for exam­ple, manages some 150,000 trees along the city streets and at least 20,000 of them are pruned annually. The biomass made available by pruning comes to a little less than 10,000 tons of wood annually which could meet the heating heeds of some 600 families rather than weigh on the system for the management of refuse already congested and on the point of collapse.

The “ping pong” of regulations

From January 2008 to August 2010 (D.Lgs 4/2008), Public and private urban greenery maintenance subproducts are considered urban refuse and cannot be used for generating energy in simple heating plants or remote burners but vegetable materials subproducts from agriculture can be used for this purpose.

Beginning August 19, 2010 (law August 13 2010, no. 129) definition of subproduct extended to include “Fecal materials and vegetable materials from mowing from maintenance of public and private maintenance or agricultural operations also for use outside the location of production or given to third parties or farm or inter-agency plants .

From December 25 2010 (D.Lgs Decembe 3 2010, no. 205) “An inclination to enact European Parliament Directive 2008/98 regarding refuse.” an unexplainable return back without discussion of subproducts whereas materials from maintenance of public and private greenery are returned to the refuse description.

From August 25 2016 (Agriculture Association - Law July 28 no. 1154) with article 41, a measure changing environment code (Digs 152/2006) fixing materials not under refuse discipline “... mowing and pruning of green areas such as gardens, parks and cemeteries.”


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