Greenhouse gas emissions monitoring of the integrated waste management system in Siena

Aim:The aim of the project is to identify actions to reduce the GHG emissionsof the integratedwaste managementsystem in the Province of Siena and monitor the effects of these actions over the years.

Subject:The GHG inventorieshave been processedintime series(2008-2011)and includeseven disposalplants for themunicipal solid waste(MSW) and industrialnon-hazardous waste in the ProvinceofSiena:

  • n.3landfills(Poggio alla Billa, Torre a Castello and Le Macchiaie – almost 35,000 t of conferred waste per year),
  • n.1incinerator(Pian dei Foci – maximum 225 t per day of treated waste with 30,000,000 kcal per hour),
    • n.2composting plants(Poggio alla Billa and Le Cortine – almost 1,400 t of treated waste per month with 300/400 t of produced compost),
    • n.1selectionplant(Le Cortine – almost 55,500 t of treated waste per year),
    • n.1 valorization plant (Le Cortine – almost 17,000 t of treated paper/cardboard and 8,000 t of multi-materialper year).

Methodology: The assessment is based on the2006IPCCGuidelinesthat regulate GHG inventories at the national scale. This methodology has been implemented by Ecodynamics Group for accounting the atmospheric emissions and removalsofCO2fromlocal systemsand specificproduction processes,such asthe integratedwaste managementsystem in the Province ofSiena. The study considersthe emissionsof carbon dioxide (CO2), methane(CH4) and nitrous oxide(N2O), due to theWaste andEnergysectorsidentified by the2006 IPCC methodology. Direct emissions,that occurwithin the considered productive sites(geographical criteria),were distinguishedfrom the indirect emissions,that occuroutsidethe waste disposal plants (responsibility criteria). All GHG emissions other than CO2 were transformed into CO2 equivalents (CO2eq), using appropriate conversion factors, namely Global Warming Potential.

Context:InItaly, operators of high potential waste disposal plants have to follow directives of the Emission Trading Scheme and operate a continuous monitoring of GHG emissions. Siena Ambiente S.p.A. does not belong this category, however, the development of a GHG emission accounting system has been considered as an essential tool to identify solutions and improve the environmental performance of the integrated waste management system. The management plan aims at an increase of the production of electricity from renewable resources and a careful disposal of waste inputs, reducing the GHG emissions to the atmosphere.

Results: Results show the impact provided by the incinerator since 2009. A progressive decrease in the total emissions of the integrated waste management system is observed, though a significant increasing amount of burned waste over the years. 12% of the emission reduction was estimated due to a progressive improvement of the management of landfills from 2009 to 2011(increased biogas recovery to be flared and to produce electricity). Before the activation of the incinerator, waste disposal in landfill (in particular “Torre a Castello”) produced an amount of CO2eq emission per ton of treated waste higher than the incinerator(-18% from 2008 to 2011).

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Good practices: In the future, possible scenarios for improving environmental performances include a series of mitigation actions/compensations:

  • increasing of electricity production from renewable (photovoltaic panels) or alternative resources (incinerated waste and biogas recovery from landfills) for a reduction of GHG emissions by approximately 34%,
  • burning in the incinerator of waste types with a low fossil carbon content (organic, wood and undifferentiated MSW),
  • equipping the incinerator of a specific systemforCO2 emission recovery due to the combustion of the fossil carbon fraction in the burned waste,
  • disposal in landfills of waste types which decompose slowly such as plastic and inert (wood and paper are not considered inert),
  • oxygenation of waste cumulous in composting and selection plants, through mechanical turning and verifying the correct operation of the aerators,
  • improvement of the bio-filter action in the composting and selection productive lines in order to allow the recovery of N2Osynthesizedduring the ammonia oxidation,
  • replacement of diesel with fuels at lower environmental impact (e.g. methane and bio-fuels produced from waste),
  • use of the electricity produced inside the waste disposal plants in order to replace the imported electricity from the national grid.

Besides the ethical environmental value, the GHG emission reduction from waste disposal plants can produce VER (Verified Emission Reduction) credits, which after the ISO 14064 validation/certification, are potential objects of trade on the voluntary market of carbon credits. These credits can be bought from other companies that want to reduce their GHG emissions.

This study was elaborated by Dr. Michela Marchi in the program “Researcher in Enterprise”, funded by the Province of Siena.

Ref.: Marchi, M., Niccolucci, V., Menghetti, F., Mangiavacchi, S., Bastianoni, S., 2014. Greenhouse gas emissionaccounting for the waste management at local scale. In: Marchettini, N., Brebbia, C.A., Pulselli, R.M., Bastianoni, S. (Eds.), The Sustainable City IX – Urban Regeneration and Sustainability. WIT Press Publications, Southampton and Boston. Volume 2, pp. 1291-1300.