Acerra: Advancing the Thermal Treatment of Municipal Solid Waste

Organisations Involved: City of Naples, Fisia Italimpianti SpA, Impregilo SpA, Kommunal GmbH, Deutsche Anlagen GmbH, EVO Energieversorgung Oberhausen AG, Partenope Ambiente

The Challenge:

Landfills are overflowing with municipal solid waste. This alternative energy source is an underutilized asset. Domestically produced energy is a big step forward but it is one that Acerra, Italy realized it needed to take. The goal was to use trash to generate electricity, bringing stability to both the price of the electricity and the availability. With the waste to energy process there are no wide fluctuations or availability shortages. These facilities can operate twenty-four hours a day every single day of the year, providing more than enough electricity to meet the local community needs.

Greenhouse gas emissions play a huge role in global warming. This alternative energy generation method does not release even a fraction of the emissions that fossil fuel power plants do. These power plants must go through very strict emissions testing and every aspect of the process is monitored closely. In fact, these facilities must meet stricter operating standards than any other type of power plant, and if these are not met the plant is immediately shut down.

The Solution: 

Work began in August 2004. In Oct 2008, A2A business unit Partenope Ambiente took over management of the €355mn project and it was partially commissioned in March 2009. The three-line plant is by some measures the largest single-unit WTE plant in the world. Design throughput is around 600,000 tpy. The WtE plant consists of three identical lines for furnace, steam generator and flue gas cleaning. Each line is designed for a throughput of 27.1 tonnes/hour (650 tonnes/day) with a LHV of 15.1 MJ/kg. The plant design is governed by the high revenues for the produced electricity that are guaranteed for the life of the plant. Thus the plant is optimized for a high electrical efficiency. Therefore steam parameters of 500°C / 90 bar (932 F / 1305 psi) were chosen. The steam of all three lines is converted into electrical power by one turbine/generator unit.

Quality control occurs at the inception of the process. Two overhead refuse grabs which hold 5 tons each, mix the waste in the bunker to create a homogeneous mixture. A crane feeds the mixed waste into the feeding hoppers of one of two forward feeding grates capable of processing 24 ton/hour. Each of these production lines feeds a boiler that operates at a temperature above 1560°F for 2 seconds. The intense heat ignites the waste moving along the forward feeding grates until only bottom ash, which is treated in a separate facility, remains at the end of the grate. 

Careful monitoring of the incineration process guarantees complete burning of the combustible material in an environmentally safe manner. Sophisticated computerized controls maintain the temperature, grate speed, amount of air used and all other aspects of the process that enables proper incineration to occur at optimum levels. 

The Acerra plant has been in full-time, full scale commercial operation since 2009, achieving more than 90% availability each year, processing as-received post-recycled curb side-collected solid waste and recovering electricity, ferrous and non-ferrous metals, commercial-grade hydrochloric acid, and gypsum. The residual materials (largely fly and bottom ash, accounting for approximately 15% of the input material) from WtE Naples are sent directly to landfill. 

Acerra is locally situated, offering many advantages to the community. Jobs are created, taxes are paid, supplies are purchased at local businesses and stores, and energy is provided for a reasonable cost that does not pollute or harm the environment. 

The Acerra facility uses municipal waste that would otherwise take up space in a landfill and contribute to environmental pollution. Waste is an unlimited resource. With all the garbage generated daily, in addition to the contents of existing landfills, there is enough waste to satisfy the demand for electricity. 

Using waste to generate energy is a process that does not harm the environment or the earth. There are no dangerous chemicals or toxins used to poison wildlife and contaminate the land and water in the area, and pollution and greenhouse gas emissions are far less than using coal or other resources.

The Outcome:

The success of the Acerra waste to energy plant is a testament to the reliability, economic feasibility and environmentally responsible nature of the thermal treatment technology for high energy production and material recovery.

The Acerra facility uses state-of-art web based monitoring platforms in a telemetry format which gives the Italian Environment Agency complete disclosure on the plants operating data. This also provides the plant owner with complete control over the emissions using a state-of-the-art data management and diagnostics platform. This is a powerful tool which enhances the process knowledge, control and management.

Accres also uses data recording and analysis systems which gives the commercial and industrial facilities an efficient and user friendly control system. Users will have the ability to combine the process data with a systems analyses platform including batch reports, trends, traceability reports, alarm/event histories, component performance and efficiency reports, downtime/uptime comparisons, component failure histories and more. All captured data is backed up with double redundancy- assuring that all information is protected.

This plant addresses more than one environmental problem as the power generated reduces the need for foreign oil or fossil fuel use in the community it also offer many benefits to people and the environment.