Magħtab incinerator’s harmful emissions to be kept within legal limits

The proposed incinerator at Magħtab will emit dangerous chemicals such as harmful nitrogen oxide and sulphur dioxide, but the amounts released in the atmosphere will be kept within EU limits through “best available technology” and the export of hazardous residues, an Environmental Impact Study claims.

A separate treatment facility will be required for the incinerator’s bottom ash, and consequently more land to accommodate it.

The emissions released into the air will consist of carbon dioxide, oxygen, water vapour and small amounts of chemicals including NOx, SO2, ammonia, organic carbon dioxins and dust. Emissions will also include metals like cadmium, mercury, arsenic and small amounts of lead.

EU deposition limits for arsenic are four micrograms (4 µg) per square metre every day. Air dispersion models foresee a maximum daily concentration of 3.2 µg/sq.m per day. A model study foresees a maximum daily concentration of 1.9 µg/m2 per day for cadmium, which is limited to 2 µg at EU law. Dioxins and furans will be limited to 1.08 µg/sq.m per day, well below the 4 µg limits.

The study does not consider the “canyon effect” that occurs in cities with densely packed buildings, which aggravate the impact of chemicals on human populations. Instead, the areas affected by atmospheric fallout in Malta are characterized by agricultural areas “where the existence of a canyon effect cannot be assumed”.

The air dispersion is estimated will not exceed a 6km radius from the incinerator chimney.

The facility will however lead to a reduction in landfill gases, limiting further the country’s generation of greenhouse gas emissions from landfilling.

How the plant will keep emissions within the law

The incinerator and its abatement equipment has been designed to ensure that gaseous emissions released during operation remain below the limits of both the Industrial Emissions Directive (IED) and the EU bureau for the Intergovernmental Panel on Climate Change.

The treatment of flue gas will generate air pollution control residues (APCr), a hazardous waste which currently cannot be treated in Malta. This waste will be transported from the flue gas treatment facility to a dedicated silo, until its removal offsite to be shipped abroad for treatment and disposal.

An EIA is short on detail on how this toxic waste will be transported, but it will be “intensively treated” before its release into the atmosphere.

The incinerator’s chimney will have a continuous emissions monitoring system (CEMS) to measure exhaust gases before release into the atmosphere.

The plant will also produce a residue left over from the incineration of the waste, known as incinerator bottom ash (IBA). IBA will be transported by conveyer belt from the furnace to a storage area located underneath a grate. It will be left in storage to mature and dry out, for the removal of its chlorides and sulphates. Once dried, the IBA is treated in a facility, where any metals that can be recovered will be re-used in the construction industry. Unburned residue will be returned for incineration.

The IBA will require another 12 weeks in storage for its carbonisation, which is where the residue will meet its end-of-waste criteria. It is only then that it can be reused as aggregate material for construction.

The large storage area required for IBA is being proposed on a 3,000sq.m area on the Zwejra engineered landfill. The facility’s plans are yet to be presented, since the Zwejra area has to be appropriately capped.