‘Low’ impact from diesel plant that will plug summer energy shortage

The emission of harmful pollutants from a temporary diesel plant at Delimara are expected to be high only in “worst-case scenarios”.

The new plant will be used to plug spikes in energy demand during hot summer days.

Pollutants like Nitrogen Oxide (NOx) could be high when added to the more severe impact of car usage during calm summer days – because in good weather the emissions settle in the immediate neighbourhood of the plant – when peak energy demand kicks in, Enemalta said in studies for a permit for the new plant.

But overall, the impact on air quality is expected to be low, only as long as the use of the plant is kept to the envisaged total 21-day period during which the plant – expected to be used for the next three years – will be operational.

Enemalta and UNEC Ltd submitted the study to amend the Delimara power plant’s IPPC (Integrated Pollution Prevention and Control) permit for the new diesel plant, whose emissions on the surrounding area must be monitored at law.

UNEC, an offshoot of the Bonnici Brothers Group, recently won a tender to supply the diesel plant.

The Environment and Resources Authority, which has exempted the new plant from a full environment impact assessment, is receiving feedback from the public on the proposed amendment to the IPPC permit.

Overall, the studies conclude that the impact on air quality will be low mainly because the plant will only be used for a limited period of time, pointing out that such an impact depends “on the extent to which the plant is required to operate”.

The impact will itself be “negligible” when weather conditions facilitate the dispersion of emissions to the atmosphere, for example during storm events when the LNG tanker is put on the storm moorings and gas supply is suspended. In this case, emissions from the emergency plant will replace those from the main D4 plant, and also be rapidly dispersed, Enemalta said.

The impact on air quality will be greater when the plant is used to make up for shortages in energy supply during peak demand in February, and particularly in the summer months, when the new emissions are added to the cumulative impact of other pollution sources.

Emissions from the existing power plant are not the major source of pollution in the area. A review of national emissions highlights the high contribution of road transport to various pollutants including NOx, carbon dioxide (CO2) and PM (particulate-matter) values. NOx emissions from diesel combustion will be adverse, but the impact is only mitigated by limiting the operational hours of the plant to not more than 500 operating hours per year.

So even the limited use of the emergency plant during low wind conditions can be expected to result in “a transient cumulative impact”, added to those already experienced in other localities largely derived from road transport.

Given that the emergency plant can be expected to be used for just 21 days over three years “in the worst-case scenario, the significance of this impact is deemed to be low.”

Noise emissions are also deemed to be be minimal, with each individual diesel generator unit placed in noise suppression enclosures to reduce generated noise to the surrounding areas.  The combined noise impact during full operation will be just 100dB – the equivalent of the noise made by a hair dryer – at 15m from each site.

But the studies warn that just a simple malfunction – such as a damaged bearing on a ventilator fan – may cause “disproportionate nuisance”, and called for regular inspections.

The temporary plant will give the country an extra 60MWe – 60 million Watts of electric capacity.

The new temporary plant was proposed after Malta endured 10 days of power cuts amidst record heat waves in July 2023. In a letter urging ERA to exempt the project from an Environment Impact Assessment, Enemalta warned that it would not be able to guarantee the country “security of energy supply” during peak summer months, without the new plant.