I refer to the letter to the editor entitled Rehabilitation of Maghtab (TMID, 12 March). The letter, by E.A. Mallia, raises four main points which I would like to clarify. The first issue is the composition of the gas. The usual landfill gas composition is 60 per cent methane and 40 per cent carbon dioxide. Maghtab however is not a usual site as uncontrolled burning of the waste is occurring within the site with the consequent release of emissions.

Prof. Mallia also referred to the dioxin production during treatment of the abstracted gases. The gas treatment system has been selected as the best method of destroying all VOCs with gas of this quality. No practical cost-effective alternative exists for dealing with this type of gas. Part of the treatment system installed uses a catalytic reaction to destroy the VOCs. The temperature is maintained at 900ºC to ensure complete oxidation in a chemical reaction on the heated ceramic plates. Energy for the reaction comes from the low levels of methane in the extracted gas.

As a final back-up, an additional activated carbon filter can be installed for final gas cleaning if monitoring of the exhaust gases indicates that this is required. The emissions from the plant will therefore be free of any harmful chemicals.

With reference to the monitoring of the treatment process in Germany, the contract for the rehabilitation works has been awarded to a Maltese-German joint venture organisation. The German company engaged in this joint venture, Haase, manufactured, installed and is currently operating this specialist gas treatment plant at Maghtab.

A requirement of the works contract is the monitoring of gas both from the disused landfill and from the exhausts from the treatment plant. Such monitoring will be done remotely via a communication link. It is perfectly possible, therefore, to monitor this facility from anywhere, including Germany as well during the period in which the contractor remains responsible.

Finally, given that both the facilities at Ta’ Zwejra and Ghallis represent conventional facilities, the quality of the gas that will be recovered will be more in line with that of a typical landfill which should be suitable for electricity generation.

Dr Eng. Christopher Ciantar

Director (Environment Policy and Initiatives)

Rural Affairs and the Environment Ministry