The Drehid Waste Management Facility is a 670-acre AES Bord na Móna owned site located approximately 5km north of Allenwood in Co. Kildare. The site is one of the largest landfill’s in the country with a capacity to handle 120,000 tonnes of municipal waste per annum. There is also a composting facility attached to the site, which has a capacity to process 25,000 tonnes of organic waste into compost for agricultural use.
Coffey, in conjunction with Bord na Móna and their designers, Tobin Consulting Engineers, is expanding the waste disposal capacity at Drehid via the construction of 4 (no) individual lined compartments or ‘cells’ into which municipal waste is packed down before being covered. The construction of cells 1 (no) and 2 (no) was completed in late 2020 and work has commenced on cells 3 (no) and 4 (no). The project involves the excavation of an individual pit for each cell, the installation of a drainage pipe network in the base of each cell and lining the cell base and walls with a bentonite/clay mixture over-layed with a 2mm High Density Polyethylene (HDPE) liner. Bentonite is an expandable clay with two features which makes it useful as a lining material – (i) it exhibits a strong sorption for heavy metals and (ii) Bentonite expands when mixed with water and becomes a very effective water-proof material. The bentonite clay/liner structure is protected with a layer of grit and a geotextile is applied as the finish layer. This engineered liner system acts as a barrier for leachate and prevents the transportation of contaminants to the surrounding environment.
The decomposed waste leachate produced on the Drehid site is channeled through the drainage pipe network to a control point where methane gas is extracted and used to generate electricity. Currently enough methane is being produced to generate up to 5.6 megawatts of renewable power – enough to power 8,500 homes. After gas extraction, the remaining leachate is collected and treated offsite before disposal.
The expected completion date for the works is September 2021.
Thanks to Seamus Conneely and Henry Feeney for their assistance on this news update.