Move to harness methane gas from landfills for power generation

MUSCAT, DEC 24 – Be’ah — the Sultanate’s solid waste management flagship — is weighing options to harness the prodigious quantities of methane gas emanating from landfills around Oman for generating electricity. According to a senior official, more than half of the gas emissions discharged by the engineered landfill at Barka — one of the largest in the Sultanate — comprises methane, a gas that can be used as a fuel resource. If effectively captured and processed, this gas can be used to generate electricity, albeit in modest quantities, said Dr Said Mohammed al Touqi, Landfills Specialist at be’ah.
Examples abound of electricity production based on landfill-generated methane gas as a fuel, said Dr Al Touqi. He cited in particular the case of a landfill in Vienna-Austria which yields enough methane gas to produce 8 megawatt-hours of electricity. Speaking at a recent forum on Waste Management, he acknowledged however that any replication of ‘landfill-generated methane gas-to-energy’ projects in the Sultanate would not be simple. “In Oman, where gas and energy are relatively cheap, any decision on such a project will not be easy because these are capital intensive investments,” he said.
Landfill gas, the expert noted, is one of several challenges that need to be tackled in order to secure the safe and sustainable disposal of municipal waste. Another challenge, he pointed out, is leachate — noxious liquids that ooze from organic and food waste disposed of in landfills. Unless collected and treated, this highly polluting liquid — which is 50 — 200 times more harmful than household sludge — has the potential to contaminate groundwater, he warned.

Dr Said Mohammed al Touqi

But treating this “highly concentrated bad stuff”, Dr Al Touqi explained, is both expensive and challenging. The engineered landfill at Barka, for example, has been producing around 80 cubic metres of leachate daily — volumes that filled up a pair of leachate evaporation ponds. This aggregates 5,000 cubic metres of capacity, within two months of their construction. Pending the completion of a study for the suitable and cost-effective treatment of this liquid, be’ah has resorted to an interim solution — recycling the leachate back into the landfill. “be’ah is currently weighing options to treat the leachate via investments in wetlands or by reverse osmosis (RO), a system presently being used at the Al Multaqa landfill in Muscat Governorate,” Dr Al Touqi stated.
Meanwhile, the wholly government owned solid waste management company is making steady headway in the safe closure of the estimated 300-plus unsanitary waste dumpsites that have been in use around the Sultanate until recently.
Around two-thirds of these sites — long a nuisance to local communities because of fire hazards, toxic fumes, infestation by pests and insects, and unsafe scavenging by recyclers – have since been closed, said Dr Al Touqi.
In place, be’ah has constructed 10 engineered landfills — one for each governorate. While eight of them are in operation, the remaining two — in Khasab and Duqm — are nearing completion.
Designed to international standards, these landfills have linings in place to prevent contaminants polluting the groundwater, as well as systems for leachate collection, venting of gases, and groundwater monitoring.

Conrad Prabhu