Converting Waste and Landfill Gas into Energy

Sudokwon (metropolitan area) Landfill Site is the world’s largest landfill site established to stably process the wastes discharged by metropolitan areas (Seoul, Incheon, and Gyeonggi Province) after Nanji Island Landfill Site was decommissioned, accepting the first shipment of waste in 1992. Located in Incheon in the area of around 16 million square meters, the Site processes the landfill of about 15,000 tons of wastes each day released by some 25 million people in the metropolitan area. Sudokwon Landfill Site Management Corporation (“SL Corp.”), operator of the large Site, goes beyond just stably disposing of the wastes, and is taking the initiative in building resource-recycling society through the construction and expansion of waste-to-energy facilities. Instead of releasing landfill gas generated by the landfill of wastes into the atmosphere, SL Corp. collects most of the gas and uses it as a fuel to generate power, not only reducing greenhouse gas emissions but also creating economic values by earning carbon credit through CDM project. SL Corp. also uses biogas generated in the process of food-waste treatment as a fuel, replacing the use of fossil fuels.

Converting Wastes into Resources

Sudokwon Landfill Site is a massive site, without a comparable site anywhere around the world. Sitting on a coastal reclamation land created in 1990, the Site processes about 15,000 tons of wastes each day, released by homes, construction sites, and business sites in metropolitan areas that host around half of the nation’s population, by applying cutting-edge waste-management technologies. SL Corp. is particularly striving to recycle resources by reusing waste resources and by turning them into energy. A good example is turning high-quality biogas from food wastewater into substitute fuel for sludge-resource facilities, creating an effect of removing fossil fuel import worth 8.4 billion won a year.


Converting Food Wastewater into Biogas

Food wastewater shipped from Seoul, Incheon, and Gyeonggi Province goes through an anaerobic digestion[1] process in the facility at the Site to be broken down to CH4 (65%) and CO2 (35%), and CH4 (methane gas) is used as a source of heat. Methane gas is a good replacement for liquefied natural gas (LNG) and fuels for power generation, and when refined to high concentration (95%), it may be used to fuel automobiles when mixed with LNG. Since May 2016, the methane gas, generated by food wastewater biogas conversion facilities, has been used as a drying-heat source for the facility to convert wastewater sludge into resource, replacing previous heat source of LNG. The reduction of LNG use itself reduces the emissions of carbon dioxide by around 35,500 CO2 tons a year.         

Furthermore, biogases are also being produced through the treatment of leachate and food wastewater in the leachate treatment facility at the Site, and the produced gas fuels the heating of SL Corp. buildings and electric power generation. And highly-refined quality methane gas is mixed with LNG (ratio of 15:85) and used to fuel 200 city buses per day and street-cleaning vehicles.


▲ Diagram of Biogas Production Process and Conversion into Energy


Turning Landfill Gas into Resource

Methane (CH4) accounts for over 50% of landfill gas, and its global warming index is known to be 21 times greater than that of carbon dioxide, a main culprit of global warming. Instead of releasing stenchful landfill gases into the air, SL Corp. collects them to fuel electric power generation in “50MW Landfill Gas Power Plant.” The following is how landfill gases are created and recovered for power generation. Once the waste is received and buried, organic matters in the waste decompose and release landfill gases that contain about 45-50% of methane. Landfill gas collected is processed to be converted into fuel for power generation. Then the processed gas is burned to generate steam, which turns a turbine to produce electricity.

The 50MW Landfill Gas Power Plant, which has been in operation since March 2007, is producing electric power for about 100,000 households, generating an income of 35.3 billion won[2] per year from the sale of power. The power generation from landfill gas not only creates economic benefits but also creates pleasant environment by removing stenches from the landfill gas. Moreover, burning methanol doubles the benefits of greenhouse gas emissions reduction as the landfill gas, used as a fuel from renewable energy, replaces conventional fossil fuels. 


▲ View of 50MW Landfill Gas Power Plant


Earning CER from the Conversion of Landfill Gas into Energy

In April 2007, SL Corp. was registered, for the first time in Korea, as Clean Development Mechanism (CDM) partner with the United Nations Framework Convention on Climate Change (UNFCCC). Of UNFCCC-approved CDM project in the category of waste, SL Corp. performs the largest scale of project, earning 880,000 CO2 tons of Emissions Reduction (CER) per year over the project period of ten years, or 8,821,017 CO2 tons up to 2018. This is said to have an equivalent effect of planting 1.3 billion 30-year-old pine trees. The CERs are being traded on carbon trading markets at home and abroad, and half of the CERs earned have been sold so far, bringing 46.3 billion won in profit to SL Corp. Since 2016, the money from the sale of CER has been reinvested into further reducing greenhouse gases. This reinvestment is part of SL Corp.’s carbon-neutral management policy to additionally reduce greenhouse gas emissions by reinvesting revenues from greenhouse gas emissions reduction into new projects for the same purpose.      


[1] Biological treatment process in the absence of oxygen

[2] Annual average of accumulated electric power sales (353 billion won) from March 2007 to December 2016

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