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[Waste] Gwangju (Republic of Korea)

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Resource Circulation with Food Waste

- ​Environmental Corporation of Gwangju (ECO-G)

 

1. Resource Circulation : Start with Food Waste!
- A small action to safeguard the entire earth! -

The greatest danger facing mankind at present is global warming. One of the causes of global warming is food waste that is abandoned indiscriminately. The amount of food waste generated in Gwangju exceeds 500 tons per day in 2017 due to eating habits that include many side dishes, soups and stews coupled with an increasing population and a higher standard of living. Leftover food turns into garbage that is costly to process. Environmental Corporation of Gwangju currently runs two food waste recycling facilities to efficiently treat food waste while minimizing the generation of air pollutants under the catch phrase of “Turn all food waste into recycled resource.

51b11a80f57e810773b9b7f96cfd35db_1531469

Fig 1. Food waste recycling facility

 

 

The city’s two food waste recycling facilities turn 450 tons of food waste into 45 tons of animal feed per day through a dehydration processing method. The Corporation uses the dried feed as poultry feed for chickens and domestic duck. It recycles high-quality biogas (methane) produced in the process of treating high-concentration wastewater into clean energy used to fuel dehydration processing facilities.

In addition, Environmental Corporation of Gwangju has also launched the ‘Reduce Food Waste by 30%’ campaign in partnership with the Gwangju Metropolitan Government to reduce the food waste generation itself. 

 

 

51b11a80f57e810773b9b7f96cfd35db_1531469

Fig 2. Food waste reduction campaign

The multi-year campaign was targeted to reduce the city’s food waste by 5% until 2016 and aims to curtail 15% and 30% of the city’s food waste by 2018 and 2020, respectively through citizens’ field trips to food waste recycling facilities and environmental education customized to different citizen groups on how to reduce food waste. By 2020, when the current municipal efforts are completed, Gwangju Metropolitan City will have reduced its food waste by around 151,000 tons, saving KRW 22.2 billion in food waste processing cost, and curtailing its GHG emissions by 224,000 tons – equivalent to the effect of planting 80 million pine trees.

2. Turn Food Waste into a Value Resource!
- Revenue generation through the sales of single ingredient feed and fractions -

 

▷ Single ingredient feed

 

Single ingredient feed refer to animal, vegetable or mineral materials used as raw materials for assorted feeds. Environmental Corporation of Gwangju turns its single ingredient feed (15,000 tons/year) - the final by-product of its food waste treatment process – into a useful resource worth more than KRW 500 million each year. It is also carrying out research to boost the value and reliability of its recycled feed.

51b11a80f57e810773b9b7f96cfd35db_1531469

Fig 3. Animal feed

<Annual Sales Volume of Animal Feed>

 Year

 2013

2014

2015 

2016 

Sales volume (ton)​

 4,136

 12,649

14,697

14,558 

 

Oil generated from food wastewater

 

 

The wastewater generated by the food waste recycling facilities of Environmental Corporation of Gwangju contains about 2% of animal/vegetable oil. Having noticed the fact that oil rises to the upper part of the wastewater reservoir by a specific gravity difference after a certain period of time, the Corporation strove to develop technology required to recover only animal/vegetable oil from wastewater.

51b11a80f57e810773b9b7f96cfd35db_1531469

Fig 4. Oil separation equipment

As a result, the Corporation developed its own oil recovery system of a float ball type to recover oil from the reservoir surface. In the second half of 2014, it recovered and sold 101 tons of oil and earned KRW 37 million in revenue.

<Oil Production and Sales in 2016>

 Year

Yearly Production

Monthly Average 

Annual Revenue 

 2016

450 tons 

37.58 tons 

about KRW

200 million 

 

The Corporation has since arranged for 3-phase centrifugal separators to be installed by a private investor, recovered oil from food waste and earned about KRW 200 million in revenue each year. The recovered oil is used as bio diesel and cosmetic ingredients by related businesses.

 

3. Rebirth of Biogas
- From surplus resources to clean energy -

 

 

When wastewater generated during the process of turning food waste into animal feed undergoes the anaerobic digestion process for about 20 days, an average of 20,000 of biogas with around 60% methane (CH4) content is produced each day. The Corporation recycles the biogas as the heat source of its own dehydration facility boilers, saving KRW 2 billion in LNG costs annually.

Discarded biogas to turn into electricity

The 2nd food waste recycling facility of Environmental Corporation of Gwangju is carrying out a project designed to install and operate a facility that will recycle the biogas being discarded in the food waste treatment process as fuel to generate electricity. When the project is completed, the Corporation will be able to produce about 1,800 MW of electricity annually with 1,343,000Nm3 of discarded biogas through its 1,000 kW cogeneration facility.

 

Total Q'ty 

 Recycling

Surplus 

Year 

 Biogas (m3/year)

 5,299,412

3,956,226 

 1,343,186

 2016

 Ratio (%)

 100

 74.7

 25.3

 2016

 

The project draws keen interest from many as it will enable Gwangju Metropolitan City not only to earn KRW 400 million in annual revenue but also reduce its GHG emissions and establish a resource circulation structure turning waste into energy. 

 

 51b11a80f57e810773b9b7f96cfd35db_1531470

  Fig 5. Biogas Storage Facility

 51b11a80f57e810773b9b7f96cfd35db_1531470

  Fig 6. Generation of electriity flow chat

 


 

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