1 An everyday waste problem Food waste separation and collection - - PDF document

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Hong Kong University of Science and Technology

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Integrated Food Waste Management with Renewable Energy Production

Professor Irene M. C. LO

PhD, JP, M.EASA, F.ASCE, F.HKIE, F.HKGSA, M.AEE, CAP, BEAM Pro, GB Faculty

Chair Professor of Civil and Environmental Engineering Academician, European Academy of Sciences and Arts

14 June 2018

Hong Kong University of Science and Technology

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Energy  electricity  carbon emission

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Electricity consumption accounted for ~67% of total carbon emission in Hong Kong in 2018.

Hong Kong University of Science and Technology

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Fuel mix of electricity production in HK

Source: Environment Bureau, 2014

Coal 46%

Natural Gas 28%

Nuclear 23% Others 3%

Hong Kong University of Science and Technology

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Carbon emission from different energy sources

CO2e (g/kWh) Coal-fired (Castle Peak Power Station) 975 Gas-fired (Black Point Power Station) 414 Nuclear power (Daya Bay Nuclear Power Plant) Renewable energy (solar, wind) Renewable energy from waste-to-energy facility (e.g. anaerobic digestion/co-digestion, incineration, landfill) Low CO2e

Need to explore the potential RE from WTE facility in HK due to its lower impact on climate change

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Waste Tonnes/day Municipal SolidWaste (in which 40% is food waste) 9,000 (3600) ConstructionWaste 3,350 Sewage Sludge 950 OtherWastes 200 Total : 13,500

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An everyday waste problem …

Waste disposed of at landfills in HK

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How to collect food waste efficiently and effectively?

simple sorting with less behavioral change!

Food waste separation and collection

Photo courtesy of Environment Bureau

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Advanced technology for food waste collection -optic bag system

Refuse transfer station Optical sorting system Packed food waste Other packed MSW IWTF OWTF Food waste Other MSW Optic bag (green bag)

Common plastic bag or designated bag if MSW charging scheme by bag is launched

Garbage bin Refuse collection vehicle

Hong Kong University of Science and Technology

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Optical sorting plant in Oslo, Norway

• Haraldrud Plant

 In operation since 2009

• The world’s

largest optical sorting plant Handles wastes approximately 150,000 tonnes/year

Video courtesy of Envac Company

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Hong Kong University of Science and Technology

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Food waste separated from other MSW in RTS Wastewater treatment Anaerobic co- digestion Biogas generation Sewage sludge Food waste A portion of food waste can be sent to sewage treatment works and mixed with sewage sludge Anaerobic digestion (OWTF) Biogas generation

(Co-)digestion of food waste with sewage sludge for biogas generation

500 tonne/day

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Parameters Shatin STW Tai Po STW Shek Wu Hui STW Yuen Long STW Treated Sewage (million m3) 85 36 31 10 Biogas produced (million m3) 5.6 2.0 1.2 0.6

Biogas Production from Anaerobic Digestion of Sludge at 4 Secondary STWs in 2013 in HK

Source: “From Sewage to Energy” presented at HKIE Environmental Division Annual Seminar 2014

Using the spare capacity of the 4 STW for anaerobic co- digestion, it is estimated that 500-600 tpd food waste can be handled (based on HRT of 22 days and sludge to food waste ratio of 10 : 3 by mass).

Hong Kong University of Science and Technology

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Food waste  biogas  various energy forms

Electricity City gas Biogas fuel

Food waste Organic waste treatment facility (OWTF) Sludge digester at STWs

Anaerobic digestion Anaerobic co-digestion

Biogas

Petrol; Diesel; LPG

Hong Kong University of Science and Technology

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Potential renewable energy in Hong Kong

Sources of Renewable Energy % of total electricity consumption in 2014 (total = 43,932 GWh) 1 Sewage sludge incineration facility at Nim Wan 0.4% 2 Municipal solid waste incineration at Shek Kwu Chau 1.45% 3 Food waste (assume 80% recovery) – Biogas generated from AD at organic waste treatment facility 1.67% 4 Anaerobic co-digestion of sewage sludge & food waste for biogas generated at 2 secondary STWs + 3 new cavern STWs 0.43% 5 Landfill gas recovery with 3 landfill extension 0.7% 6 Wind (Lamma Winds, proposed Offshore Wind Farm) 1.2%

Total 5.85%

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Hong Kong University of Science and Technology

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Comparison of life cycle carbon emission from food waste valorization options

CO2e (g/kWh) Food waste valorization to replace CLP electricity 23 Food waste valorization to replace Towngas 148 Food waste valorization to replace petrol as vehicle fuel

• 181 *

Food waste valorization to replace diesel as vehicle fuel

• 149 *

Food waste valorization to replace LPG as vehicle fuel

• 125 *

* A negative value indicates a better environmental performance. It means that the avoided carbon emission from the fuel substitution exceed the direct emission from the processes of biofuel production. Source: Woon et al., 2016. (Values are recalculated with unit conversion)

Hong Kong University of Science and Technology

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Example: Linköping in Sweden

Food waste produces biogas fuel to ~6% of the vehicle use in Linkoping

Biogas-fueled bus Biogas waste truck fleet Biogas-fueled car

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Bern, Switzerland Stockholm, Sweden Haarlem, the Netherlands Oslo, Norway

More examples of cities turning food waste into biogas fuel for vehicle use!

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How can it be implemented in Hong Kong?

Government service cars Public transport Private cars

Biogas-fueled cars (i.e., hybrid gas cars)

~1,000 tpd food waste Fuel ~12,000 private cars/day Reduce ~ 130,000 tonne CO2/year

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Hong Kong University of Science and Technology

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Conclusions

 Simple yet effective food waste separation and collection system

• optic bag system

 Valorization of food waste to renewable energy: AD & Co-AD

• Renewable biogas: electricity, city gas, and biogas fuel for

vehicle use

(1) Recycling 80% food waste can further achieve ~30% of waste reduction target; (1) Producing renewable energy; (3) Creating low carbon economy (waste into business).

Hong Kong University of Science and Technology

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HKUST

Growth of environmental industry & business in Korea is highly related to the environmental policy

Hong Kong University of Science and Technology

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Optic bag (HKD 0.1/bag based

• n Swedish

case)

• Enable separation at source with

less behavioral change

• Eliminate the need for extra

storage space for the waste fractions

• Perform recycling in existing

buildings

Advantages of optic bag system