1/38 21 – Landfill gas 21 Landfill gas 1

2/38 21 – Landfill gas “Landfill gas is an explosive topic” (J.Jacobs, 2006)

3/38 21 – Landfill gas 21 Landfill gas Overview 21.1 Landfil gas production 21.2 Prognosis of landfill gas production 21.3 Extraction systems 21.4 Production monitoring 21.5 Flaring, electricity and heat production

4/38 21 – Landfill gas 21.1 LFG production n Waste contains a certain amount of degradable organic matter n Microbiological processes result in the formation of landfill gas (LFG) 21.1 – Landfill gas Biological processes

5/38 21 – Landfill gas 21.1 Landfill gas production n Degradation follows 4 biological stages during waste disposal: 1. Hydrolosis 2. Acidogenesis 3. Acetogenesis 4. Methanogenesis 21.1 – Landfill gas production

6/38 21 – Landfill gas Biological processes 21.1 – Landfill gas production

7/38 21 – Landfill gas Hydrolosis In the first stage complex solid organic material is solubilized by enzymes excreted by hydrolytic micro-organisms 21.1 – Landfill gas production

8/38 21 – Landfill gas Acidogenesis In the second stage soluble organic components including the products of hydrolysis are converted into organic acids and alcohols 21.1 – Landfill gas production

9/38 21 – Landfill gas Acetogenesis In the third stage the products of acidogenesis are converted into acetic acid, hydrogen and carbon dioxide 21.1 – Landfill gas production

10/38 21 – Landfill gas Methanogenesis In the fourth and final stage methane is formed mainly from acetic acid or from hydrogen and carbon dioxide. Methane can also be formed directly from products of the acidogenesis such as formic acid and methanol 21.1 – Landfill gas production

11/38 21 – Landfill gas Composition n LFG primarily consists out of methane (CH 4 ) and carbondioxide (CO 2 ) n Ratio CH 4 :CO 2 = 50:50 (theoretically) CH 3 COOH (Acetic acid) --> CH 4 + CO 2 n CO 2 is more soluble in water, ratio shifts to 60: – Landfill gas production

12/38 21 – Landfill gas Composition (cont’d) n CH 4 is a green house gas (GHG) with a GHG potential of 21 times that of CO 2 n 1 ton of CH 4 has an equivalent of 21 ton of CO 2 n LFG can contain traces of hydrocarbons, halogenated hydrocarbons and sulphur compounds 21.1 – Landfill gas production

13/38 21 – Landfill gas 21.2 Prognosis of LFG production n Modelling with LFG production models n Only two models are validated n First order model n Multi phase first order model 21.2 – Prognosis of landfill gas production

14/38 21 – Landfill gas First order model 21.2 – Prognosis of landfill gas production

15/38 21 – Landfill gas First order model – organic content 21.2 – Prognosis of landfill gas production

16/38 21 – Landfill gas Multi phase first order 21.2 – Prognosis of landfill gas production

17/38 21 – Landfill gas Multi phase first order – organic content 21.2 – Prognosis of landfill gas production

18/38 21 – Landfill gas Organic matter and Organic C 21.2 – Prognosis of landfill gas production

19/38 21 – Landfill gas Prognosis of LFG production 21.2 – Prognosis of landfill gas production

20/38 21 – Landfill gas Prognosis of LFG production n Only two models are validated n Uncertainty depending on: 1. Waste composition 2. Degree of pre-treatment 3. Type and degree of compaction, method of operation, type and thickness of cover material 4. Quantity of refuse, geometry and hydrogeolocic properties of landfill 5. Climatic conditions 21.2 – Prognosis of landfill gas production

21/38 21 – Landfill gas 21.3 Extraction systems n Lay out of an extraction system n Various types of extraction systems n Recovery efficiency 21.3 – Extraction systems

22/38 21 – Landfill gas Lay out flaring and/or utilisation production emission oxidation extraction 21.3 – Extraction systems

23/38 21 – Landfill gas Various types of extraction systems 1. Vertical 2. Horizontal 3. Slope 4. Point 21.3 – Extraction systems

24/38 21 – Landfill gas Vertical Conventional Cell wise Build upBuild up + early extraction GRAVEL HDPE piping (perforated) HDPE piping (non - perforated) 21.3 – Extraction systems

25/38 21 – Landfill gas Horizontal 21.3 – Extraction systems

26/38 21 – Landfill gas Slope 21.3 – Extraction systems

27/38 21 – Landfill gas Point 21.3 – Extraction systems

28/38 21 – Landfill gas Gas well connection RULE OF THUMB: 4 GAS WELLS PER HA 21.3 – Extraction systems

29/38 21 – Landfill gas Gas well connection 21.3 – Extraction systems

30/38 21 – Landfill gas Recovery efficiency 21.3 – Extraction systems

31/38 21 – Landfill gas 21.4 Production monitoring n Monitoring equipment Anemo meterDigital mano meter Gas analyser 21.4 – Production monitoring

32/38 21 – Landfill gas n Gas analyser can measure: 1. CH 4 2. CO 2 3. O 2 4. N 2 (= 100% - CH 4 % - CO 2 % - O 2 %) 21.4 – Production monitoring

33/38 21 – Landfill gas n If CH4 and O2 concentration respectively in a gas well is: > 50% and < 1%thenmore extraction 1%then less extraction 21.4 – Production monitoring

34/38 21 – Landfill gas n If N 2 :O 2 ratio is: > 5 indicator suction of ambient air < 4 indicator leakage piping extraction system 21.4 – Production monitoring

35/38 21 – Landfill gas 21.5 Flaring, electricity and heat production n A suitable nearby use for LFG must be identified n The landfill must have a depth of at least 5 m. and preferably 10 m. of unsaturated biodegradable waste n Amount of waste deposited: 0.5 Million tonnes n Waste should not be too old (between 5 – 10 years, less if mainly food and vegetable wastes) n Leachate level should be at least 5 m. below the landfill surface 21.5 – Flaring, electricity and heat production

36/38 21 – Landfill gas Flaring Open flare Enclosed flares Passive flare 21.5 – Flaring, electricity and heat production

37/38 21 – Landfill gas Heat production LFG fired boilers Heat exchangers WWTP 21.5 – Flaring, electricity and heat production

38/38 21 – Landfill gas Electricity production 21.5 – Flaring, electricity and heat production