Post on 05-Oct-2021
Prof Klaus Fricke
Are ‘batch garage digesters’
a viable alternative to
in-vessel composting in Australia?
Johannes Biala (j.biala@uq.edu.au)
Organics Processing Facilities
Year No facilities Tonnage input
2004/05 178 4.2 M
2011/12 206 5.5 M
Source: MRA Consulting
Richgro
Earthpower
ReWaste
Spring Farm
Composting Facilities 2016
Tunnel Composting is Popular
Kembla Grange - Soilco
Grafton – JR Richards & Sons
Bulla – Veolia
Tunnel Composting – Tunnel Digestion
If tunnel composting,
why not tunnel digestion?
Development of Biogas Plants and Installed Electrical
Generation Capacity [MW] in Germany
Small Proportion of AD Capacity in Germany
serves Waste Sector
Predominantly
Municipal
Organics (FOGO)
75 plants
2.4 M tpa (total)
1.9 M tpa (AD)
52 MWel
Predominantly
Commercial
Organics (FO)
38 plants
1.9 M tpa
50 MWel
2014/15
Development of FOGO Processing in Germany
40%
60%
Composting Anaerobic Digestion
Source: Bundesgütegemeinschaft Kompost
Anaerobic Digestion Processing Options
Anaerobic Digestion
mesophilic - thermophilic
Continuous process Dis-continuous process
Wet digestion
DM < 12 - 15% Dry digestion
DM > 25 - 35%
Dry digestion
DM > 33 - 50%
Single stage
process
Multi stage
process
Anaerobic Digestion Processing Options
Used for FOGO in Germany (2013)
330,350
1,028,649
537,249 491,400
0.00
200,000.00
400,000.00
600,000.00
800,000.00
1,000,000.00
1,200,000.00
Nass Trocken Trocken, kontinuierlich Trocken, diskontinuierlich
t/a
8
46
23
17
23
Wet Dry
total Dry
contin.
Dry
dis-contin.
Dry AD Technologies
- Continuous Processing
DRANCO
HITACHI ZOSSEN INOVA - KOMPOGAS
LARAN - STRABAG
THÖNI
BEKON /
Eggersmann
Dry AD Technologies
- Dis-continuous Processing
Zero
Waste
Energy
“Batch
Garage
Digesters”
Batch Garage Digesters
Key Components & Processing Schematic
Source: BEKON
CHP
Batch Garage Digesters
Processing Stages
Stage 1: Aerobic, Heating Stage 2: Anaerobic, Percolation, Methane
Generation
Stage 3: Aerobic
Source: BIOFerm
Biogas Generation at Various Temperatures
Days
Re
lati
ve
Bio
ga
s Y
ield
[%
]
Thermophilic process increases
biogas yield markedly
at any given retention time
Biogas Generation over Time
Days
Re
lati
ve
Bio
ga
s Y
ield
[%
]
0 10 20
Days
Daily Methane Yield from FOGO
[m3/m2 digester surface area]
Multiple Digesters for Constant Biogas Supply
Days
Re
lati
ve
Bio
ga
s Y
ield
[%
]
0 10 20
Days
Daily Methane Yield from FOGO
[m3/m2 digester surface area]
Date
Bio
gas
Yie
ld [
m3/d
ay]
Minimum of 4 Digesters
Biogas Yield
Rule of thumb: 1 t FOGO generates 100 m3 biogas with 60% methane
and energy content of 600 kWh
Raw Material Quantity
[m3 / t fermenter
input]
CH4
[vol.-%]
FOGO (mixture of food and
garden organics) 75 – 136 53 - 65
Food organics 123 – 178 53 - 68
Potential Options for Utilising Biogas
Purification (removal of H2O, CO2, H2S, NH3)
Biogas (crude)
CHP Unit
Heat &
Electricity
‘Aspirational Targets’
CHP Efficiency Parameter
%
Total energy 100
Electrical efficiency 33 - 45
Thermal efficiency 35 - 56
Loss 10 - 15
CHP efficiency 85 - 90
Operational use 20 - 30
Gross surplus energy 58 – 72
Curing / vehicles 25 - 30
Net surplus energy 30 – 45
Energy in generated gas 100%
Source: Clark Energy
Investment and operating costs for 18,000 tpa
dry batch digestion facility (Germany, 2012) (Converted at exchange rate of €1.00 = AUD1.35)
Total ($) Per tonne
input ($/t) Investment costs (digestion only)* 5,494,500 305
Capital costs (12 yrs, 5%) 619,650 34.43
Processing costs 486,570 26.87
Costs for digestion
(processing & capital costs) 1,103,400 61.30
Income from sale of energy
(20% - 50% of income in Germany) 139,140 – 347,760 7.73 – 19.32
Treatment costs - digestion 755,640 – 964,260 41.98 - 53.57
Treatment costs - composting 540,000 30.00
Income from sale of compost 270,000 15.00
Treatment costs - total 1,025,640 – 1,234,260 56.98 – 68.57
* Excludes costs for land purchase, site development, infrastructure and profit margin
Integrated Recovery, Processing & Utilisation
of Organic Resources