Results
summary |
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Lowest tonnage
input and biogas yield estimate, Middle tonnage and biogas yield estimate,
Highest tonnage and biogas yield estimate |
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The Lowest,
middle and high values are defined by the entries on the FeedStockProperties
sheet |
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Input feed properties |
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Estimates |
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Lowest |
Middle |
Highest |
(Biomass) |
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Lorry loads of delivery
each day |
6.5 |
9.1 |
19.8 |
lorries/day |
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from FeedTransportCosts sheet |
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Total
tonnes per day |
292.4 |
330.4 |
482.4 |
tonnes/day |
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from InputFeedMix sheet |
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Dry
solids content range of feed |
9.1% |
11.4% |
12.7% |
% |
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from InputFeedMix sheet. This should be between
6-15%. If too low, remove water or add dryer feed. If too high, add water. |
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Total dry
solids per day |
26.74 |
37.56 |
61.03 |
tonnes/day |
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from InputFeedMix sheet |
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VS
content of dry solids |
86.8% |
87.3% |
87.5% |
% |
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from InputFeedMix sheet |
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Total
volatile solids per day |
23.21 |
32.78 |
53.42 |
tonnes/day |
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from InputFeedMix sheet |
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Volatile
solids loading rate |
3.92 |
4.90 |
5.47 |
kg/m^3/day |
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from InputFeedMix sheet. This can be up to
about 6-7 for a single stage, and 25-50 for a two-stage
acidogenesis+methanogenesis system |
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Carbon:Nitrogen
ratio |
40.4 |
37.7 |
36.6 |
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from CarbonNitrogen sheet. This should be
between 20 and 30, optimum 25. Add Paper/sawdust to increase, blood or slurry
to decrease |
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If Carbon/Nitrogen ratio is not in the 20-30
target range, biogas yields will be reduced |
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HRT and SRT |
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Two stage
process ? |
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NO |
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from BiogasYields sheet |
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HRT, 1st
phase |
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20 |
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from ParametersPlant sheet |
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HRT, 2nd
phase |
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NA |
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from ParametersPlant sheet |
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SRT, 1st
phase |
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20 |
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from BiogasYields sheet |
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SRT, 2nd
phase |
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NA |
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from BiogasYields sheet |
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SRT ratio
2nd phase/1st phase |
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NA |
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5-15 for a two-stage process |
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Digester properties |
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Input buffer diameter |
11.27 |
11.74 |
13.32 |
m |
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from DigesterSizing sheet |
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Input
buffer height |
11.27 |
11.74 |
13.32 |
m |
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from DigesterSizing sheet |
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Pasteuriser
diameter (each) |
2.08 |
2.17 |
2.46 |
m |
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from DigesterSizing sheet |
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Pasteuriser
height (each) |
2.08 |
2.17 |
2.46 |
m |
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from DigesterSizing sheet |
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1st stage
diameter (each) |
15.56 |
16.21 |
18.39 |
m |
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from DigesterSizing sheet |
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1st stage
height (each) |
15.56 |
16.21 |
18.39 |
m |
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from DigesterSizing sheet |
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2nd stage
diameter (each) |
NA |
NA |
NA |
m |
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from DigesterSizing sheet |
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2nd stage
height (each) |
NA |
NA |
NA |
m |
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from DigesterSizing sheet |
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Digestate
buffer diameter |
19.04 |
19.73 |
22.33 |
m |
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from DigesterSizing sheet |
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Digestate
buffer height |
19.04 |
19.73 |
22.33 |
m |
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from DigesterSizing sheet |
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Temperatures |
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Pasteuriser |
70.0 |
70.9 |
70.9 |
C |
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from ThermalBalance sheet |
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1st
stage digester |
38.0 |
38.0 |
38.5 |
C |
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from ThermalBalance sheet |
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2nd stage
digester |
NA |
NA |
NA |
C |
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from ThermalBalance sheet |
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Process problems affecting
biogas yields |
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Approximate biogas yield
(relative to baseline) due to inadequate SRT |
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93% |
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from BiogasYields sheet |
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Approximate
biogas yield (relative to baseline) due to imperfect C:N ratio |
35% |
55% |
66% |
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from BiogasYields sheet |
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Approximate biogas yield
(relative to baseline) due to temperature excursions |
100% |
100% |
99% |
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from BiogasYields sheet |
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Approximate biogas yield
(relative to baseline) due to all above factors |
32% |
51% |
60% |
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Biogas/methane power
outputs |
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Total biogas per day |
2773.39 |
10472.94 |
28795.91 |
m^3 |
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from BiogasYields sheet |
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Average biogas per tonne
feed input (including water) |
9.5 |
31.7 |
59.7 |
m^3/tonne |
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from BiogasYields sheet |
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Average
biogas per tonne feed input (excluding water) |
30.0 |
80.3 |
102.0 |
m^3/tonne |
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from BiogasYields sheet |
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Methane
content range of biogas |
50% |
60% |
65% |
% |
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from BiogasYields sheet |
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Total
methane per day |
1386.70 |
6283.76 |
18717.34 |
m^3 |
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from BiogasYields sheet |
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kWh per
day @ 11.04 kWh/m^3 |
15309.13 |
69372.74 |
206639.42 |
kWh/day |
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from BiogasYields sheet |
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kW average
power (methane) |
637.88 |
2890.53 |
8609.98 |
kW |
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from BiogasYields sheet |
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Energy |
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Total methane energy
yielded, of which |
637.9 |
2890.5 |
8610.0 |
kW |
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from BiogasYields sheet |
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Engine heat lost |
74.8 |
260.1 |
774.9 |
kW |
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from EngineSize sheet |
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Generator
heat lost |
10.4 |
49.1 |
146.4 |
kW |
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from EngineSize sheet |
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Process heat required |
110.9 |
204.6 |
292.6 |
kW |
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from ThermalBalance sheet |
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Process
electrical required |
145.3 |
88.5 |
140.3 |
kW |
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from ElectricalLoads sheet |
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Surplus
electricity for export (import if negative) |
52.1 |
845.2 |
2640.7 |
kW |
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from ElectricalLoads sheet |
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Surplus
heat (available for CHP export) |
244.4 |
1443.0 |
4615.1 |
kW |
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from ThermalBalance sheet |
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Check energy sum |
637.9 |
2890.5 |
8610.0 |
kW |
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Sum energy breakdown to check consistency |
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Surplus CHP water
temperature |
61 |
75 |
80 |
C |
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from ThermalBalance sheet |
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Surplus
CHP water at mass flow rate |
1.11 |
5.13 |
15.28 |
kg/s |
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from ThermalBalance sheet |
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Surplus
CHP water must be returned at or above above |
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8 |
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C |
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from ParametersEngine sheet |
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Efficiency of electrical
export, as a proportion of methane energy |
8% |
29% |
31% |
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Potential
total efficiency of electrical plus CHP energy |
46% |
79% |
84% |
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Profitability
index calculation, NPV using primary discount rate figure, for the 10-year
investment |
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Plant capital cost |
£6,392 |
£7,149 |
£9,494 |
£1000s |
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Invested
capital amount (minus grant) |
£6,392 |
£7,149 |
£9,494 |
£1000s |
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Total net
present value of project at primary discount rate |
-£1,843 |
£5,498 |
£34,950 |
£1000s |
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Profitability
index (=NPV/Capital investment) |
-0.29 |
0.77 |
3.68 |
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Internal
rate of return (IRR) |
1.6% |
14.9% |
20.5% |
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