| 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 |
8.2 |
12.3 |
17.6 |
lorries/day |
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from FeedTransportCosts sheet |
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| Total
tonnes per day |
116.4 |
176.2 |
251.8 |
tonnes/day |
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from InputFeedMix sheet |
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| Dry
solids content range of feed |
9.2% |
11.9% |
14.6% |
% |
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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 |
10.68 |
21.00 |
36.80 |
tonnes/day |
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from InputFeedMix sheet |
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| VS
content of dry solids |
75.7% |
75.2% |
74.8% |
% |
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from InputFeedMix sheet |
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| Total
volatile solids per day |
8.09 |
15.79 |
27.53 |
tonnes/day |
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from InputFeedMix sheet |
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| Volatile
solids loading rate |
3.43 |
4.43 |
5.40 |
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 |
22.1 |
20.0 |
18.6 |
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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 |
8.29 |
9.52 |
10.72 |
m |
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from DigesterSizing sheet |
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| Input
buffer height |
8.29 |
9.52 |
10.72 |
m |
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from DigesterSizing sheet |
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| Pasteuriser
diameter (each) |
1.53 |
1.76 |
1.98 |
m |
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from DigesterSizing sheet |
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| Pasteuriser
height (each) |
1.53 |
1.76 |
1.98 |
m |
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from DigesterSizing sheet |
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| 1st
stage diameter (each) |
11.45 |
13.14 |
14.81 |
m |
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from DigesterSizing sheet |
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| 1st
stage height (each) |
11.45 |
13.14 |
14.81 |
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 |
14.00 |
15.98 |
17.90 |
m |
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from DigesterSizing sheet |
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| Digestate
buffer height |
14.00 |
15.98 |
17.90 |
m |
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from DigesterSizing sheet |
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| Temperatures |
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| Pasteuriser |
70.9 |
70.9 |
70.9 |
C |
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from ThermalBalance sheet |
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| 1st
stage digester |
38.0 |
38.0 |
38.0 |
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 |
146% |
139% |
133% |
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from BiogasYields sheet |
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| Approximate biogas yield
(relative to baseline) due to temperature excursions |
100% |
100% |
100% |
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from BiogasYields sheet |
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| Approximate biogas yield
(relative to baseline) due to all above factors |
136% |
129% |
123% |
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| Biogas/methane power
outputs |
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| Total biogas per day |
4015.86 |
6866.41 |
11987.92 |
m^3 |
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from BiogasYields sheet |
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| Average biogas per tonne
feed input (including water) |
34.5 |
39.0 |
47.6 |
m^3/tonne |
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from BiogasYields sheet |
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| Average
biogas per tonne feed input (excluding water) |
34.5 |
39.0 |
47.6 |
m^3/tonne |
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from BiogasYields sheet |
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| Methane
content range of biogas |
51% |
58% |
67% |
% |
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from BiogasYields sheet |
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| Total
methane per day |
2045.11 |
3989.62 |
8058.59 |
m^3 |
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from BiogasYields sheet |
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| kWh per
day @ 11.04 kWh/m^3 |
22577.98 |
44045.43 |
88966.85 |
kWh/day |
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from BiogasYields sheet |
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| kW
average power (methane) |
940.75 |
1835.23 |
3706.95 |
kW |
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from BiogasYields sheet |
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| Energy |
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| Total methane energy
yielded, of which |
940.7 |
1835.2 |
3707.0 |
kW |
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from BiogasYields sheet |
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| Engine heat lost |
96.8 |
165.2 |
333.6 |
kW |
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from EngineSize sheet |
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| Generator
heat lost |
15.7 |
31.2 |
63.0 |
kW |
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from EngineSize sheet |
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| Process heat required |
81.1 |
116.7 |
160.4 |
kW |
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from ThermalBalance sheet |
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| Process
electrical required |
31.5 |
48.2 |
70.7 |
kW |
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from ElectricalLoads sheet |
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| Surplus
electricity for export (import if negative) |
266.1 |
544.5 |
1126.7 |
kW |
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from ElectricalLoads sheet |
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| Surplus
heat (available for CHP export) |
449.7 |
929.4 |
1952.6 |
kW |
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from ThermalBalance sheet |
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| Check energy sum |
940.7 |
1835.2 |
3707.0 |
kW |
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Sum energy breakdown to check consistency |
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| Surplus CHP water
temperature |
73 |
76 |
79 |
C |
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from ThermalBalance sheet |
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CHP water at mass flow rate |
1.65 |
3.26 |
6.58 |
kg/s |
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from ThermalBalance sheet |
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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 |
28% |
30% |
30% |
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| Potential
total efficiency of electrical plus CHP energy |
76% |
80% |
83% |
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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 |
£3,967 |
£5,042 |
£6,314 |
£1000s |
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| Invested
capital amount (minus grant) |
£2,777 |
£3,529 |
£4,419 |
£1000s |
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| Total
net present value of project at primary discount rate |
-£4,982 |
-£4,676 |
-£3,847 |
£1000s |
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| Profitability
index (=NPV/Capital investment) |
-1.79 |
-1.32 |
-0.87 |
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| Internal
rate of return (IRR) |
43.9% |
72.8% |
-98.8% |
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