| 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 |
17.8 |
26.8 |
35.8 |
lorries/day |
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from FeedTransportCosts sheet |
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| Total tonnes per day |
269.0 |
398.0 |
527.0 |
tonnes/day |
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from InputFeedMix sheet |
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| Dry solids content range of feed |
6.7% |
11.9% |
14.9% |
% |
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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 |
17.97 |
47.33 |
78.49 |
tonnes/day |
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from InputFeedMix sheet |
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| VS content of dry solids |
76.6% |
76.7% |
76.1% |
% |
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from InputFeedMix sheet |
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| Total volatile solids per day |
13.77 |
36.32 |
59.73 |
tonnes/day |
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from InputFeedMix sheet |
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| Volatile solids loading rate |
2.53 |
4.51 |
5.60 |
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 |
15.2 |
15.2 |
14.7 |
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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 |
10.96 |
12.49 |
13.72 |
m |
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from DigesterSizing sheet |
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| Input buffer height |
10.96 |
12.49 |
13.72 |
m |
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from DigesterSizing sheet |
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| Pasteuriser diameter (each) |
2.03 |
2.31 |
2.54 |
m |
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from DigesterSizing sheet |
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| Pasteuriser height (each) |
2.03 |
2.31 |
2.54 |
m |
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from DigesterSizing sheet |
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| 1st stage diameter (each) |
15.13 |
17.25 |
18.94 |
m |
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from DigesterSizing sheet |
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| 1st stage height (each) |
15.13 |
17.25 |
18.94 |
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 |
18.61 |
20.97 |
22.88 |
m |
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from DigesterSizing sheet |
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| Digestate buffer height |
18.61 |
20.97 |
22.88 |
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 |
38.1 |
38.6 |
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 |
113% |
113% |
110% |
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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 |
105% |
104% |
100% |
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| Biogas/methane power
outputs |
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| Total biogas per day |
6955.78 |
15438.10 |
21734.37 |
m^3 |
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from BiogasYields sheet |
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| Average biogas per
tonne feed input (including water) |
25.9 |
38.8 |
41.2 |
m^3/tonne |
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from BiogasYields sheet |
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| Average biogas per tonne feed input (excluding water) |
27.4 |
40.3 |
42.4 |
m^3/tonne |
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from BiogasYields sheet |
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| Methane content range of biogas |
51% |
59% |
67% |
% |
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from BiogasYields sheet |
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| Total methane per day |
3573.30 |
9075.10 |
14519.44 |
m^3 |
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from BiogasYields sheet |
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| kWh per day @ 11.04 kWh/m^3 |
39449.22 |
100189.07 |
160294.62 |
kWh/day |
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from BiogasYields sheet |
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| kW average power (methane) |
1643.72 |
4174.54 |
6678.94 |
kW |
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from BiogasYields sheet |
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| Energy |
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| Total methane energy
yielded, of which |
1643.7 |
4174.5 |
6678.9 |
kW |
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from BiogasYields sheet |
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| Engine heat lost |
147.9 |
375.7 |
601.1 |
kW |
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from EngineSize sheet |
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| Generator heat lost |
27.9 |
71.0 |
113.5 |
kW |
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from EngineSize sheet |
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| Process heat
required |
170.1 |
242.9 |
318.8 |
kW |
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from ThermalBalance sheet |
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| Process electrical required |
70.8 |
108.9 |
145.1 |
kW |
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from ElectricalLoads sheet |
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| Surplus electricity for export (import if negative) |
460.1 |
1239.5 |
2012.2 |
kW |
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from ElectricalLoads sheet |
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| Surplus heat (available for CHP export) |
766.8 |
2136.6 |
3488.2 |
kW |
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from ThermalBalance sheet |
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| Check energy sum |
1643.7 |
4174.5 |
6678.9 |
kW |
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Sum energy breakdown to check consistency |
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| Surplus CHP water
temperature |
71 |
77 |
79 |
C |
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from ThermalBalance sheet |
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| Surplus CHP water at mass flow rate |
2.92 |
7.41 |
11.86 |
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 |
28% |
30% |
30% |
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| Potential total efficiency of electrical plus CHP energy |
75% |
81% |
82% |
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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 |
£6,292 |
£8,047 |
£9,611 |
£1000s |
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| Invested capital amount (minus grant) |
£3,146 |
£4,024 |
£4,806 |
£1000s |
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| Total net present value of project at primary discount rate |
-£1,591 |
£546 |
£2,045 |
£1000s |
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| Profitability index (=NPV/Capital investment) |
-0.51 |
0.14 |
0.43 |
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| Internal rate of return (IRR) |
-8.2% |
9.9% |
12.7% |
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