Results summary 

















































Lowest
tonnage input and biogas yield estimate, Middle tonnage and biogas yield
estimate, Highest tonnage and biogas yield estimate 












The Lowest,
middle and high values are defined by the entries on the
FeedStockProperties sheet 










































Input feed
properties 


























Estimates 























Lowest 
Middle 
Highest 
(Biomass) 




















Lorry loads of delivery
each day 
17.8 
26.8 
35.8 
lorries/day 


from FeedTransportCosts sheet 















Total tonnes per day 
269.0 
398.0 
527.0 
tonnes/day 


from InputFeedMix sheet 















Dry solids content range of feed 
6.7% 
11.9% 
14.9% 
% 


from InputFeedMix sheet. This should be
between 615%. If too low, remove water or add dryer feed. If too high,
add water. 





Total dry solids per day 
17.97 
47.33 
78.49 
tonnes/day 


from InputFeedMix sheet 















VS content of dry solids 
76.6% 
76.7% 
76.1% 
% 


from InputFeedMix sheet 















Total volatile solids per day 
13.77 
36.32 
59.73 
tonnes/day 


from InputFeedMix sheet 















Volatile solids loading rate 
2.53 
4.51 
5.60 
kg/m^3/day 


from InputFeedMix sheet. This can be up to
about 67 for a single stage, and 2550 for a twostage
acidogenesis+methanogenesis system 




Carbon:Nitrogen ratio 
15.2 
15.2 
14.7 



from CarbonNitrogen sheet. This should be
between 20 and 30, optimum 25. Add Paper/sawdust to increase, blood or
slurry to decrease 











If Carbon/Nitrogen ratio is not in the 2030
target range, biogas yields will be reduced 









HRT and SRT 
























Two stage process ? 

NO 




from BiogasYields sheet 















HRT, 1st phase 

20 




from ParametersPlant sheet 















HRT, 2nd phase 

NA 




from ParametersPlant sheet 















SRT, 1st phase 

20 




from BiogasYields sheet 















SRT, 2nd phase 

NA 




from BiogasYields sheet 















SRT ratio 2nd phase/1st phase 

NA 




515 for a twostage process 








































Digester properties 
























Input buffer
diameter 
10.96 
12.49 
13.72 
m 


from DigesterSizing sheet 















Input buffer height 
10.96 
12.49 
13.72 
m 


from DigesterSizing sheet 















Pasteuriser diameter (each) 
2.03 
2.31 
2.54 
m 


from DigesterSizing sheet 















Pasteuriser height (each) 
2.03 
2.31 
2.54 
m 


from DigesterSizing sheet 















1st stage diameter (each) 
15.13 
17.25 
18.94 
m 


from DigesterSizing sheet 















1st stage height (each) 
15.13 
17.25 
18.94 
m 


from DigesterSizing sheet 















2nd stage diameter (each) 
NA 
NA 
NA 
m 


from DigesterSizing sheet 















2nd stage height (each) 
NA 
NA 
NA 
m 


from DigesterSizing sheet 















Digestate buffer diameter 
18.61 
20.97 
22.88 
m 


from DigesterSizing sheet 















Digestate buffer height 
18.61 
20.97 
22.88 
m 


from DigesterSizing sheet 








































Temperatures 












Pasteuriser 
70.9 
70.9 
70.9 
C 


from ThermalBalance sheet 


1st stage digester 
38.0 
38.1 
38.6 
C 


from ThermalBalance sheet 


2nd stage digester 
NA 
NA 
NA 
C 


from ThermalBalance sheet 














Process problems
affecting biogas yields 











Approximate biogas
yield (relative to baseline) due to inadequate SRT 

93% 




from BiogasYields sheet 


Approximate biogas yield (relative to baseline) due to imperfect
C:N ratio 
113% 
113% 
110% 



from BiogasYields sheet 


Approximate biogas
yield (relative to baseline) due to temperature excursions 
100% 
100% 
99% 



from BiogasYields sheet 


Approximate biogas
yield (relative to baseline) due to all above factors 
105% 
104% 
100% 




















Biogas/methane power
outputs 











Total biogas per day 
6955.78 
15438.10 
21734.37 
m^3 


from BiogasYields sheet 


Average biogas per
tonne feed input (including water) 
25.9 
38.8 
41.2 
m^3/tonne 


from BiogasYields sheet 


Average biogas per tonne feed input (excluding water) 
27.4 
40.3 
42.4 
m^3/tonne 


from BiogasYields sheet 


Methane content range of biogas 
51% 
59% 
67% 
% 


from BiogasYields sheet 


Total methane per day 
3573.30 
9075.10 
14519.44 
m^3 


from BiogasYields sheet 


kWh per day @ 11.04 kWh/m^3 
39449.22 
100189.07 
160294.62 
kWh/day 


from BiogasYields sheet 


kW average power (methane) 
1643.72 
4174.54 
6678.94 
kW 


from BiogasYields sheet 














Energy 











Total methane energy
yielded, of which 
1643.7 
4174.5 
6678.9 
kW 


from BiogasYields sheet 


Engine heat lost 
147.9 
375.7 
601.1 
kW 


from EngineSize sheet 


Generator heat lost 
27.9 
71.0 
113.5 
kW 


from EngineSize sheet 


Process heat
required 
170.1 
242.9 
318.8 
kW 


from ThermalBalance sheet 


Process electrical required 
70.8 
108.9 
145.1 
kW 


from ElectricalLoads sheet 


Surplus electricity for export (import if negative) 
460.1 
1239.5 
2012.2 
kW 


from ElectricalLoads sheet 


Surplus heat (available for CHP export) 
766.8 
2136.6 
3488.2 
kW 


from ThermalBalance sheet 


Check energy sum 
1643.7 
4174.5 
6678.9 
kW 


Sum energy breakdown to check consistency 

Surplus CHP water
temperature 
71 
77 
79 
C 


from ThermalBalance sheet 

Surplus CHP water at mass flow rate 
2.92 
7.41 
11.86 
kg/s 


from ThermalBalance sheet 

Surplus CHP water must be returned at or above above 

8 

C 


from ParametersEngine sheet 

Efficiency of
electrical export, as a proportion of methane energy 
28% 
30% 
30% 







Potential total efficiency of electrical plus CHP energy 
75% 
81% 
82% 


















Profitability
index calculation, NPV using primary discount rate figure, for the 10year
investment 








Plant capital cost 
£6,292 
£8,047 
£9,611 
£1000s 






Invested capital amount (minus grant) 
£3,146 
£4,024 
£4,806 
£1000s 






Total net present value of project at primary discount rate 
£1,591 
£546 
£2,045 
£1000s 






Profitability index (=NPV/Capital investment) 
0.51 
0.14 
0.43 







Internal rate of return (IRR) 
8.2% 
9.9% 
12.7% 
































































































































































































































































































































































































































































































































































































