[Digestion] energy calculations

[Johan Carels]

Hi Kshanika Gooneesekera,

 

the biogas-value of food waste depends on the fat-, protein and carbo
hydrate - content of this substrate and his dry matter content.

The average we experience here in Belgium with food waste of 25% DM is:

 



So,  max.  about  170 MJ per day  with the above amount of food waste at 25%
DM.

 

K rgds

Johan Carels

www.jcarels.be

 

 

 

 

Van: digestion-bounces at lists.bioenergylists.org
[mailto:digestion-bounces at lists.bioenergylists.org] Namens Kshanika
Goonesekera
Verzonden: vrijdag 4 maart 2011 4:51
Aan: For Discussion of Anaerobic Digestion
Onderwerp: Re: [Digestion] energy calculations

 

Hi all, 

 

I've got a proposal for a biogas plant at our textile factory in Sri Lanka.
I need to verify the energy per day to assess the feasibility of this
project.

The contractors propose a 90m3 plant (comprising of 3 tanks - 60m3, 20m3 and
10m3) for a daily input of 450kg of food waste from the canteen. 

 

My question is will this plant supply enough gas to cover the present LPG
consumption?

 

 


Present LPG consumption in the kitchen:

 


 cylinders per day

3

 


cylinders per month

60

 


Gas weight per cylinder 

37.5

kg


Energy requirement per day 

4,950

MJ/kg


 

 

 


food waste

450

kg/day


 

 

 

 

 

Assuming a food:biogas of 1:1,  450m3 of biogas will be produced per day. Of
which 60% is CH4 hence, energy obtained = 13,500MJ/day (calorific value of
CH4 taken as 50.09MJ/m3)

 

However, calculating the energy obtained using the equation below and taking
15% of the food waste as Carbon content,  

Coe/Co = 0.014T + 0.28

 

Gives the energy per day as 3,763MJ/day

Which of these values am I to trust? 

 

Thanks and regards

Kshanika Goonesekera

Sri Lanka

 

 

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