[Digestion] energy calculations

[Anand Karve]

The slurry from one digester can be used as input for another, if the slurry
still contains undigested matter. In the case of food waste, it is not
likely to happen, but you can always try.
Yours
A.D.Karve

On Mon, Mar 7, 2011 at 1:05 PM, Kshanika Goonesekera <
KshanikaG at masholdings.com> wrote:

>  Hi all,
>
>
>
> Thank you Mr. Karve and Johan Carels for the valuable information. The
> contractor assures me that by reducing the input of water the CH4 content
> can be increased, and the 3 digesters will maximize biogas output further
> due to consecutive digestion. Is this possible?
>
>
>
> Has anyone any experience with the 1:1, food(dry matter):biogas output?
>
>
>
> Regards
>
> Kshanika
>
>
>  ------------------------------
>
> *From:* digestion-bounces at lists.bioenergylists.org [mailto:
> digestion-bounces at lists.bioenergylists.org] *On Behalf Of *Anand Karve
> *Sent:* Sunday, March 06, 2011 8:30 AM
> *To:* For Discussion of Anaerobic Digestion
> *Subject:* Re: [Digestion] energy calculations
>
>
>
> Dear Mr. Goonesekera,
>
>  You have to assess the water content in the food waste to get a correct
> estimate. Starch and sugar produce almost twice as much biogas as green
> vegetable waste. So, the composition of the food waste is also important.
> The rule of thumb followed by us is that a kg dry weight of human food waste
> would produce about 600 to 700 litres of biogas and that it would replace
> about 200 to 250 g LPG. Assuming your daily food waste to be 450 kg to have
> a dry weight of 225 kg and that it contains some portion of leafy and
> lignocellulosic vegetable waste, one would get daily about 225 X 200 =
> 45,000 g or 45 kg equivalent of LPG.
>
> Yours
>
> A.D.Karve .
>
> On Fri, Mar 4, 2011 at 11:51 AM, Kshanika Goonesekera <
> KshanikaG at masholdings.com> wrote:
>
> 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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>
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>
> for more information about digestion, see
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
>
>
>
>
> --
> ***
> Dr. A.D. Karve
> President, Appropriate Rural Technology Institute (ARTI)
>
> *Please change my email address in your records to: adkarve at gmail.com *
>
>
>
> _______________________________________________
> Digestion mailing list
>
> to Send a Message to the list, use the email address
> Digestion at bioenergylists.org
>
> to UNSUBSCRIBE or Change your List Settings use the web page
>
> http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org
>
> for more information about digestion, see
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
>
>
>


-- 
***
Dr. A.D. Karve
President, Appropriate Rural Technology Institute (ARTI)

*Please change my email address in your records to: adkarve at gmail.com *
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