At an estimated HRT (hydraulic retention time) of 50 days, you would need 20 kg (L) of household waste per day. With 20 kg of household waste you can produce approximately 4000 m² per day of Biogas (equivalent to about 2500 m² Biomethane). With this you would haffe sufficient Biomethane for a household. However, within one household you never have 20 kg of Biowaste pe day, you would need 10 households' waste to run one digester.

I think that volume should be enough for a family with those characteristics. According to my experience, the most important factor to take into account is the temperature in order to estimate the retention time. Is it going to work at constant or at ambient temperature ?

I am not familiar with the regulations in your community, but in parts of China and India they use human feces to produce biogas. Would it be feasible to combine both wastes to increase biogas production? According to the author David House, 1000 lbs of human waste produces about 0.6 cubic meters of biogas.

Hi, I propose the following estimate, I leave this link with data from an EPA model free (LandGEM), with this you can calculate how much biogas and in what time you can get this... course, is designed to work in to landfills, but in the end, the equations are the same.

This is the tutorial with the equations: http://www.epa.gov/ttncatc1/dir1/landgem-v302-guide.pdf

This is the place where you can download: http://www.epa.gov/ttn/chief/efpac/esttools.html

regards,

In India, ARTI in Pune and Biotech in Trivandrum make systems to process food waste for households. They have both won Ashden awards, so you can read about their systems at www.ashden.org and also see pictures and videos. Using a family's own food waste allows people to replace 25% of their LPG. If waste can be collected from elsewhere (e.g. food processing), people can replace 100% of their LPG. Both groups use a 1 cu.m digester, although they claim that plastic gas drums are cheaper than GI. Biotech Ltd do use a brick main tank, although it is easier to make it underground than build it above ground. Above ground tanks need steel reinforcement to give them strength. If you live in a tropical or sub-tropical area, you do not need to insulate or heat the plant. It is more difficult where the outside temperature is much lower, as a biogas plant needs to be at 30 deg. C or warmer.

Thanks a lot to all for the answers.

Dear Heribert Insam, if the digester is run by only one household @ say 1.0 Kg per day, then is the system is likely to work? On continuous addition of daily waste, let there be gas production after 10 / 15 days, no problem. But it should work. The ambient temperature --- (a) Maximum 36 degree and minimum 25 degree during summer (b) Maximum 22 degree and minimum 12 degree during winter.

Dear Jose Leiton, at present, the system will be based on the kitchen waste only. There will not be any scope for mixing human feces, not even cow dung on regular basis. However, cow dung will be used at the time of starting and cow dung may be used time to time later on.

Dear David Fulford, Yes, I have seen the ARTI Model and I am planning to follow that.

Thanking you once again.

With Regards.

Nripendra Kumar Sarma

Guwahati, Assam, India

There is optimism in yield in generation of bio-gas.What I have experienced is that many times anaerobic conditions are get disturb and it yields CO2 instead of CH4.

My other potential question is that house hold waste is rich source of carbon if we remove moisture and properly palletised it will yield more energy in terms of Calarries because 100 % of carbon will get utilize while considering bio-gas where maximum 65 % of total carbon available for energy generation.

as a dynamic process (addtion of kg to kg) anaerobic digestion in household scale should work (as far as i know there is a project in Australia). however, the problem will be to start the process and to keep it running (e.g. oxygen imput when the feed is added). anohter question would be safty (pathogens!!!!, gas,...).

Dear Nripendra and all!

Good Q and good A! I totally agree that using only kitchen solid biodegradable waste would be more efficient to produce biosolids (humus) than methane. The composters that can do this are readily available on the market.

Still, if you would like to produce methane, then have a look to over 3000 years of chinese experiences ... where all household and stable biodegradable waste is digested in underground very simple, but cleverly designed digesters.

BTW: Fine grinding of all the solids before digestion makes miracles!

Plz... see :

www.skatmk.itu.edu.tr/dosyalar/istanbul/8feb/IzzetOzturk.pdf

Hi, Niprendra,

Heribert Insam probably means that 20 kg kitchen waste per day produces about 4 m3 biogas per day, containing about 2.5 m3 methane. An Indian household of 2 adults and 4 children requires about 2m3 biogas for 2 hrs cooking per day. If mainly vegetable waste is fed into the reactor, the gas production is slow and requires the 50-60 days retention period. However, if sweet fruit left-overs and food left-overs including starchy prodcts like rice and chappatti are fed into the reactor (ARTI model) the gas production is much higher and the retention time can be shorter.

When rural people have animals such as goats or chicken, these will eat most of the kitchen waste, especially the proteins an strarch elements. A good analysis of the components iof the g]kitche (and garden) waste is important to make realistic estimates.

It would be possible to combine from several families kitchen waste, but than only one family will have the benefit of some cooking gas.This is an organisational problem. The benefit will be that the other families do not have to dump their waste and also less fly or rodent population will be the result.

Boris Kompare indicated that fine grinding or shredding is indeed important.

The feed pipe should not allow to include oxygenor air and starting up the reactor is preferably with a good portion of cow-dung.

The ARTI model is small and based on feeding human or animal food (starch) into the reactor. This option to add human food to the reactor may not appeal to many people. When adding soft and green kitchen waste (having carbon) the retention time increases.

With vegetable and green kitchen waste you must ensure that the flow inside the reactor is continuous and one-directional without the possibility that new feed is mixed with old feed to ensure the full retention period of the vegetable matter. The S shape of the digester will avoid mixture.Tunnel digesters also reduce mixing.

Making brick domes largely under ground is a good option and will keep the temperature stable. However, good quality controll of the inside plaster coat and several layers of rubber based paints are required to eliminate leaks.Cracking of the dome can be avoided by an outside steel mesh or chicken wire reinforcement.

With a low winter temperature of only 12 Celsius the digestion process will considerably slow down and thermal insulation is therefore recommended. A steel tank or steel com ponents will be a thermal conductor and is not recommended; a HDPE tank is much better. An environmental temperature of 20-25 degrees will provide good daily gas, but large temperature changes should be avoided for the methane bacteria. If sun-exposed, the top of the reactor should be shaded in the hot summer.

If you do not introduce human solid feaces (unacceptable with many hindu), the patogen issue is not very relevant with a retention period of one month.

The output slurry is still a useful and good fertilizer for own vegetable gardens. It can also be sundried for reucing volume and sell as dry fertilizer.

You'll have two big problems: final waste after biogas generation and leachate. Moreover, biogas generation in small scale couldn't be as efective as generation at big scale (municipal biogas facilities).

I agree

Nripendra, with the various answers, you may come to the conclusion that it is not very economic to build a one-family reactor unless you apply special (purchased) feed like the Arti set-up. Also for such a small unit you need ALL day management, without gaps for holidays, otherwise you would not have gas. A back-up gas system remains necessary. As a last, but not least, building an above ground brick container requires corrosion free (galvanised iron) steel mesh reinforcement or glasfibre web (Vitrulan) around the outside. In addition you need to do a good planning of your site since you cannot use that land and cannot remove the unit.

Dear All,

Keep in view of your advice, I started using one Biogas Plant ( approx. 1.0 cm capacity) in my home in the 1st week of Feb'13. It was made overground with HDPE Container ( Black in colour) and the feed was only the biodegradable portion of our Kitchen waste.

After an initial hiccup due to leakage in the feeding pipe, the process was restarted on 27th Feb'13. After continuous operation for 50 days, it is observed that the Gas holder is lifted upwards by approx. 0.6m. So today, I tried to study the type of Gas formed inside the Gas holder. I wanted to know about the status of formation of bio-methane. So I connected the Gas holder to a LPG Burner.

But, unfortunately, the gas was not burned and there was no flame at all. I could not make up the issue, what has gone wrong?

Now, I have released a major portion of the Gas to air and the Gas holder has come down approx. by 0.45 m. So now I will wait for generation of better quality of Gas to be used to replace LPG, at least for some time.

I would like to request the Sector Experts to guide me in this regard to overcome the problems. Meanwhile I have two photographs of my Biogas Plant ( one at starting time and another after 50 Days of operation ).

Thanking you all and waiting for responses.

Warm Regards.

Nripendra Kumar Sarma

Guwahati, Assam, India

Sorry that the photograph of the Biogas Plant at starting time is not uploaded. The same is again uploaded here.

Thanks and Regards.

From the needed waste ressources needed it could be more interesting to make a larger tank and to make it used cooperativly in a house block, so it will have sufficent ressources and users

i'm not a specialist here, but can't we use feces and urine too inside the tank to generate more biogaz?

Thanks Perrin Joachim, for your feedback. But I am sorry that there is no scope at present for mixing human feces / urine and not even cow dung on regular basis. However, cow dung was used at the time of starting time as a Start-UP.

So far sizes are concerned, it is tried on household basis only at present. One important point is that looking at the extent of lifting of the Gas holder, it may perhaps be concluded that Gas is formed. But the issue is about the quality of that Gas and it's content of Biomethane.

Thanks and Regards.

Nripendra Kumar Sarma

Guwahati, Assam, India

Kitchen waste has slow gas production and is best cobined with feaces. When the methane gas productio is low you need to increase the starch and sugar containing waste products. The Arti construction is fed with concentrated starch or flour products. If you do not the same , your installation is too small. Gas from vegetable kitchen waste has a lot of humidity ad when the pressure at the burner is too high it does not easily burn. The installation needs to be supported along the sides that the upper container rises vertical.

In addition I would recommend that the kitchen waste is shredded or chopped fine, that will slightly speed up processing and avoids clogging. As indicated above temperature differences between day and night will reduce fermentation. If nights are cool, some thermal insulation of both barrils may be advised.

Hello, You should be aware of the ammonia produced inside your plant, as ammonia acts as biogas AD inhibitor. I also have designed a mineature kvic type model which runs fine But uses cow dung rather than kitchen wastes. In my opinion, using kitchen waste should increase the retention time. Further, you can`t use the same lpg burner as it is for Biogas. There is a pin hole nozzle present in the burner pipe(put burner upside down). After removing the nozzle, your burner should work fine. 

For gas quality check:-

Lead acetate paper can be used to determine the presence of h2s. You will have to take the help of a lab testing institutions for gas chromatography,  that will determine the % of methane,co2, h2s and water vapour.

If you want, I can show you my design also. I have used an old oil drum for the model.

There are two groups installing small-scale food waste biogas systems in India: ARTI in Pune (http://www.arti-india.org/) and Biotech Ltd in Trivandrum (http://www.biotech-india.org/). They have both won Ashden Awards (www.ashden.org) for their work. SANDEC at EAWAG have produced useful reports on both systems (http://www.eawag.ch/forschung/sandec/publikationen/swm/index_EN#owm) as well as a book on the subject.

My own book (Small-scale, rural biogas programmes, published Jan 2015, Practical Action) looks mainly at plants using cattle-dung, but does include some information on food waste as well. 

The World Bank had a conference on food waste plants in Kathmandu in June 2014 (poweringnepal.org), at which I gave a talk. There are several groups looking at larger-scale systems in India.

http://www.eawag.ch/forschung/sandec/publikationen/swm/index_EN#owm

http://www.arti-india.org/

http://www.biotech-india.org/

www.ashden.org

poweringnepal.org