Biogas Kitchen. How to calculate your Biodigester (and III)
Are you interested in cooking replacing firewood by biogas?
Do you have any cattle or other livestock with fresh manure to get daily? Do you have plenty of water to mix? Perhaps you may be interested in this post about calcualate your own biodigester to generate biogas to cook.
This post is inspired by an excellent PDF (Spanish) of Jaime Marti (see link on bottom).
Family low-cost biodigesters
A biodigester is a natural system that uses anaerobic digestion (in the absence of oxygen) of bacteria that already live in the manure, to transform them into biogas and fertilizer. Biogas, mainly methane, can be used as fuel for cooking, heating or lighting (direct combustion) and engine power to generate electricity.
The fertilizer, called biol, can be used as natural fertilizer that strongly improves crop yields.
Case study: design of a digester for three hours daily cooking.
A small family in the highlands of Bolivia, which has a yoke of oxen, cooks with wood about two hours a day and want to replace firewood with biogas (3h). Considering consumption of 140 liters an hour, three hours represent 420 liters of biogas a day.
According to a table of production of biogas manure of livestock species, in cattle is necessary to divide the liters of biogas by the ratio 35.3 to see the manure needed. In this example: 420 l biogas / 35.3 = 12 kg of fresh manure daily.
Next step is mixing manure with water at a ratio of 1 (manure) to 3 (water) in cattle. So every day mix 12 kg of manure with 36 liters of water, giving a daily load of 48 liters a biodigester.
Being in a cold climate of the plateau, the retention time will be over about 60 days. The liquid volume is obtained by multiplying the retention time (60 days) by daily load (48 l) = 2880 liters.
The liquid volume 2.880 m3 will involve three-quarters of the total volume and a quarter will be for the gas. To the biogas it is assigned a third of the liquid volume (2880 / 3 = 960 liters). The total volume of the biodigester will be 2880 + 960 = 3.840 m3.
Biodigester dimensions will depend on the widths of tubular polyethylene roll available on the market. The optimum ratio of diameter / length of the cylinder of the biodigester is a ratio of 1:7. That is, the length is about 7 times the diameter. Continuing with the example of 3,840 m3, if we have a roll of 1.50m wide, we will have a diameter of 0.96 m and a length of 5.4 m.
Finally, you just have to ditch that will contain the polyethylene biodigester with these measures: Lower widths=0.50m / Width top=0.70m / Height=0.80m and Length=5.40m.
Do you know cases of biodigesters for cooking? Find out the advantages, disadvantages and dangers? Your opinion matters to us all. We can learn from your experience!! Thanks
BIODIGESTORES FAMILIARES. Jaime Martín.
Video construccion biodigestor
Related posts: Biogas Kitchen. DIY your Low Cost Biodigester (II)
Biogas Kitchens. Low Cost Biodigesters (I)
Related articles
- Biogas Kitchens. Low Cost Biodigesters (I) (albertcampi.me)
- Biogas Kitchen. DIY your Low Cost Biodigester (II) (albertcampi.me)
I’d found your post interesting and I’d been wanting to take on renewable energy as part of my project work in the University. I believe your blog would be resourceful for me. Though was thinking of production of biodiesel but now this post is giving me some form of extention to Biogas and looking at the resources required, its certainly cheap to get. I am a Chemical Engineering student in the University of Abuja, Nigeria. Would often need your help. Thank You!