My Indian friend mentioned this idea to me a few months back when we were discussing things we can do in the farm when we retire :-). The thing that interested me to this project once our house is constructed is its sustainability. It is ideal for me and my wife as we will be staying in the province:

1. Your input to a bio-digester is simply any biodegradle waste, even human waste for that matter :-). I plan to raise some pigs/chicken in my backyard which is why it's just right for our home. I also saw some video in YouTube that indian families living in subdivision did this by using daily kitchen waste products (just not sure if this is really viable in a PH environment).

2. A 2500 liter bio-digester can produce biogas (60% methane ; 40% carbon dioxide) which can be use for 5-hours of cooking EVERYDAY. You just put the amount of input (feed stock) based on the capacity of your bio-digester and you will be producing biogas everyday.
You can easily convert an LPG stove (1-2 burner) to a biogas stove by just simply enlarging the size of the nozzle in the stove. A company in PH that is selling this technology built a biogas system in a baranggay in Palawan to promote their system in which they explained how to do this.
With the price of LPG always increasing, it really makes sense to have this in your house as you will be able to recover your cost in no time. For people living in the city, not applicable. For people living in subdivision, please carefully re-assess the situation in your area.
In China they are already selling generators that runs on biogas. So getting one in PH should not be a problem (I think). If you cannot find a local supplier, you can buy (online) one from China. Just a note, if you plan to use biogas to power a generator in case of brownouts, you need a bigger capacity.

3. The by-product of the bio-digester is an "odorless" (I cannot confirm this yet) liquid sludge that is rich in nitrogen that you can use as a natural fertilizer for your vegetable garden, which I recommend you also do if you plan to do this project.

4. Think of the whole biogas process as just like having another pet/animal in your house or farm - the animals are the microbes (inside the digester) that you feed ; the food is the waste you put into the digester ; the by-product of the microbes when they eat the food is the biogas that you use everyday.

5. A good input to the bio-digester is cassava (kamoteng kahoy) or sugar cane (tubo) as they are rich in starch/sugar - you just don't use yung bunga, you use everything, the whole plant. When eaten by the microbes it produces more biogas. So if you also plant a few of this in your backyard around the perimeter (plus kitchen waste if you don't have animal manure), the whole process/system cycle will be self-sufficient end-to-end 🙂 he he he ...

6. The materials to build the biogas system is readily available in PH. You can either built it above ground based on the ARTI design using PVC Water Tank (e.g. BesTank) or underground (there are a lot of designs available in the internet) using concrete. A lot of filipinos have already installed a biogas system in their home, mostly in the province area.

7. With a little ingenuity, biogas can be scrubbed (process of increaseing methane in the gas by removing the carbon-dioxide) and stored in an LPG tank which you can use for your car. Some DIYers in other countries are already doing this using what's called the water base method. It's still not that very clear to me as I'm not an engineer. But basically, its the same process that companies use to produce electricity using methane gas (biogas from dump site) as source to run power plants.

Below is the website in which you can read more about the ARTI (Appropriate Rural Technology Institute) Biogas System that was developed in India and how to built it using existing materials in PH. You can also watch a lot of videos in You Tube about biogas and ARTI ...

http://www.completebiogas.com/B_ARTI.html

Boo