Compressed Biogas Bottles

LPG – Liquid Petroleum Gas
Butane and propane that make up LPG turn to liquid at very low pressure around 40 – 60 psi at average ambient temperature.
So with safety as the major priority, LPG cylinders are designed to hold a max pressure around 400psi.

The cylinders can be relatively lightweight allowing them to be easily portable.

LNG – Liquid Natural Gas
The combustable component of biogas is Methane, which is Natural Gas.
Methane does not like to liquify, and will only do so at -162degC. This process is a whole different level of technology, and only possible at industrial level.

CNG – Compressed Natural Gas
So the most simple low-tech method of getting large quantities of natural or biogas into a small space is to compress it at very high pressure. Biogas in these cylinders is at a max of 3,000 psi. CNG cylinders are similar to industrial gas cylinders, and are extremely heavy.

For example, a single cylinder pictured here will contain about the same amount of gas as a 12kg LPG cylinder, that is around 30m3. Where an empty LPG cylinder weights a manageable 20 – 25kg, the empty CNG cylinder weights 130kg. So portability at a domestic level is completely non viable.

Hence the trailer. We can move around 100m3 in a single trailer. The cylinders remain on the trailer, that is plugged into the point of use like a commercial kitchen, restaurants, school’s, or mini-grided apartments, flats and slums. Different Pay As You Go -PAYG metering systems for payment models.

When the gas is used up, a replacement trailer is brought in and the empty taken for refill.

So in short, mini-grid biogas networks can be setup in urban centers where there is no space for digesters, and the biogas can be supplied in trailer form.