What kind of waste and how much is needed?
The raw material used for biogas production is biological waste in form of household waste, industrial waste, sludge, agriculture products like energy plants, manure, slaughterhouse waste, waste from fish farms and aquatic waste etc. etc.
A combination of the above material of around 25 000 ton per year is needed in order to reach maximum production.
What is biogas and what differs from natural gas?
Biogas is produced from renewable biological material or waste and is a mixture of gases mainly carbon dioxide (CO2) and methane (CH4). The biogas coming out from the digestion chamber is called raw gas and contains around 50 % methane.
The raw gas can be upgraded mainly meaning reducing the CO2 content. If you end up with methane content of at least 97 %, the biogas is called vehicle gas and is allowed for use in gas engines for transport and industry.
Natural gas is a fossil gas and limited resource coming from the earth. Natural gas is distributed in liquid form or in pressurized form. The methane content is above 97 %.
Thus upgraded biogas and natural gas both contains methane and can be mixed. The difference is that biogas is fossil free, renewable, and CO2 neutral compared to natural gas.
What can biogas be used for?
Biogas can be used in many different ways. First as a fuel for heating homes and buildings, Secondly in various kinds of industrial processes where you need heat and third when you upgrade biogas to vehicle gas you can use it in the transportation sector from cars to heavy-duty transports on land and on sea.
You can also produce electricity by using the gas in fuel cells or in gas generators.
Production of biogas is the only energy producing method where you manage waste and get bio fertilizer at the same time.
How do you produce electricity on the plant?
There are mainly two ways to produce electricity. First one is to use a high temp fuel cell and use the raw gas as fuel. Secondly you can run gas generators on the upgraded vehicle gas.
These two ways produces a lot of heat. The heat itself can be used for warming of households, public building and industries.
You can also produce more electricity by using a heat power system witch converts waste heat into clean electricity thus making electric production more efficient.
What do you use the CO2 for?
Carbon dioxide (CO2) can be used in many ways. One way is to feed it into greenhouses and the plants will use it within the photosynthesis. Another way is to use it within industrial processes where you need carbonic acid.
The most interesting way to use CO2 is to make ethanol.
What’s the difference between pressurized and liquefied gas?
The thing is how you store the gas. Pressurized gas is stored in gas cylinders made of steel or composite. The pressure is normally between 200 – 300 bar. Liquefied gas is gas cooled down to a temperature where the gas turns into a liquid stage. In order to store liquefied gas you need a thermos container in order to avoid that the liquid turns into gas. Over time the liquid will heat up.