Biogas system is used for fueling engines, the plant must produce at least 10 m3 biogas per day. For example, to generate 1 kWh electricity with a generator, about 1 m3 biogas is required. Small-scale systems are therefore unsuitable as energy suppliers for engines. Biogas engines are generally suitable for powering vehicles like tractors and light-duty trucks and mainly producing AC current to power all households appliances.