Biofuel gives heat as a result of vital functions of the bacteria, which decomposes organic substance. Good biofuel should be friable, contain enough of nitrogenous substances and 65-70 % of moisture. In such nutrient medium of a bacterium quickly breed, and in biofuel the heat is settled.
The best biofuel is horse manure. It contains a considerable quantity of nitrogen, has normal humidity, and is quickly warmed up - in 7-10 days after stuffing of hotbeds the temperature reaches 70°C.
The cow manure contains superfluous quantity of moisture, is warmed up more slowly. After a warming up of manure the temperature, as a rule, does not exceed 40°C. Thermal properties of the cow manure improve by addition of dry leaves and sawdust.
The sheep and goat manure contains many nitrogenous substances, but it demands of humidifying. For the best burning the cow and sheep manure mix with horse manure (60 % of horse manure and 40 % of cow or 30 % of horse, 40 % of cow and 30 % of sheep manure).
The organic waste also is considered one of the best kinds of biofuel with normal density and humidity, the temperature in it exceeds 65 ° and long it keeps. If the waste very humid, dry materials are added. Dry waste is humidified or mixed with the cow manure.
Heat of the sun (or heat of vaporization) is used along with biological fuel for heating hotbeds.