Biomass is one of the most valuable renewable energy on Earth. The most widely used biomass is wood. Wood as fuel is used in three different forms and dimensions:                                                    Logs, wood chips and pellets. Wood should be properly dried, the drying takes more than a year. Biomass is stored in specially built warehouses. In Beltinci biomass is heating the church, Home of pensioners and a few blocks. The calorific value of wood affected by the following factors: 1. The water content or humidity of the wood 2. Chemical structure of wood 3. The density of wood 4. Tree species and tree parts 5. Health status The water content in wood represents the ratio between the weight of water and the total weight of wood and water. Humidity of wood, the ratio between the weight of water and total dry weight of wood.