Ключевые слова: alternative energy, backgrounds, beech, biofuel, biomass, biomasse, black, briqettes, brown, bundle, closeup, cylinder, energy, environment, fossil fuel, fuel and power, group of objects, heap, horizontal, large group of objects, material, nature, oak, organic, pellet, pellet gun, pellets, pine, renewable energy, sunflower pellets, wood, wood chip, wood pellet, wood pellets,