Biomass may be counted as renewable source of energy, but it isn’t as clearcut a source as the likes of solar or wind energy. The main issue is that burning biomass waste releases CO2 and carbon monoxide into the atmosphere. Because plants and trees can be planted to replace those used in the process, it’s still technically a renewable energy source, but those harmful effects of biomass production have meant that many energy suppliers are now reconsidering its place in their fuel mixes.