Biomass

Biomass is an important source of energy for about half of the human population. Biomass is in essence organic materials that can be used to create heat and fuel when they combust. It is considered a CO2-neutral and renewable resource.

Types of biomass
Lumber, hay, manure, organic waste from landfills and sewage are all amongst what we use as biomass today. Additionally, biogases, such as methane, can be used as fuel, for instance in buses. Bioalcohols like bioethanol and biomethanol, as well as biodiesel, are all examples of liquid biofuels that are often used in transportation. These can be derived from oils that are also produced for food, such as rapeseed oil.

Sustainability
As long as we don't extract biomass as fuel in large quantities at a time or too quickly, it can be considered a form of renewable energy, because our supplies can be replenished as long as plants can grow and organic waste is created. This gives it an edge over fossil fuel, because it's not something that will ever run out with conscientious usage.

CO2 neutrality
Even though carbon dioxide is released with the combustion of biomass, it is considered a CO2-neutral resource because the carbon dioxide that is released is used back up when the resource is replenished, for instance through plants growing. In other words, no more carbon dioxide is added to the atmosphere when we use biomass as fuel.

The problem with biomass as a resource
Despite the CO2 neutral aspect of biomass, it is still not a perfect source of renewable or eco-friendly energy. The problem lies in the collection and production of the biomass, which is often not done through completely sustainable means. That means that the use of biomass (because that includes how we manufacture them) often releases carbon dioxide, even though the act of burning them doesn't increase atmospheric carbon load. An example of this is for instance that the machines we use to cut down trees that will be used as biomass may run on fuel derived from fossil energy, as well as the cars used to transport them and the storage facilities for the biomass. In this way, we do release carbon dioxide into the atmosphere, even with a renewable energy source.

This is also an issue because it means that biomass isn't a good competitor or replacement for fossil fuel usage, as we need the fossil fuel to be able to use biomass in the first place. However, most people will agree that the lesser release of carbon dioxide compared to from fossil fuels makes using them a good first step in avoiding fossil fuels (and eventually cutting them out altogether), and thereby also the enormous carbon dioxide emissions that follow.