Hydropower, solar, wind: The planet is full of energy sources.
Another, biomass, is becoming increasingly important as we look to diversify the way energy is produced.
Here, Sustainable Energy breaks down biomass, looking at its uses, its potential and how it can help the planet.
What then, is biomass?
As the U.S. Energy Information Administration (EIA) puts it, biomass refers to "organic material" which comes from animals and plants. It encompasses everything from wood and crops to rubbish.
The U.S. Department of Energy (DOE) has described biomass as being the planet's only renewable energy source that is able to "offer a viable supplement to petroleum-based liquid transportation fuels… in the near to mid-term."
Once you have your biomass, you need to turn it into something useful.
The European Commission describes bioenergy as being produced when biomass sources are converted to produce a range of "useful energy carriers" such as electricity, heat and fuels for transport.
The International Energy Agency (IEA) has described bioenergy as the world's "single largest renewable energy source today."
The IEA adds that it is responsible for around 10 percent of the world's primary energy supply.
It's important to note that biomass, and the products produced from it, such as biofuels, have an impact on the environment, and it's not always positive.
Many people are reliant on biomass for cooking their food, over 2.7 billion according to the IEA.
This, the organization says, is "associated with the approximately 3.5 million deaths annually from indoor air pollution."
The World Wide Fund For Nature (WWF) says that while biofuels could make a "massive contribution to sustainable development" bioenergy production can have a big impact both environmentally and socially.
According to the WWF, "swathes of forests and other valuable ecosystems are often cleared" in order to grow the crops used to make biofuels.
This, according to the environmental group, contributes to climate change, ruins livelihoods and homes, and destroys the habitats of endangered species.