I will assume you don’t have a nuclear reactor. With that assumption all the rest of the energy of the world originates from the sun, with some help from gravity. Fossil fuels, wind, hydro, and animals are all different forms of solar energy. Fossil fuels are plants and animals squished under layers of sedimentary rock. Wind is formed by differences in temperature creating areas of more or less dense air, and gravity is constantly trying to level out those differences. Solar energy also does the extremely heavy lifting of evaporating water...think of all the potential energy in the water lifted up into the sky. Last but not least, the current collection of solar energy by plants that feeds all of the life on earth, large and small.
As a sustainable designer that is our job, making sure every life form in our care has enough to eat. We get ourselves in trouble by just trying to feed our families. This is not woo woo hippy stuff. There are many types of soil organisms in a heathy soil ecosystem. These organisms do valuable work (ever pay for fertilizer?). They break down organic matter and convert it into usable forms of nutrients that our plants need access to. In return, our plant roots send them little thank you notes in the form of squirts of sugars (exudates). These little squirts of sugars combined with, organic matter, and the soil life are what give healthy soil its rich smell and slightly sticky crumb structure. Healthy soil creates bioavailable nutrients which creates healthy plants and the base of the food chain.
If we are only worried about feeding ourselves, and destroy the soil life, we will have to attempt to find a way to provide all the nutrition our plants need. It’s my opinion (and many others), that this is a big part of why we have seen culture of sickness forming. We are not capable of providing the proper nutrition to the plants like a heathy soil ecosystem is. Scientists are measuring lower and lower levels of nutrients in our food supply, because the soil ecosystem has been continually abused. Without the proper building blocks you can't build a healthy ecosystem.
Before the industrial revolution allowed our current situation, many civilizations would cut or burn down a forest to gain access to the forest soil. Modern farming only worries about the three nutrients critical for plant growth (N, P, K). Moving forward we want to do all we can to capture as much incoming solar energy as we can, converting it into fertilizer, feed, food, fuel, and building materials that provide for all we need, with some left over.