The problem with industrial outdoor farming isn't the efficiency, it's the toxic pesticide applications, the environmental pollution in air and soil getting in the crops, and lack of nutritious crop diversity leading to inefficient food supply chains. Growing plants with coal indoors isn't a solution either but hyper-efficient indoor and vertical farming is getting closer by the day and more funding needs to go into new evidence based controlled environment farming techniques. Check out https://youtu.be/VIrXQo00OWc for an example of what hyper efficient indoor farming looks like.