We began producing biogas for cooking fuel at LEF in 2019. It is a well established technology in common use worldwide. Basically a liquid compost pile, archea (ancient microorganisms, even older than bacteria) digest food scraps and other organic matter in anaerobic conditions. The system produces liquid effluent which can be used for fertilizer, and biogas, which is mostly methane and with minor modifications can be used just like natural gas for cooking or heating. We have found biogas to be an excellent supplement to our solar electric cooking.
The Chinese Biogas Manual is a great source of information about building biogas digesters, and is available for free online.