Start killing the hog aliens that charge you and research their carapaces. Once you've completed the second research item you can make biomass from the carapaces to the tune of 100 biomass per carapace.
Also, until you unlock coal, you definitely want to automate the creation of biofuel. I have a cargo container that feeds into a constructor that feeds into another container, all placed next to where I have my burners. I manually make biomass (because that's WAY faster than automating it) dump a bunch into the first cargo container and then every once in a while when I'm in base, I drop by the container with biofuel to grab some and fill the burners.