If you're ready to tackle something related to energy, power, and the environment but want to push the envelope a bit farther than the cool (but maybe not quite cutting-edge-enough-for-you and just a bit ubiquitous) Veggie-Powered Batteries, pull on your rubber gloves, grab a nose-plug (totally optional), and check out the ins and outs of biomass and biogas.
From Trash to Gas: Biomass Energy (grades 6-8) has you roll up your sleeves, fill up some soda bodies, and monitor differences in biogas production. In other words... what waste will inflate the balloon fastest?
My daughter is doing a similar biogas experiement to your From Trash to Gas: Biomass Energy with the balloons but using light/dark and warm/cold to be the variables. But the balloons are not growing veyr much. It has been 1 week so far. How long should it take to see the biogas start to develop? Wondering if we need to start over. Thanks.