We've seen various incarnations of the "indoor" composter. Some seem promising, but most conceal some inconvenient truths: The units are often huge, exceptionally expensive, or made from low-quality plastic that's guaranteed to failThe best solution we've found so far seem to be Bokashi-style fermentation bins, which require no electricity (that's good), but necessitate getting your hands dirty (that's bad) by draining the Bokashi "juice" (that's just gross).
That's why NatureMill's Pro edition is an indoor composter we can pretty much dig. Using minimal electricity, a small motor turns a heavy-duty mixing bar, heats the mixing chamber (no sunlight needed) and powers an air pump that works with a carbon air filter to help reduce smell (each filter lasts 4 to 5 years).
Using the NatureMill is unbelievably simple and hassle-free, from set-up to clean-up to soil-ready. Just add starter dirt and sawdust pellets (combats odors), and dump your food scraps in. NatureMill recommends that you cut organic material into four-inch bits before plopping it in. We didn't, but aside from the motor making some gnarly noises, it didn't seem to affect compost production. NatureMill's Pro version also features some automatic activation. We were able to leave ours sitting for weeks without pushing the button even once; it mixed and heated itself just fine. Only thing it didn't do? Tell us what to plant with our brimming tray of moist, nutrient-rich soil. Amorphophallus, anyone?