Last week, GoodCleanTech received the NatureMill Pro XE automatic indoor composter for testing. As one of the first media outlets to receive this next-generation model in the NatureMill line, we couldn't wait to fire this baby up. Also, as the coordinator of our office composting program, I looked forward to potentially having an in-office alternative to dumping our kitchen scraps (currently, I cart them to a nearby farmer's market once a week). So week by week, I will be posting our testing experience and results, along with writing about some of the topics and issues raised with this kind of device.
How It Works. The NatureMill composter has a chamber at the top where you deposit your scraps, mixed with sawdust. The chamber has a motorized arm that mixes and aerates the material. There is also a heating element to achieve the optimal temperature for breaking down the scraps, as well as a filter to eliminate odor. In a couple weeks, the finished compost drops into a container at the bottom and is ready for use.
According to NatureMill, the Pro XE model includes a stronger motor, better filter, and more efficient operation. The main advantages of the Pro XE, according to NatureMill, are that the device is cleaner, easier, and more compact than a typical composter. Also, the device cuts down the composting time significantly--from a few months to a couple weeks. The biggest drawback so far, in my opinion, is the price. The Pro XE sells for $399, and while there are less-expensive models, a composter over $200 is still going to prevent many from becoming early adopters.
Form Factor. The device is much lighter (and a bit less sturdy) than it appears in product images. The body is made from a high-grade polypropylene, and the internals are stainless steel and aluminum. There are a few LED lights on the front to indicate the power's on, a composter jam, a full chamber, and so on. It also has a button to transfer the finished compost to a plastic trough at the bottom. The composter comes with two bags of sawdust pellets (pretty much the same stuff that's sold as commercial cat litter), a box of baking soda (more on that in a sec), and a measuring cup.
Setup. We set up the Pro XE in PC Labs by simply plugging it in. For the initial batch, though, there is a specific procedure to establish the bacteria that breaks down your scraps. The first batch calls for a cup of basic outdoor soil (not packaged topsoil, potting soil, or finished compost), a couple tablespoons of baking soda, a cup of sawdust pellets, and a few cups of scraps. After liberating a cup of dirt from a large planter in front of our office building, I also added some banana peels, a few apple cores, and some petals from a flower bouquet, cutting everything into small pieces as directed.
Initial Results: Week 1. The instruction manual for the Pro XE warns that the motor can be noisy the first week of operation. PCMag Senior Editor Sean Carroll, whose office is near the composter, reported that he did hear it whirring occasionally, but the noise was not loud enough to be distracting. After running it for a week, we checked the results.
The finished compost was dry and dusty, seeming to consist almost completely of sawdust. This is very different from most finished compost, which looks and feels like moist, rich soil. When I spoke to a NatureMill rep about this, she said this was most likely due to the low moisture content of my scraps. She then suggested I put the finished stuff back into the chamber to let it mix with the next round.
Also, it appears that I put in too many sawdust pellets. As it turns out, the Pro XE does not require the same ratio of brown matter (sawdust, leaves, hay, etc.) to green matter (kitchen scraps) as an outdoor compost pile--typically more brown than green.
Next Week. In my next post, I will discuss the results of Week 2, as well as go through the power usage of the Pro XE and some pros and cons.