Introduction

Welcome to another episode of Hacker Public Radio. This episode is inspired by HPR episode 3157 entitled Compost by Klaatu. During the early 2000's, I lived in a single family home which had a number of oak trees around it. Between the trees, other foliage, and grass, there was a large amount of yard waste. While my city (Baltimore, MD in the US) will pick up your yard waste if you put it in bags by the curb [1], I would use the oak leaves as mulch, and did have a mulch pile of leaves and other yard waste. At that time, I thought about composting food waste, but there is a big issue with rats in Baltimore, and I didn't look into ways to compost. I just knew I couldn't randomly mix it into my mulch pile.

I am currently living in a different house, without any oak trees, and not as much yard waste (particularly since we hire someone to mow the grass every couple weeks). After listening to the Compost episode, I was inspired to look into the best way to do it given my current living situation. The first thing I did was to look and see if there are any laws against composting in Baltimore City. The rat problem is big enough that the City purchased and distributed a large green plastic trash bin to every physical mailing address in the city. This is the bin you are required to use when putting out your trash. Given the situation, I wasn't sure it would be legal to do composting in your back yard. Much to my surprise, it is not only legal, but the city website has a web page on how to compost [2] and just recently started a pilot program for food scrap drop off with seven locations around the city [3].

Kitchen Compost Bin

After determining I wasn't going to be a scofflaw, I went to the Internet to see what kind of bins are available for purchase. While Klaatu gives great suggestions for low cost composting bins, I wanted something that would look nice sitting out on a shelf for the small inside bin. I found the Utopia Kitchen Compost Bin [4]. The bin is made of stainless steel and has a volume of 1.3 gallons (4.9 liters). The lid is rounded and has a series of holes around the top. The inside of the lid holds a circular shaped charcoal filter. The combination of holes and charcoal filter capture any odors generated by the food scraps. It works amazingly well and even with onion scraps you need to stick your nose to the holes and inhale deep to smell anything when the lid is closed. It holds three to seven days worth of food scraps, most of which end up being coffee grinds. We have had this bin for 10 months, and the charcoal filter is still effective. There are replacement filters available for this bin, but you could also cut other charcoal filters to fit inside the lid.

Outside Compost Bin

Given the potential rat and other small critter issues, I wanted the main, outside composter to be fully enclosed, and preferably not sitting directly on the ground. A quick search brings up a number of options, both composters that sit on the ground and ones that are tumbler style, which hang on a frame. I went with a tumbler style compost bin. This provided the desired feature of not being on the ground, and has the added advantage of making it easy to turn the compost every second or third day by just rotating the bin slowly for three or four full turns. I purchased the FCMP Outdoor IM4000 Tumbling Composter [5]. The composter is octagonal shaped column with two chambers inside it. This allows you to fill one chamber while the other side is finishing the composting process. There are also aeration holes for each chamber which can be open to different levels to moderate the amount of moisture. The combined volume of the two chambers is approximately 37 gallons (140 liters).

My Composting Experience

So far I have been very happy with this combination. I just emp