In very basic terms the microbes that decompose the waste feed on oxygen, and they need a lot of it. Tumbling composters are good but studies have shown that the oxygen levels decrease within minutes of the action stopping. Spinning the tumbler once or twice a day does help to make compost decompose faster, but most people aren’t consistent in the frequency require to spin the bin for the weeks or even months required to finish compost. If you search for “compost aerators” you’ll find tools, which look like dirt corkscrews, but honestly if you’re not going to spin a tub twice a day, every day for a month and a half, using a dirt corkscrew for the same time frame is not realistic.
Also, Tumblers are also too small for large home composting, or small farms or businesses. A single horse can produce 50 pounds of waste a day. A tumbler composter may be able to only hold a single day or two of manure. So if it takes says 2 months for a tumbler to fully compost when turned every day. That would be 40-60 tumblers per horse, turned every day. Don't get me wrong, I love tumblers, I have one for kitchen waste, but for horse/chicken manure, grass clippings, and brush clean up it all goes in to the aerated pile.
Forced air systems allow people to compost who would otherwise have to throw the waste away, or simply make their existing systems more efficient and maximize the available space as a well set up forced air composting system can reduce the time to finished compost to 3 – 5 weeks. Yes, you read that correctly, less than or about a month.
If forced air systems are so great why doesn’t everybody have one ? Simply put, they’re unneeded for the average household, and for those who could benefit from an aerated composting system, those systems usually are too expensive (Custom 3 bin aerated system holding 400 cubic feet starting at $5,000) and/or are too large or overboard for what is needed; i.e. a small family hobby farm doesn’t need the smallest industrial composting system, when the smallest system is $100,000 and 5,000 cubic feet of compostable waste. This is a scalable middle ground between a backyard worm bin and a $4,000 custom set up or $100,000 industrial system.