As bababrown has said, the size does not matter, but insuring that it is completely sealed from any leaks does matter -- critically! Some of my Bin Sensor customers have built large capacity bins (one even modified a steel dumpster bin!) to increase the time between their bin servicing intervals. Another factor is the strength of the materials used to build a bin -- one large advantage of a cylindrical bin is that the structure is inherently strong and harder to crush than a cube from external pressure. A square or rectangular wall is weaker, so materials need to be stronger to tolerate the external pressure. But, common waste receptacles like a Rubbermaid "Big Brute" are not strong enough either. I use a 55 gallon polyethylene food drum that is very robust.