Circuit Training HELP

Hi MFP’s
I have almost completely replaced my cardio with circuit training. I really, really enjoy it so much but I am not sure that the circuit that I am doing is burning enough calories and fat. I know that cardio burns calories because I can see that from my HRM, but circuit training is a little more difficult to evaluate since standard HRM’s aren’t really meant for that form of measurement. All I know is that I am dead tired when I am finished and I am usually sore for a day or two. I think that is a good sign? Any fitness experts or exercise physiologists out there who can evaluate my workout? I would greatly appreciate it. I need to know if this is effective enough to get some good results. Since I have bad knees, I had to create a circuit that didn’t put too much pressure on them but still gave me a full body workout. I have 100 pounds to lose, so I need to do the most effective work outs possible. Since squats and lunges hurt my knees, this is what I came up with:
15 – 30 minute warm-up on treadmill followed by 30 minute circuit, 30 sec. each exercise with no rest in between –repeat as many times as possible
1. 30 sec. Kettlebell swings with 10lb. kettlebell
2. 30 sec. Arm press while balancing on a resistance ball with 8lb. dumbbell in each hand
3. 30 sec. Toe touches
4. 30 sec. Rows with 8lb. dumbbell right side, then left side
5. 30 sec. Wall push ups
6. 30 sec. Heavy punching bag

10 sec. rest

Repeat

I still try to get in a 3 mile walk 1 or 2 times per week and zumba 1 day per week. I work out for a total of about 4/5 days per week