Are biodegradeable bags OK in the yard waste bin?

I noticed that QFC sells BioBags, a biodegradable trash bag. "Great", I thought, "there's the solution I needed for collecting organic food scraps in the kitchen that can go into the yard waste bin".

Indeed, King County seems to encourage the use of these bags. But Seattle Public Utilities says:

Why can’t we use Biodegradable Bags in the Yard Waste carts?

Currently, all of the yard debris/foodscraps collected from residents and business in Seattle are sent to the Cedar Grove Composting Facility for composting.

Cedar Grove is in the process of testing corn plastic bags from different manufacturers to see if they are truly biodegradable in their specific composting process. Even though a bag is labeled as "biodegradable" some of them are actually petroleum based and some that are corn-starch based don't break down in all full-scale composting processes.

Seattle Public Utilities only accepts Cedar Grove-approved compostable bags for our food and yard waste carts. We do not accept other biodegradable (like corn plastic) bags or other plastic bags in the yard waste carts.

Dear City of Seattle, please provide actual information I can use. You're just begging the question: which bags ARE Cedar Grove-approved, then?

If you actualy go to the Cedar Grove website you find a page of approved bag types. The ones sold at QFC are included.

Alrighty then.