Thanks Karen! Sorry for taking so long to respond! I had to contend with a couple of deadlines.
For fire testing naturally sourced or "wild" clay, I think you're right in that I need to find a test kiln. To find something more cost effective, I might actually try creating an outdoor fire kiln at home for some initial tests. I've heard that microwave kilns can work too, though they don't go to high temperatures. If anyone has any personal experience with any of those processes, or with temperature-measuring devices like pyrometric cones or a thermocouple, I'm all ears.
But I'm also planning to test my designs with normal commercial clay too. The clay channel extruder can use in-house clay bodies, and it would be nice to see my hydroponic system in action, even with purchased clay. I can pick a low-fire clay that only needs a bisque fire as the channels don't need durability or glazes.
For more information on the project, I recently had to put together a full report in PDF, so I've shared it here too as an attachment.