[Answer] The owner of Robolights in Palm Springs is obsessed with robots. His backyard sculpture garden is also the largest residential light display in the US. What are his 1,000 tons of art made of?

Step 1 : Introduction to the question " The owner of Robolights in Palm Springs is obsessed with robots. His backyard sculpture garden is also the largest residential light display in the US. What are his 1,000 tons of art made of? "

...1. desert sand 2. Burning Man and Coachella refuse 3. cacti 4. donated scraps