Q. A socially responsible alternative for people who buy bottled water. is the corn based biodegradable plastic used in the UK. And available now in Canada. The corn-starch bottles are made from a type of plastic called polylactic acid (PLA). The bottles could be commercially composted back to soil in 12 weeks. Since corn starch is kitniyos, can they be used on Pesach?

A. As the name implies, corn starch biocompostables are made from corn starch. The starch is converted into a polymer, the main ingredient in materials that have a plastic-like feel. The plastics can be clear or opaque, soft or hard. A kind of acid called polylactic acid (PLA) is made from the corn starch. This is why corn starch biocompostables are sometimes called PLA plastics.
In the past there were shailes in regards to paper plates, paper towels and napkins that generally also contain starch. Some forms of raw starch are kitniyos, such as corn starch, while other forms of starch, such as wheat starch, are actual chametz. In the U.S, it can safely be assumed that starch used in manufacturing is kitniyos, most probably corn-based. Many contemporary Poskim maintain that though one should not intentionally add kitniyot to food, with respect to paper goods this is not a concern because the starch that is part and parcel of the paper itself is nifsal mei’achila (inedible). (If paper goods contain wheat starch, the fact that it is nifsal mei’achila may not suffice to permit their use, see Magen Avrohom 442:4). Based on the above, in the US, OU rules that one may use paper plates, paper towels and napkins even if not certified for Passover. (See: oukosher.org/passover/guidelines/non-food-items/non-food-items/.)
Horav Shlomo Miller’s Shlit’a opinion is that one can be lenient when necessary.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a