That's an excellent and practical question! For a rectangular-shaped public waste bin, the "best" liner truly depends on a few key factors: fit, durability, and cost-effectiveness.
First and foremost, a custom-fit rectangular trash bag is ideal. Using standard round or tall kitchen bags will leave gaps at the corners, causing litter to get behind the liner and creating a mess. Look for bags specifically labeled for "rectangular bins" or "commercial rectangular cans." Measure your bin's interior length, width, and depth to ensure a proper fit.
Material strength is critical. Heavy-duty, high-density polyethylene (HDPE) or low-density polyethylene (LDPE) bags are the standard. For public bins, I'd recommend a thickness of at least 1.5 mils, but 2 mil or more is better for heavy, sharp, or wet waste. These resist tears and punctures.
Consider features like drawstrings or flaps for easy tying and removal, and leak-proof technology (often a star-sealed bottom) to contain liquids. For high-traffic areas, dark-colored bags (like black) are preferable as they hide contents and appear cleaner longer.
In summary, the best liner is a properly sized, heavy-duty rectangular plastic bag that snuggly fits your specific bin. It might cost a bit more than generic bags, but it saves on cleanup time and maintains a more hygienic public environment. Many janitorial supply companies offer them in bulk rolls.