That's an excellent and very practical question for anyone involved in urban planning or public space management. Getting the number of trash bins right is crucial for cleanliness, user satisfaction, and efficient operations. Here’s a natural, step-by-step approach you can follow, blending common sense with some basic calculations.
First, you need to define the scope. How large is the square in square meters or square feet? What are its primary functions? A square with food vendors and seating will generate far more waste than a simple transit corridor. Sketch a basic layout, noting key areas like entrances, seating clusters, food kiosks, and walkways.
Next, estimate the peak pedestrian traffic. This is often more important than the average. How many people are likely to be in the square during a busy lunch hour or a weekend event? You can often get projections from architectural plans or similar public spaces. Let's say your peak occupancy is estimated at 300 people.
Now, consider waste generation rates. A common benchmark is that a person in a public space might generate 0.1 to 0.2 liters of waste per hour. For a square where people might eat, a rate of 0.15 liters/person/hour is a reasonable starting point. During a 2-hour peak period, 300 people would generate: 300 people * 0.15 L/person/hour * 2 hours = 90 liters of waste.
Then, look at bin capacity and collection frequency. Standard public bins often have a capacity of 120 to 240 liters. A key rule is never to let bins exceed 80% capacity—it looks messy and discourages use. If you choose 120-liter bins and plan for a collection every 4 hours during peak times, each bin's *usable capacity* is 120 L * 0.8 = 96 liters.
The basic calculation for the number of bins needed is: Total Waste Volume / Usable Bin Capacity. From our example: 90 liters / 96 liters per bin ≈ 0.94 bins. This seems less than one, but that's just for the total volume. Placement is critical.
This leads to the most important step: placement and convenience. People won't walk more than 30-40 meters to dispose of trash. Bins should be highly visible at all natural stopping points: every seating area, near food vendors, at all entrances/exits, and along major pathways. Even if your volume calculation suggests few bins, you need enough to cover the area effectively. A good minimum is often one bin per 30-50 meters of seating or per 500-1000 sqm of open area.
Finally, adapt and iterate. Once the square is open, monitor the bins. Are they overflowing? Are there litter hotspots where an additional bin is needed? Be prepared to adjust the number and locations based on real-world use.
So, in short: Estimate peak waste volume, choose an appropriate bin size and collection schedule, calculate a baseline number, and then strategically place more bins than the bare minimum suggests to ensure convenience and cleanliness. It's a mix of math and observing human behavior. Good luck with your new public square