"Plastic bags are not allowed in Rwanda. Please remove any belongings, including duty-free shopping, from their plastic bags and leave the bags on board."

Um, what?

I looked around and saw plastic bags being tucked into the pockets of my fellow passengers' seats. I removed the T-shirt that I'd bought at Schiphol Airport in Amsterdam and left its plastic shopping bag behind.

After waiting in line to purchase my Rwandan visa, then waiting in a second line to have my passport stamped, I finally reached the immigration desk, where the officer handed the passport back to me with a big smile and said, "Welcome to Rwanda."

All I could think about was the genocide of 20 years ago — and yet, somehow, I felt like I'd just been welcomed by the concierge of an eco-friendly resort.

Waiting at the luggage carousel, I saw a man selling cloth bags. I was extremely jet-lagged and wasn't overthinking anything at that point. I simply observed, albeit with a foggy brain and a great thirst for water — or some other clear beverage with a slice of lime in it.

On the drive from the airport to my hotel, I noticed how incredibly clean the streets were. I have spent enough time in other African cities — littered with plastic bags, bottles and tall mounds of trash — and had never seen anything as cleanly swept as the well-paved streets of Kigali.

I didn't start to look into this until a) jet-lag started to lift the next day and b) I discussed plans for a day trip that Saturday. My colleague Mathilde advised me to have a relaxing morning and not plan anything until after 11 a.m. "Why?" I asked. "Because traffic is not allowed, stores will not be open, there will be no services except at your hotel until then," she said.

I learned that it was Umuganda — set aside as the last Saturday of each month. Its meaning is rooted in the intertwined sense of both "community" and "payment." The concept dates to when Rwanda was part of Belgium's colonized empire and its practice bolstered one's civic responsibility.

After taking office in 2000, President Paul Kagame revived, if you will, Umuganda to help clean up his still-shell-strewn capital a few years after one of the world's most swift (100 days) genocides. Under a law that took effect in 2005, all able-bodied people (including the president) between 18 and 65 are required to participate in cleaning up their neighborhoods' streets and sidewalks. Of course, a (perhaps unintended) consequence of this community service is less litter dropped on the streets — one will just have to do more work on the day of Umuganda if one litters. Another consequence (intended) is that clean cities can reflect public health and environmental health, and that can attract investment and development aid. Hence, another contributing factor to Kigali's cleanliness, in addition to Umuganda and a culture of non-littering, is the ban on plastic bags.

According to the 2014 Mercer Global Financial list of the world's cleanest cities, Calgary is followed by Adelaide, Australia; Honolulu; Minneapolis, and Kobe, Japan. To anyone who travels much to Africa, Kigali would most certainly be on the list for the continent. In fact, I find less litter here in Kigali than in Minneapolis — and I have yet to see any gum stuck on sidewalks.

Rwanda has a ways to go for a full-fledged democracy, but it's true that Umuganda does instill a sense of collective citizenship and civic engagement — even if it is with a strong hand. It has taken hold culturally, it seems, when I ask people who speak (at least openly) positively about it.

Perhaps the concept behind Umuganda, and the ban on plastic bags, will inspire replication not only in Africa but across the world — including Minneapolis ("City checking out plastic bag ban," July 25).

I, for one, haven't missed the plastic bag I left behind on the aircraft.

Karen Louise Boothe Acharya, of Minneapolis, is a former journalist and now works as a Communications for Development (C4D) consultant. She has worked in and/or traveled to more than 60 countries.