I live in an apartment building, like many city dwellers and some suburbanites. I live in an apartment not only because the rent is generally cheaper than a detached home- at least, a detached home in any neighbourhood that my wife would feel safe in- but also because apartments are a more eco-friendly choice. A few shared walls dramatically lowers heating and cooling costs, and smaller spaces both lower utility use and lead to less retail consumption. But this post isn't about my building, it's about my washing machine.
In my building, there are 28 apartments- 14 single bedroom units and 14 two-bedrooms. There is also one laundry room, near the elevator, with three washers and three dryers in it. When I moved into my present building, I was worried that waiting to do my laundry would be a frequent occurrence, especially since I was moving from an apartment with in-unit laundry. My fears were entirely unfounded. Even though I share three washing machines with 27 other households, I rarely need to wait to launder my clothes- and I am usually able to do two loads at once, saving me time and reducing wait times for everyone else in the building. Rather than having to have one machine per home, 28 households are able to do all of their washing with only three machines.
Of course, it isn't just the washing machines. We have a pool and spa on our property, which 112 households have access to. It isn't always empty, but there's always been plenty of space for everyone to use. We have a gym as well, and a basketball court. These are all things that you might expect to find in the garage or backyard of a suburban home- serving one household, laying around underutilized most of the time. On one apartment property, just one of each of these resources is used by 112 people, largely without any problems.
The point I'm making here is that cities are about economies of scale. When people concentrate themselves in one place, and get comfortable about sharing resources with others (parks, transit vehicles, pools, community centres, etc.), fewer resources are needed to serve a larger community than would be necessary in a place where people are spread out. The fewer resources we consume, the less impact we make on our planet- and ultimately, the more sustainable our civilization will be. Those who see the cities as polluted and the suburbs and rural areas as pure are missing this point entirely. Of course, we should care about pollution in our cities- but the solution to pollution isn't sprawl.