This entry is the latest in a Worldwatch blog series on innovations in the climate and energy world.
Like any major city, Philadelphia generates a lot of municipal solid waste (MSW). The trash cans in the central downtown area collect 30–40 tons every day. Where that waste goes, and how it is dealt with, are important issues, with greenhouse gas and other environmental ramifications. But simply managing the waste collection is a daunting task as well.
Until recently, Philadelphia had to make pickups in the city center three times a day, which stretched the city’s already thin municipal resources. Installing solar-powered trash compactors, however, has allowed Philadelphia to reduce its trash pickup burden dramatically, with associated savings and ancillary benefits such as reduced greenhouse gas emissions, less crowded streets, and increased recycling.
These compactors, which have replaced 700 conventional trash cans on Philadelphia street corners (as well as in many other cities, campuses, and other locations around the United States), allow for up to 5 times as much trash to be held within a single 32-gallon container. They run similarly to any other trash commercial compactor in that a laser eye detects when the trash reaches a certain height within the collector and triggers a compaction cycle, condensing the trash into a smaller space.
There’s a good reason you haven’t seen compactors on street corners until now, however. They require electricity, and no one was about to run wires to trash cans on every corner. That is where the built-in solar panel comes in. A 30-watt solar panel generates electricity and is connected to a maintenance-free 12-volt battery to provide consistent power for the unit. The panel does not need any direct sunlight, and so the compactors can be placed in shaded as well as sunny areas.
The electrical equipment inside the compactor also includes an SIM card, which allows each individual unit to be monitored remotely from the sanitation department headquarters. This monitoring system tells the operator when a unit is nearing its full capacity, so that when tracking a group of units, the trash collection schedule can be optimized. System operators can also track any maintenance issues as they arise, and even how often each unit is opened.
Does it pass the laugh test?
Solar-powered trash compactors simply take two technologies with proven track records and bring them together. And to look at them, they seem like any other trash can, just with a solar panel on top.
What does it bring to the table?
Being able to store up to 5 times as much trash in each receptacle, and knowing exactly how full each unit is at all times, allows for fewer trips for trash pickup. In Philadelphia, downtown trash cans were emptied 17 times per week before the installation of the compactors, and this number is now down to 5. This means significant reductions in fuel consumption—leading to lower expenditures and reduced greenhouse gas emissions—and in the labor needed for waste management. It also reduces city traffic and wear on heavily trafficked streets.
Philadelphia used to have 33 staff positions servicing trash receptacles; it has been able to cut that number to 9. The workers no longer needed for trash collection are now collecting recycling. Much of this recycled material is due to the compactors as well. Many come with recycling units attached, which are the first curbside recycling systems in Philadelphia.
How scalable is it?
Any sanitation department could benefit from these compactors. The large percentage of MSW generated at individual homes and businesses, however, falls outside the purview of the compactor systems as they are currently used, limiting the degree to which they can be scaled. But that limit is not even on the horizon.
How close is it to commercialization?
Philadelphia has saved over $850,000 in one year and is projecting $13 million in savings over 10 years. Other cities using these systems include Boston, Banff (Canada), and Chicago, and many universities, including Arizona State, Georgetown, and Iowa State, have installed solar compactors as well. Payback periods can be as short as 3 years.
What is the biggest obstacle to success?
Though these systems are economical over a longer time horizon, the initial cost of these systems is huge: around $3,800 versus roughly $100 for a conventional trash can. Even for municipalities that find the long-term savings attractive this may simply be too high a bill.
The final word(s):
A useful advance in waste management.
Solar-powered trash compaction seems like an example of a renewable energy-based product that fills a useful niche. It may not be long before such systems are commonplace in large cities and open, overflowing trash cans are considered obsolete.