Many resources flow into cities to make them run; people, products, information, energy, water, food, money. What flows out? Products, air emissions, waste water, and of course, trash.  As more cities are discovering, both the waste water and trash can prove to be new sources of value creation as well as promising opportunities for closing the resource loop, taking them one big step down the path of sustainability.

Cities on islands are particularly good examples of managing trash, since space for landfills is in short supply and exporting general waste is cost prohibitive. Taiwan now has 2,000 recycling companies operating in a $2.2 billion market, as reported recently in the New York Times. The market is driven by fees on producers and importers that are then redistributed to recyclers. This has led to thriving markets and technology advancements particularly in recapturing and reprocessing waste from the electronics manufacturing sector, which often yields high value metals. This “urban ore” can yield as much gold in 1 ton as 5 to 15 metric tons of typical gold ore, and copper, aluminum and rare metals are similarly recoverable.  Even the compost in Taiwan is valuable for agriculture, and it’s not uncommon to place compost into refrigerated cases in apartment building garages to prevent odors and pest issues.

Fast growing cities with less formalized waste collection and processing systems have sometimes sprouted landfill communities that manually sift through the trash to glean items of value. One community in Paraguay received attention for remanufacturing its waste into instruments for a children’s orchestra. This isn’t foreign to U.S. cities, where bottle & can scavenging and even the rise of Freeganism point to the uncaptured value in our waste.

Compost to energy

Last month the first large commercial dry fermentation anaerobic digester was launched in San Jose, California to process 90,000 tons of organic waste annually and be a net energy generator of 1.6MW of renewable energy. Two future phases will increase the waste processed and energy generated to 4.8MW, creating enough to feed back into the electricity grid. The project is the result of collaboration between four entities: the city, which provided land, a waste collector, a resource management and processing company, and technology provider. It took strong leadership and a clear vision to make this type of investment, but this is just the start.

These projects have triggered wide interest in this technology, as a new facility is now planned for South San Francisco which will be able to divert almost 95 percent of organic waste feedstock from landfills. Each collection vehicle will collect enough organic waste during one route to fuel it for an entire day on compressed natural gas, creating a closed loop system. And since the anaerobic digestion process saves at least a ton of greenhouse gases for every ton of food waste diverted, there is a clear carbon impact.

On the East Coast, Massachusetts is deploying digesters at facilities like dairy farms, municipal landfills and wastewater treatment plants. Over the past year, the Massachusetts Clean Energy Center has awarded 18 grants worth $2.3 million to study, design and construct anaerobic digesters and other organics-to-energy facilities across the state. With a new commercial food waste ban going into effect July 2014, many states will be watching Massachusetts’ progress.

In addition to the focus on food waste, methane recapture from landfills is another significant source of energy which is reaching scale through companies like Clean Energy Fuels, which is distributing a renewable natural gas vehicle fuel to fleets throughout the country and 35 public stations in California. Renewable Natural Gas, or RNG, could become the next new fuel source created by large dairies, landfills, and sewage plants. Every city can create value off the back-sides of their residents.

Can recycling be made public?

Of course, processing the wastes may be relatively straightforward compared to the collection process. Most cities are targeting commercial or residential sectors to get access to the most concentrated and purest waste streams. New York officials are working to launch a cloud-based software platform that will track waste and evaluate it for more efficient pickup or delivery, in support of their Food Waste Challenge which has diverted 2,500 tons of waste from 100 restaurants over six months. At that rate, San Francisco could divert up to 133,000 tons, which amounts to 26,000 elephants, saving significant costs in the process.

However, outside of our homes and workplaces public recycling infrastructure is still proving to be a challenge in recovering clean waste streams. High rates of contamination stymy most attempts at composting or recycling. Making bins visible and intuitive is difficult across varied city infrastructure such as parks, transit hubs, libraries, and city facilities. Perhaps this is an area ripe for innovation in the cities of tomorrow. Public space recycling, sometimes called recycling on the go (“ROGO”), faces challenges in being simple to follow, widely available, and cost effective. Recycling bins could potentially serve dual purposes such as parking kiosks (recycle two cans and get 30 minutes of parking), WiFi hubs, or sculptural pieces. From a public engagement standpoint, participation metrics like this bike counter that has been deployed in Copenhagen, Seattle, and San Francisco could even be leveraged.

Of course, some cities have been removing trash bins in sensitive areas due to security concerns that they could serve as potential targets for explosive attacks. The remedy might be to use plastic bags suspended from hoops which have an added benefit of showing the type of trash or recycling and how full it is, or investing in bomb-proof trash cans.

In actuality, public space recycling might come down to a few simple principles, as noted in this America Recycles Day site which has information for cities on applying for grants, design toolkits, and mapping recycling bins. The best practices guide boils the process down to ten tips, starting with understanding the waste stream (is it a stadium or a library), selecting bins, and deploying communications. Public space recycling may prove challenging to get a clean waste stream such as compost, but the main opportunity could be in public education and engagement.

Just like many industrial and consumer products companies now are finding value as they strive to achieve zero waste, trash can be a raw material for cities. Future infrastructure such as park benches, bike racks, and bus stops can be made from local, recycled material, just as recycled polyester is making it into jeans, backpack, and other gear. Or if there’s enough nostalgia then selling trash is always an option, as the San Francisco 49ers football team is with their old stadium seats.

At the W hotel in Taipei, 300,000 plastic water bottles are being turned into coasters, games and key- and change-holders for use throughout the property, with the help of local designers who had been awarded grants from the Taipei city government. With enough creativity and participation cities can surely find more dollars in their waste.