By Tina Casey
Not too long ago, cities could be labeled strictly as takers: taking in food, water, energy and other resources, while dumping out mountains of garbage and oceans of polluted wastewater. But take a look at the gigantic egg-shaped structures that dominate New York City’s Newtown Creek wastewater treatment plant, and you’re looking at the key to a sustainable future.
The distinctive landmarks are digesters that convert municipal wastewater into biogas, and New York has just announced a new food waste recycling/wastewater project that will enable the digesters to accept food scraps from households, schools, and other institutions.
The new project is a giant step forward for New York, because it will enable the city to sell biogas from the digesters into the commercial natural gas market.
Although the city has long reclaimed some of the biogas to help power operations at Newtown Creek, the raw gas is unsuitable for domestic purposes because it is too “wet” and rich in carbon dioxide.
San Antonio, Texas actually lays claim to the first commercial wastewater biogas hookup in the US, but if the Newtown Creek project is adopted at the city’s 13 other treatment plants, the New York project will be by far the largest.
In partnership with the company Waste Management and utility National Grid, the Newtown Creek project will convert food waste/wastewater biogas to a commercial-grade product that can be sold off site, with the goal of reclaiming 100 percent of biogas generated by the digesters.
The implications for sustainable urban development are enormous. One critical obstacle that cities face is the skyrocketing cost of wastewater treatment, so the prospect of offsetting costs by generating and reclaiming energy would enable more wastewater treatment projects to get off the ground more quickly.
It’s worth noting here that digesters house a process that is, literally, natural digestion. Digesters create an optimal environment for microbes to feed on the organic materials in wastewater. Along with generating gas, the microbial process provides an additional level of wastewater treatment without added chemicals and with a minimal use of energy.
The digestion process also yields an organic soil-like material that can be reclaimed as compost. In short, digesters provides a sustainability three-for-one: cleaner effluent, a soil enhancer to grow more biomass, and reusable biogas.
The reclamation of biogas from human waste also offers an intriguing window into next-generation urban sustainability, by harnessing the energy generated by huge numbers of people as they move through the processes of daily life.
Another good example of urban energy harvesting from “people power” is piezoelectricity, in which certain materials generate electricity when exposed to stress. This effect is being explored as a means of generating energy from crowded urban facilities such as train station platforms and even dance floors.
Devices that harvest kinetic energy from the simple act of walking are also in development, and the principle of kinetic energy can also be applied to people-powered devices common in the urban environment such as turnstiles and revolving doors.
By extending the people power principle to the mechanics of urban life, you get energy harvesting opportunities from roadways as well elevators, commuter trains, and stop-and-go traffic in the form of regenerative braking.
Put it all together and you have the city of the future as a gigantic energy generating and resource reclamation dynamo.
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