Net Zero Lessons From A Wastewater Treatment Plant

If you think that achieving net-zero energy consumption is an impossible ambition for your place of business, take a look at the goal that New York City has embarked upon. Last spring the city updated its sustainability roadmap, OneNYC, including the colossal task of achieving net zero energy at its wastewater treatment plants by 2050. We should say impossible task because within this densely packed city are 14 massive treatment plants that pump, filter, aerate and treat 1.3 billion gallons of wastewater daily, accounting for an enormous amount of energy consumption.

However, take a look at one recently announced upgrade, at the city's Port Richmond wastewater treatment plant on Staten Island, and you can see that net zero energy is not such a faraway dream, even in some very unlikely of places.

Net zero for NYC wastewater treatment

New York is focusing on reducing energy-related emissions from wastewater treatment because, to paraphrase the infamous early 20th century bank robber Willie Sutton, "that's where they keep the emissions." Wastewater treatment is an energy-intensive process that typically accounts for a big chunk of energy use in cities, and New York is no exception.

According to the city (see page 170 of OneNYC), the combined emissions of its water supply and wastewater systems account for almost 20 percent of all emissions attributed to city government, and wastewater treatment alone accounts for 90 percent of that.

To make matters more complicated, the typical New York City treatment plant is wedged into neighborhoods, sometimes literally across the street from homes and other occupied buildings. Building a large ground-mounted solar display or installing a wind turbine is out of the question.

One advantage that Port Richmond does have is a roof over the main part of the facility. That's a big contrast with most treatment plants, which are typically open-air facilities located on the outskirts of a town or city. The latest net-zero announcement for Port Richard actually follows upon an earlier upgrade of the roof, which achieved "cool roof" status back in 2012. The cool roof reduces heat gain in the building by reflecting solar energy upward.

The full fruits of that upgrade were realized in the following years, when a massive new solar array was added to the roof. The new array, one of the largest rooftops solar systems in New York, is a partnership with ConEdison Solutions. It provides for about 10 percent of the treatment plant's overall power requirements. The cool roof helps to make the array more efficient because the solar modules convert light reflected from the cool roof, in addition to converting direct sunlight.

The newest addition to Port Richmond's net-zero upgrade consists of three new boilers and a a new exhaust-capture system. The boilers replace older -- as in, 1970s -- oil-burning models and run on biogas captured from the wastewater treatment process as well as natural gas.

Biogas reclamation is the key element that makes the net-zero goal realistic. In the past, raw wastewater was simply considered a nuisance in need of disposed. With biogas reclamation, wastewater is treated as another source of incoming energy.

Since the new boilers will run on a combination of biogas and fossil natural gas, it appears that New York City does not have net-zero plans for the Port Richmond plant specifically. However, Port Richmond is among the smaller of the city's treatment plants. The city can leverage more energy-harvesting opportunities at its larger treatment plants to keep driving the entire group toward the overall net-zero goal.

A long (or short) road to net zero

While net zero tends to conjure up images of high-tech, ultra energy-efficient buildings, the Port Richmond upgrades illustrate that you can get a lot of mileage by retrofitting older buildings with technology that has already been mainstreamed, including cool roofs and rooftop solar.

The Port Richmond upgrade shows that high energy consumption doesn't necessarily prevent a facility from achieving net zero energy.  Before dismissing net zero as an unrealistic goal out of hand, it makes sense to analyze the facility and ensure that all energy-harvesting opportunities have been investigated.

New York's net zero for wastewater goal also provides a path forward for companies that own or operate multiple facilities. While net zero may not be realistic for each facility alone, when treated as a group the opportunities for achieving net zero may become more clear.

The use of biogas capture also shows how facilities can leverage incoming fuel aside from sun and wind energy. That applies to biogas from livestock and from agricultural and food waste as well as municipal wastewater.

Speaking of food waste, New York City's net-zero goal may also provide the local food-service industry with another green branding opportunity. The city has been experimenting with commingling food waste and wastewater, providing local businesses with the opportunity to contribute to biogas capture without having to install a biogas system on their premises.

As for next steps for New York City and other municipalities, this could be a long way down the road, but new advances in wastewater treatment are emerging that enable treatment plants to leave their energy-sucking past behind and even go beyond the net-zero goal, to produce more energy than they consume.

Image credit (cropped): Port Richmond rooftop solar array via NYC DEP.