Team:Northeastern/Integrated Practices
Integrated Practices
Visiting Deer Island
about our visit
As part of our integrated practices we visited Deer Island, a wastewater treatment plant near the Logan Airport. The facility is unique in several ways, not least of which is its use of anaerobic digesters.
The twelve 46-meter digesters, called the “giant eggs,” are unmistakable to anyone flying into or out of Logan airport. Each contains an anaerobic consortium of bacteria—unmodified—that convert the reduced energy from sludge into methane. Interestingly, the island has generators on site strictly to utilize the digesters’ methane output, converting the gas into steam for heat and electrical power. This recycled energy provides 26 percent of the islands energy needs and saves the facility $15 million per year in fuel oil costs and $2.8 million per year in electricity savings. The facility is also notable for being the second largest in the United States. All told it treats wastewater from 43 cities and towns.
By visiting Deer Island we were able to see first-hand a plant which might benefit from microbial electrolysis cell technology. Compared to an average treatment facility, however, Deer Island is already advanced. In fact, anaerobic digesters are considered by some to be efficient enough to prevent microbial fuel cells (not to be confused with electrolysis cells), from reaching mass adoption. Therefore it was interesting to walk around the technology that represents the greatest challenge to microbial electrolysis cell adoption.
H2 vs CH4! The benefit to anaerobic digesters over microbial fuels cells is the low cost of production at scale. While microbial fuel cells scale poorly (with increased distance between electrodes having a significant deleterious effect on power generation and hydrogen production), digesters scale well, as evidenced by the 46-meter digesters. The benefit of microbial electrolysis cell is the greater energy density of hydrogen relative to methane. If some future microbial electrolysis cell can circumvent the technologies scalability challenges, it may represent a significant advance.
