The Inland Empire’s cadre of water treatment plants clean millions of litres of waste water every day. But what to do with all that left over poo? Normally, it’s unceremoniously dumped in a local landfill, but at Regional Water Recycling Plant No. 1, that massive pile of crap is put to a better use — making electricity with the largest biogas fuel cell generator in America.
Located in Ontario, California, just east of LA county, Plant No. 1 filters solid waste and sanitises 166 million litres of water per day. The clean water is then used to irrigate city parks while conserving potable water for the Empire’s 850,000 residents through conventional sanitation methods. The strained solid waste is then dumped into an anaerobic digester where colonies of bacteria break down the poo into its base chemical components.
Problem is, the bacteria excrete methane while they eat, a leading contributor to global warming. Since the plant can’t just vent this greenhouse gas into the atmosphere, it instead uses it to power an onsite 2.8-megawatt fuel cell generator to provide some 60 per cent of the treatment plant’s operating energy. Anaergia of Canada installed the generator at no cost to the IEUA last October and will eventually recoup that money by selling the energy that the fuel cell produces back to the utility.
The Ontario fuel cell works just like any other fuel cell, generating electricity via an oxidizing reaction. Electrons stripped from the fuel material — typically hydrogen or hydrocarbons, like methane — create an electric current as they flow from the cell’s positive to negative terminals, much like a battery. However, a fuel cell actively produces current (so long as fuel is available), rather than simply store it as a battery does. In addition to electricity, the oxidizing reaction also generates heat and water as by-products. This waste heat generated by the utility’s fuel cell is reused, pumped back into the digester to keep the bacteria at their preferred feeding temperature. The system as a whole is exceedingly clean — save for the poopy bits of course — producing little more than electricity and water with 70 per cent efficiency and minimal emissions.
The IEUA hopes to replicate the Ontario plant’s success across all six of its district treatment facilities with the goal of becoming fully self-sustaining by 2020.
[Slate, IEUA 1, 2, 3, Wikipedia]
Picture: Anaergia