How New Water Tech Uses Wastewater To Meet Energy Needs
Clean water and energy are limited resources under increasing demand, but waste is in high supply. Necessary for the health of people and ecosystems, wastewater treatment has also been very energy-intensive. Though most are looking to reduce energy use, power still accounts for 25%-40% of the operating costs of treatment plants. Indeed, wastewater treatment uses an estimated 1.5% of the total energy consumed in the United States. Most of this energy is used during the secondary treatment, activated sludge, but new tech companies are using innovations that take advantage of the “waste” in wastewater to reduce energy consumption and to produce renewable energy, while making a profit in the process.
Some technologies use microbial fuel cells in the sludge to actually generate electricity. The Electrogenic Bioreactor developed by the three-time Artemis Top 50 winner, Emefcy, harvests electrons released by the oxidation of dissolved organic chemicals. This technology produces less volume of waste than activated sludge and generates electricity.
Gasification is a process by which the latent energy in biosolids is harvested upon applying heat to wastewater sludge and creating a synthetic gas or fuel. BlackGold Biofuels harvests wastewater from grease traps, separates out the dry fats, oils and greases (FOG) from the water, and converts it to biofuel that is then processed into glycerin, biobunker fuel, and biodiesel. 2011 Top 50 winner BlackGold states, “Conversion to biodiesel is the highest and best use for FOG. With energy recovery at close to 80%, the economic trajectory and fungibility of a liquid transportation fuel, the ability to meet EPA’s Sulfur limits for on-road and stationary applications, and a federal renewable fuel standard providing insulation against market dips, biodiesel is the only beneficial reuse with the long-term stability that the pumping and food service industries require to reliably conduct business”. Another company, M2Renewables has developed a Solids Separator that collects cellulose from paper, imbedded organic material and FOG from sewers or point-of-entry to wastewater treatment plants and offers gasifiers specialized to create hot air, hot water, steam, electricity or hydrogen, depending upon the local needs. In addition to producing energy, M2R reports reductions in energy use of up to 85% from conventional wastewater treatment.
A final innovation in wastewater treatment uses supercritical water oxidation, a process by which water, oxygen, and high temperatures and pressure convert wastewater to a phase similar to both liquid and gas known as the supercritical phase. Another three-time Top 50 Winner, SCFI is a leader in this technology, having marketed their AquaCritox® product. At the supercritical phase the organic material in sludge can be broken down with no harmful emissions to the air or water and the process can generate more energy than it consumes because oxidation is much quicker than traditional sludge activation and the steam produced can be used to generate electricity.
These new technologies are highly efficient solutions to problems we face in wastewater management, but they are also underused. The Artemis Project’s Top 50 Water Technology Competition aims to promote companies offering sustainable innovations and demonstrating good business practices. The judges look forward to reading this year’s applications from start-ups in water tech- and we all look forward to their impressions and insight.