It may appear to be an idea too farfetched at the moment, but latest research and developments hint at the possibility of using sewage for creating fuel. If achieved, this is to be considered a milestone achievement and is expected to contribute towards the preservation of energy resources as well as the reduction in greenhouse emissions.
While sewage waste has been used as a source for manufacturing fertilizers for many years, its utilization for the creation of fuel is surely to extend support to the causes of environment conservation and relevant cost reduction.
The first plant for converting sewage into energy was set up in Chiclana de la Frontera, Spain. It functions to generate algae-based biofuel through microbe activity. While the fact that microbes are able to produce fuel is not a newfound revelation but the waste treatment plant has set a precedent by using this information to advance the commercial production of fuel.
Conventional Conversion Process
As stated earlier, conventional conversion of sewage into fuel involves anaerobic respiration by microbes. Anaerobic respiration effects a combustible reaction that releases biogas and generates energy. However, the energy produced is not sufficient and it is for this reason that a need for technological advancements was felt in this regard.
While considerable technological advancements have been made with respect to using sewage for fuel production, their complete functional and production capacity is yet to be determined. Nevertheless, the latest findings are in practice now and are mainly concerned with two principle processes for fuel production.
The first one depends on bacterial activity to generate electric current and subsequently energy. The second process involves the passing of electric current through sewage waste to release vapor. This vapor is put through the process of condensation to be converted into diesel, which may be further burned for energy generation.
Biocrude Oil from Wastewater Treatment
A research conducted by the Department of Energy’s Pacific Northwest National Laboratory (PNNL) concludes that sewage waste can be treated to create biocrude oil. The suggested process for this purpose is based on the principle of hydrothermal liquefaction technology that allows the imitation of Earth’s geological forms under high temperature and pressure settings. The technology also leads to the speeding up the production of biocrude oil, the production process taking no more than mere minutes. On the other hand, natural production of biocrude oil is a process that spans over a time period of millions of years.
The final product generated through this process resembles petroleum, as pumped from the ground, and also consists of a minimal percentage of water combined with oxygen as impurities. Hence, post the production the resultant substance is further refined through traditional petroleum refining procedures.
This development holds even more relevance in the light of the information that around 34 million gallons of wastewater is treated per day across the US, which has the potential to generate up to about 30 million barrels of oil annually. Prior to this, many were not convinced of wastewater’s utility for fuel generation, deeming it too wet a substance that needed drying. This implication led to the belief that the process required undue expenditure and would be very time consuming. The employment of hydrothermal liquefaction technology for this purpose nullifies the aforementioned implication, as it eliminates the necessity to dry wastewater before treating it for fuel production.
The technology primarily supports the breaking down of waste material into simpler compounds. It includes the pressurizing of sewage to 3000 pounder per square inch which is followed by processing the waste through a reactor system that maintains a temperature of 660°F. This leads to the resolution of the wastewater into biocrude oil and a liquid substance as a byproduct.
The resultant biocrude oil can be further processed to yield jet fuels, gasoline and diesel. Similarly the byproduct liquid phase may be treated for the production of other useful chemical substances as well as fuels.
Sewage Waste to Electrical Energy and Renewable Hydrogen
Another development in this sector concerns the conversion of toilet waste into electrical power and renewable hydrogen. In this regard, a precedent has been set up by FuelCell energy Inc. that runs the world’s first tri-generation plant in Los Angeles. The plant is dedicated to converting sewage waste into electrical energy for industrial use as well as hydrogen to be used as fuel for transport.
The plant sources out biogas, released through the treatment of wastewater, and processes it using a 300kWh molten carbonate fuel cell to produce hydrogen, heat and electricity. The resultant hydrogen is compressed and supplied to filling stations.
It is calculated that the plant generates 100 kg of hydrogen daily, which is sufficient for fueling up to 50 cars.
As already established, wastewater treatment for fuel production can significantly contribute towards energy cost reduction. While there is room for further development in this area, beneficial results of the application are already quiet visible, which apart from cost reduction also include support for enhanced water treatment, environment conservation and promotion of energy sustainability.