How to Turn Sewage Sludge into Fuel


The race to develop advanced biofuels from waste is entering a hot phase.

One promising area is the conversion of sewage sludge into fuel for transport.



1. SEWAGE SLUDGE CAN BE CONVERTED INTO SYNTHETIC BIOFUEL


I have previously elaborated on the potential of sewage sludge to be used as an energy source and have mentioned that sewage sludge and waste-to-energy more generally is also a good investment opportunity in 2019. Sewage sludge has even more potential, because one can extract phosphorus from dry sludge, through the incineration process. Among other options, sewage sludge can be turned into jet fuel through hydrothermal liquefaction, as the Australian Energy Agency has mentioned.

This is an exiting new development, that I would like to look at further. In fact, the European Union invests heavily in this area in a project which has been named TO-SYN-FUEL, with the goal to make it cost-competitive on the market. In the United States, we have the first attempts to commercialize algae fuel, as ExxonMobil and FuelCell Energy Inc. agreed to work together to increase the energy output of carbonate fuel cells.


2. PROCESS BREAKS DOWN THE CHEMICAL COMPOUNDS INTO THEIR INDIVIDUAL COMPONENTS. THE CONVERSION OF SEWAGE SLUDGE INTO FUEL SUPPORTS THE CIRCULAR ECONOMY.


In fact, turning waste products into fuel is a growing trend in the whole industry, such as turning plastics into diesel fuel. The American Chemistry Council pointed out the advantages of converting plastics into fuel, to be turned into jet fuel for example whereby one would decrease greenhouse gas emissions by 60 to 70 percent. So there are various attempts in the waste to industry to reuse non-recycled plastics, meaning plastics that cannot be reused without multiple steps to process the material.

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3. THROUGH HYDROTHERMAL LIQUEFACTION, SEWAGE SLUDGE CAN BE USED AS JET FUEL


Jet fuel in particular has a low temperature threshold, which allows it to fligh at high altitude without the jet fuel losing its viscosity. Admixture of biofuel would increase that threshold, which is why biofuels compose roughly 10% of the fuel. As the United States is not particularily well suited to growing algae at a large scale, as the United States is located further away from the equator.

It has been found that sewage has many of the same characteristics as algae biofuel, although the process is different to the one that is being used to turn sugarcane into fuel. So turning sewage into fuel has garnered a lot of attention as of late. That was reported by Samantha Larson in the magazine Crosscut in November 2016.


4. WE SHOULD CONSIDER BIOGAS AS A BY-PRODUCT OF THE FUEL PRODUCTION PROCESS


Equally important in this process of turning sewage sludge into fuel is the production of biogas, that can be processed into liquid biomethane. The United States is a leading player in that. As CNBC reported, SUEZ and Cryo Pur have commercialized such a solution and succeeded in turning two metric tons of biogas into one metric ton of biomethane in 2017.


5. HIGH ENERGY CONVERSION FACTOR; ONE OF THE HIGHEST IN THE WASTE-TO-FUEL ECONOMY


According to the Water Research Foundation, 99% of all organic material from sewage sludge can be turned into fuel, which is actually one of the highest percentages you will find anywhere in the waste industry, which means that fuel made from sewage sludge can replace a signficant percentage of crude oil that has to be imported to the United States.


6. CONCLUSION


The key question we have to ask ourselves is this:

How renewable are biofuels?

Do we rely on other energy sources to convert biomass into fuel?

How high is the energy yield?


7. REFERENCES:


ArenaWire (2018): Sewage sludge to jet fuel, viewed 18 01 2019, https://arena.gov.au/blog/sewage-sludge-to-jet-fuel/.

American Chemistry Council: What are plastics-to-fuel technologies? [pdf], viewed 18 01 2019, https://plastics.americanchemistry.com/Product-Groups-and-Stats/Plastics-to-Fuel/What-Are-Plastics-To-Fuel-Technologies.pdf.

ExxonMobil (2018). Advanced biofuels and algae research: targeting the technical capability to produce 10,000 barrels per day by 2025, viewed 18 01 2019, https://corporate.exxonmobil.com/en/Research-and-innovation/Advanced-biofuels/Advanced-biofuels-and-algae-research.

Frangoul, A. (2017). The business turning sewage sludge into fuel, CNBC, viewed 18 01 2018, https://www.cnbc.com/2017/05/11/the-business-turning-sewage-sludge-into-fuel.html.

Larson, S. (2016). Sewage could power jumbo jets, Crosscut, viewed 18 01 2019, https://crosscut.com/2016/11/science-can-now-turn-sewage-into-jet-fuel.

The Water Research Foundation (2016) Genifuel Hydrothermal Processing Bench-Scale Technology Evaluation Project [pdf], viewed 18 01 2018, https://www.werf.org/i/a/ka/Search/ResearchProfile.aspx?ReportId=LIFT6T14.

TO-SYN-FUEL, Turning sewage sludge into fuels and hydrogen, viewed 18 01 2019, http://www.tosynfuel.eu.


Many thanks for the shared interest in the energy world!



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