Energy

Mimicking nature turns sewage into biocrude oil in minutes

Sludge from Metro Vancouver’s wastewater treatment plant has been dewatered prior to conversion to biocrude oil at Pacific Northwest National Laboratory
Sludge from Metro Vancouver’s wastewater treatment plant has been dewatered prior to conversion to biocrude oil at Pacific Northwest National Laboratory
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Sludge from Metro Vancouver’s wastewater treatment plant has been dewatered prior to conversion to biocrude oil at Pacific Northwest National Laboratory
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Sludge from Metro Vancouver’s wastewater treatment plant has been dewatered prior to conversion to biocrude oil at Pacific Northwest National Laboratory
Biocrude oil, produced from wastewater treatment plant sludge, looks and performs virtually like fossil petroleum
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Biocrude oil, produced from wastewater treatment plant sludge, looks and performs virtually like fossil petroleum

Biofuels are often touted as an alternative to fossil fuels, but many depend on raw materials that would quickly become scarce if production were scaled up. As an alternative to these alternatives, the US Department of Energy's Pacific Northwest National Laboratory (PNNL) has found a way to potentially produce 30 million barrels of biocrude oil per year from the 34 billion gal (128 billion liters) of raw sewage that Americans create every day.

According to PNNL, the problem with using sewage as a source material for biocrude is it's too wet and requires drying before more conventional processes can handle it. PNNL's approach is to use HydroThermal Liquefaction (HTL) to turn the sewage into oil, which removes the need for drying.

In HTL, the raw sewage is placed in a reactor that's basically a tube pressurized to 3,000 lb/in2 (204 atm) and heated to 660° F (349° C), which mimics the same geological process that turned prehistoric organic matter into crude oil by breaking it down into simple compounds, only with HTL it takes minutes instead of epochs.

"There is plenty of carbon in municipal waste water sludge and interestingly, there are also fats," says Corinne Drennan, who is responsible for bioenergy technologies research at PNNL. "The fats or lipids appear to facilitate the conversion of other materials in the waste water such as toilet paper, keep the sludge moving through the reactor, and produce a very high quality biocrude that, when refined, yields fuels such as gasoline, diesel and jet fuels."

Biocrude oil, produced from wastewater treatment plant sludge, looks and performs virtually like fossil petroleum
Biocrude oil, produced from wastewater treatment plant sludge, looks and performs virtually like fossil petroleum

The end product is very similar to fossil crude oil with a bit of oxygen and water mixed in and can be refined like crude oil using conventional fractionating plants. PNNL estimates a single person could produce enough waste for two or three gallons (7.6 or 11 L) of biocrude each year. This won't put fear into the heart of the oil companies, but it does provide not only a fuel source, but also an alternative to treating, transporting, and disposing of sewage sludge.

Other benefits of the HTL process are that it can also be used with agricultural waste and other wet materials, the liquid phase can be turned into fuel and useful chemicals using a catalyst, and the small leftover solid residue contains phosphorus and other nutrients for fertilizers.

Drennan says the simplicity of the process has allowed for rapid development in only six years and it is now continuous and scalable. PNNL has licensed the process to Genifuel corporation in Utah, which has partnered with Metro Vancouver in Canada to build a Can$8 to $9 million (US$5.9 to $6) pilot plant that's expected to go online in 2018.

The video below shows how the process turns sewage into biocrude.

Source: PNNL

From the Toilet to the Tank – Biofuels from Sewage

18 comments
Racqia Dvorak
If I calculate that correctly, then this, if implemented nationwide, could nearly double our oil output. Of one day of oil production. "PNNL estimates a single person could produce enough waste for two or three gallons (7.6 or 11 L) of biocrude each year." That's 2.5 gal x roughly 375 million people. 937,500,000 gal crude. 42 gal in a barrel, so 22,321,428 barrels of crude in a year. The US produces 11,973,000 barrels per day. About 187 times that, so, no, I don't think the oil companies will be quaking, but they might invest in it to divert attention from viable biofuels.
William H Lanteigne
The volume produced wouldn't matter if the cost is competitive with, or cheaper than fossil crude. Every little bit helps.
Paul Anthony
How many gallons of this crude that is being made is required to make a gallon of this crude?
Richard Bolman
True, it may just be a drop in the bucket (no pun intended), but it also helps mitigate other issues related to environmental impacts of waste. Not to mention the benefits from getting farms added to the mix.
guzmanchinky
How much energy is required to stir, pressurize and heat?
habakak
Fantastic. If we can use a waste product instead of extracting oil out of the ground, as long as it's cost-competitive and hopefully environmentally more sound, why not. We will use oil for the foreseeable future. Even if our electricity generation goes fully renewable and all personal and public light vehicle transportation goes battery electric, we will still use at least 10 million barrels of oil per day. Maybe in another half a century we will use very insignificant amounts of oil, but it will be a long time still until we can do without it.
VirtualGathis
This same method also produces crude from algal sources. The ironic part is that a simple harvesting and drying method could turn the Florida blue green algae bloom problem into a resource. since the Algae do not need to be totally dry the first pass belt drying method could allow simple harvesting. Run that through this process in a continuous process, rather than as a batch process, and both problems become a revenue stream.
ToddFahrner
Applying the necessary heat and pressure requires how much energy relative to the product?
Alien
This sounds great but how cost effective is all the high temperature and pressure treatment required to produce the end product? Perhaps some cost could be offset against the currently normal sewage processing costs but it would easier to evaluate if more information were forthcoming.
GeneMoore
this is stupid, why make more black stinky stuff, and then burn it? That is contributing to the problem all over again, Man has to get over this as fuel, or we will be tossed off this planet and in a another million years or so another "sentient" species will give it a go. Wake up!!! life is a circle and has nothing to do with "the bottom line" or domination over this planet.