When Lewis and Clark moved across the U.S., in the winter of 1804-05 they camped close to the native Mandan and Mintari villages on the Missouri river. Having come to their wits end over trying to find a fuel source, they mimicked the natives, who were using buffalo dung to fuel their teepees. While back then, excrement had the advantage of being a scarce fuel source in the great plains, and a safer fuel due to fewer sparks, humans have since developed many new energy technologies to avoid using waste as a fuel.
With the industrialization-associated human population boom, there is an ever-increasing concern over the biohazards associated with excrement. Going back to using this product as a fuel source is proving to be considerable improvement on current waste processing, from creating a new fuel source, to disease control.
Human sludge is the solid product of primary sewage treatment. Most primary-treatment sewage plants have two byproducts: a relatively clean water, and this sludge. Relatively recently, in 1987, scientists in Japan looked into turning this product into heavy oil as a replacement for crude oil. The modern science varies, but thermochemical or hydrothermal liquefaction (turning human solid waste into hydrocarbon liquids) has come a long way with startups such as Danish Mash Biotech starting operations in Africa and Asia. In the US, Utah’s Genifuel has partnered with the Pacific Northwest Laboratory to build a $6 million pilot plant that’s set to launch in 2018. The DOE has announced over $13 million for similar projects to help evaluate companies offering different tweaks on the technology.
The processes take the sludge, pressurize it to 200 times atmospheric pressure (3000 psi), heat it up to a good roasting temperature (315 Celsius, 600 Fahrenheit), and create liquid bio-crude and a small amount of phosphorus-rich solids, which can be used as disease-free fertilizer. If using only human solids of 10 litres (2.6 gallons) of biofuel per year, this sustainable fuel source can supply about 0.5% of the world’s crude oil. If animal byproducts are also included, this number changes to about 1-1.2%, around the annual crude production of the UK or Colombia. In the US alone, this translates to 30 million BOE per year for humans, and over 50 million BOE per year if livestock are included. Related: Refiners Stand To Lose From Trump’s Border Tax Plan
This type of technology has further advantages to the current treatment of human waste. Currently. waste is often mixed with fertilizer to help grow crops. However, if the waste isn’t treated sufficiently as is sometimes the case, diseases can pass through the treatment processes and into the crops. This liquefaction process guarantees that all diseases are eliminated from the waste, while still producing some byproducts useful for agriculture.
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However, as with all technologies that are still in the development stage, the jury is still not out in terms of its viability. Turning corn to ethanol proved to be too costly and a poor use of prime agricultural land. Fuel from algae, which has the physical scale to replace all crude oil production, cost about $7.50 per gallon in 2014 to produce, is still quite a few years away from commercial-parity to crude oil. When the pilot and demonstration scale plants go online in 2018, we will better understand the true cost of sludge-crude.
The advantage that sludge has over crop-based biofuel is that a considerable amount of money is currently being spent to process this biological waste. If turning it into fuel neutralizes the biohazard while creating an agricultural-friendly byproduct at a reasonable cost, this solution may move faster to market than algae oil or corn ethanol. While ground transportation technology can move away from hydrocarbons, the aviation industry can also go green by using renewable hydrocarbons.
By Matt Slowikowski for Oilprice.com
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