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BGU Finds Energy Potential In An Unlikely Source

BGU Finds Energy Potential In An Unlikely Source

December 1, 2021

Alternative Energy, Research News

Popular Science–It was another hot day in the Negev desert of Israel, and several researchers from Ben-Gurion University were setting up a field lavatory. Essentially a toilet seat stuck over a metal frame with a plastic bag receptacle underneath, this makeshift privy was an artifact of minimal convenience, typically used when scientists work in remote places where even portable jones and outhouses don’t exist, or when the surrounding ecosystems are too fragile to process human waste. But in this case, the toilet itself was part of a study. The research was focused on the toilet’s content and its potential to power human civilization. In simple terms, scientists wanted to see if they could convert poop to coal.

According to the team’s math, the world’s poultry dung can replace approximately 10 percent of the coal used in electricity production, reducing fossil fuel use. And the liquids can be channeled to the agricultural fields—not unlike how it was pumped to the successful sewage farms of the 19th century, and fully pathogen free.

Cooks like to experiment with the recipes to achieve the best results, and the Ben-Gurion researchers were no exception. They experimented with various cooking times and temperatures. They heated up their batches to 180C, 210C and 240C. They let some of them simmer for 30 minutes, some for an hour and others for two hours. Yet, all batches had one thing in common—they were cooked with water, but without oxygen.

Called hydrothermal carbonization or HTC, this method produced hydrochar—a brown slurry of water and burnt aka carbonated biomass particles. Unlike charcoal or biochar that’s made by smoldering dry biomass, hydrochar is simmered in water. Because no heat is spent to evaporate water, this method takes less energy to make.

Amit Gross, chair of the Department of Environmental Hydrology and Microbiology at BGU

“Removing water is energy expensive,” explains Amit Gross, chair of the Department of Environmental Hydrology and Microbiology at BGU, whose team focuses on ways to transform waste to resources. “By leaving water in and using higher pressure and lower temperature, we use a lot less energy.”

That hydrochar slurry has a double use. The particles can be separated into a powder with coal-like combustion properties and can be fed into an industrial furnace of a coal-powered electricity plant. And the liquid can be used as a safe organic fertilizer since no pathogens can survive the cooking.

The reason hydrochar burns just like coal is because it was formed in a similar way. The conditions the Ben-Gurion team used to create it mimic, to a certain extent, the geological conditions occurring within the earth that lead to the creation of fossil fuels. Fossil fuels owe their name to the fossilized remains of ancient organisms and plants—dead and buried underneath the many layers of other organic matter. Coal deposits began to form about 300 million years ago during the Carboniferous period when earth was covered with dense forests. When seas occasionally flooded the woodlands, trapping trees and plants in swampy wetlands, the plants got buried under layers of vegetation, which turned into peat bogs. The ever-piling layers of vegetation pressed the plant material deeper into the earth, where higher pressure and temperature coupled with the lack of oxygen slowly turned the organic molecules into long-chain hydrocarbons that comprise coal.

Gross’s foray into the “waste cooking business” started with the poultry industry excrement. Globally, the world’s poultry farms dish out between 625 and 938 million metric tons of litter a year, depending on the source. Poultry litter is high in carbon and nitrogen, the chemical elements needed for energy generation. And compared to cow manure that can be spread out on pastures, poultry dung is amassed within enclosures. It was an attractive form of waste, so the team gathered droppings from a nearby farm, ground them into powder with a mortar and pestle and cooked them up—dry, wet, varied temperature, and so on. The resulting hydrochar proved so similar to coal that it could be immediately sent to the electricity-generating plants, says Vivian Mau, another researcher on the project. It even came in the already powdered form, which is what many plants prefer because they pulverize coal. “It’s actually such a perfect fit that it can be fueling generators now,” Mau says.

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