PROGRESS: Convert hog manure to oil? You bet

SALEM, Ohio – Swine manure may look like a mess to some, but one Illinois researcher looks at the sludge and sees dollars.

Hog manure might be the surprising key to reducing crude oil imports and creating a new industry in the United States, said Yuanhui Zhang, an Illinois agricultural engineer.

Zhang is converting manure to crude oil in his University of Illinois lab using a thermochemical conversion process.

Economics. The economic impact of the technology could be dramatic.

“If 50 percent of swine farms adopted this technology, we could see a $1.5 billion reduction in crude oil imports every year,” Zhang said.

But the most recognizable impact will come in the bottom line on each farm.

Zhang’s research calculations show each hog generates the manure equivalent of half a barrel of crude oil each year.

At current $40-per-barrel crude prices, each hog is worth around $20 more than its butcher shop value.

Zhang underestimates the production process to give hog farmers a more realistic idea of the power available in their pork sludge.

“Even if it was $10 extra per hog, a 10,000-head farm can get $100,000 extra each year,” he said.

“Look at the return rates. The cost [of the technology] could be practical over a few years,” he said.

Zhang wants to get costs low enough so most hog farms could afford a processor.

He estimates a reactor to handle a 10,000-head unit would cost around $250,000 today, but said the price will drop “substantially” as the technology matures toward mass production.

Better environment. Zhang said the environmental benefits of this research are numerous.

As a researcher, he’s concentrated on waste treatment technology for eight years.

“Hog farmers used to use all their fertilizer on the land, but there are large farms that can’t. We’re converting [manure] to a useful product,” he said.

In the manure-to-oil conversion, minerals are preserved in the after-treatment stream, odor is reduced and the oxygen demand of manure is reduced by 70 percent, he said.

The process. Thermochemical conversion is a chemical process that reforms organic compounds in a heated and pressurized enclosure to produce oil and gas.

Biomass and manures are prime fuels for the process because they’re essentially free.

The process Zhang developed uses swine manure as the organic material and converts it to crude oil using a small-scale batch reactor developed by the Illinois research team.

Zhang said the laboratory reactor is only the size of a cooking pot, but real-life models could be the size of a household furnace.

The laboratory process can process a half-gallon of liquid sludge manure at a time in 15-30 minutes. Yield is about 100 grams of crude oil, he said.

The oil has many applications, including burning for power generation or uses in plastics and inks.

A new twist. According to Zhang, his team tested variables that affected the oil conversion efficiency and oil quality.

“The process we have developed is quite different from most conventional thermochemical conversion processes,” Zhang said.

“There is no need for the addition of a catalyst, and our process does not require pre-drying of the manure. Swine manure containing 80 percent water can be fed directly into the reactor.”

Efficiency. With the batch reactor, researchers achieved an average of 70 percent conversion from swine manure volatile solids to oil.

At that conversion efficiency, the manure excreted by one pig during the production cycle could produce up to 21 gallons of crude oil.

A swine farm producing 10,000 market hogs per year could produce 5,000 barrels of crude oil per year.

The next step. The next step for Zhang’s research team is to develop the batch process into the more complicated continuous-mode process.

“In a continuous thermochemical conversion process, the heat generated from the process can be recycled more efficiently, reducing the operating costs,” Zhang said.

“Reactor volume can be reduced for the same capacity, which reduces the investment costs, and automated controls can be adapted more readily, which reduces the labor costs.”

Eventually, Zhang hopes to develop a pilot plant that will increase production capacity and allow them to analyze the oil properties and seek alternative applications of the oil, such as making plastics or ink.

“Developing a continuous reactor will advance this technology one step closer to a pilot plant,” Zhang said.

More uses. Zhang said the thermochemical conversion process is useful for turning any type of livestock manure into a useful product.

More biomass research needs conducted to determine the process and yields for other species’ waste.

That research, he said, will be determined by the availability of funding and interest.

(Reporter Andrea Myers welcomes reader feedback by phone at 1-800-837-3419, ext. 22, or by e-mail at amyers@farmanddairy.com.)