Rural landscapes of the future might have pyrolysis plants instead of grain elevators on every horizon—processing centers where farmers would bring bulky crops such as switchgrass to be made into crude oil.

Those pyrolysis plants would pass that crude bio-oil on to refineries elsewhere to be made into drop-in fuels and industrial chemicals; they would capture and use for their own energy needs a byproduct called syngas made up of hydrogen, carbon monoxide, and perhaps carbon dioxide; and they would send farmers away with an important byproduct called "bio-char" that could go back on the land to help rebuild damaged soils, sequester carbon, and alter greenhouse gas emissions.

Sound futuristic? It's also a current research focus at South Dakota State University.

A major new study by South Dakota State University researchers working with a U.S. Department of Agriculture colleague explores how to get the most from such a production system. The USDA is funding the project with a grant of $1 million—$200,000 annually for the next five years—to help scientists design a feedstock production system for optimum energy production of bio-oil, and also to explore the possible ecological benefits from the use of bio-char.

The grant was selected by the USDA's National Institute of Food and Agriculture's flagship competitive grants program called AFRI, or the Agriculture and Food Research Initiative. It was selected in the sustainable bioenergy challenge area. Typically fewer than 10 percent of proposals are funded, with awards based on external peer reviews of a proposal's scientific merit.

"We're looking at this from a whole system approach, and we're looking at various components in this whole system," says SDSU professor Tom Schumacher, the project director.

"Historically, the distributive nature of crop production gave rise to a network of grain elevators to separate and coordinate the flow of grain to the processing industry.

A network of rail lines added new infrastructure to improve efficiency," he says, adding that for certain feedstocks "a corollary to the grain elevator would be a collection point that would be within 10 to 30 miles of production fields."

Those collection points wouldn't be for long-term storage, but to receive, sort, and pre-process or process feedstocks using pyrolysis to break them down into bio-oil, syngas, and bio-char. Making crude bio-oil would have the effect of densifying the material to a liquid form that is easier to transport for further processing.

Meanwhile, the bio-char likely would be used in fields in the service area of the pyrolysis plant.

Pyrolysis is a process that uses elevated temperatures in the absence of oxygen to break down organic materials. The SDSU study more specifically will use a technique called microwave pyrolysis that heats the feedstock by exciting the individual molecules, making it accurate and easy to control.

Process engineers and soil scientists are collaborating in the research project to learn what happens to bio-oil and bio-char production when they vary the pyrolysis processing parameters.

Researchers hypothesize that bio-char has different physical and chemical properties depending on the feedstock and the way it is processed. That could affect its usefulness as a soil additive. They'll examine the characteristics of bio-char from three feedstocks: corn stover, switchgrass, and woody biomass.

"There's a lot that's unknown about specific types of bio-char. There is no single characteristic that can be used to evaluate the effectiveness of bio-chars," Schumacher says.

Bio-char's pH and other characteristics can vary widely depending on what feedstock and process was used to produce it, Schumacher says. That could make bio-char beneficial to the environment, neutral, or possibly even harmful, depending on its characteristics. But scientists are excited about the possibility of finding beneficial uses for a consistent, well-characterized bio-char product.

"In particular, we're interested in it as a soil amendment for soils that have erosion and degradation problems, with the idea that the bio-char could be used to improve those soils," Schumacher says. "There's some indication that some bio-chars can improve water-holding capacity. Bio-char also interacts with soil nutrients, holding them, keeping them from leaching. At least there's some indication that some bio-chars will do it—others may not."

Microbial activity may improve with the use of some particular kinds of bio-char. And importantly, bio-char is thought to have the ability to tie up carbon for centuries or even for thousands of years, meaning it could be used as a tool to slow global warming.

"We also want to explore the effects of the bio-char on herbicide absorption and leaching, and how it interacts with herbicides. Does it tie it up so it's not as effective? Does it make it more active? It may have some potential to be used in certain environmentally sensitive areas as a filter, if you would, that would tie up certain chemicals or keep them from moving," says Professor Jim Julson, in SDSU's Department of Agricultural and Biosystems Engineering.

Some types of bio-char also might play a similar role in helping to tie up phosphorus to prevent it from washing out of a field with runoff—an important consideration for managing nutrients such as manure.

SDSU researchers will do laboratory and greenhouse studies, and ultimately field studies as well. The work will characterize different types of bio-char in order to build a better picture of how a pyrolysis treatment plant could produce both bio-oil and bio-char, in addition to the syngas that would be used for helping to supply the plant's energy needs.