Iowa State University researchers find biochar ideal for slow-release fertilizer

June 20, 2019 |

In Iowa, Iowa State University researchers weren’t looking for a slow-release fertilizer that could feed crops while protecting water quality, but they may have found one.

Researchers looking to add value to biochar – a solid, porous co-product of heating corn stalks and other sources of biomass to produce liquid bio-oil in a process called pyrolysis – were studying its physical and chemical properties.

So, what could add value to this black powder, making pyrolysis a more economically attractive biofuel technology?

Maybe biochar could be mixed with biomass to improve the quality of biogas from anaerobic digestion? Or maybe it could help control livestock odors? Or, maybe it could be mixed with composted manure and the fibrous leftovers of anaerobic digestion to produce a fertilizer?

The application of nutrients via biochar – unlike some fertilizers used today – is stable in the soil and won’t wash away in the rain or leach into groundwater. That could improve the quality of water running off farm fields, decreasing the nutrients that feed algal blooms that take up oxygen in water, helping to create the Gulf of Mexico’s “dead zone.”

Researchers also found biochar doesn’t release adsorbed phosphate quickly. He’s calculated that it releases nearly 18 milligrams of phosphorous per kilogram of soil after three continuous leaching events with water – just about equal to the 22 milligrams of phosphorous per kilogram of soil that’s recommended for growing crops.

By oxidizing the iron in the pretreatment process, they said even more phosphate can be adsorbed and released, nearly 23 milligrams per kilogram of soil after three continuous leaching events.

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Category: Research

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