Turning waste into a natural resource with Johannes Lehmann

Johannes Lehmann is a soil scientist at Cornell University. He’s also an expert on biochar. That’s a natural resource that’s created when biomass – things like leftover crops, manure, and yard waste – are heated and charred.

Johannes Lehmann: You make a resource out of your waste stream.

Charring is different from burning, Lehmann said. If something is charred, it retains its carbon, rather than releasing it. That’s why, he explained, charring can turn waste into a valuable resource for farmers.

Johannes Lehmann: One possible biochar system is, for instance, a poultry farmer who would otherwise not know where to put poultry litter.

Lehmann went on to explain that fertilizer made from chicken manure is a source of water pollution. But if the manure were converted to biochar, Lehmann said, the charring process could create enough energy to heat the farm’s chicken coop. And, the biochar itself could be used to enrich the farm’s soil. Lehmann hopes more small farmers will use biochar to create a more sustainable and localized agricultural system.

Johannes Lehmann: To deal with biomass locally, where you can take care of waste, generate electricity, and generate product that will enhance soil health locally is a smart idea.

Lehmann said biochar’s ability to return carbon to the soil – and keep it there – might help reduce carbon dioxide emissions. But, he added, this value of biochar will vary, depending on what the biochar is made from, and how it is produced. Lehmann said that biochar, buried in the soil, stores carbon longer than biomass, because it takes longer to decompose.

Johannes Lehmann: The relatively rapid return of carbon as carbon dioxide from the soil, and to the atmosphere, and the much slower cycling biochar cycle in soil, makes the difference for the emissions reductions that can be achieved by transforming by biomass into biochar.

While biochar has been touted by its advocates as carbon-negative – meaning, it stores more carbon than it releases – Lehmann said that not all biochar systems are created equal, and careful development work is needed.

Johannes Lehmann: If you take an old growth forest, and harvest that forest to produce biochar, that would be emission generation.

Basically, if there’s a change in land use for the purpose of producing biochar, it can do more harm than good. The point, said Lehmann, is to use biomass that would otherwise have decomposed in a short period of time or been burned. Lehmann sees biochar as a way to improve local agricultural productivity, while at the same time preserving nearby ecosystem services and biodiversity.

Johannes Lehmann: The trick is now to find out for a certain farmer or a certain agricultural landscape, what is the most appropriate, the most sustainable way of dealing with our scarce resources.

He said that biochar is just one of many tools that can be used to create a more sustainable planet.

Johannes Lehmann: Biochar is an approach which is unique in how it links energy and crop residue management with soil enhancement.

Read more: New biomass map takes stock of Earth’s carbon