Biochar from Livestock Waste: A Pathway to Sustainable Agriculture and Climate Change Mitigation.

Livestock manure is not only a major global source of greenhouse gases from agriculture but also an important source of nutrients for crop production. Judicious management of livestock manure should deliver an effective way to both promote crop growth and mitigate greenhouse gas emissions. Here, we show using the global change analysis model (GCAM) integrated assessment model augmented with a pyrolysis module (GCAM-pyrolysis) that biochar production from global livestock manure may intensify agricultural systems through a 10% (median, 3-27% CE) increase in crop yields. GCAM-pyrolysis estimates that in 2050 widespread pyrolysis of livestock manures will cause an expansion of 415,000 km2 of cropland for food production (median, 376,000-473,000 km2 CE) compared to the reference scenario, at the expense of forests, pastures, and crops purposely grown to produce bioenergy (corn, sugar, palm fruit, oil crops), to produce an additional 5.1 Pcal (median, 3.2-6.7 Pcal CE) of food. Biochar presents significant opportunities in allowing productive land use change and increased crop production while increasing carbon dioxide removal and reducing greenhouse gas emissions. However, widespread adoption of pyrolysis may require food equity and land conservation regulations to mitigate its undesirable effects, such as an estimated increase in staple food prices in certain regions.