The problem of climate change has led to the search for new technologies to mitigate increasing levels of atmospheric greenhouse gases. One technology is pyrolysis, which converts waste biomass to gaseous and liquid biofuels and a solid carbon-rich product, biochar. Biochar is added to soils to improve their fertility. It doesn't easily breakdown, and therefore, fixes carbon that originated in the atmosphere in the soil for long times. Thus, pyrolysis of waste for energy and biochar production can be a carbon-negative process. We discovered that adding biochar to soil can simultaneously promote the growth of plants and activate their defenses against pathogen attack.