Biochar, A Negative Emissions Technology

Danielle Gelardi

2019-2022 FFAR Fellow

University of California, Davis

Scientific and entrepreneurial interest in biochar has grown dramatically in the last 10 years. Between 2009 and 2019, the number of research publications mentioning biochar grew from 47 to 3,209 and US patent applications increased from one to 120. It is no surprise that this incredible rise occurred simultaneously with an evolving consciousness around climate change and the urgency with which the United States must act to address it. In 2018, the International Panel on Climate Change officially listed biochar as a negative emissions technology, signaling that it may hold the key to some of our most pressing environmental challenges.

So what is biochar? The International Biochar Initiative defines it as the solid obtained from the thermochemical conversion of biomass in an oxygen-limited environment. In simple terms, it’s a material similar to charcoal, but created from the waste products of agricultural or forestry operations. Waste biomass like almond shells or corn stalks can be gathered and simultaneously converted into a renewable fuel called syngas and a solid product called biochar. Without this intervention, much of that waste would decompose and emit CO2 back into the atmosphere. By converting it into biochar, the carbon is locked in a stable form. Voila! Biochar—a negative emissions technology—sequesters carbon that would otherwise be released into the air.

What can we do with biochar? The ability of this product to help the United States meet climate change reduction targets is becoming clear, but there remain questions about how to use the biochar once it’s created. If there is no use for biochar, there is no market demand for biochar.  There is evidence to suggest the material could be used as a replacement in products as wide ranging as water filters, cat litter and potting soil. There is also strong interest in using it as an additive to agricultural soils. Because the material is light, porous and has a chemically reactive surface, it may be useful in helping build soil organic matter, reducing fertilizer pollution, increasing soil drought resilience and in some contexts, increasing yields.

Despite the 3,209 scientific publications on the topic in 2019, the jury is still out on whether biochar has a viable future for use in land management. Results of these publications demonstrate that sometimes biochar can deliver on its promises, but sometimes cannot. This is in part because the majority of studies are short-term, lab experiments rather than long-term field trials. While there are some promising results from these experiments, they are difficult to extrapolate to real-world production agriculture. The inconsistency in results is also due to several variables, such as how the biochar is made, what it is made from, what kind of soils it’s amended to and what crops are grown.

My research aims to address a gap in literature by providing multi-year, multi-scale data on the impact of biochar on California’s carbon budget and cropping systems. To date, results from my short-term lab experiments demonstrate that biochar can indeed improve fertilizer retention, crop growth and soil water dynamics.  Results from a three-year field trial, in which tomatoes were grown in two different soil types using seven different biochars, are still pending. We don’t yet know if we’ll see these same benefits at field-scale. The goal of this multi-scale work is to link the results from real-world production agriculture to those from the lab, in order to determine which biochar and soil properties may optimize benefits. At the completion of all trials, data from the lab and the field will be used in a life cycle assessment (LCA), or a model which helps determine the quantitative environmental impact of a product or service. This LCA can be used as a decision-making tool by land managers and policymakers who are interested in reducing the environmental impact of cropping systems in California.

My research is made possible by the support of the UC Davis Environmental Soil Chemistry Lab, under the direction of Dr. Sanjai Parikh. It is also supported by the Foundation for Food & Agriculture Research Fellowship, my industry sponsor the Almond Board of California and my mentor Dr. Amrith Gunasekara at California’s Office of Environmental Farming and Innovation.