Can human engineering play a supporting role to nature? That’s a question that grows in relevance and urgency, given the gap between where global emissions stand and where they need to be. The sheer quantity of excess greenhouse gases means natural processes can’t do it all when it comes to carbon sequestration. Select nascent technologies show some promise to supplement terrestrial, coastal, and ocean sinks.

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Engineered sinks could mean a variety of technologies. Direct air capture, for example, is a means by which carbon is captured directly from the air using technology plants. However, this process is energy intensive and expensive, ranging from $600-$1000 per ton of carbon removed. While the techniques such as direct air capture can be effective, they are still too costly to implement on a mass scale. The trade-off between energy involved in a process and the resulting carbon sequestered is an important question we are looking to answer.

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Biochar is a promising low-cost solution; it involves the slow baking of biomass in the absence of oxygen. This can be buried to sequester carbon and potentially enrich soil. Biochar is a carbon-rich, highly stable soil amendment produced as a by-product of pyrolysis, which generates energy from biomass in the absence of oxygen. When biomass decomposes, carbon and methane escape into the atmosphere. Biochar retains most of the carbon. If we bury it, that carbon can be held for centuries in the soil. Applying biochar to soils can reduce other soil greenhouse gas emissions. In infertile soils, biochar can reduce loss of nutrients through leaching.