Achieving negative emissions through oceanic sequestration of vegetation carbon as Black Pellets

Abstract

Natural processes and human activities produce vast amounts of dead vegetation which return CO2 to the atmosphere through decay and combustion. If such vegetation could be converted into biocoal and sequestered on the ocean floor, it could reduce the accumulation of atmospheric CO2 without involving sequestration in the form of CO2. Given that raw vegetation is unsuitable for large-scale energy applications, a process was developed to convert raw vegetation into a form of biocoal, termed Black Pellets, that solves the logistical and energy conversion problems of using raw vegetation for power generation. Seemingly overlooked is that properties of Black Pellets—higher density than seawater and resistance to microbial decay—may offer an environmentally safe way of sequestering vegetation carbon on the sea floor. Sequestering vegetation carbon by depositing biocoal as Black Pellets in the deep ocean (oceanic sequestration of biocoal—OSB) would be a means of achieving long-lasting negative emissions. Sacrificing the energy content of the deposited pellets would require substituting energy from other sources. If the substitute energy could be from lower-carbon natural gas or carbon-free sources, the effects would be less accumulation of atmospheric CO2 compared to using the pellets for energy and a nearly 60 to 100% reduction in the need for geologic sequestration compared to bioenergy carbon capture and storage (BECCS). If confirmed by research, OSB would be an addition to the sparse toolbox of negative emission technologies (NETs) which would give humankind more flexibility in meeting the goals of the Paris Agreement.

Sustainable scale-up of negative emissions technologies and practices: where to focus

“…The authors suggest that lignocellulosic materials are highly stable in the marine environment, yet it is hard to foresee the associated environmental impacts due to the lack of experimental studies. Biochar may be more suitable for this application than raw biomass, given that it is more resistant to microbial degradation and it would not require ballasting because of its higher density (Miller and Orton 2021).…”