New Delhi: Accidentally stumbling upon an over 3,000-year-old piece of buried wood in Quebec, Canada led a group of scientists to propose a novel method of storing carbon in deadwood using a nature-based strategy. Researchers from the University of Maryland in the United States have described how embalming wood in clay and storing it underground can prevent its decay, and dramatically reduce carbon emissions from decomposed wood, effectively creating a carbon capture solution.
The study describing the findings was published Thursday in the journal Science.
The scientists proposed this method to help meet the 2015 Paris Agreement goals of reducing carbon emissions and preventing global warming from breaching 2 degrees Celsius above pre-industrial levels.
The study emerged when the authors, led by Ning Zeng, a professor in the Department of Atmospheric and Oceanic Sciences at the University of Maryland, found in 2013 a log of eastern red cedar wood buried 6 feet underground in Saint-Pie, Quebec.
The piece of wood, which was found covered in a layer of clay soil, was cleaned and left to naturally dry for nine years. Then, in 2022, it was carbon-dated by scientists and found to be around 3,775 years old. Despite being so old, it was remarkably well-preserved. A comparison of the physical properties of this ancient piece of wood with a modern sample of the same type of wood showed that over the past 3,000 years, the buried log had only lost 5 percent of its carbon.
“The wood was carbon-14 dated to be 3775 ± 35 years old, providing direct evidence for the viability of wood burial as an approach for carbon removal and durable storage,” the study said.
Through the natural experiment of carbon analysis of this piece of wood, the researchers want to put forth a strategy of carbon capture that relies on burying dead wood, agricultural waste, and biomass in a burial chamber that essentially delays or stops their decomposition process.
This proposal is based on the understanding that decomposition and burning of biomass releases a ton of carbon dioxide into the atmosphere, which can be prevented or reversed through carbon capture methods such as wood burials. The study said that wood from tree felling, trees damaged from storms and winds, and urban deforestation could potentially be used in this new sequestration process.
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How helpful wood burials can be
The study explained how natural processes like photosynthesis, where carbon dioxide is converted into oxygen, remove 220 gigatonnes of carbon dioxide every year from the atmosphere. This is almost six times the total carbon emissions released by fossil fuels, which is 37 gigatonnes per year. However, a large amount of the carbon dioxide removed by autotrophs (organisms producing their own food using light, water, carbon dioxide and other chemicals) is also released back into the atmosphere by the natural process of decomposition.
“Cutting off the return pathway of even a small fraction of the photosynthetic carbon, say 4.5 percent of NPP, would allow longer-term sequestration of 10 GtCO2 year,” the study said, adding that the process was discovered by the scientists through the ‘wood burial’.
What the scientists have proposed is a form of natural carbon sequestration, where the carbon dioxide present in trees, plants and other bio-organisms is captured and stored within the organism itself instead of being allowed to enter the atmosphere again. If even 4.5 percent of the 220 gigatonnes of carbon dioxide removed every year from the atmosphere is not allowed to return to the atmosphere right away, it would amount to 27 percent of the current emissions by fossil fuels.
There are other forms of carbon capture and sequestration available in the market, including direct carbon capture from the atmosphere using chemical reactions. These processes involve passing air through filters which have chemicals that bind to carbon dioxide and are then extracted. Afforestation is also considered a natural form of carbon capture since trees and plants perform photosynthesis. However, these artificial forms of carbon capture do have the challenge of being energy-intensive, and hence, could be counter-intuitive to the main goal of emissions reduction.
What is the process of wood burial?
Through the analysis of wood buried for a long time, scientists showed that the layer of clay over the wood prevented it from accessing oxygen, which is necessary for decomposition. Other factors that interacted to preserve the log were temperature and moisture levels—the average temperature in Montreal was around seven degrees Celsius, and the log of wood was in a permanent state of waterlogging, which again contributed to depriving it of oxygen.
The engineered wood burial that the scientists suggest is a ‘vault’ a few feet underground, covered in clay, which will cut off access to oxygen while also maintaining the right temperature level. Burying it not too deep will help contribute to deoxygenating the biomass since the active biosphere layer, which consists of roots of plants and other vegetation, also consumes oxygen from the soil.
The authors are yet to conduct more holistic research on this wood vault technique and its applicability across wood and soil types. The total energy consumption from this process also needs to be calculated, to discover the net ‘carbon negativity’ of this solution, which means how much carbon dioxide the process saves as opposed to what it emits.
However, the authors have already calculated the viability of their wood vault solution. According to their market research on carbon capture solutions, they estimate that their project would cost about $100-200 per tonne of carbon dioxide in the next 10 years and could even go as low as $30-100 per tonne, based on scaling up, in the next 20 years. This is opposed to current carbon sequestration solutions like direct air capture, which currently costs $100-300 per tonne of carbon dioxide.
“In practice, it can be incorporated into a sustainable forest management plan, providing a new income source for a struggling industry and local communities around the world,” the study said.
(Edited by Radifah Kabir)