That is a significant amount of carbon, the process can be accomplished with existing technology and it can be done year after year, according to Stuart Strand, a University of Washington research professor. Further the technique would sequester – or lock up – the carbon in seafloor sediments and deep ocean waters for thousands of years, he says.
All these things cannot be said for other proposed solutions for taking carbon dioxide out of the atmosphere, methods such as ocean fertilization, growing new forests or using crop residues in other ways, says Strand, who is lead author of a paper on the subject in the journal Environmental Science & Technology, published by the American Chemical Society.
Strand has devised a formula to measure the carbon-sequestration efficiency of this process and others using crop residues, something no one has done before.
Carefully tallying how much carbon would be released during the harvest, transportation and sinking of 30 percent of U.S. crop residues and comparing that to how much carbon could be sequestered, Strand says the process would be 92 percent efficient. That's more efficient than any other use of crop residue he considered, including simply leaving crop residue in the field, which is 14 percent efficient at sequestering carbon, or using crop residue to produce ethanol, which avoids the use fossil fuels, but is only 32 percent efficient.
Worldwide, farming is mankind's largest-scale activity. Thirty percent of the world's crop residue represents 600 megatons of carbon that, if sequestered in the deep ocean with 92 percent efficiency, would mean the amount of carbon dioxide in the atmosphere would be reduced from 4,000 megatons of carbon to 3,400 megatons annually, Strand says. That's about a 15 percent decrease.
The proposed process would remove only above-ground residue. Strand bases his calculations on using 30 percent of crop residue because that's what agricultural scientists say could sustainably be removed, the rest being needed to maintain carbon in the soil. Crop residue would be baled with existing equipment and transported by trucks, barges or trains to ports, just as crops are. The bales would be barged to where the ocean is 1,500 meters, or nearly a mile, deep and then the bales would be weighted with rock and sunk.
"The ocean waters below 1,500 meters do not mix significantly with the upper waters," Strand says. "In the deep ocean it is cold, oxygen is limited and there are few marine organisms that can break down crop residue. That means what is put there will stay there for thousands of years."
The article calls for research on the environmental effects of sinking crop residues in the ocean, effects that most likely will be borne by organisms living in the ocean sediments where the bales fall.
Strand says one way to minimize environmental effects would be to drop the residue onto alluvial fans found off the continental shelf wherever rivers pour into the ocean. Alluvial fans, sometimes call submarine fans when underwater, form as silt and debris from river water settles to the seafloor. Runoff from current agricultural fields means alluvial fans in the ocean are already partly made up of crop residue. Any bales dumped there would quickly be covered with silt, further ensuring the carbon would be sequestered for long periods.
Effects might also be minimized by concentrating the residue in a compact area. At the Mississippi alluvial fan in the Gulf of Mexico, spreading 30 percent of U.S. crop residue in an annual layer 4 meters, or 13 feet, deep would cover 260 square kilometers, or 100 square miles. That's about 0.02 percent of the area of the Gulf of Mexico, Strand says.
"Whatever the environmental impacts of sinking crop residue in the oceans turn out to be, they will need to be viewed in light of the damage to oceans because of acidification and global warming if we don't remove carbon dioxide from the atmosphere," Strand says.
Co-author of the paper is Gregory Benford, a professor of physics at the University of California, Irvine.
Strand, a faculty member with the UW's College of Forest Resources, is an environmental engineer known for his work on using plants to remediate contaminated groundwater, soil and sediment. He said he's been interested in ways to remove carbon dioxide from the atmosphere for nearly a decade and first read about sequestering crop residue in the deep ocean in Climatic Science in 2001. Benford was a co-author on that paper.
Strand says he thinks any method for removing excess carbon dioxide must do seven things: move hundreds of megatons of carbon, sequester that carbon for thousands of years, be repeatable for centuries, be something that can be implemented immediately using methods already at hand, not cause unacceptable environmental damage and be economical. He says sequestering crop residue in the deep ocean fits the criteria better than any other proposed solution.
"To help save the upper ocean and continental ecosystems from severe disruption by climate change, we must not only stop our dependence on fossil fuels, but also go carbon negative," Strand says. "Fossil fuels that are removed from sediments and burned are producing the increased atmospheric carbon that is driving climate warming. Sequestering crop residue biomass in the deep ocean is essentially recycling atmospheric carbon back into deep sediments."For more information:
Sandra Hines | Newswise Science News
Further reports about: > Carbon > Climate > Earth's Climate Troubles > Face Bones > Strand > Technology > carbon dioxide > carbon-sequestration efficiency > crop > crop residues > deep ocean > deep ocean water > environmental risk > forests > global carbon dioxide > global crop residues > ocean fertilization > seafloor sediments
How does the loss of species alter ecosystems?
18.05.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig
Excess diesel emissions bring global health & environmental impacts
16.05.2017 | International Institute for Applied Systems Analysis (IIASA)
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy