February 18th, 2013 by Joshua S Hill
Turn the clock back a decade and we had all sorts of grand plans for reducing our greenhouse gas emissions levels, hoping that by 2020 we would be on the path to saving our planet.
Welcome to 2013 and … not so much.
Unsurprisingly, scientists at Stanford University have recently come out and said that curbing our CO2 emissions may simply not be enough any more. Instead of simply hoping the long-tail of emissions reductions do something, they believe we need to start looking at carbon-negative technologies that actively remove carbon dioxide from the atmosphere.
“To achieve the targeted cuts, we would need a scenario where, by the middle of the century, the global economy is transitioning from net positive to net negative CO2 emissions,” said report co-author Chris Field, a professor of biology and of environmental Earth system science at Stanford. “We need to start thinking about how to implement a negative-emissions energy strategy on a global scale.”
The Stanford scientists findings are summarised in a report by Stanford’s Global Climate and Energy Project (GCEP), which describe a suite of emerging carbon-negative solutions to global warming.
“Net negative emissions can be achieved when more greenhouse gases are sequestered than are released into the atmosphere,” explained Milne, an energy assessment analyst at GCEP. “One of the most promising net-negative technologies is BECCS, or bioenergy with carbon capture and storage.”
For example, a BECCS system could convert woody biomass, grass, and other vegetation into electricity, chemical products, or fuels such as ethanol, leaving the CO2 emissions released during the process to be captured and stored.
Estimates show that by 2050 BECCS technologies could sequester 10 billion metric tonnes of industrial CO2 emissions from installations like power plants, paper mills, ethanol processors, and other manufacturing facilities. But we have a ways to go before we are technologically able to manage this.
Biochar is a plant byproduct similar to charcoal that is made from lumber waste, dried corn stalks, and other plant residues. A process called pyrolysis — which heats the vegetation slowly without oxygen — produces carbon rich chunks of biochar that can be placed in the soil as a fertiliser, which locks the CO2 underground instead of letting the CO2 re-enter the atmosphere as the plant decomposes as it naturally would.
EHowever, long-term sequestration “would require high biochar stability,” they wrote. “Estimates of biochar half‐life vary greatly from 10 years to more than 100 years. The type of feedstock also contributes to stability, with wood being more stable than grasses and manure.”
Another option included in the GCEP report is the idea of net-negative farming. The authors cited research done by Jose Moreira of the University of Sao Paulo who found that from 1975 to 2007, ethanol production from sugar cane in Brazil resulted in a net-negative capture of 1.5 metric tons of CO2 per cubic meter of ethanol produced.
“In this model, the system took 18 years to recoup carbon emissions, with most reductions coming from soil replenishment from root growth and replacement of gasoline with ethanol,” the GCEP authors wrote.
However, questions remain about the long-term effects of ethanol combustion on climate.
The report also explored other options, such as sequestering carbon in the ocean, specifically the problem of ocean acidification. Currently, the more CO2 the oceans absorb the more acidic they become, resulting in algae blooms often seen in locations throughout Asia as well as the Gulf of Mexico in the US.
However, research by David Keith of Harvard University suggests that adding magnesium carbonate and other minerals to the ocean to reduce acidity would also sequester atmospheric CO2 in absorbed in seawater.
For more information on these options, check out the full report here.
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