Stuart Strand takes climate change seriously, and I'm not just talking about the groovy recumbent bicycle he rides to work.
The environmental engineer from the University of Washington was searching for a way to reduce the amount of greenhouse gas in the atmosphere when he came across an intriguing report. Its authors suggested that annual carbon emissions could be reduced on a global scale if we humans dump a large portion of our crop residue in the sea. Left on dry land, all those corn stalks and potato stems decompose after the harvest and release carbon into the atmosphere. But at depths of around 1,500 feet, vegetable matter decomposes extremely slowly. And because the deep layers of the ocean rarely mix with surface layers, the carbon emitted from such decomposition
The report lacked a few hard facts, though. So Strand began crunching numbers. He now thinks deep ocean sequestration could cut global carbon emissions by 15 percent each year. He also estimates that the sequestration process itself would produce relatively little in the way of new carbon emissions. Sure, all those bales of corn stover and wheat husks would have to be hauled to the seaside, loaded on barges and dumped in the waves, but the carbon emitted from the diesel engines involved would add up to about 8 percent of the carbon being sequestered. In other words, deep sea sequestration could prove to be 92 percent efficient. That's a heck of an improvement over the other popular solution for the climatic problem posed by crop waste: cellulosic ethanol. According to Strand, ethanol's carbon efficiency rolls in somewhere around the 30 percent mark.
As yet, there are some kinks left to be worked out, and some of them are fairly significant. For example, researchers don't know what what will happen to deep sea ecosystems when all those bales plummet down from above. What will become of the pesticides and fertilizers that the crops were grown with? Crop waste sequestration doesn't change the fact that we're producing too much carbon waste. It just gives us somewhere else to dump it.
But if Strand's proposal makes it off the drawing board, it might prove a popular option on the carbon market. At the moment, popular commercial carbon offset programs -- tree planting, and no-till soil sequestration -- can't reliably promise to store carbon for much longer than a century. After all, the future is uncertain. Forests burn and fallow fields can always be put back under the plow, and meanwhile, we're going to be dealing with climate change for a lot longer than a century. It's a multi-millenia problem. As Strand puts it, "At the end of 100 years, you're still going to get cooked." Against that backdrop, the 1,000 year time frame of deep sea sequestration looks pretty good.
For a picture of mother earth's respiration rate, check out the graph above. Every year, carbon concentrations in the atmosphere fluctuate in time with the growth rates of the northern hemisphere. As plants grow, they suck up carbon. Then they die, and release that carbon back into the atmosphere. The result can be seen in the tight serrations in the black line. If Strand get his way, carbon levels would continue to dip with every growing season, but they wouldn't rebound quite so high in between. The serrated line generally bends upward because humans just keep releasing more carbon into the atmosphere.