![]() And, of course, wind, solar and tidal power emit no carbon dioxide to the atmosphere to start with.Īneja, V.P., W.H. Increasing forest biomass provides a great storage capacity for atmospheric carbon dioxide. Essentially you get 10 times the carbon storage per unit of nitrogen when the carbon is stored in wood versus soil organic matter. Trees store carbon with much less nitrogen the C/N ratio in wood is often 150 or more. ![]() But, purposeful carbon sequestration in soil organic matter will require huge amounts of additional fertilizer production, with its own contributions to fossil fuel emissions and contamination of surface and groundwater. Soil organic matter is helpful to farmers, and it sequesters carbon. For instance, the production of nitrogen fertilizer currently accounts for about 3% of fossil fuel emissions. Moreover, the production of nitrogen and phosphorus fertilizer is not without its own fossil fuel emissions. Phosphorus supplies are not unlimited, and we’d need to more than double our current use of P fertilizer to accommodate carbon sequestration in soils. Similarly, for phosphorus, sequestration of 9 x 1015 g C each year would require 37 to 75 x 1012 gP/yr as fertilizer, compared to current global production of P fertilizer-about 34 x 1012 gP/yr. A rate of 1%/yr would add ~6 x 1012 g of nitrous oxide to the atmosphere, doubling the current emissions from agricultural soils globally and negating nearly all of the benefits of additional carbon storage in soil organic matter. When nitrogen fertilizer is applied a small percentage-1 to 2%–is converted to nitrous oxide, which escapes to the atmosphere, where it acts as a powerful greenhouse gas. Even more N would be needed to support crop growth. Ignoring the current environmental problems associated with excessive use of nitrogen fertilizer, we’d need to use 4 times as much as today, just to sequester our fossil fuel carbon dioxide in soils. For comparison, current production of nitrogen fertilizer is about 150 x 1012 gN/yr. ![]() With fossil fuel emissions of 9 x 1015 gC each year, and a 15-to-1.0 ratio of carbon to nitrogen in humus, the sequestration of carbon emitted from fossil fuel combustion would take 600 x 1012 g of nitrogen each year. Carbon sequestration in soils requires outside sources of nitrogen. ![]() That amount would soak up the total carbon dioxide emitted from fossil fuel combustion each year.īut a couple of simple calculations show the futility of this approach, based on the nitrogen and phosphorus content in soil organic matter. One group has set an aspirational goal to increase the total amount of soil organic matter globally by 0.4% per year-what is often called the 4 per mille initiative. The chemistry of humus substances includes a substantial amount of nitrogen and phosphorus that will limit our efforts. But, however we do it-fertilization, irrigation, manuring, reduced tillage, and planting cover crops-increasing soil organic matter doesn’t look like such a good idea to mitigate climate change. Sign up for Rural RoundUp: Stories from rural and regional Australia, in your inbox every Friday, or for Rural news daily.In the past few years, many agronomists have promoted the sequestration of carbon in soils as a means of mitigating climate change by reducing the amount of carbon dioxide that accumulates in the atmosphere.įor a long time, farmers have realized that soil organic matter improves the quality of soils, by improving water-hold capacity, friability, and nutrient content.Visit ABC Rural for agriculture and mining news, including weather and the markets. ![]() "There's a significant financial upside there for producers in terms of generating additional revenue stream … we're still producing just as much food as we were in the past and we'll make a significant contribution to offsetting global emissions." Get the latest rural news "If we can build our soil organic carbon levels – even by one per cent – across the majority of the Australian landscape that farmers manage, that will have a profound productivity benefit. "First and foremost, that's the reason for focus on soil organic carbon," he said. Wilmot general manager Stuart Austin said boosting soil carbon had an immediate productivity benefit on the farm's beef production business. Because the credits were purchased in a private market, the emissions offset would not count towards Australia's net zero target. ![]()
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