In my latest Greenhouse Gas (GHG) Progress Report I talk about the potential for soil carbon sequestration as a tool for mitigating climate change. In fact, one of my four recommendations is that “the Ontario government investigate and publicly report on the potential for soil carbon sequestration as a GHG mitigation strategy.”
At the press conference following the release of my report, one member of the media asked why I was recommending a strategy that was costing billions of dollars in Alberta with very little in the way of results to show for all that expense. It was clear that the questioner had confused carbon capture and storage (CCS) with soil carbon sequestration – an understandable mistake given that the former has received a great deal of publicity and the latter practically none.
A World of Difference
Yet there is a world of difference between the two. CCS is a high-tech, high-risk, costly, and as-yet-unproven approach with no co-benefits. Soil carbon sequestration is a low-tech (but quite scientific), low-risk, inexpensive, and proven approach with a myriad of co-benefits. The table below compares and contrasts these two distinct methods for reducing carbon in the atmosphere.
| Approach | Carbon capture and storage | Soil carbon sequestration |
| How it works | Carbon dioxide (CO2) is captured at source as a gas (usually from the emissions of an industrial process), liquefied under pressure, and transported by pipeline to a site where it is injected deep underground or into the ocean. The CO2 can be captured before or after combustion. The goal is to trap the CO2 in geological formations or in the deep ocean where, ideally, it will remain indefinitely. | In nature, the secretions and remains of plants and animals add carbon to soil on an on-going basis. Carbon, in the form of CO2, is also released from soil on an on-going basis, as microbes break down soil organic matter (SOM). This is known as the carbon cycle. An equilibrium in any given soil is reached when inputs equal outputs, on average, over time. Â Conventional agricultural methods (e.g., tilling the soil, leaving soil bare, using inorganic fertilizers) lower the carbon content in soils by accelerating the decomposition – i.e., the loss – of SOM. Such methods have depleted carbon stocks in agricultural soils worldwide by up to 75 per cent.Alternatively, methods that increase SOM (e.g., no-till, manure and compost application, cover crops, green manures, etc.) raise the carbon content in soils and reduce atmospheric CO2. |
| Benefits |
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| Relative cost | Still unknown, but expected to be very high. This is because CCS requires significant amounts of energy. | Varies with method used, but in general quite low and offset by co-benefits. |
| Permanence | Proponents believe that carbon storage via CCS will be permanent but some feel that there is a risk that the CO2 will gradually leak out through escape routes and return to the atmosphere. | Changes in agricultural management practices must be maintained for the sequestration to be permanent. However, as mentioned above, these practices also bring co-benefits, off-setting maintenance costs. |
Will Soil Carbon Sequestration Work?
I’ve used very conservative assumptions in my report. Projecting forward, I think it is reasonable to expect that an enhancement in recommended management practices (RMPs) could result in the sequestration of close to 10 million tonnes (Mt) of CO2 per year by 2020. It’s an exciting opportunity and I look forward to the government’s response to my recommendation to investigate and report on soil carbon sequestration’s potential in more detail.
Resources:
For more detailed information on CCS, see the Pembina Institute’s Canadian Primer on the subject at http://pubs.pembina.org/reports/CCS_Primer_Final_Nov15_05.pdf)
For more detailed information on Soil Carbon Sequestration, see the Ohio State University’s Extension Factsheet entitled Soil Carbon Sequestration – Fundamentals, at
http://www.envirothon.org/pdf/CG/carbon_sequestration.pdf
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