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Carbon sequestration and carbon credits

A possible opportunity for new revenue.

When it comes to climate change and the development of Canadian standards for greenhouse gas emission reductions, regulated industries may be looking to farmers for a source of carbon credits to use in the carbon offset system.  In fact, this is already happening in Alberta.  There, farmers are earning carbon credits by sequestering carbon in the soil. “Carbon in the soil is a pretty dynamic item,” says University of Guelph professor emeritus Dr. Bev Kay.  “It comes into the soil from the atmosphere as the plants fix carbon by photosynthesis and create organic matter. Organic matter goes into the soil, microorganisms decompose the organic matter and convert it to carbon dioxide, and the carbon dioxide goes back into the atmosphere.”  Kay likens this process to a bank account: it is the rates of deposit and withdrawal that determine the final amount of carbon in the soil.

Adding a cover crop like clover actually does more to increase carbon sequestration than altering tillage practices, and boosts yields in subsequent crops. Advertisement

Changes in land management can change the equilibrium level of soil carbon.  For example, the conversion of forest or prairie to agriculture generally results in an overall loss of soil carbon to the atmosphere. “When we started tilling the land, we introduced air into the soil and exposed it to the sun so it warmed up, so the carbon was being removed faster than it was being replaced,” explains Edgar Hammermeister, past president of the Saskatchewan Soil Conservation Association.  “Now we’re into the tougher organic matter, so the rate of reduction has declined greatly.”

Different land uses such as fallow, annual crops or perennial crops have different equilibrium levels of soil carbon associated with them.  The idea of carbon sequestration then, is to adopt a management practice that maximizes the amount of carbon in the soil, reasons University of Guelph professor Dr. Bill Deen, who studies cropping and tillage practices.  Management practices and climate interact to produce differences in the amount of carbon that can be sequestered in different regions.

Cross-Canada differences in potential carbon sequestration
Long-term research indicates that although measurable increases in soil carbon are occurring with the adoption of no-till practices in western Canada, there is a much smaller effect in eastern Canada.  “In western Canada, the adoption of no till was associated with two results: increased water conservation and reduced fallow use,” explains Deen.  “By improving water conservation and decreasing fallow use, they were able to increase biomass production per unit area through increased yields and by adding crops in place of fallow ground.  This resulted in increased biomass being returned to the soil.”  And more biomass means more carbon.

In contrast, the adoption of no-till practices in eastern Canada has had less of an effect on the amount of biomass than in western Canada.  Historically, the use of summer fallow has been less prevalent in eastern Canada, eliminating the potential for a large decrease in fallow use and a corresponding increase in biomass.  Also, Deen has found no evidence of yield improvements in long-term no-till experiments near Woodstock, Ontario.  He says that this lack of improvement might indicate that the amount of biomass being returned to the soil has not increased much over that under conventional tillage.

In addition to greater moisture conservation and decreased summer fallow with the adoption of no till in the dry climate of western Canada, Dr. Brian McConkey, research scientist with Agriculture and Agri-Food Canada in Swift Current, Saskatchewan, cites differences in the primary tillage methods as a factor affecting the different potential for carbon sequestration between eastern and western Canada.  “The nature of tillage is completely different,” says McConkey.  “In eastern Canada you have more use of the moldboard plow, so you get soil inversion.  In western Canada, there is usually no inverting tillage, and they only till 7 to 10 cm deep (2.75 to 4.0 inches).”

Kay also notes the effect of tillage method.  He explains that with the moldboard plow, the soil is inverted up to 30 cm (12 inches) in depth, distributing organic matter throughout this depth.  In going from conventional moldboard tilling to no till, more carbon accumulates near the soil surface, but the carbon that was previously mixed deep in the soil slowly decreases because it is only replaced by the death of deep plant roots and some transport by soil organisms.  The balance is that the distribution of carbon through the soil layer has changed, but there has been little increase overall, so there is little increase in carbon sequestration.

However, Kay is quick to note that no-till practices can provide other benefits such as better water infiltration and water-holding capacity and decreased erosion.

Management for carbon sequestration in eastern CanadaDespite the lower potential for no-till systems to sequester carbon in eastern Canada than in western Canada, both Deen and Kay point to the potential for crop rotation practices to sequester carbon. Deen has performed long-term experiments at Elora, Ontario, to examine the effects of tillage and rotations on soil carbon. “Our data clearly demonstrate that if you want to alter soil carbon, the best way to do it is not by altering your tillage system, but by altering your rotation,” says Deen. In western Canada, no-till practices have altered the rotation by getting rid of summer fallow.

In eastern Canada, Deen recommends a shift to a more diverse rotation that includes high-biomass crops, perennials and legumes, as well as crops that increase the biomass of subsequent crops. As an example, he compares a corn/soybean/wheat rotation with a corn/soybean/wheat/red clover rotation. His data show that not only does the latter rotation have more biomass because of the red clover, but also, red clover increases the yields of the next corn and soybean crops, and may have a positive effect on the subsequent wheat yield, which also adds to the biomass.  Interestingly, Deen found that the highest soil carbon levels occurred in a perennial alfalfa plot from which biomass was harvested every year, likely because alfalfa is a perennial legume that produces a lot of belowground biomass in the form of roots. Thus, for both tillage and rotation, the effect on carbon sequestration ultimately depends on how much biomass is left behind in the field.  It is also important to remember that there is an upper threshold to the amount of carbon the soil can hold and thus to carbon sequestration.

Potential for carbon credits
In March 2008, the Government of Canada published greenhouse gas emissions reductions targets for specific industries that are to be regulated, including combustion-based electricity generation, oil and gas, pulp and paper, iron and steel, smelting and refining, and cement, lime, potash, chemical and fertilizer industries. These industries must meet emission reductions by 2010 via specific mechanisms; one option is the carbon offset system. Nonregulated industries such as agriculture that voluntarily reduce their emissions below business-as-usual practices can obtain carbon offsets, or credits, which can be sold to regulated industries through a carbon market.

So how can Canadian farmers who switch to improved management practices obtain carbon credits?  “Currently, there is only one mandatory offset system in the country that is operational, and that’s in Alberta,” says Don McCabe, vice president of both the Soil Conservation Council of Canada and the Ontario Federation of Agriculture.  The first deadline for industry compliance in Alberta was July 2007.

According to Karen Gorecki, policy analyst at Climate Change Central, three of seven projects that received carbon offsets in Alberta’s first compliance period were for reduced-tillage practices.  Each of these projects was registered by an aggregator who bought offsets from individual farmers and sold them to industries, much like a grain elevator buys and sells grain.  Gorecki estimates that roughly 1100 farmers participated.  These reduced-tillage projects were calculated to account for the removal of 587,692 tonnes of carbon dioxide equivalent, which was 37 percent of the total registered tonnage for 2007 compliance.  It is estimated that companies paid $6 to 13 per tonne and farmers received $4 to 9 per tonne, with aggregators taking 35 to 40 percent of the cut.  This margin is expected to narrow as the market matures.

The amount of carbon dioxide equivalent that is sequestered by the adoption of reduced- and no-till is calculated following Alberta’s Quantification Protocol for Tillage System Management.  Regional coefficients for broad soil-type and climate zones are used to calculate the carbon offsets associated with reduced and no-till.  This protocol can be applied regardless of the historical management practice, which means that a farmer who has been using reduced tillage for years does not have to convert to conventional till and then back to reduced till to benefit from carbon offsets.

A national offset system, administered by Environment Canada, is currently under development.  Selected external offsets protocols such as Alberta’s tillage protocol are currently under review to meet ISO standards.  Protocols are developed by organizations outside the federal government, and each protocol describes the methods required to quantify the greenhouse gas reductions achieved by that specific project type, e.g., reduced tillage.

The Industry Provincial Offsets Group (IPOG), a collection of industry and provincial government stakeholders, is one of these protocol developers.  “IPOG is working very diligently right now to get protocols to Environment Canada,” says McCabe, who is involved with IPOG through the Soil Conservation Council of Canada.  “We have to get the rules down as quickly as possible so we can get the knowledge out to farmers who want to participate.” After all, industries have to meet the first deadline for emissions reductions in 2010.

In Ontario, the provincial government is currently evaluating a draft protocol for tillage system management that draws on Alberta’s protocol, but is revised for Ontario’s different carbon sequestration conditions.  To this end, as many as 40 farmers who have been practicing reduced or no till for several years are participating in a pilot project with the Ontario Ministry of Agriculture, Food, and Rural Affairs (OMAFRA) and Ministry of the Environment.  The project is measuring the changes in tillage practices from which greenhouse gas reductions could be calculated, says Elizabeth McClung of OMAFRA.  The project should wrap up in early 2009.

Tillage practices are just one of the ways that farmers may benefit from carbon credits.  Other protocols may include livestock feeding, manure management and nutrient management.  Whether crop rotation practices will have their own protocol for carbon credits remains to be seen.