A broad survey of farmers has documented a yield boost from the use of cover crops in corn and soybeans. The increased yields reflect an upward trend in all of the benefits that come from planting cover crops, including reduced soil erosion and compaction, improved weed control and the availability of “free” nitrogen through soil fixation by legumes and others.
Another benefit of equal, if not greater, importance to those who study the greenhouse gas (GHG) emission-reducing value of renewable energy feedstocks is an increase in organic matter cover crops leave in the soil. That means cover crops, as well as the conventional crops grown between cover crops, retain more carbon in the soil.
The survey – funded by the North Central Region Sustainable Agriculture Research and Education (SARE) program and carried out by the Conservation Technology Information Center (CTIC) – reached out to nearly 2,000 growers, both users and non-users of cover crops, and found that cover crop acreage increased among survey respondents by 30 percent annually from 2009 through 2013.
Given that cover crops are often used for renewable energy feedstocks, or that growing corn and soybeans for biofuel feedstock can result in greater carbon retention in the soil if a cover crop is rotated in, the survey is the latest in a long line of developments and disclosures that highlight the significant role crops grown to produce energy feedstocks play in the nation’s carbon emission-reduction strategy.
In the low carbon future that is still evolving, the greenhouse gas emission reduction benefits of biofuels as well as the carbon sequestration that is a co-benefit of biofuel feedstock production need to be recognized as well as valued. In calling on EPA to maintain congressionally authorized biofuel blending levels under the federal Renewable Fuel Standard (RFS), the 25x’25 Alliance has long cited the well-proven, lifecycle reductions in GHGs that come from using biofuels in our transportation sector, including first-generation ethanol.
But another area in which the value of renewables should be fully measured is the Obama administration’s Clean Power Plan. Released in June 2014, the 69-page plan establishes state-by-state carbon emissions rate reduction targets, and it offers a framework under which states may meet those targets. The plan aims, among other goals, to reduce national electricity sector emissions by an estimated 30 percent below 2005 levels by 2030.
The plan offers a number of options states can use to cut carbon emissions, including making greater use of biomass solution sets. The plan supports the finding that use of waste-derived feedstocks and certain forest-derived industrial byproducts are likely to have minimal or no net atmospheric contributions of biogenic carbon emissions. However, how agricultural- and forest-derived feedstocks will be treated under the plan remains a bit uncertain.
In a transmittal memo explaining EPA’s plans for addressing biogenic carbon dioxide emissions from stationary sources, Janet McCabe, Acting Assistant Administrator for Air and Radiation, says “sustainably-derived” agricultural and forest-derived feedstocks may also be an approvable element in state [carbon dioxide] compliance plans.
Standards called for under the plan are not expected to be finalized until June 1 of next year. Until that time, there is expected to be an intense debate over the definition of “sustainably derived.” How it is treated in the final rule will, to a large degree, determine whether bioenergy solutions sets are allowed to reach their full potential.
The evidence of what biofuels and biomass bring to the table to is readily available. For example, in a study of South Dakota agricultural practices over the past 25 years, a team of ten scientists at South Dakota State University (SDSU) show that modern farming practices measurably increase the yield potential of the soil, and capture carbon in the environment. The study specifically determined the South Dakota surface carbon sequestration potential and associated partial carbon footprint for corn-based ethanol production. Findings support the theory that many of the surface soils in the region became carbon sinks when seeded with corn.
The 25x’25 Alliance calls on federal regulators to examine the SDSU findings, along with a wide range of other studies that demonstrate the merit of bioenergy solutions in meeting the administration’s goals of reducing the nation’s emissions and make the term “sustainably derived” a criteria that gets the most benefit out of these solutions.