BioCycle August 2010, Vol. 51, No. 8, p. 52
Mark Jenner

WE are all drawn to BioCycle because of its focus on adding value to residual, under-valued carbon. Organic surpluses and wastes like manure, biosolids, wastewater and solid waste, are merely undervalued leftovers. In the broader public debate, carbon dioxide (CO2) emissions are viewed as an environmental hazard that is best buried rather than utilized. To the contrary, I believe that CO2 emissions are just another undervalued, surplus carbon product, waiting for a market.
Many economic analyses discuss the “carbon price” as some yet to be determined artifact of policy. Yet we already have some pretty solid carbon data on everyday commodities. The carbon value of food, for example, is about $2 to $5/lb. The value of gasoline and ethanol as a carbon product at the pump is about $0.50/lb. Feedstuffs for livestock fall below $0.10/lb. Generic crop inputs like bulk compost tend to have a lower value than that. These represent the value of established markets for carbon-based products. CO2 is a limited or scarce input into photosynthesis and biomass production. Shouldn’t this drive a market “carbon price” rather than one driven by policy?
Fear and uncertainty play an enormous role in this adventure. One school of thought focuses on burying carbon as quickly as possible to get it out of the atmosphere. If the worst predictions from greenhouse gas emissions are true, perhaps that is the best strategy.
CO2 CAPTURE AND STORAGE
Last year, the U.S. Department of Energy (DOE) announced its intent to spend $1.4 billion in federal funding for carbon capture and storage (CCS) projects. The initial 12 projects in Phase 1 were announced in October 2009. As these move forward, literally millions of tons of CO2 exhausted from industrial processes will be pumped underground for storage.
Three Phase 1 projects will receive more funding in Phase 2. Two will be in Texas and Louisiana and will pump CO2 into oil fields to extend output, capturing CO2 underground. The third CCS Phase 2-funded project will be in Illinois, and will pump surplus CO2 more than a mile underground to remove it from the atmosphere.
CCS projects that bury carbon are large-scale, rapid solutions to balancing CO2 emissions. However, we already pay billions of dollars to bury carbon in our landfills. And the CCS projects are not the best use of our extra CO2.
CO2 FOR PLANT ENRICHMENT
CO2 is a fundamental input of photosynthesis in green plants. This is why significant efforts are currently directed at using algae to recycle and sequester carbon from stack emissions. Algae growth sequesters CO2 – and often residual wastewater nutrients – storing energy in sugars, starches, oils and fibers. Very little algal carbon gets buried on a long-term basis, but the liquid, solid and gaseous fuels produced from algae will offset ancient CO2-emitting fossil fuels.
Algae has been producing food nutrients for humans commercially for a number of years. The latest algae production excitement created two algae industry associations in 2008. It is largely driven by the multiple market opportunities, as well as the versatile environments in which algae can grow.
Just as aquatic plants can recycle and sequester CO2, so can terrestrial plants. It surprises me that we haven’t put more research and funding into using our surplus CO2 to grow terrestrial plants. Greenhouse operators, growing very high-value plants, can afford to enrich the CO2 levels two to three times greater than the 380 ppm CO2 in the ambient atmosphere.
Enriching CO2 levels doesn’t increase carbohydrate production in all green plants. CO2 response in green plants is greater in Calvin Cycle (C3) plants than in the more efficient C4 plants like corn, sugar cane and switchgrass. Pumping high volumes of exhaust CO2 through C3 crops could remediate emissions and boost yields.
The soybean is a C3 plant and therefore responsive to elevated levels of CO2. Recent work at the University of Illinois, Champaign showed that soybeans grown at CO2 concentrations elevated by 50 percent to 550 ppm, would increase grain yield by 15 percent. An earlier meta-analysis study of 111 research trials indicated that soybean bean yields could be increased as much as 24 percent with elevated levels of CO2.
A crop production technology that boosts yield by 15 percent is impressive, especially when we need biomass. What is even more compelling about CO2 enrichment is that increased CO2 concentrations lower water requirements. When green plants aren’t gasping to get more CO2, they close their stomata (breathing ports). As a result less water is lost to the atmosphere in transpiration than at ambient CO2 levels.
While a 3-month soybean crop will not sequester much CO2, this process could be easily expanded to a timber stand or a hybrid poplar plantation. These perennial crops would begin photosynthesizing CO2 to O2 as soon as the sap began flowing in the spring until it stopped in the fall. Increased biomass yields could offset fossil fuel use.
Feeding crops with exhaust CO2 would require a manifold that allowed the high volumes of CO2 to be piped alongside roads radiating out from the CO2 production source to the field. Piping gases is pretty routine. In fact, piping digester and landfill biogas to use in manufacturing is becoming fairly common. Plus we know how to manage irrigation pipes above and below ground.
The irony of this scenario is that the current CO2 emission phobia that demands a penalty be paid to CO2 emitters, could shift to more efficient systems that pay a small premium to high volume CO2 providers. This is my kind of save-the-world-with-undervalued-carbon story!
Mark Jenner, PhD, and Biomass Rules, LLC, has joined the California Biomass Collaborative. Burning Bio News and other biomass information is available at www.biomassrules.com.