Reconsidering bioenergy

Accelerated restoration in progress at the Malheur National Forest, Oregon  [photo: U.S. Forest Service] 

Protecting the Earth's climate takes on greater urgency every day. The vast majority of carbon dioxide (CO2) and other climate-wrecking greenhouse gas (GHG) emissions comes from the unmitigated use of fossil fuels. But that doesn't mean that every form of alternative energy is helpful for the planet. Case in point: bioenergy, such as liquid biofuels to replace oil or forest products to replace coal.

Indeed, using biomass for energy at large scales does not belong on the short list of actions to take for climate protection. This is the conclusion of a commentary by Bill Schlesinger and myself just published in the Proceedings of the National Academy of Sciences. Given the real-world limitations of not only technology but also land-use governance, we argue that the priority policymakers have given to promoting bioenergy is profoundly misplaced.

Biofuels vs. Biodiversity and the Need to Think Beyond Carbon Neutral

Seminar given at the University of Michigan, Thursday, February 8, 2018, as part of the 2016-2018 "Beyond Carbon Neutral" seminar series.

Download the presentation slides [PDF]

ABSTRACT

Just over a decade ago, policymakers gave a big boost to biofuels through the Renewable Fuel Standard (RFS) and similar policies. These policies included sustainability provisions for protecting sensitive lands; the intent was to spur the production of advanced biofuels that would be sustainable in many ways including low CO2 emissions. Now, new studies appear each year revealing the destruction of diverse habitats as biofuel production amplifies the global demand for land. There have also been multiple bankruptcies of highly-subsidized advanced biofuel operations. What went wrong and how can we find a better path forward?

The need to speed up carbon uptake

Last week I gave a talk, entitled "Net Ecosystem Production and Actionable Negative Emissions Strategies," at the American Geophysical Union (AGU) fall meeting in San Francisco. It was presented in a session on negative emissions strategies, which refers to the topic of removing CO2 from the air in order to slow -- and hopefully one day reverse -- the buildup of carbon in the atmosphere.

Net ecosystem production (NEP) is the net rate at which carbon is taken up by a terrestrial ecosystem. It determines the amount of carbon that becomes available for some use (e.g., crop or timber harvest) or for sequestration on the land. Scientifically speaking, any parcel of land with living organisms on it is an "ecosystem," including farm land or managed forests as well as natural lands and parts of the built environment that aren't totally paved with sterile concrete.

Plants and other organisms that carry out photosynthesis in the terrestrial biosphere actively remove CO2 from the air. Thus, they provide a fundamental mechanism for pursuing negative emissions. However, to be meaningful for climate mitigation -- which is the sense in which the term negative emissions is used -- carbon must be removed from the air more quickly than it is already being removed. That's what "the need to speed up carbon uptake" means and for the terrestrial biosphere, that means increasing NEP.

The fact that terrestrial carbon management is an actionable ("here-and-now") strategy and that using it for negative emissions requires increasing NEP are the main points of my talk. It can be download here in PDF format including both the narrative and slide images.

Thinking Beyond Carbon Neutral

Global climate change is a defining challenge of the 21st century and efforts to address it have many dimensions. Reducing greenhouse gas (GHG) emissions through higher energy efficiency, using solar, wind and nuclear energy, deploying carbon capture and storage (CCS), reducing deforestation, reducing methane emissions and minimizing other causes of excessive radiative forcing are all important. No one option will suffice and it is crucial to integrate technology solutions with policy drivers.

Because the carbon dioxide (CO2) emitted by fossil fuel use is the largest source of anthropogenic GHG emissions, the climate challenge is often characterized as the need to "decarbonize" the economy by eliminating fossil fuels. However, carbon is literally the fuel of life; the natural carbon cycle annually circulates twenty times as much carbon as released from fossil fuels and the majority is biogenic carbon fixed through photosynthesis. Although rapid release of fossil carbon is the primary cause of rising atmospheric CO2 concentrations, the real problem is an imbalance in the carbon cycle rather than fossil fuel use per se. Thus, the real need is to bring the carbon cycle into balance and eventually restore a global net carbon sink.